View source for Astronomy:HIP 11915

{{Short description|Star in the constellation Cetus}}
{{Starbox begin
| name = HIP 11915
}}
{{Starbox observe
| epoch    = J2000
| constell = [[Astronomy:Cetus|Cetus]]
| ra       = {{RA|02|33|49.026}}<ref name=SIMBAD/>
| dec      = {{DEC|–19|36|42.500}}<ref name=SIMBAD/>
| appmag_v = 8.58<ref name=Extrasolar/>
}}
{{Starbox character
| type = [[Astronomy:Main sequence|Main sequence]]
| class = G5V<ref name=Extrasolar/>
}}
{{Starbox astrometry
| radial_v = +14.1 ± 0.5<ref name=SIMBAD/>
| prop_mo_ra = {{val|225.590|0.082}}<ref name="SIMBAD"/>
| prop_mo_dec = {{val|35.400|0.090}}<ref name="SIMBAD"/>
| parallax = 18.63
| p_error  = 0.29
| parallax_footnote = <ref name=SIMBAD/>
| absmag_v = 4.83<ref name=Anderson2012>{{citation
 | title=XHIP: An extended hipparcos compilation
 | last1=Anderson | first1=E. | last2=Francis | first2=Ch.
 | journal=Astronomy Letters | arxiv=1108.4971
 | volume=38 | issue=5 | pages=331 | year=2012
 | bibcode=2012AstL...38..331A | doi=10.1134/S1063773712050015
 | s2cid=119257644 | postscript=. }}</ref>
}}
{{Starbox detail
| mass = {{val|0.991|0.003}}<ref name="Galarza2021"/>
| radius = ~1.01
| temperature = {{val|5773|2}}<ref name="Galarza2021"/>
| rotational_velocity = 0.99 ± 0.15
| gravity = {{val|4.47|0.008}}<ref name="Galarza2021"/>
| luminosity = {{val|1.0|0.13|0.12}}<ref name="Sousa2011"/>
| metal_fe = {{val|−0.057|0.003}}<ref name="Galarza2021"/>
| age_gyr = {{val|3.87|0.39}}<ref name="Galarza2021"/>
}}
{{Starbox catalog
| names = HD&nbsp;16008, HIP&nbsp;11915, [[Astronomy:Smithsonian Astrophysical Observatory Star Catalog|SAO]]&nbsp;148468, BD-20°481<ref name=SIMBAD/>
}}
{{Starbox reference
| Simbad = HIP+11915
| EPE = HIP+11915
}}
{{Starbox end}}
'''HIP 11915''' is a [[Astronomy:G-type main-sequence star|G-type main-sequence star]] located about 190 [[Astronomy:Light-year|light-year]]s from [[Astronomy:Earth|Earth]] in the constellation [[Astronomy:Cetus|Cetus]].<ref name="Extrasolar">{{cite web |title=Planet HIP 11915 |url=http://exoplanet.eu/catalog/hip_11915/ |access-date=17 July 2015 |archive-date=26 January 2020 |archive-url=https://web.archive.org/web/20200126210623/http://exoplanet.eu/catalog/hip_11915/ |work=[[Astronomy:Extrasolar Planets Encyclopaedia|Extrasolar Planets Encyclopaedia]] |url-status=dead }}</ref> It is best known for its characteristics, which are very similar to those of the [[Astronomy:Sun|Sun]], including the mass, radius, temperature, metallicity and age, which means that it is almost a solar twin, being just 500 million years younger than the Sun and with a lower [[Astronomy:Metallicity|metallicity]].{{efn|An exact solar twin would be a G2V star with a {{val|5,778|u=K}} temperature, be 4.6 billion years old, with the correct metallicity and a 0.1% [[Astronomy:Solar luminosity|solar luminosity]] variation.<ref>{{cite web|url=https://science.nasa.gov/science-news/science-at-nasa/2013/08jan_sunclimate/|title=Solar Variability and Terrestrial Climate - NASA Science|access-date=8 January 2013}}</ref><ref name="nssdc"/> }} It is also known for its planetary companion, [[Astronomy:HIP 11915 b|HIP 11915 b]], which has a mass and orbital distance very similar to that of [[Astronomy:Jupiter|Jupiter]], but probably with a slightly higher [[Astronomy:Orbital eccentricity|orbital eccentricity]].

This star is entry number 11915 in the Hipparcos Catalogue. The star is located at 02:33:49.02495 [[Right ascension|right ascension]], −19° 36' 42.5032" [[Declination|dec]].<ref name="SIMBAD">{{cite simbad|title=HD 16008|access-date=29 March 2018}}</ref><ref name=eso1529b>{{cite web |title=The star HIP 11915 in the constellation of Cetus |url=http://www.eso.org/public/images/eso1529b/ |publisher=[[Organization:European Southern Observatory|European Southern Observatory]] |date=15 July 2015 |access-date=17 July 2015}}</ref> Too faint to be seen with the unaided eye, the star can be spotted with good binoculars.<ref name=eso1529b />

==Stellar characteristics==
HIP 11915 is a G-type main sequence star that is just about the same mass of and likely 101% the radius of the [[Astronomy:Sun|Sun]]. It has a temperature of 5760 K and is 4.16 billion years old,<ref name=Extrasolar/><ref name="dossantos"/> nearly 500 million years younger than the Sun, which is about 4.6 billion years old<ref>{{cite web |url=http://www.universetoday.com/18237/how-old-is-the-sun/ |title=How Old is the Sun? |author=Fraser Cain |date=16 September 2008 |work=Universe Today |access-date=19 February 2011}}</ref> and has a temperature of 5778 K.<ref>{{cite web |url=http://www.universetoday.com/18092/temperature-of-the-sun/ |title=Temperature of the Sun |author=Fraser Cain |date=15 September 2008 |work=Universe Today |access-date=19 February 2011}}</ref>

The star is slightly poor in metals, with a [[Astronomy:Metallicity|metallicity]] ([Fe/H]) of about −0.059, or about 87% of the amount of iron and other heavier metals found in the Sun.<ref name=dossantos>{{cite journal |title=The Solar Twin Planet Search: IV. The Sun as a typical rotator and evidence for a new rotational braking law for Sun-like stars |last1=Dos Santos|first1=Leonardo A.|display-authors=0|year=2016|arxiv=1606.06214|doi=10.1051/0004-6361/201628558|volume=592|journal=Astronomy & Astrophysics|page=A156|bibcode=2016A&A...592A.156D|s2cid=53533614}}</ref> Given the similar properties of the Sun, HIP 11915's luminosity is likely close to the same as the Sun (give or take about 10% in uncertainty).

==Planetary system==
{{OrbitboxPlanet begin
| table_ref=<ref name="Extrasolar" />
}}
{{OrbitboxPlanet
| exoplanet = [[Astronomy:HIP 11915 b|b]]
| mass = 0.99 ± 0.06
| period = 3830.0 ± 150
| semimajor = 4.8 ± .01
| eccentricity = 0.1 ± 0.07
| radius = ~1
}}
{{Orbitbox end}}

The system contains a gas giant, '''HIP 11915 b''', with a mass and orbit very similar to that of [[Astronomy:Jupiter|Jupiter]], located at approximately the same distance from its star. The discovery of HIP 11915 b is significant, because it is the first, and to date only, distant planetary system found that may be somewhat like the [[Astronomy:Solar System|Solar System]].<ref name="Jupiter's twin spotted">{{cite news|title=Jupiter's twin spotted|url=http://www.business-standard.com/article/news-ians/jupiter-s-twin-spotted-115071600300_1.html|access-date=16 July 2015|agency=IANS|publisher=business standard|date=July 16, 2015}}</ref> The radial velocity data also indicates that there is no large gas giant in this system with an orbital period of less than 1000 days. This means that there could be one or more terrestrial planets in the inner parts of the system, and the possibility of a habitable [[Astronomy:Earth analog|Earth-like planet]].

This new discovery was made at the La Silla Observatory in {{wipe|Chile}}, using the [[Astronomy:High Accuracy Radial Velocity Planet Searcher|High Accuracy Radial Velocity Planet Searcher]] instrument mounted on the [[Organization:European Southern Observatory|European Southern Observatory]]'s [[Astronomy:ESO 3.6 m Telescope|3.6-meter telescope]].<ref name="HIP 11915b: Jupiter Twin Found Orbiting Sun-Like Star">{{cite news|title=HIP 11915b: Jupiter Twin Found Orbiting Sun-Like Star|url=http://www.sci-news.com/astronomy/science-hip11915b-jupiter-twin-sun-like-star-03021.html|access-date=16 July 2015|agency=Sci-News.com|date=Jul 15, 2015}}</ref><ref name="Jupiter Look-Alike Discovered Orbiting Sun-Like Star; Could There Be An Earth Twin?">{{cite news|last1=Bora|first1=Kukil|title=Jupiter Look-Alike Discovered Orbiting Sun-Like Star; Could There Be An Earth Twin?|url=http://www.ibtimes.com/jupiter-look-alike-discovered-orbiting-sun-star-could-there-be-earth-twin-2011228|access-date=16 July 2015|agency=ib times|date=16 July 2015}}</ref>

According to Jorge Meléndez, who led the University of São Paulo, {{wipe|Brazil}} team that discovered HIP 11915 b, "the quest for an Earth 2.0, and for a complete Solar System 2.0, is one of the most exciting endeavors in astronomy".<ref name="JupiterTwin">{{cite web|title=Jupiter Twin Discovered Around Solar Twin|url=http://www.eso.org/public/news/eso1529/|publisher=[[Organization:European Southern Observatory|European Southern Observatory]]|access-date=16 July 2015}}</ref>

==Comparison to the Sun==
This chart compares the properties of the Sun to HIP 11915.

{| class="wikitable" style="text-align: center; white-space: nowrap;"
|-
!rowspan="2"| Identifier
!colspan="2"| [[Astronomy:J2000|J2000]] Coordinates
!rowspan="2"| Distance<br>(ly)
!rowspan="2"| [[Astronomy:Stellar classification|Stellar<br>Class]]
!rowspan="2"| Mass<br>({{solar mass}})
!rowspan="2"| Radius<br>({{solar radius}})
!rowspan="2"| Temperature<br>(K)
!rowspan="2"| Metallicity<br>(dex)
!rowspan="2"| Age<br>(Gyr)
!rowspan="2"| Notes
|-
! [[Right ascension]]
! [[Declination]]
|-
|style="text-align:left;"| [[Astronomy:Sun|Sun]]
| —
| —
| 0.00
| G2V
| 1
| 1
| 5,778
| +0.00
| 4.6
| <ref name=nssdc>{{cite web |last=Williams |first=D.R. |url=http://nssdc.gsfc.nasa.gov/planetary/factsheet/sunfact.html |title=Sun Fact Sheet |publisher=[[Organization:NASA|NASA]] |year=2004 |access-date=2009-06-23 }}</ref>
|-
|style="text-align:left;"| {{CelestialRefAll|HIP 11915}}
| {{RA|02|33|49.02}}
| {{DEC|-19|36|42.5}}
| 190
| G5V
| 0.99
| 1.01
| 5,760
| −0.059
| 4.1
| <ref>{{cite journal|author1=M. Bedell |author2=J. Meléndez |author3=J. L. Bean |author4=I. Ramírez |author5=M. Asplund |author6=A. Alves-Brito |author7=L. Casagrande |author8=S. Dreizler |author9=T. Monroe |author10=L. Spina |author11=M. Tucci Maia |title=The Solar Twin Planet Search II. A Jupiter twin around a solar twin|journal=Astronomy & Astrophysics |volume=581  |pages=A34 |date=June 26, 2015 |url=http://www.eso.org/public/archives/releases/sciencepapers/eso1529/eso1529a.pdf|access-date=17 July 2015|bibcode=2015A&A...581A..34B |doi=10.1051/0004-6361/201525748 |arxiv=1507.03998 |s2cid=56004595 }}</ref>
|-
|}

==Footnotes==
{{notelist}}

==References==
{{reflist|refs=

<ref name="Galarza2021">{{cite journal | last1=Galarza | first1=Jhon Yana | last2=Meléndez | first2=Jorge | last3=Karakas | first3=Amanda I | last4=Asplund | first4=Martin | last5=Lorenzo-Oliveira | first5=Diego | display-authors=1 | title=Explosive nucleosynthesis of a metal-deficient star as the source of a distinct odd-even effect in the solar twin HIP 11915 | journal=Monthly Notices of the Royal Astronomical Society: Letters | date=29 January 2021 | volume=502 | issue=1 | pages=L104–L109 | arxiv=2101.10182 | bibcode=2021MNRAS.502L.104Y | doi=10.1093/mnrasl/slab010 }}</ref>

<ref name="Sousa2011">{{cite journal | last1=Sousa | first1=S. G. | last2=Santos | first2=N. C. | last3=Israelian | first3=G. | last4=Mayor | first4=M. | last5=Udry | first5=S. | display-authors=1 | title=Spectroscopic stellar parameters for 582 FGK stars in the HARPS volume-limited sample | journal=Astronomy & Astrophysics | date=September 2011 | volume=533 | at=A141 | arxiv=1108.5279 | bibcode=2011A&A...533A.141S | bibcode-access=free | doi=10.1051/0004-6361/201117699 | doi-access=free }}[http://vizier.cfa.harvard.edu/viz-bin/VizieR-5?-ref=VIZ5abd2cf917676&-out.add=.&-source=J/A%2bA/533/A141/table1&recno=38 Vizier catalog entry ]</ref>

}}

{{Stars of Cetus}}
{{Sky|02|33|49.025|-|19|36|42.5032}}

{{DEFAULTSORT:HIP 11915}}
[[Category:Planetary systems with one confirmed planet]]
[[Category:G-type main-sequence stars]]
[[Category:Henry Draper Catalogue objects|016008]]
[[Category:Hipparcos objects|011915]]
[[Category:Durchmusterung objects|BD-20 0481]]

{{Sourceattribution|HIP 11915}}