View source for Astronomy:KIC 8462852

{{short description|Star noted for unusual dimming events}}
{{Starbox begin
 | name = KIC 8462852
 }}
{{Starbox image
 | image = [[File:KIC 8462852 in IR and UV.png|300px]]
 | caption = KIC 8462852 in infrared and ultraviolet
 }}
{{Starbox observe
 | epoch = [[Astronomy:J2000.0|J2000.0]] ([[Astronomy:International Celestial Reference System|ICRS]])
 | constell = [[Astronomy:Cygnus (constellation)|Cygnus]]
 | ra = {{RA|20|06|15.4527}}
 | dec = {{DEC|+44|27|24.791}}
 | appmag_v = {{val|p=+|11.705|0.017}}
 }}
{{Starbox character
 | type = [[Astronomy:Main sequence|Main sequence]]<ref name="arXiv:1509.03622"/>
 | class = [[Astronomy:F-type main-sequence star|F3V]]
 | r-i = 0.305
 | v-r = 0.349
 | b-v = 0.557
 | j-h = 0.212
 | j-k = 0.264
 }}
{{Starbox astrometry
 | radial_v = <!-- Radial velocity (in km/s) -->
 | prop_mo_ra = {{val|-10.422|0.040}}
 | prop_mo_dec = {{val|-10.288|0.041}}
 | parallax = 2.2185
 | p_error = 0.0243
 | parallax_footnote = <ref name="Soubiran2018">{{cite journal |url=http://vizier.u-strasbg.fr/viz-bin/VizieR-5?-out.add=.&-source=I/345/gaia2&-c=301.56432344243%20%2044.45684219166,eq=ICRS,rs=0.005 |title=Gaia DR2 2081900940499099136: Gaia Data Release 2. The catalogue of radial velocity standard stars |journal=Astronomy & Astrophysics |first1=C. |last1=Soubiran |display-authors=0 |date=April 2018 |doi=10.1051/0004-6361/201832795 |bibcode=2018A&A...616A...7S |arxiv=1804.09370}}<!--Future bibcode? 2018yCat.1345....0G--></ref>
 | absmag_v = 3.08<ref name="arXiv:1509.03622"/><ref name="Bibcode:2013ApJS..208....9P"/><!--The 3.08 figure is quoted from Boyajian T. S et al 2015 despite the fact that a considerably dimmer value of 3.42 would be assumed if the Absolute Visual Magnitude was simply calculated from the apparent magnitude and distance. This is because the star lies more than 1000 light years away and so therefore a good percentage of its shortwave visible radiation has been scattered long before reaching Earth. So, the Absolute Visual Magnitude of 3.08 was calculated instead from a Bolometric Correction value taken from Pecaut & Mamajek 2013 -->
 }}
{{Starbox detail
 | mass = 1.43<ref name="arXiv:1509.03622"/>
 | radius = 1.58<ref name="arXiv:1509.03622"/>
 | luminosity_bolometric = 4.68<ref name="arXiv:1509.03622"/>
 | luminosity_visual = 
 | gravity = {{val|4.0|0.2}}<ref name="Marengo2015"/>
 | temperature = {{val|6750|120}}<ref name="arXiv:1509.03622"/>
 | metal = {{val|0.0|0.1}}<ref name="arXiv:1509.03622"/>
 | rotation = {{val|0.8797|0.0001}} days<ref name="arXiv:1509.03622"/>
 | rotational_velocity = {{val|84|4}}<ref name="arXiv:1509.03622"/>
 | age = <!-- Age (in years) -->
 }}
{{Starbox catalog
 | names = {{nowrap|Tabby's Star}}, {{nowrap|Boyajian's Star}}, {{nowrap|WTF Star}}, {{nowrap|[[Astronomy:Tycho-2 Catalogue|TYC]] 3162-665-1}},<ref name="arXiv:1509.03622"/> {{nowrap|[[Astronomy:2MASS|2MASS]] J20061546+4427248}},<ref name="arXiv:1509.03622"/> {{nobr|LGM-2}}<ref name="HuffPost-2016-08-25">{{cite news |url=http://www.huffingtonpost.com/entry/are-space-aliens-behind-the-most-mysterious-star-in-the-universe_us_57bb5537e4b00d9c3a1942f1 |title=Are Space Aliens Behind The 'Most Mysterious Star In The Universe?' |work=The Huffington Post |first=David |last=Freeman |date=25 August 2016 |accessdate=11 December 2016}}</ref>
 }}
{{Starbox reference
 | Simbad = TYC+3162-665-1
 | KIC = 8462852
 }}
{{Starbox end}}

'''KIC 8462852'''<ref name="arXiv:1509.03622" /> (also '''Tabby's Star''' or '''Boyajian's Star''') is an [[Astronomy:F-type main-sequence star|F-type main-sequence star]] located in the [[Astronomy:Constellation|constellation]] [[Astronomy:Cygnus (constellation)|Cygnus]] approximately {{convert|1470|ly|pc}} from Earth.<ref name="Soubiran2018" /> Unusual light fluctuations of the star, including up to a 22% dimming in brightness, were discovered by citizen scientists as part of the [[Astronomy:Planet Hunters|Planet Hunters]] project. In September 2015, astronomers and citizen scientists associated with the project posted a [[Preprint|preprint]] of an article describing the data and possible interpretations.<ref name="arXiv:1509.03622" /> The discovery was made from data collected by the [[Engineering:Kepler (spacecraft)|''Kepler'']] space telescope,<ref name="arXiv:1509.03622" /><ref name="ATL-20151013" /> which observes changes in the brightness of distant stars to [[Astronomy:Methods of detecting exoplanets|detect exoplanets]].<ref name="VRG-20151016">{{cite news |url=https://www.theverge.com/2015/10/16/9553033/kepler-alien-megastructure-dyson-sphere-kic-8462852 |title=Why it's so hard for astronomers to discuss the possibility of alien life |work=[[The Verge]] |last=Grush |first=Loren |date=16 October 2015 |accessdate=17 October 2015}}</ref>

Several hypotheses have been proposed to explain the star's large irregular changes in brightness as measured by its [[Astronomy:Light curve|light curve]], but none to date fully explain all aspects of the curve. One explanation is that an "uneven ring of dust" orbits KIC 8462852.<ref name="NASA-20171004" /><ref name="ApJ-20171003" /><ref name="PHY-20171005" /><ref name="NatGeoJan3">{{cite news |url=https://news.nationalgeographic.com/2018/01/mystery-of--alien-megastructure--star-has-been-cracked/ |title=Mystery of 'Alien Megastructure' Star Has Been Cracked |work=National Geographic |last=Drake |first=Nadia |date=3 January 2018 |accessdate=4 January 2018}}</ref><ref name="AXV-20180102" /><ref name="AXV-20180102deeg">{{Cite journal|title=Non-grey dimming events of KIC 8462852 from GTC spectrophotometry |journal=Astronomy & Astrophysics |volume=610 |issue=12 |pages=L12 |arxiv=1801.00720 |first1=H. J. |last1=Deeg |first2=R. |last2=Alonso |first3=D. |last3=Nespral |first4=Tabetha |last4=Boyajian |doi=10.1051/0004-6361/201732453 |year=2018 |bibcode=2018A&A...610L..12D }}</ref> In another explanation, the star's luminosity is modulated by changes in the efficiency of heat transport to its photosphere, so no external obscuration is required.<ref name="Foukal2017">{{cite journal |title=An Explanation of the Missing Flux from Boyajian's Mysterious Star |journal=The Astrophysical Journal Letters |first=Peter |last=Foukal |volume=842 |issue=1 |at=L3 |date=June 2017 |doi=10.3847/2041-8213/aa740f |bibcode=2017ApJ...842L...3F |arxiv=1704.00070}}</ref> A third hypothesis, based on a lack of observed infrared light, posits a swarm of cold, dusty comet fragments in a highly eccentric orbit,<ref name="NASA-20151124">{{cite web |url=http://www.nasa.gov/feature/jpl/strange-star-likely-swarmed-by-comets |title=Strange Star Likely Swarmed by Comets |publisher=[[Organization:NASA|NASA]] |last1=Clavin |first1=Whitney |last2=Johnson |first2=Michele |date=24 November 2015 |accessdate=24 November 2015}}</ref><ref name="independent20151125">{{cite news |url=https://www.independent.co.uk/news/science/star-that-could-have-alien-megastructure-around-it-is-almost-certainly-covered-by-a-swam-of-comets-a6748021.html |title=Star that could have 'alien megastructure' around it is almost certainly covered by a swarm of comets, Nasa says |work=The Independent |first=Andrew |last=Griffin |date=25 November 2015 |accessdate=26 November 2015}}</ref><ref name="ARX-20151127">{{cite journal |title=KIC 8462852: Transit of a Large Comet Family |arxiv=1511.08821 |class=astro-ph.EP |last1=Bodman |first1=Eva H. L. |last2=Quillen |first2=Alice |date=27 November 2015 |doi=10.3847/2041-8205/819/2/L34 |volume=819 |issue=2 |journal=The Astrophysical Journal |page=L34 |bibcode=2016ApJ...819L..34B}}</ref> however, the notion that disturbed comets from such a cloud could exist in high enough numbers to obscure 22% of the star's observed luminosity has been doubted.<ref name="SLT-20151015" /> Another hypothesis is that a large number of small masses in "tight formation" are orbiting the star.<ref name="ATL-20151013" /> Furthermore, spectroscopic study of the system has found no evidence for coalescing material or [[Astronomy:Circumstellar dust|hot close-in dust]] or circumstellar matter from an evaporating or exploding planet within a few [[Astronomy:Astronomical unit|astronomical unit]]s of the mature central star.<ref name="NASA-20151124" /><ref name="Lisse2015" /> It has also been hypothesized that the changes in brightness could be signs of activity associated with [[Philosophy:Extraterrestrial intelligence|intelligent extraterrestrial life]] constructing a [[Astronomy:Dyson sphere#Dyson swarm|Dyson swarm]].<ref name="ATL-20151013" /><ref name="WP-20151015">{{Cite news |url=https://www.washingtonpost.com/news/morning-mix/wp/2015/10/15/the-strange-star-that-has-serious-scientists-talking-about-an-alien-megastructure/ |title=The strange star that has serious scientists talking about an alien megastructure |work={{wipe|The Washington Post}} |first=Sarah |last=Kaplan |date=15 October 2015 |accessdate=15 October 2015}}</ref> The scientists involved are very skeptical, however, with others describing it as implausible.<ref name="SLT-20151015">{{Cite news |url=http://www.slate.com/blogs/bad_astronomy/2015/10/14/weird_star_strange_dips_in_brightness_are_a_bit_baffling.html |title=Did Astronomers Find Evidence of an Alien Civilization? (Probably Not. But Still Cool.) |work=Slate |first=Phil |last=Plait |date=14 October 2015 |accessdate=15 October 2015}}</ref><ref name="Sigurdsson2016" />

KIC 8462852 is not the only star that has large irregular dimmings, but all other such stars are [[Astronomy:Young stellar object|young stellar object]]s called YSO dippers, which have different dimming patterns. An example of such an object is [[Astronomy:EPIC 204278916|EPIC 204278916]].<ref name="EPIC">{{cite journal |title=The peculiar dipping events in the disk-bearing young-stellar object EPIC 204278916 |journal=[[Organization:Monthly Notices of the Royal Astronomical Society|Monthly Notices of the Royal Astronomical Society]] |first1=S. |last1=Scaringi |first2=C. F. |last2=Manara |first3=S. A. |last3=Barenfeld |first4=P. J. |last4=Groot |first5=A. |last5=Isella |first6=M. A. |last6=Kenworthy |first7=C. |last7=Knigge |first8=T. J. |last8=Maccarone |first9=L. |last9=Ricci |first10=M. |last10=Ansdell |display-authors=5 |volume=463 |issue=2 |pages=2265–2272 |date=December 2016 |doi=10.1093/mnras/stw2155 |bibcode=2016MNRAS.463.2265S |arxiv=1608.07291}}</ref><ref name="Phys2016Org">{{cite news |url=http://phys.org/news/2016-08-irregular-dimming-young-stellar-astronomers.html |title=Irregular dimming of a young stellar object investigated by astronomers |work=Phys.org |last=Nowakowski |first=Tomasz |date=30 August 2016 |accessdate=5 September 2016}}</ref>

New light fluctuation events of KIC 8462852 began in the middle of May 2017.<ref name="AXV-20180102">{{Cite journal|title=The First Post-Kepler Brightness Dips of KIC 8462852 |journal=The Astrophysical Journal |volume=853 |pages=L8 |arxiv=1801.00732 |first1=Tabetha S. |last1=Boyajian |display-authors=0 |doi=10.3847/2041-8213/aaa405 |year=2018 |bibcode=2018ApJ...853L...8B }}</ref> Except for a period between late-December 2017 and mid-February 2018 when the star was obscured by the Sun, the fluctuations have continued {{as of|2018|07|lc=on}}.

==Nomenclature==
KIC is an acronym for the [[Astronomy:Kepler Input Catalog|Kepler Input Catalog]], 8462852 being the star's catalog number. Colloquially the names "Tabby's Star" and "Boyajian's Star" refer to the initial study's lead author, Tabetha S. Boyajian;<ref name="popmech20160209">{{cite news |url=http://www.popularmechanics.com/space/telescopes/a19346/james-webb-telescope-alien-megastructure/ |title=NASA's Next Great Telescope Will Settle This Alien Megastructure Mystery For Good |work=Popular Mechanics |first=John |last=Wenz |date=9 February 2016 |accessdate=13 February 2016}}</ref><ref name="PSU-20160830">{{cite web |url=http://sites.psu.edu/astrowright/2016/08/30/what-could-be-going-on-with-boyajians-star-part-i/ |title=What Could Be Going on with Boyajian's Star? Part I |work=AstroWright |publisher=[[Organization:Pennsylvania State University|Pennsylvania State University]] |last=Wright |first=Jason T. |date=30 August 2016 |accessdate=12 September 2016}}</ref> KIC 8462852 is sometimes called the "WTF Star", after the study's subtitle "Where's The [[Physics:Radiative flux|Flux]]?"<ref name="PSU-20151015" /><ref name="CNN-20151016">{{cite news |url=http://www.cnn.com/2015/10/15/world/extraterrestrial-intelligence-anomaly |title=Space anomaly gets extraterrestrial intelligence experts' attention |work=CNN News |last=Newsome |first=John |date=16 October 2015 |accessdate=16 October 2015}}</ref><ref name="FN-20151015">{{cite news |url=http://fox43.com/2015/10/15/discovery-of-a-strange-star-could-mean-alien-life |title=Discovery of a strange star could mean alien life |work=Fox News |date=15 October 2015 |accessdate=16 October 2015}}</ref><ref name="UT-20151016">{{cite news |url=https://www.universetoday.com/122865/whats-orbiting-kic-8462852-shattered-comet-or-alien-megastructure/ |title=What's Orbiting KIC 8462852 – Shattered Comet or Alien Megastructure? |work=Universe Today |last=King |first=Bob |date=16 October 2015 |accessdate=16 October 2015}}</ref> (a joking reference to the colloquial expression of disbelief "WTF").<ref>{{cite news |url=https://www.smh.com.au/technology/its-either-aliens-or-a-swarm-of-comets-scientists-baffled-by-wtf-001-our-galaxys-strangest-star-20151015-gk9iwj.html |title=It's either aliens or a swarm of comets: scientists baffled by WTF 001, our galaxy's strangest star |work=The Sydney Morning Herald |first=Marcus |last=Strom |date=15 October 2015 |accessdate=16 October 2015}}</ref>

==Location==
[[File:NGC 6866 map.png|thumb|right|Map showing location of NGC 6866. KIC 8462852 is northeast between NGC 6866 and ο¹ Cygni.]]
[[File:KIC8462852BlueSquare&NearbyStars-20180603.jpg|thumb|right|[[Astronomy:Finderscope|Finder image]]: KIC 8462852 (blue square) and nearby stars - stable reference stars are in red circles.<small>(FOV=12.5 x 9.6 [[Minute and second of arc|'arc]], NE at [[Relative direction|upper-left]])</small><ref name="BG-20180603">{{cite web |last=Gary |first=Bruce L. |title=KIC 8462852 Hereford Arizona Observatory Photometry Observations #6 - Bruce Gary, Last updated: 2018.06.02 20 UT |url=http://www.brucegary.net/ts6/ |date=3 June 2018 |deadurl=yes |archiveurl=https://web.archive.org/web/20180603125601/http://www.brucegary.net/ts6/ |archivedate=3 June 2018 |work=BruceGary.net |accessdate=3 June 2018}}</ref>]]
KIC 8462852 in the constellation [[Astronomy:Cygnus (constellation)|Cygnus]] is located roughly halfway between the bright stars [[Astronomy:Deneb|Deneb]] and [[Astronomy:Delta Cygni|Delta Cygni]] as part of the [[Astronomy:Northern Cross (asterism)|Northern Cross]].<ref>{{cite web |url=https://archive.stsci.edu/kepler/kic10/search.php?kic_kepler_id=8462852&action=Search |title=KIC10 Search Results |publisher=Space Telescope Science Institute |accessdate=16 October 2015}}</ref><ref name="STPSA">{{Cite book |title=Sky & Telescope's Pocket Sky Atlas |publisher=Sky Publishing |location=Cambridge, Massachusetts |first=Roger W. |last=Sinnott |edition=3rd |date=2010 |isbn=978-1-931559-31-7}}</ref> KIC 8462852 is situated south of [[Astronomy:31 Cygni|31 Cygni]], and northeast of the [[Astronomy:Star cluster|star cluster]] [[Astronomy:NGC 6866|NGC 6866]].<ref name=STPSA/> While only a few arcminutes away from the cluster, it is unrelated and closer to the Sun than it is to the star cluster.

With an [[Astronomy:Apparent magnitude|apparent magnitude]] of 11.7, the star cannot be seen by the [[Astronomy:Naked eye|naked eye]], but is visible with a {{convert|5|in|mm|adj=on}} telescope<ref name="VT-20151016">{{cite web |url=http://www.virtualtelescope.eu/2015/10/16/kic-8462852-a-star-and-its-secrets/ |title=KIC 8462852: A star and its secrets |work=The Virtual Telescope Project 2.0 |last=Masi |first=Gianluca |date=16 October 2015 |accessdate=22 October 2015}}</ref> in a dark sky with little [[Astronomy:Light pollution|light pollution]].

==History of observations==
KIC 8462852 was observed as early as the year 1890.<ref name="NS-20160115">{{cite news |url=https://www.newscientist.com/article/dn28786-comets-cant-explain-weird-alien-megastructure-star-after-all/ |title=Comets can't explain weird 'alien megastructure' star after all |work=New Scientist |last=Aron |first=Jacob |date=15 January 2016 |accessdate=16 January 2016}}</ref><ref name="ARX-20160113">{{cite journal |title=KIC 8462852 Faded at an Average Rate of 0.165+-0.013 Magnitudes Per Century From 1890 To 1989 |last=Schaefer |first=Bradley E. |arxiv=1601.03256 |class=astro-ph.SR |date=13 January 2016 |doi=10.3847/2041-8205/822/2/L34 |volume=822 |issue=2 |journal=The Astrophysical Journal |page=L34 |bibcode=2016ApJ...822L..34S}}</ref><ref name="AXV-20160208">{{Cite journal |title=KIC 8462852 did likely not fade during the last 100 years |journal=The Astrophysical Journal |volume=825 |pages=73 |last1=Hippke |first1=Michael |last2=Angerhausen |first2=Daniel |arxiv=1601.07314 |date=8 February 2016 |doi=10.3847/0004-637X/825/1/73 |bibcode=2016ApJ...825...73H}}</ref> The star was cataloged in the [[Astronomy:Tycho-2 Catalogue|Tycho]], [[Astronomy:2MASS|2MASS]], UCAC4, and [[Astronomy:Wide-field Infrared Survey Explorer|WISE]] [[Astronomy:Astronomical catalog|astronomical catalog]]s<ref>{{cite web |url=http://simbad.u-strasbg.fr/simbad/sim-id?Ident=TYC%203162-665-1 |title=TYC 3162-665-1 |work=[[Astronomy:SIMBAD|SIMBAD]] |accessdate=17 June 2016}}</ref> (published in 1997, 2003, 2009, and 2012, respectively).<ref>{{cite web |url=http://sci.esa.int/hipparcos/ |title=Hipparcos |publisher=European Space Agency |accessdate=17 June 2016}}</ref><ref>{{cite web |url=http://www.ipac.caltech.edu/2mass/overview/about2mass.html |title=About 2MASS |publisher=[[Organization:California Institute of Technology|California Institute of Technology]] |accessdate=17 June 2016}}</ref><ref>{{cite web |url=http://www.usno.navy.mil/USNO/astrometry/optical-IR-prod/ucac |title=USNO CCD Astrograph Catalog (UCAC) |publisher=United States Naval Observatory |accessdate=17 June 2016}}</ref><ref>{{cite web |url=http://www.nasa.gov/mission_pages/WISE/news/wise20120314.html |title=NASA Releases New WISE Mission Catalog of Entire Infrared Sky |publisher=NASA |first1=Whitney |last1=Clavin |first2=J. D. |last2=Harrington |date=14 March 2012 |accessdate=17 June 2016}}</ref><!--Time range?:  The star was observed by SuperWASP ground observatories for three seasons.<ref>https://arxiv.org/pdf/1509.03622v2.pdf</ref> -->

The main source of information about the luminosity fluctuations of KIC 8462852 is the [[Engineering:Kepler (spacecraft)|''Kepler'' space observatory]]. During its primary and extended mission from 2009 to 2013 it continuously monitored the [[Astronomy:Light curve|light curve]]s of over 100,000 stars in a patch of sky in the constellations Cygnus and Lyra.<ref>{{cite web |url=http://kepler.nasa.gov/Mission/faq/|archive-url=https://web.archive.org/web/20160706213754/http://kepler.nasa.gov/Mission/faq/|archive-date=6 July 2016|title=Kepler: FAQ |publisher=NASA |accessdate=17 June 2016}}</ref>

==Luminosity==
Observations of the [[Astronomy:Luminosity|luminosity]] of the star by the ''Kepler'' space telescope show small, frequent, non-periodic dips in brightness, along with two large recorded dips in brightness roughly 750 days apart. The amplitude of the changes in the star's brightness, and the aperiodicity of the changes, mean that this star is of particular interest for astronomers.<ref name="SLT-20151015" /> The star's changes in brightness are consistent with many small masses orbiting the star in "tight formation".<ref name="ATL-20151013" />

The first major dip, on 5 March 2011, reduced the star's brightness by up to 15%, and the next 726 days later (on 28 February 2013) by up to 22%. (A third dimming, around 8%, occurred 48 days later.) In comparison, a planet the size of Jupiter would only obscure a star of this size by 1%, indicating that whatever is blocking light during the star's major dips is not a planet, but rather something covering up to half the width of the star.<ref name="SLT-20151015" /> Due to the failure of two of ''Kepler''{{'s}} [[Engineering:Reaction wheel|reaction wheel]]s, the star's predicted 750-day dip around February 2015 was not recorded.<ref name="arXiv:1509.03622" /><ref name="NSCI-20150918">{{Cite news |url=https://www.newscientist.com/article/dn28191-citizen-scientists-catch-cloud-of-comets-orbiting-distant-star/ |title=Citizen scientists catch cloud of comets orbiting distant star |work=New Scientist |last=Aron |first=Jacob |date=18 September 2015 |accessdate=15 October 2015}}</ref> The light dips do not exhibit an obvious pattern.<ref name="Michael2016">{{Cite journal |url=https://www.skeptic.com/reading_room/the-great-et-paradox/ |title=The Great ET Paradox: Why We are Likely to Find Them Before They Find Us |journal=[[Religion:Skeptic (U.S. magazine)|Skeptic]] |first=George |last=Michael |volume=21 |issue=1 |pages=16–18 |date=January 2016}}</ref>

In addition to the day-long dimmings, a study of a century's worth of photographic plates suggests that the star has gradually faded from 1890 to 1989 by about 20%, which would be unprecedented for any F-type main-sequence star.<ref name="NS-20160115"/><ref name="ARX-20160113"/> Teasing accurate magnitudes from long-term photographic archives is a complex procedure, however, requiring adjustment for equipment changes, and is strongly dependent on the choice of comparison stars. Another study, examining the same photographic plates, concluded that the possible century-long dimming was likely a data artifact, and not a real astrophysical event.<ref name="AXV-20160208"/> Another study from plates between 1895 and 1995 found strong evidence that the star has not dimmed, but kept a constant flux within a few percent, except a 8% dip on 24 October 1978, resulting in a period of the putative occulter of 738 days.<ref>{{Cite journal |arxiv=1609.09290 |last1=Hippke |first1=Michael |title=Sonneberg plate photometry for Boyajian's Star in two passbands |journal=The Astrophysical Journal |volume=837 |issue=837 |pages=85 |last2=Kroll |first2=Peter |last3=Matthei |first3=Frank |last4=Angerhausen |first4=Daniel |last5=Tuvikene |first5=Taavi |last6=Stassun |first6=Keivan G |last7=Roshchina |first7=Elena |last8=Vasileva |first8=Tatyana |last9=Izmailov |first9=Igor|last10=Samus|first10=Nikolay N |last11=Pastukhova |first11=Elena N |last12=Bryukhanov |first12=Ivan |last13=Lund |first13=Michael B |year=2016 |doi=10.3847/1538-4357/aa615d |bibcode=2017ApJ...837...85H}}</ref>

A third study, using light measurements by the ''Kepler'' observatory over a four-year period, determined that KIC 8462852 dimmed at about 0.34% per year before dimming more rapidly by about 2.5% in 200 days. It then returned to its previous slow fade rate. The same technique was used to study 193 stars in its vicinity and 355 stars similar in size and composition to KIC 8462852. None of these stars exhibited such dimming.<ref name="Montet2016">{{cite journal |title=KIC 8462852 Faded Throughout the ''Kepler'' Mission |arxiv=1608.01316 |class=astro-ph |first1=Benjamin T. |last1=Montet |first2=Joshua D. |last2=Simon |date=3 August 2016 |doi=10.3847/2041-8205/830/2/L39 |volume=830 |issue=2 |journal=The Astrophysical Journal |page=L39 |bibcode=2016ApJ...830L..39M}}</ref>

In 2018, a possible {{convert|1574|day|year|adj=on|abbr=off}} periodicity in dimming of the star was reported.<ref name="AAVSO-2018">{{cite journal |url=https://www.aavso.org/apps/jaavso/article/3327/ |title=A 1,574-Day Periodicity of Transits Orbiting KIC 8462852 |journal=The Journal of the American Association of Variable Star Observers |first1=Gary |last1=Sacco |first2=Linh D. |last2=Ngo |first3=Julien |last3=Modolo |display-authors=1 |volume=46 |issue=1 |page=14 |date=June 2018 |bibcode=2018JAVSO..46...14S |arxiv=1710.01081}}</ref>

==Hypotheses==
Originally it was erroneously thought that, based on {{nowrap|KIC 8462852's}} spectrum and stellar type, its changes in brightness could not be attributed to [[Astronomy:Variable star|intrinsic variability]].<ref name="arXiv:1509.03622" /> Consequently, a few hypotheses have been proposed involving material orbiting the star and blocking its light, although none of these fully fit the observed data.<ref name="DISC-20170630">{{cite web |last1=Powell |first1=Corey S. |last2=Wright |first2=Jason T. |title=The Strangest (and Second-Strangest) Star in the Galaxy |url=http://blogs.discovermagazine.com/outthere/2017/06/30/wright/ |date=30 June 2017 |work=Discover |accessdate=10 September 2017}}</ref>

Some of the proposed explanations involve interstellar dust, a series of giant planets with very large ring structures,<ref name="AT-20151016" /><ref name="FRB-20151016">{{cite news |url=https://www.forbes.com/sites/ethansiegel/2015/10/16/bizarre-star-kic-8462852-an-alien-paradise-or-a-catastrophic-wasteland/ |title=No, Astronomers Probably Haven't Found 'Alien Megastructures' |work={{wipe|Forbes}} |last=Siegel |first=Ethan |date=16 October 2015 |accessdate=17 October 2015}}</ref> a recently captured [[Astronomy:Asteroid|asteroid]] field,<ref name="arXiv:1509.03622" /> the system undergoing [[Astronomy:Late Heavy Bombardment|Late Heavy Bombardment]],<ref name="NASA-20151124"/><ref name="Lisse2015">{{cite journal |title=IRTF/SPeX Observations of the Unusual Kepler Light Curve System KIC8462852 |journal=The Astrophysical Journal Letters |first1=Carey |last1=Lisse |first2=Michael |last2=Sitko |first3=Massimo |last3=Marengo |volume=815 |issue=2 |pages=L27 |date=December 2015 |doi=10.1088/2041-8205/815/2/L27 |bibcode=2015ApJ...815L..27L |arxiv=1512.00121}}</ref> and an artificial megastructure orbiting the star.<ref name="arXiv:1510.04606" />

As of 2018, the leading hypothesis suggests that the "missing" heat flux involved in the star's dimming can be stored within the star's interior. Such variations in luminosity might arise from a number of mechanisms affecting the efficiency of heat transport inside the star.<ref name="Innate Processes?">{{Cite news |url=http://aasnova.org/2017/07/07/another-possibility-for-boyajians-star/ |title=Another Possibility for Boyajian's Star |work=AAS Nova |last=Kohler |first=Susanna |date=7 July 2017 |access-date=14 July 2017}}</ref><ref name="Foukal2017" />

===Circumstellar dust ring===
[[File:PIA22081-KIC8462852-TabbysStar-UnevenDustRing-Illustration-20171004.png|thumb|Artist's concept of an "uneven ring of dust" orbiting KIC 8462852<ref name="NASA-20171004" /><ref name="ApJ-20171003" /><ref name="PHY-20171005" />]]

{{quote|[[Philosophy:Smoking gun|The smoking gun]]: Researchers found less dimming in the [[Physics:Infrared|infrared light]] from the star than in its [[Physics:Ultraviolet|ultraviolet light]]. Any object larger than [[Astronomy:Cosmic dust|dust particles]] would dim all [[Physics:Light|wavelengths of light]] equally when passing in front of Tabby's Star.|author=[[Organization:NASA|NASA]]|source=4 October 2017<ref name="NASA-20171004" /><ref name="ApJ-20171003" /><ref name="PHY-20171005" />}}

Meng et al. (2017) suggested that, based on observational data of KIC 8462852 from the Swift Gamma-Ray Burst Mission, [[Astronomy:Spitzer Space Telescope|Spitzer Space Telescope]] and [[Astronomy:Interface Region Imaging Spectrograph|Belgian AstroLAB IRIS Observatory]], only "microscopic fine-dust screens", originating from "circumstellar material", are able to disperse the starlight in the way detected in their measurements.<ref name="NASA-20171004">{{cite web |url=https://www.jpl.nasa.gov/news/news.php?feature=6963 |title=Mysterious Dimming of Tabby's Star May Be Caused by Dust |publisher=NASA |first=Elizabeth |last=Landau |date=4 October 2017 |accessdate=4 October 2017}}</ref><ref name="ApJ-20171003">{{cite journal |title=Extinction and the Dimming of KIC 8462852 |journal=The Astrophysical Journal |first1=Huan Y. A. |last1=Meng |first2=George |last2=Rieke |first3=Franky |last3=Dubois |first4=Grant |last4=Kennedy |first5=Massimo |last5=Marengo |first6=Michael |last6=Siegel |first7=Kate |last7=Su |first8=Nicolas |last8=Trueba |first9=Mark |last9=Wyatt |first10=Tabetha |last10=Boyajian |first11=C. M. |last11=Lisse |first12=Ludwig |last12=Logie |first13=Steve |last13=Rau |first14=Sigfried |last14=Vanaverbeke |display-authors=1 |volume=847 |issue=2 |pages=131 |date=October 2017 |doi=10.3847/1538-4357/aa899c |bibcode=2017ApJ...847..131M |arxiv=1708.07556}}</ref><ref name="PHY-20171005">{{cite web |url=https://www.nasa.gov/feature/ames/the-scientific-quest-to-explain-kepler-s-most-enigmatic-find |title=The Scientific Quest to Explain Kepler's Most Enigmatic Find |publisher=NASA |first=Abby |last=Tabor |date=4 October 2017 |accessdate=5 October 2017}}</ref><ref name="INV-20170908">{{cite news |url=https://www.inverse.com/article/36239-tabby-s-star-not-alien-megastructures-new-study-kic-8462852-nasa |title=We Finally Have Proof the Alien Megastructures Star is Not Aliens |work=Inverse |last=Patel |first=Neel V. |date=8 September 2017 |accessdate=10 September 2017}}</ref> Based on these studies, on 4 October 2017, NASA reported that the unusual dimming events of KIC 8462852 are due to an "uneven ring of [[Astronomy:Cosmic dust|dust]]" orbiting the star.<ref name="NASA-20171004" /> Although the explanation of a significant amount of small particles orbiting the star regards "long-term fading" as noted by Meng,<ref name="ApJ-20171003" /> the explanation also seems consistent with the week-long fadings found by amateur astronomer [[Astronomy:Hereford Arizona Observatory|Bruce L. Gary]] and the Tabby Team, coordinated by astronomer Tabetha S. Boyajian, in more recent dimming events.<ref name="NatGeoJan3"/><ref name="AXV-20180102" /><ref name="BG-20171004" /><ref name="WTFlux-20171004">{{cite web |first=Tabetha S. |last=Boyajian |title=Dip update 98/n |url=http://www.wherestheflux.com/single-post/2017/10/04/Dip-update-98n |date=4 October 2017 |work=WheresTheFlux.com |accessdate=4 October 2017}}</ref><ref name="NYT-20180110">{{cite news |last=Overbye |first=Dennis |authorlink=Dennis Overbye |title=Magnetic Secrets of Mysterious Radio Bursts in a Faraway Galaxy |url=https://www.nytimes.com/2018/01/10/science/neutron-star-fast-radio-bursts.html |date=10 January 2018 |work={{wipe|The New York Times}} |accessdate=11 January 2018}}</ref> A related, but more sophisticated, explanation of dimming events, involving a transiting "[[Astronomy:Brown dwarf|brown dwarf]]" in a 1600-day eccentric orbit near KIC 8462852, a "drop feature" in dimness and predicted intervals of "brightening", has been proposed.<ref name="BG-2017">{{cite web |last=Gary |first=Bruce L. |title=KIC8462852 Hereford Arizona Observatory Photometry Observations #5 |url=http://www.brucegary.net/ts5/ |date=16 December 2017 |deadurl=yes |archiveurl=https://web.archive.org/web/20171216160904/http://www.brucegary.net/ts5/ |archivedate=16 December 2017 |work=BruceGary.net |accessdate=16 December 2017}}</ref><ref name="ARX-20171111">{{cite arxiv |title=KIC 8462852 Brightness Pattern Repeating Every 1600 Days |eprint=1711.04205 |class=astro-ph.EP |first1=Bruce L. |last1=Gary |first2=Rafik |last2=Bourne |date=11 November 2017}}</ref><ref name="ARX-20171128-pdf">{{Cite journal|title=Recent Photometric Monitoring of KIC 8462852, the Detection of a Potential Repeat of the Kepler Day 1540 Dip and a Plausible Model |journal=Monthly Notices of the Royal Astronomical Society |volume=475 |issue=4 |pages=5378–5384 |arxiv=1711.10612 |first1=R. |last1=Bourne |first2=B. L. |last2=Gary |first3=A. |last3=Plakhov |doi=10.1093/mnras/sty097 |year=2018 |bibcode=2018MNRAS.475.5378B }}</ref><ref name="ARX-20171120">{{cite arxiv |title=KIC 8462852: Potential repeat of the Kepler day 1540 dip in August 2017 |eprint=1711.07472 |class=astro-ph.EP |first1=Rafik |last1=Bourne |first2=Bruce L. |last2=Gary |date=20 November 2017}}</ref> Dimming and brightening events of KIC 8462852 continue to be monitored; related light curves are currently updated and released frequently.<ref name="BG-2018" /><ref name="SPC-20180608">{{cite web |last=Redd |first=Nola Taylor |title=High School Students Help Unravel Mystery of Weirdly Dimming 'Tabby's Star' |url=https://www.space.com/40836-tabbys-star-mystery-dimming-student-discovery.html |date=8 June 2018 |work=Space.com |accessdate=8 June 2018}}</ref>

Nonetheless, data similar to that observed for KIC 8462852, along with supporting data from  the [[Astronomy:Chandra X-ray Observatory|Chandra X-ray Observatory]], were found with dust debris orbiting [[Astronomy:WD 1145+017|WD 1145+017]], a [[Astronomy:White dwarf|white dwarf]] that also has unusual light curve fluctuations.<ref name="arXiv-20170924">{{Cite journal|title=WD 1145+017: Optical Activity During 2016-2017 and Limits on the X-Ray Flux |journal=Monthly Notices of the Royal Astronomical Society |volume=474 |pages=933–946 |arxiv=1709.08195 |first1=S. |last1=Rappaport |first2=B. L. |last2=Gary |first3=A. |last3=Vanderburg |first4=S. |last4=Xu |first5=D. |last5=Pooley |first6=K. |last6=Mukai |display-authors=1 |doi=10.1093/mnras/stx2663 |year=2018 |bibcode=2018MNRAS.474..933R }}</ref> Further, the highly variable star [[Astronomy:RZ Piscium|RZ Piscium]], which brightens and dims erratically, has been found to emit excessive [[Physics:Infrared|infrared radiation]], suggesting that the star is surrounded by large amounts of gas and dust, possibly resulting from the [[Astronomy:Disrupted planet|destruction of local planets]].<ref name="AJ-20171221">{{cite journal |title=Is the Young Star RZ Piscium Consuming Its Own (Planetary) Offspring? |journal=The Astronomical Journal |first1=K. M. |last1=Punzi |first2=J. H. |last2=Kastner |first3=C. |last3=Melis |first4=B. |last4=Zuckerman |first5=C. |last5=Pilachowski |first6=L. |last6=Gingerich |first7=T. |last7=Knapp |display-authors=1 |volume=155 |issue=1 |pages=33 |date=January 2018 |doi=10.3847/1538-3881/aa9524 |bibcode=2018AJ....155...33P |arxiv=1712.08962}}</ref><ref name="NASA-20171221">{{cite web |last1=Reddy |first1=Francis |last2=Garner |first2=Rob |title=New Study Finds 'Winking' Star May Be Devouring Wrecked Planets |url=https://www.nasa.gov/feature/goddard/2017/new-study-finds-winking-star-may-be-devouring-wrecked-planets |publisher=NASA |date=21 December 2017 |accessdate=22 December 2017}}</ref>
{{clear}}

===A cloud of disintegrating comets=== 
[[File:PIA20053-PossibleCometSwarmAroundKIC8462852-ArtistConcept-20151124.jpg|thumb|left|Artist's impression of an orbiting swarm of dusty comet fragments]]
One proposed explanation for the reduction in light is that it is due to a cloud of disintegrating [[Astronomy:Comet|comet]]s orbiting the star elliptically.<ref name="arXiv:1509.03622" /><ref name="NASA-20151124" /><ref name="ARX-20151127" /><ref name="PS-20151013">{{cite news |url=http://www.popsci.com/have-we-detected-alien-megastructures-around-distant-star |title=Have We Detected Megastructures Built By Aliens Around A Distant Star? Or Just A Cloud Of Comets? Scientists Want To Investigate Further |work=Popular Science |last=Fecht |first=Sarah |date=13 October 2015 |accessdate=14 October 2015}}</ref> This scenario would assume that {{nowrap|KIC 8462852's}} planetary system has something similar to the [[Astronomy:Oort cloud|Oort cloud]] and that gravity from a nearby star caused comets from said cloud to fall closer into the system, thereby obstructing {{nowrap|KIC 8462852's}} spectra. Evidence supporting this hypothesis includes an M-type [[Astronomy:Red dwarf|red dwarf]] within {{convert|885|AU|e9km|0|order=flip|sp=us|lk=out}} of {{nowrap|KIC 8462852}}.<ref name="arXiv:1509.03622" /> The notion that disturbed comets from such a cloud could exist in high enough numbers to obscure 22% of the star's observed luminosity has been doubted.<ref name="SLT-20151015" />

Submillimetre-wavelength observations searching for farther-out cold dust in an asteroid belt akin to the Sun's Kuiper Belt suggest that a distant "catastrophic" planetary disruption explanation is unlikely; the possibility of a disrupted asteroid belt scattering comets into the inner system is still to be determined.<ref name="Thompson201605">{{cite journal |title=Constraints on the circumstellar dust around KIC 8462852 |journal=Monthly Notices of the Royal Astronomical Society: Letters |last1=Thompson |first1=M. A. |last2=Scicluna |first2=P. |last3=Kemper |first3=F. |last4=Geach |first4=J. E. |last5=Dunham |first5=M. M. |last6=Morata |first6=O. |last7=Ertel |first7=S. |last8=Ho |first8=P. T. P. |last9=Dempsey |first9=J. |last10=Coulson |first10=I. |last11=Petitpas |first11=G. |last12=Kirstensen |first12=L. E. |display-authors=5 |volume=458 |issue=1 |pages=L39–L43 |date=May 2016 |doi=10.1093/mnrasl/slw008 |bibcode=2016MNRAS.458L..39T |arxiv=1512.03693}}</ref>
{{clear}}

===Younger star with coalescing material around it=== 
[[File:Artist’s Impression of a Baby Star Still Surrounded by a Protoplanetary Disc.jpg|thumb|right|Artist's impression of a young star with coalescing material around it]]
Astronomer Jason T. Wright and others who have studied KIC 8462852 have suggested that if the star is younger than its position and speed would suggest, then it may still have coalescing material around it.<ref name="UT-20151016" /><ref name="Laker">{{cite news |url=http://home.bt.com/news/science-news/alien-megastructure-may-explain-light-patterns-from-bizarre-star-say-scientists-11364010755958 |title='Alien megastructure' may explain light patterns from 'bizarre' star, say scientists |work=BT.com |first=Chris |last=Laker |date=16 October 2015 |accessdate=17 October 2015}}</ref><ref name="PSU-20151015" />

A [[Physics:Infrared#Regions within the infrared|0.8–4.2-micrometer]] spectroscopic study of the system using the [[Organization:NASA Infrared Telescope Facility|NASA Infrared Telescope Facility]] (NASA IRTF) found no evidence for coalescing material within a few [[Astronomy:Astronomical unit|astronomical unit]]s of the mature central star.<ref name="NASA-20151124"/><ref name="Lisse2015"/>

===Planetary debris field=== 
[[File:PIA18469-AsteroidCollision-NearStarNGC2547-ID8-2013.jpg|thumb|left|Artist's impression of a massive collision with a proto-planet]]
High-resolution [[Physics:Astronomical spectroscopy|spectroscopy]] and imaging observations have also been made, as well as [[Physics:Spectral energy distribution|spectral energy distribution]] analyses using the [[Astronomy:Nordic Optical Telescope|Nordic Optical Telescope]] in Spain.<ref name="arXiv:1509.03622"/><ref name="AT-20151016">{{cite news |url=https://arstechnica.com/science/2015/10/something-were-not-sure-what-is-radically-dimming-a-stars-light |title=Something—we're not sure what—is radically dimming a star's light |work=[[Ars Technica]] |last=Rzetelny |first=Xaq |date=16 October 2015 |accessdate=17 October 2015}}</ref> A massive collision scenario would create warm dust that glows in [[Physics:Infrared|infrared]] wavelengths, but there is no observed excess infrared energy, ruling out massive planetary collision debris.<ref name="SLT-20151015"/> Other researchers think the planetary debris field explanation is unlikely, given the very low probability that ''Kepler'' would ever witness such an event due to the rarity of collisions of such size.<ref name="arXiv:1509.03622" />

As with the possibility of coalescing material around the star, spectroscopic studies using the NASA IRTF found no evidence for hot close-in dust or circumstellar matter from an evaporating or exploding planet within a few astronomical units of the central star.<ref name="NASA-20151124"/><ref name="Lisse2015"/> Similarly, a study of past infrared data from NASA's [[Astronomy:Spitzer Space Telescope|Spitzer Space Telescope]] and [[Astronomy:Wide-field Infrared Survey Explorer|Wide-field Infrared Survey Explorer]] found no evidence for an excess of infrared emission from the star, which would have been an indicator of warm dust grains that could have come from catastrophic collisions of meteors or planets in the system. This absence of emission supports the hypothesis that a swarm of cold comets on an unusually eccentric orbit could be responsible for the star's unique light curve, but more studies are needed.<ref name="NASA-20151124"/><ref name="Marengo2015">{{cite journal |title=KIC 8462852: The Infrared Flux |journal=The Astrophysical Journal Letters |first1=Massimo |last1=Marengo |first2=Alan |last2=Hulsebus |first3=Sarah |last3=Willis |volume=814 |issue=1 |pages=L15 |date=November 2015 |doi=10.1088/2041-8205/814/1/L15 |arxiv=1511.07908 |bibcode=2015ApJ...814L..15M}}</ref>
{{clear}}

===Consumption of a planet===
In December 2016, a team of researchers proposed that KIC 8462852 swallowed a planet, causing a temporary and unobserved increase in brightness due to the release of gravitational energy. As the planet fell into its star, it could have been ripped apart or had its moons stripped away, leaving clouds of debris orbiting the star in eccentric orbits. Planetary debris still in orbit around the star would then explain its observed drops in intensity.<ref name="Metzger2016">{{cite journal |title=Secular Dimming of KIC 8462852 Following its Consumption of a Planet |first1=Brian D. |last1=Metzger |first2=Ken J. |last2=Shen |first3=Nicholas C. |last3=Stone |journal=Monthly Notices of the Royal Astronomical Society |volume=468 |issue=4 |pages=4399–4407 |date=December 2016 |doi=10.1093/mnras/stx823 |bibcode=2017MNRAS.468.4399M |arxiv=1612.07332}}</ref> Additionally, the researchers suggest that the consumed planet could have caused the star to increase in brightness up to 10,000 years ago, and its stellar flux is now returning to the normal state.<ref name="Metzger2016"/><ref>{{cite news |url=https://www.iflscience.com/space/alien-megastructure-star-eaten-a-planet/ |title=The Alien Megastructure Star May Have Eaten A Planet |work=IFL Science |first=Jonathan |last=O'Callaghan |date=11 January 2017}}</ref>
{{clear}}

===Large planet with oscillating rings===
Sucerquia et al. (2017) suggested that a large planet with oscillating rings may help explain the unusual dimmings associated with KIC 8462852.<ref name="arXv-20170815">{{Cite journal|last=Sucerquia |first=Mario |display-authors=0. |title=Anomalous lightcurves of young tilted exorings |journal=Monthly Notices of the Royal Astronomical Society: Letters |volume=472 |issue=1 |pages=L120–L124 |arxiv=1708.04600 |doi=10.1093/mnrasl/slx151 |year=2017 |bibcode=2017MNRAS.472L.120S }}</ref><ref name="NBC-20170901">{{cite news |last=Shostak |first=Seth |title=Has Tabby's Star Mystery Finally Been Solved? From alien megastructures to super-Saturns, all sorts of explanations have been offered for star's weird behavior. Here's where we stand now. |url=https://www.nbcnews.com/mach/science/tabby-s-star-mystery-still-hasn-t-been-solved-ncna797741 |date=1 September 2017 |work=NBCNews |accessdate=3 September 2017}}</ref>
{{clear}}

===Large ringed planet followed by Trojan swarms===
Ballesteros et al. (2017) proposed a large, ringed planet trailed by a swarm of [[Astronomy:Trojan asteroid|Trojan asteroid]]s in its L5 [[Astronomy:Lagrangian point|Lagrangian point]], and estimated an orbit that predicts another event in early 2021 due to the leading Trojans followed by another transit of the hypothetical planet in 2023.<ref name="Ballesteros2017">{{Cite journal|title=KIC 8462852: Will the Trojans return in 2021?|journal=Monthly Notices of the Royal Astronomical Society: Letters |volume=473 |pages=L21–L25 |arxiv=1705.08427 |first1=Fernando J. |last1=Ballesteros |first2=Pablo |last2=Arnalte-Mur |first3=Alberto |last3=Fernandez-Soto |first4=Vicent J. |last4=Martinez |doi=10.1093/mnrasl/slx105 |year=2018 |bibcode=2018MNRAS.473L..21B }}</ref> The model suggests a planet with a radius of 4.7 [[Astronomy:Jupiter radius|Jupiter radii]], large for a planet (unless very young). An early [[Astronomy:Red dwarf|red dwarf]] of about {{Solar radius|0.5}} would be easily seen in [[Physics:Infrared|infrared]]. The current radial velocity observations available (four runs at σ<sub>''v''</sub> ≈ 400&nbsp;m/s) hardly constrain the model, but new radial velocity measurements would greatly reduce the uncertainty. The model predicts a discrete and short-lived event for the May 2017 dimming episode, corresponding to the [[Astronomy:Methods of detecting exoplanets#Transit photometry|secondary eclipse]] of the planet passing behind KIC 8246852, with about a 3% decrease in the stellar flux with a transit time of about 2 days. If this is the cause of the May 2017 event, the planet's orbital period is more precisely estimated as 12.41 years with a semi-major axis of 5.9 AU.<ref name="Ballesteros2017"/><ref>{{cite web |url=https://pbs.twimg.com/media/DAjVXoeW0AEYZJn.jpg |format=JPG |title=Orbital Diagram Hypothesis of KIC 8462852 |work=[[Company:Twitter|Twitter]] |accessdate=28 May 2017}}</ref>
{{clear}}

===Intrinsic luminosity variations===

The reddening observed during the deep dimming events of KIC 8462852 is consistent with cooling of its photosphere.<ref>{{cite journal |last1=Foukal |first1=Peter |title=Reddened dimmimg of Boyajian's star supports internal storage of its "missing" flux |journal=Res Notes AAS |date=15 December 2017 |volume=1 |issue=1 |pages=52 |doi=10.3847/2515-5172/aaa130 |arxiv=1712.06637 |bibcode=2017RNAAS...1a..52F}}</ref> It does not require obscuration by dust. Such cooling could be produced by a decreased efficiency of heat transport caused e.g. by decreased effectiveness of convection due to the star's strong differential rotation, or by changes in its modes of heat transport if it is located near the transition between radiative and convective heat transport. The "missing" heat flux is stored as a small increase of internal and potential energy.<ref name="Foukal2017" />

The possible location of this early F star near the boundary between radiative and convective transport seems to be supported by the finding
that KIC 8462852's observed brightness variations appear to fit the "avalanche statistics" known to occur in a [[Physics:Self-organized criticality|system close to a phase-transition]].<ref name="Sigurdsson2016" /><ref name="Sheikh2016">{{cite journal |title=Avalanche Statistics Identify Intrinsic Stellar Processes near Criticality in KIC 8462852 |journal=Physical Review Letters |last1=Sheikh |first1=Mohammed A. |last2=Weaver |first2=Richard L. |last3=Dahmen |first3=Karin A. |volume=117 |issue=26 |pages=261101 |date=19 December 2016 |doi=10.1103/PhysRevLett.117.261101 |pmid=28059527 |bibcode=2016PhRvL.117z1101S}}</ref> "Avalanche statistics" with a self-similar or power-law spectrum are a [[Universality (dynamical systems)|universal property]] of [[Complex system|complex dynamical systems]] operating close to a [[Physics:Phase transition|phase transition]] or bifurcation point between two different types of dynamical behavior. Such close-to-critical systems are often observed to exhibit behavior that is [[Edge of chaos|intermediate between "order" and "chaos"]]. Three other stars in the [[Astronomy:Kepler Input Catalog|Kepler Input Catalog]] likewise exhibit similar "avalanche statistics" in their brightness variations, and all three are known to be [[Physics:Stellar magnetic field#Magnetic stars|magnetically active]]. It has been conjectured that stellar magnetism may be involved in KIC&nbsp;8462852.<ref name="Sheikh2016" />
[[File:Dyson Swarm - 2.png|thumb|right|Artist's impression of a Dyson swarm]]

===An artificial megastructure=== 
Some astronomers have speculated that the objects eclipsing KIC 8462852 could be parts of a [[Engineering:Megastructure|megastructure]] made by an [[Philosophy:Extraterrestrial intelligence|alien civilization]], such as a Dyson swarm,<ref name="ATL-20151013">{{cite news |url=https://www.theatlantic.com/science/archive/2015/10/the-most-interesting-star-in-our-galaxy/410023/ |title=The Most Mysterious Star in Our Galaxy |work=The Atlantic |last=Andersen |first=Ross |date=13 October 2015 |accessdate=13 October 2015}}</ref><ref name="PSU-20151015">{{cite web |url=http://sites.psu.edu/astrowright/2015/10/15/kic-8462852wheres-the-flux/ |title=KIC 8462852: Where's the Flux? |work=AstroWright |publisher=[[Organization:Pennsylvania State University|Pennsylvania State University]] |last=Wright |first=Jason T. |date=15 October 2015 |accessdate=16 October 2015}}</ref><ref name="arXiv:1510.04606" /><ref name="PS-20151013" /> a hypothetical structure that an advanced civilization might build around a star to intercept some of its light for their energy needs.<ref name="JonesM2015">{{cite journal |title=Reconsidering macro-artefacts in SETI searches |journal=Acta Astronautica |last=Jones |first=Morris |volume=116 |pages=161–165 |date=November–December 2015 |doi=10.1016/j.actaastro.2015.07.011}}</ref><ref name="DC-20151014">{{cite news |url=http://news.discovery.com/space/alien-life-exoplanets/has-kepler-discovered-an-alien-megastructure-151014.htm |title=Has Kepler Discovered an Alien Megastructure? |work=Discovery.com |last=O'Neill |first=Ian |date=14 October 2015 |accessdate=17 October 2015}}</ref><ref name="SR-20150929">{{cite web |url=http://www.spaceref.com/news/viewsr.html?pid=47887 |title=Prepared Statement by Andrew Siemion – Hearing on Astrobiology |work=House Committee on Science, Space, and Technology |publisher=SpaceRef.com |last=Siemion |first=Andrew |date=29 September 2015 |accessdate=19 October 2015}}</ref> According to Steinn Sigurðsson, the megastructure hypothesis is implausible and disfavored by [[Occam's razor]] and fails to sufficiently explain the dimming. He says that it remains a valid subject for scientific investigation, however, because it is a falsifiable hypothesis.<ref name="Sigurdsson2016">{{cite journal |title=New Clues as to Why Boyajian's Star is Dimming |journal=Physics |first=Steinn |last=Sigurðsson |volume=9 |pages=150 |date=19 December 2016 |doi=10.1103/Physics.9.150 |bibcode=2016PhyOJ...9..150S}}</ref> Due to extensive media coverage on this matter, {{nowrap|KIC 8462852}} has been compared by Kepler's Steve Howell to {{nowrap|KIC 4150611}},<ref>{{cite news |url=https://mashable.com/2015/10/18/alien-megastructure-kepler|title=Scientists have not actually found an alien megastructure orbiting a distant star |work=Mashable |first=Miriam |last=Kramer |date=18 October 2015 |accessdate=27 October 2016}}</ref> another star with an odd light curve that was shown, after years of research, to be a part of a five-star system.<ref>{{cite conference |title=A Syzygy of KIC 4150611 |conference=221st Meeting of the American Astronomical Society. 6–10 January 2013. Long Beach, California. |last1=Gregg |first1=Trevor A. |last2=Prsa |first2=A. |last3=Welsh |first3=W. F. |last4=Orosz |first4=J. A. |last5=Fetherolf |first5=T. |at=142.12 |date=January 2013 |bibcode=2013AAS...22114212G}}</ref> The likelihood of extraterrestrial intelligence being the cause of the dimming is very low;<ref name="NYT-20180110" /> however, the star remains an outstanding [[Astronomy:Search for extraterrestrial intelligence|SETI]] target because natural explanations have yet to fully explain the dimming phenomenon.<ref name="PSU-20151015" /><ref name="arXiv:1510.04606" /> Latest results ruled out explanations involving only opaque objects such as stars, planets, swarms of asteroids, or alien megastructures. <ref>https://arxiv.org/pdf/1809.00693.pdf A Reassessment of Families of Solutions to the Puzzle of Boyajian’s Star</ref>

==Follow-up studies==
Numerous [[Astronomy:Optical telescope|optical telescope]]s continually monitor {{nowrap|KIC 8462852}} in anticipation of another multi-day dimming event, with planned follow-up observations of a dimming event using large telescopes equipped with [[Physics:Astronomical spectroscopy|spectrographs]] to determine if the eclipsing mass is a solid object, or composed of dust or gas.<ref name="followup">{{cite news |url=http://www.space.com/30948-dimming-star-alien-megastructure-mystery.html |title='Alien Megastructure' Mystery May Soon Be Solved |work=Space.com |last=Wall |first=Mike |date=28 October 2015 |accessdate=28 October 2015}}</ref> Additional follow-up observations may involve the ground-based [[Astronomy:Green Bank Telescope|Green Bank Telescope]], the Very Large Array Radio Telescope,<ref name="AT-20151016"/><ref name="CNET-20151017">{{cite news |url=http://www.cnet.com/news/the-full-story-behind-the-alien-megastructures-scientists-may-have-found-but-probably-didnt/ |title=The story behind 'alien megastructures' scientists may have found (but probably didn't) |work=CNET |last=Mack |first=Eric |date=17 October 2015 |accessdate=19 October 2015}}</ref> and future orbital telescopes dedicated to [[Astronomy:Exoplanetology|exoplanetology]] such as [[Astronomy:Wide Field Infrared Survey Telescope|WFIRST]], [[Astronomy:Transiting Exoplanet Survey Satellite|TESS]], and [[Engineering:PLATO (spacecraft)|PLATO]].<ref name="arXiv:1510.04606" /><ref name="SR-20150929" />

A Kickstarter fund-raising campaign was led by Tabetha Boyajian, the lead author of the initial study on {{nowrap|KIC 8462852's}} anomalous light curve. The project proposes to use the Las Cumbres Observatory Global Telescope Network for continuous monitoring of the star. The campaign raised over {{US$|100,000}}, enough for one year of telescope time.<ref name="kickstarter">{{cite news |url=http://www.popsci.com/alien-megastructure-star-just-met-its-kickstarter-goal |title='Alien Megastructure' Star Kickstarter Just Met Its Goal |work=Popular Science |last=Fecht |first=Sarah |date=16 June 2016 |accessdate=16 June 2016}}</ref> Furthermore, more than fifty amateur astronomers working under the aegis of the [[Organization:American Association of Variable Star Observers|American Association of Variable Star Observers]] have been providing effectively full coverage since AAVSO's alert about the star in October 2015,<ref name="AAVSO's Continuous Coverage">{{Cite web |url=https://lsuscienceblog.squarespace.com/blog/2017/1/6/tabbys-star-the-most-mysterious-star-in-the-universe |title=Tabby's Star: The Most Mysterious Star in the Universe Needs You |website=The Pursuit |series=Physics and Astronomy |last=Jarreau |first=Paige |date=17 January 2017}}</ref> namely a nearly continuous photometric record.<ref name="Subreddit KIC 8462852 FAQ">{{Cite web |url=https://docs.google.com/document/d/1pm4lszHnawepEagciKfPKzgRHscTrOi699EYMpqMe2Q/edit |title=Subreddit FAQ |website=Subreddit}}</ref> In a study published in January 2018, Boyajian et al. reported that whatever is blocking KIC 8462852 filters different wavelengths of light differently, so it cannot be an opaque object. They concluded that it is most likely space dust.<ref name="AXV-20180102" /><ref name="NatGeoJan3" /><ref name="AXV-20180102deeg" />

===SETI results===
In October 2015, the [[Organization:SETI Institute|SETI Institute]] used the [[Astronomy:Allen Telescope Array|Allen Telescope Array]] to look for [[Engineering:Radio frequency|radio emissions]] from possible intelligent extraterrestrial life in the vicinity of the star.<ref name="SP-20151019-mw">{{cite news |url=http://www.space.com/30855-alien-life-search-kepler-megastructure.html |title=Search For Intelligent Aliens Near Bizarre Dimming Star Has Begun |work=Space.com |last=Wall |first=Mike |date=19 October 2015 |accessdate=20 October 2015}}</ref><ref>{{cite news |url=http://www.businessinsider.com/search-for-aliens-at-kic-8462852-2015-10 |title=Scientists are days from finding out if that mysterious star could actually harbor aliens |work=Business Insider |first=Jessica |last=Orwig |date=23 October 2015}}</ref> After an initial two-week survey, the SETI Institute reported that it found no evidence of technology-related radio signals from the star system.<ref name="SETI-20151105">{{cite press release |url=http://www.seti.org/seti-institute/press-release/looking-deliberate-radio-signals-kic-8462852 |title=Looking for Deliberate Radio Signals from KIC 8462852 |publisher=The SETI Institute |date=5 November 2015 |accessdate=8 November 2015 |archive-url=https://web.archive.org/web/20151107233307/http://www.seti.org/seti-institute/press-release/looking-deliberate-radio-signals-kic-8462852 |archive-date=7 November 2015 |dead-url=yes |df=dmy-all }}</ref><ref name="ARX-20151105">{{cite journal |title=Radio SETI Observations of the Anomalous Star KIC 8462852 |journal=[[Astronomy:The Astrophysical Journal|The Astrophysical Journal]] |first1=G. R. |last1=Harp |last2=Richards |first2=Jon |last3=Shostak |first3=Seth |last4=Tarter |first4=J. C. |last5=Vakoch |first5=Douglas A. |last6=Munson |first6=Chris |display-authors=5 |volume=825 |issue=2 |pages=155 |date=July 2016 |arxiv=1511.01606 |bibcode=2016ApJ...825..155H |doi=10.3847/0004-637X/825/2/155}}</ref><ref name="AXV-20151208">{{cite journal |title=Optical SETI Observations of the Anomalous Star KIC 8462852 |journal=The Astrophysical Journal Letters |first1=Marlin |last1=Schuetz |last2=Vakoch |first2=Douglas A. |last3=Shostak |first3=Seth |last4=Richards |first4=Jon |volume=825 |issue=1 |at=L5 |date=July 2016 |arxiv=1512.02388 |bibcode=2016ApJ...825L...5S |doi=10.3847/2041-8205/825/1/L5}}</ref> No narrowband radio signals were found at a level of 180–300&nbsp;[[Astronomy:Jansky|Jy]] in a 1&nbsp;[[Hertz|Hz]] channel, or medium-band signals above 10&nbsp;Jy in a 100&nbsp;kHz channel.<ref name="ARX-20151105" />

In 2016, the [[Astronomy:VERITAS|VERITAS gamma-ray observatory]] was used to search for ultra-fast [[Engineering:Optical communication|optical transients]] from astronomical objects, with astronomers developing an efficient method sensitive to nanosecond pulses with fluxes as low as about one [[Physics:Photon|photon]] per square meter. This technique was applied on archival observations of {{nowrap|KIC 8462852}} from 2009 to 2015, but no emissions were detected.<ref name="Abeysekara201602">{{cite journal |title=A Search for Brief Optical Flashes Associated with the SETI Target KIC 8462852 |journal=The Astrophysical Journal Letters |first1=A. U. |last1=Abeysekara |first2=S. |last2=Archambault |first3=A. |last3=Archer |first4=W. |last4=Benbow |first5=R. |last5=Bird |display-authors=0 |volume=818 |issue=2 |at=L33 |date=February 2016 |doi=10.3847/2041-8205/818/2/L33 |bibcode=2016ApJ...818L..33A |arxiv=1602.00987}}</ref><ref name="Holder2016">{{cite journal |title=Latest Results from VERITAS: Gamma 2016 |journal=AIP Conference Proceedings |first=Jamie |last=Holder |volume=1792 |issue=1 |at=020013 |date=9 September 2016 |doi=10.1063/1.4968898 |bibcode=2017AIPC.1792b0013H |arxiv=1609.02881}}</ref>

In May 2017, a related search, based on [[Physics:Laser|laser light emissions]], was reported, with no evidence found for technology-related signals from KIC 8462852.<ref name="ATL-20170417">{{cite news |url=https://www.theatlantic.com/science/archive/2017/04/laser-seti-extraterrestrial/523104/ |title=Searching the Skies for Alien Laser Beams |work=The Atlantic |last=Koren |first=Marina |date=17 April 2017 |accessdate=3 June 2017}}</ref><ref name="AXV-20170408">{{cite journal |title=A Search for Laser Emission with Megawatt Thresholds from 5600 FGKM Stars |journal=The Astronomical Journal |last1=Tellis |first1=Nathaniel K. |last2=Marcy |first2=Geoffrey W. |volume=153 |issue=6 |page=251 |date=8 April 2017 |arxiv=1704.02535 |doi=10.3847/1538-3881/aa6d12 |bibcode=2017AJ....153..251T}}</ref>

In September 2017, some SETI@Home workunits were created based on a previous RF survey of the region around this star.<ref name="Seti-20170907">{{cite web |last=Korpela |first=Eric |title=Data from "Tabby's Star" is flowing |url=https://setiathome.berkeley.edu/forum_thread.php?id=81903&postid=1888412#1888412 |publisher=[[Organization:University of California, Berkeley|University of California, Berkeley]] |date=7 September 2017 |accessdate=12 September 2017}}</ref> This was coupled with a doubling in the size of SETI@Home workunits, so the workunits related to this region will probably be the first workunits to have less issues with quantization noise.

===EPIC 204278916===
{{main|Astronomy:EPIC 204278916}}
A star called [[Astronomy:EPIC 204278916|EPIC 204278916]], as well as some other [[Astronomy:Young stellar object|young stellar object]]s, have been observed to exhibit dips similar to those observed in {{nowrap|KIC 8462852}}. They differ in several aspects, however. {{nowrap|EPIC 204278916}} shows much deeper dips than {{nowrap|KIC 8462852}}, and they are grouped over a shorter period, whereas the dips at {{nowrap|KIC 8462852}} are spread out over several years. Furthermore, {{nowrap|EPIC 204278916}} is surrounded by a [[Astronomy:Circumstellar disc|proto-stellar disc]], whereas {{nowrap|KIC 8462852}} appears to be a normal F-type star displaying no evidence of a disc.<ref name="EPIC" />

==2017 light fluctuations==
{{multiple image
| align             = right
| direction         = vertical
| header_align      = center
| header            = Normalized flux for KIC 8462852
| image1            = KIC 8462852 Daily Normalized Flux by Bruce Gary, 20170502-20180504.png
| width1            = 250
| footer_align      = left
| 14 May 2017 ("Elsie"; 2% dip)
| 11 June ("Celeste"; 2% dip)
| 2 August ("Skara Brae"; 1% dip)
| 5 September ("Angkor"; 2.3%;<ref name="BG-20170916" /> 3%<ref name="TWT-20170910" /> dip)
| 20 November (unnamed; 1.25%<ref name="BG-20180101" /> dip)<ref name="AXV-20180102" />
| 16 March 2018 ("Caral-Supe"; 1%;<ref name="BG-2018" /> 5%<ref name="TB-20180326" /> dip)
| 24 March ("Evangeline"; 5+% dip)}}
}}
On 20 May 2017, Boyajian and her colleagues reported, via [[Astronomy:The Astronomer's Telegram|The Astronomer's Telegram]], on an ongoing dimming event (named "Elsie"<ref name="WTFlux-20170918">{{cite web |first1=Tabetha S. |last1=Boyajian |title=Dip update 85/n - Welcome Angkor! |url=http://www.wherestheflux.com/single-post/2017/09/18/Dip-update-85n---Welcome-Angkor |date=18 September 2017 |work=WheresTheFlux.com |accessdate=18 September 2017}}</ref><ref name="AXV-20180102" />) which possibly began on 14 May 2017.<ref name="May 2017 Dimming-01" /> It was detected by the Las Cumbres Observatory Global Telescope Network, specifically by its telescope located in Maui (LCO Maui). This was verified by the Fairborn Observatory (part of the [[Organization:N2K Consortium|N2K Consortium]]) in Southern Arizona (and later by LCO Canary Islands).<ref name="AT-20170519">{{cite news |url=https://www.theatlantic.com/science/archive/2017/05/tabbys-star-alien-megastructure/527382/ |title=The 'Alien Megastructure' Star Is Dimming Again |work=The Atlantic |last=Koren |first=Marina |date=19 May 2017 |accessdate=23 May 2017}}</ref><ref name="4 a.m. Phone Call">{{Cite web |url=http://www.inquisitr.com/4231231/alien-megastructure-star-dyson-sphere-tabbys-star-spectra/ |title=That 'Alien Megastructure' Star Has Gone Haywire Again And Scientists Are Baffled |last=Arboleda |first=Lawrence |date=20 May 2017 |website=The Inquistr}}</ref><ref name="SCIMAG-20170522">{{cite journal |last=Clery |first=Daniel |title=Star that spurred alien megastructure theories dims again |url=http://www.sciencemag.org/news/2017/05/star-spurred-alien-megastructure-theories-dims-again |date=22 May 2017 |journal=Science |accessdate=25 May 2017}}</ref> Further optical and infrared spectroscopy and photometry were urgently requested, given the short duration, measured in days or weeks, of these events.<ref name="May 2017 Dimming-01" /> Observations from multiple observers globally were coordinated, including [[Physics:Polarimetry|polarimetry]].<ref name="Coordinated Observations">{{Cite web |url=http://www.wherestheflux.com/single-post/2017/05/19/WTF-Has-Gone-Into-a-Dip |title=WTF Has Gone Into a Dip! |last=Ellis |first=Tyler |date=19 May 2017}}</ref> Furthermore, the independent SETI projects [[Astronomy:Breakthrough Listen|Breakthrough Listen]] and [[Astronomy:Search for extraterrestrial intelligence#Optical experiments|Near-InfraRed Optical SETI]] (NIROSETI), both at [[Organization:Lick Observatory|Lick Observatory]], continue to monitor the star.<ref name="May 2017 Dimming-01">{{cite web |url=http://www.astronomerstelegram.org/?read=10405 |title=A Drop in Optical Flux from Boyajian's Star |work=[[Astronomy:The Astronomer's Telegram|The Astronomer's Telegram]] |first1=Tabetha S. |last1=Boyajian |author1-link=Tabetha S. Boyajian |first2=Steve |last2=Croft |first3=Jason T. |last3=Wright |display-authors=0 |date=20 May 2017 |accessdate=21 May 2017}}</ref><ref name="May 2017 Dimming-02">{{cite web |author=Steele, Iain et al. |title=Medium Resolution Spectroscopy of Boyajian's Star (KIC 8462852) |url=http://www.astronomerstelegram.org/?read=10406 |date=20 May 2017 |work=[[Astronomy:The Astronomer's Telegram|The Astronomer's Telegram]] |accessdate=21 May 2017}}</ref><ref name="YT-20170520">{{cite web |last=Wright |first=Jason T. |title=Tabby's Star is dimming right now (archived video of chat with Jason T. Wright) |url=https://www.youtube.com/watch?v=eYpIGZS8nJc&feature=youtu.be&t=52s |date=19 May 2017 |work=[[Company:YouTube|YouTube]] |accessdate=21 May 2017}}</ref><ref name="TLW-20170520">{{cite web |author=Staff |title=Mysterious Tabby's Star dims again: observations needed |url=https://angelrls.wordpress.com/2017/05/20/mysterious-tabbys-star-dims-again-observations-needed |date=20 May 2017 |work=The Lined Wolf |accessdate=21 May 2017}}</ref> By the end of the three-day dimming event,<ref name="AN-20170524">{{cite web |last=Cooper |first=Keith |title=The Galaxy's strangest star dims again |url=https://astronomynow.com/2017/05/24/the-galaxys-strangest-star-dims-again/ |date=24 May 2017 |work=[[Astronomy:Astronomy Now|Astronomy Now]] |accessdate=25 May 2017}}</ref> a dozen observatories had taken spectra, with some astronomers having dropped their own projects to provide telescope time and resources. More generally the astronomical community was described as having gone "mildly bananas" over the opportunity to collect data in real-time on the unique star.<ref name="A Dozen Observatories Take Spectra in Real Time">{{Cite web |url=https://www.washingtonpost.com/news/speaking-of-science/wp/2017/05/24/the-weirdest-star-in-the-sky-is-acting-up-again/ |title=The weirdest star in the sky is acting up again |last=Kaplan |first=Sarah |date=24 May 2017 |website=The Washington Post |series=Speaking of Science}}</ref> The 2% dip event was named "Elsie" (in reference to Las Cumbres and light curve).<ref name="Dip update 6/n">{{Cite web |url=http://www.wherestheflux.com/single-post/2017/06/03/Dip-update-6n |title=Dip update 6/n |website=WherestheFlux.com |last=Boyajian |first=Tabetha S. |date=1 June 2017 |accessdate=4 June 2017}}</ref>

Initial spectra with FRODOSpec at the two-meter [[Astronomy:Liverpool Telescope|Liverpool Telescope]] showed no changes visible between a reference spectrum and this dip.<ref name="May 2017 Dimming-02" /><ref name="YT-20170520" /><ref name="TLW-20170520" /> Several observatories, however, including the twin [[Astronomy:W. M. Keck Observatory|Keck telescopes]] ([[Astronomy:W. M. Keck Observatory#Instruments|HIRES]]) and numerous citizen science observatories, acquired spectra of the star,<ref name="May 2017 Dimming-01" /><ref name="YT-20170520" /><ref name="TLW-20170520" /> showing a dimming dip that had a complex shape, and initially had a pattern similar to the one at 759.75 days from the Kepler event 2, [[Astronomy:Epoch|epoch]] 2 data. Observations were taken across the [[Physics:Electromagnetic spectrum|electromagnetic spectrum]].

Evidence of a second dimming event (named "Celeste"<ref name="WTFlux-20170918" />) was observed on 13–14 June 2017, and which possibly began 11 June, by amateur astronomer Bruce L. Gary.<ref name="BG-20170621">{{cite web |url=http://www.brucegary.net/ts/ |title=Kepler Star KIC 8462852 Amateur Photometry Monitoring Project |website=BruceGary.net |first=Bruce L. |last=Gary |date=21 June 2017 |archiveurl=https://web.archive.org/web/20170621221807/http://www.brucegary.net/ts/ |archivedate=21 June 2017 |deadurl=yes}}</ref> While the light curve on 14 and 15 June indicated a possible recovery from the dimming event, the dimming continued to increase afterwards,<ref name="BG-20170621" /> and on 16 June, Boyajian wrote that the event was approaching a 2% dip in brightness.<ref name="TB-20170616">{{cite tweet |number=875839712682020864 |title=#TabbysStar is approaching 2% dim - Who Will Observe Tonight?!! |user=tsboyajian |first=Tabetha S. |last=Boyajian |date=16 June 2017 |accessdate=17 June 2017}}</ref><ref name="AXV-20180102" />

A third prominent 1% dimming event (named "Skara Brae"<ref name="WTFlux-20170918" />) was detected beginning 2 August 2017,<ref>{{cite web |url=http://www.wherestheflux.com/single-post/2017/08/02/Dip-update-47n |title=Dip update 47/n |work=Where's the Flux? |first=Tabetha S. |last=Boyajian |date=2 August 2017 |accessdate=11 August 2017}}</ref><ref>{{cite web |url=http://www.wherestheflux.com/single-post/2017/08/10/Dip-update-54n |title=Dip update 54/n |work=Where's the Flux? |first=Tabetha S. |last=Boyajian |authorlink=Tabetha S. Boyajian |date=10 August 2017 |accessdate=11 August 2017}}</ref> and which recovered by 17 August.<ref name="BG-20170818">{{cite web |last=Gary |first=Bruce L. |title=Hereford Arizona Observatory photometry observations of KIC 8462852 between 2 May and 17 August 2017. |url=http://www.brucegary.net/ts/ |date=18 August 2017 |work=BruceGary.net |deadurl=yes |archiveurl=https://web.archive.org/web/20170820231346/http://www.brucegary.net/ts/ |archivedate=20 August 2017 |accessdate=20 August 2017}}</ref><ref name="AXV-20180102" />

A fourth prominent dimming event (named "Angkor"<ref name="WTFlux-20170918" />) began 5 September 2017,<ref name="BG-20170908">{{cite web |last=Gary |first=Bruce L. |title=Hereford Arizona Observatory photometry observations of KIC 8462852 between 2 May and 8 September 2017. |url=http://www.brucegary.net/ts/ |date=8 September 2017 |work=BruceGary.net |deadurl=yes |archiveurl=https://web.archive.org/web/20170908212152/http://www.brucegary.net/ts/ |archivedate=8 September 2017 |accessdate=8 September 2017}}</ref> and is, as of 16 September 2017, between 2.3%<ref name="BG-20170916">{{cite web |last=Gary |first=Bruce L. |title=Hereford Arizona Observatory photometry observations of KIC 8462852 between 2 May and 16 September 2017 |url=http://www.brucegary.net/ts3/ |date=16 September 2017 |work=BruceGary.net |deadurl=yes |archiveurl=https://web.archive.org/web/20170917125504/http://www.brucegary.net/ts3/ |archivedate=17 September 2017 |accessdate=17 September 2017}}</ref> and 3%<ref name="TWT-20170910">{{cite web |last=Boyajian |first=Tabetha S. |title=Tweets: "Now @tsboyajian's star is down 3%! How low will it go? Hi-res spectra and IR photometry needed!" - Jason T. Wright |url=https://twitter.com/tsboyajian/status/906898237398962176 |date=10 September 2017 |work=[[Company:Twitter|Twitter]] |deadurl=yes |archiveurl=https://web.archive.org/web/20170917125736/https://twitter.com/tsboyajian/status/906898237398962176 |archivedate=17 September 2017 |accessdate=17 September 2017}}</ref> dimming event, making it the "deepest dip this year".<ref name="BG-20170910">{{cite web |last=Gary |first=Bruce L. |title=Hereford Arizona Observatory photometry observations of KIC 8462852 between 2 May and 10 September 2017. |url=http://www.brucegary.net/ts3/ |date=10 September 2017 |work=BruceGary.net |deadurl=yes |archiveurl=https://web.archive.org/web/20170910071659/http://www.brucegary.net/ts3/ |archivedate=10 September 2017 |accessdate=10 September 2017}}</ref><ref name="AXV-20180102" />

Another dimming event, amounting to a 0.3% dip, began around 21 September 2017 and completely recovered by 4 October 2017.<ref name="BG-20171004" />

On 10 October 2017, an increasing brightening, lasting about two weeks, of the starlight from KIC 8462852 was noted by Bruce L. Gary of the [[Astronomy:Hereford Arizona Observatory|Hereford Arizona Observatory]]<ref name="BG-2017" /> and Boyajian.<ref name="WTFlux-20171106">{{cite web |first=Tabetha S. |last=Boyajian |title=Dip update 111/n |url=http://www.wherestheflux.com/single-post/2017/11/06/Dip-update-111n |date=6 November 2017 |work=WheresTheFlux.com |accessdate=7 November 2017}}</ref> A possible explanation, involving a transiting "[[Astronomy:Brown dwarf|brown dwarf]]" in a 1600-day eccentric orbit near KIC 8462852, a "drop feature" in dimness and predicted intervals of "brightening", to account for the unusual fluctuating starlight events of KIC 8462852, has been proposed.<ref name="BG-2017" /><ref name="ARX-20171111" /><ref name="ARX-20171128-pdf" />

On 20 November 2017 (est), a fifth prominent dimming event began and had deepened to a 0.44% depth; as of 16 December 2017, the event recovered, leveled off at dip bottom for 11 days, faded again, to a current total dimming depth of 1.25%, and is now recovering again.<ref name="BG-2017"/><ref name="BG-20180101" />

Dimming and brightening events of the star continue to be monitored; related light curves are currently updated and released frequently.<ref name="BG-2018" /><ref name="BG-20171114-latest">{{cite web |last=Gary |first=Bruce L. |title=Hereford Arizona Observatory photometry observations of KIC 8462852 |url=http://www.brucegary.net/ts5/ |date=14 November 2017 |work=BruceGary.net |accessdate=17 December 2017}}</ref>
{{clear}}

==2018 light fluctuations==
The star was too close to the Sun's position in the sky from late December, 2017 to mid February, 2018 to be seen. Observations resumed in late February.<ref name="BG-2018">{{cite web |last=Gary |first=Bruce L. |title=KIC 8462852 Hereford Arizona Observatory Photometry Observations #6 |url=http://www.brucegary.net/ts6/ |date=25 February 2018 |accessdate=20 March 2018}}</ref><ref name="campaign2018">{{cite web |last=Boyajian |first=Tabetha S. |authorlink=Tabetha S. Boyajian |url=http://www.wherestheflux.com/single-post/2018/03/08/The-2018-observing-season-begins |title=Dip update 130/n - The 2018 observing campaign begins! |work=WheresTheFlux.com |date=8 March 2018 |accessdate=20 March 2018}}</ref> A new series of dips began on 16 March 2018. By 18 March 2018 the star was down by more than 1% in g-band, according to Bruce L. Gary,<ref name="BG-2018" /> and about 5% in r-band, making it the deepest dip observed since the Kepler Mission in 2013, according to Tabetha S. Boyajian.<ref name="tldr:Dipping">{{cite web |last=Boyajian |first=Tabetha S. |authorlink=Tabetha S. Boyajian |title=tldr: DIPPING!!! |url=http://www.wherestheflux.com/single-post/2018/03/19/tldr-DIPPING |work=WheresTheFlux.com |date=19 March 2018 |accessdate=20 March 2018}}</ref><ref name="TB-20180326">{{cite web |last=Boyajian |first=Tabetha S. |authorlink=Tabetha S. Boyajian |title=2018 March: dip update 7/n |url=http://www.wherestheflux.com/single-post/2018/03/26/2018-March-dip-update-7n |date=26 March 2018 |work=WheresTheFlux.com |accessdate=27 March 2018}}</ref><ref name="TT-20180327">{{cite news |last=Adamson |first=Allan |title=Alien Megastructure Star: Dimming Of Tabby's Star Sets New Record |url=http://www.techtimes.com/articles/223621/20180327/alien-megastructure-star-dimming-of-tabbys-star-sets-new-record.htm |date=27 March 2018 |work=TechTimes.com |accessdate=27 March 2018}}</ref> A second even deeper dip with a depth of 5+% started on 24 March 2018, as confirmed by AAVSO observer John Hall.<ref name="dip update 6/n">{{cite web |url=http://www.wherestheflux.com/single-post/2018/03/24/2018-March-dip-update-6n |title=2018 March: dip update 6/n |date=24 March 2018 |website=wherestheflux.com |accessdate=27 March 2018}}</ref><ref name="dip update 7/n">{{cite web |url=http://www.wherestheflux.com/single-post/2018/03/26/2018-March-dip-update-7n |title=2018 March: dip update 7/n |date=26 March 2018 |website=wherestheflux.com |accessdate=27 March 2018}}</ref> As of 27 March 2018, that second dip is recovering.<ref name="dip update 8/n">{{cite web |url=http://www.wherestheflux.com/single-post/2018/03/27/2018-March-dip-update-8n |title=2018 March: dip update 8/n |date=27 March 2018 |website=wherestheflux.com |accessdate=27 March 2018}}</ref>

==Light curve gallery==
<center><gallery widths="900px" heights="200px">
File:RoughDraft-TabbysStarDimmings-2009-to-2017.png|Rough draft of all known dimmings, from December 2009 to December 2017
</gallery><gallery widths="150px">
File:KIC 8462852 - gesamte Helligkeitsmessung von Kepler.png|All light curve data − December&nbsp;2009 to May&nbsp;2013, scan days 0066 to 1587 (''Kepler'')
File:KIC 8462852 - Helligkeitseinbruch 05. März 2011.png|5 March 2011 − day 792 <br /> 15% max dip (''Kepler'')
File:KIC 8462852 - Helligkeitseinbruch 28. Februar 2013.png|28 February 2013 − day 1519 <br /> 22% max dip (''Kepler'')
File:KIC 8462852 - Helligkeitseinbruch 17. April 2013.png|17 April 2013 − day 1568 <br /> 8% max dip (''Kepler'')
File:KIC 8462852 Daily Normalized Flux by Bruce Gary, 20170502-20180504.png|One year light curve − up to 4 May 2018 <br /> ([[Astronomy:Hereford Arizona Observatory|HAO]])<ref name="BG-20171004" /><ref name="BG-20180101" /><ref name="BG-20180504" />
</gallery></center>

==See also==
{{div col|colwidth=30em}}
* [[Astronomy:Disrupted planet|Disrupted planet]]
* [[Astronomy:Kepler object of interest#Non-planet discoveries|KOI 126]]
* [[Astronomy:1SWASP J140747.93-394542.6|1SWASP J140747.93-394542.6]] − star with unusual eclipses due to ring system
* [[Astronomy:PDS 110|PDS 110]] − star surrounded with a disk of dust
* [[Astronomy:PSR B1919+21|PSR B1919+21]] − pulsar mistaken as alien radio signal (LGM-1)
* [[Astronomy:RZ Piscium|RZ Piscium]]  − star with unusual light fluctuations
* [[Astronomy:Stars named after people|Stars named after people]]
* [[Astronomy:WD 1145+017|WD 1145+017]] − a star [[Physics:Roche limit|ripping apart]] a planetesimal, producing a dusty disk
{{div col end}}

==References==
{{reflist|30em|refs=
<ref name="arXiv:1509.03622">{{cite journal |title=Planet Hunters IX. KIC 8462852 – where's the flux? |journal=[[Organization:Monthly Notices of the Royal Astronomical Society|Monthly Notices of the Royal Astronomical Society]] |last1=Boyajian |first1=T. S. |last2=LaCourse |first2=D. M. |last3=Rappaport |first3=S. A. |last4=Fabrycky |first4=D. |last5=Fischer |first5=D. A. |last6=Gandolfi |first6=D. |last7=Kennedy |first7=G. M. |last8=Liu |first8=M. C. |last9=Moor |first9=A. |last10= Olah |first10=K. |last11=Vida |first11=K. |last12=Wyatt |first12=M. C. |last13=Best |first13=W. M. J. |last14=Ciesla |first14=F. |last15=Csak |first15=B. |last16=Dupuy |first16=T. J. |last17=Handler |first17=G. |last18=Heng |first18=K. |last19=Korhonen |first19=H. |last20= Kovacs |first20=J. |last21=Kozakis |first21=T. |last22=Kriskovics |first22=L. |last23=Schmitt |first23=J. R. |last24=Szabo |first24=Gy. |last25=Szabo |first25=R. |last26=Wang |first26=J. |last27=Goodman |first27=S. |last28=Hoekstra |first28=A. |last29=Jek |first29=K. J. |display-authors=5 |volume=457 |issue=4 |pages=3988–4004 |date=April 2016 |doi=10.1093/mnras/stw218 |bibcode=2016MNRAS.457.3988B |arxiv=1509.03622}}</ref>

<ref name="arXiv:1510.04606">{{cite journal |title=The Ĝ Search for Extraterrestrial Civilizations with Large Energy Supplies. IV. The Signatures and Information Content of Transiting Megastructures |journal=[[Astronomy:The Astrophysical Journal|The Astrophysical Journal]] |last1=Wright |first1=Jason T. |last2=Cartier |first2=Kimberly M. S. |last3=Zhao |first3=Ming |last4=Jontof-Hutter |first4=Daniel |last5=Ford |first5=Eric B. |volume=816 |issue=1 |pages=17 |date=January 2016 |doi=10.3847/0004-637X/816/1/17 |bibcode=2016ApJ...816...17W |arxiv=1510.04606}}</ref>

<ref name="Bibcode:2013ApJS..208....9P">{{cite journal |title=Intrinsic Colors, Temperatures, and Bolometric Corrections of Pre-main-sequence Stars |journal=[[Astronomy:The Astrophysical Journal|The Astrophysical Journal]] Supplement |last1=Pecaut |first1=Mark J. |last2=Mamajek |first2=Eric E. |volume=208 |issue=1 |pages=9 |date=September 2013 |arxiv=1307.2657 |bibcode=2013ApJS..208....9P |doi=10.1088/0067-0049/208/1/9}}</ref>
}}

==External links==
* [http://www.wherestheflux.com/ Where's The Flux], home page of the KIC 8462852 observation project
* [http://archive.stsci.edu/kepler/data_search/search.php?action=Search&ktc_kepler_id=8462852 ''Kepler'' light curve data] at STScI.edu
* {{YouTube|id=gypAjPp6eps|title="The Most Mysterious Star in the Universe"}}, a TED Talk by Tabetha S. Boyajian
* [https://www.dropbox.com/s/u11lv7d5opeo0rr/KIC-halpha.png Spectra (6400-6700 Å) from 20 May 2017], by FRODOSpec/[[Astronomy:Liverpool Telescope|Liverpool Telescope]]
* [https://www.dropbox.com/s/isev1ymggilx4hl/KIC-Ca.png Spectra (8400-8700 Å) from 20 May 2017], by FRODOSpec/[[Astronomy:Liverpool Telescope|Liverpool Telescope]]
* [https://twitter.com/astronomeara/status/866310803825152001 Spectra (3926-3994 Å) from 21 May 2017], by Keck Observatory
* {{YouTube|gypAjPp6eps|title=Video (13:46) − "Tabby's Star"}}, a presentation by Tabetha S. Boyajian
* {{YouTube|id=SVCpBr3fxdE|title=Video (31:00) − "Tabby's Star"}}, a presentation by Issac Arthur
* {{YouTube|nf2oc6nMsn4|title=Video (01:00) − RZ Piscium}}, star with unusual light fluctuations (21 December 2017)
{{Exoplanet}}
{{Extraterrestrial life}}
{{Stars of Cygnus}}
{{Sky|20|06|15.457|+|44|27|24.61|1500}}


[[Category:Cygnus (constellation)]]
[[Category:F-type main-sequence stars]]
[[Category:Hypothetical astronomical objects]]
[[Category:Kepler Objects of Interest]]
[[Category:Search for extraterrestrial intelligence]]
[[Category:2MASS objects]]
[[Category:Unsolved problems in astronomy]]

{{Sourceattribution|KIC 8462852|1}}