View source for Astronomy:YZ Ceti

{{Short description|Star in the constellation Cetus}}
{{Starbox begin
| name = YZ Ceti
}}
{{Starbox image
| image = [[Image:YZ Ceti.png|250px]]
| caption = Location of YZ Ceti, click for larger image.
}}
{{Starbox observe
| epoch = J2000
| constell = [[Astronomy:Cetus|Cetus]]
| ra = {{RA|01|12|30.6369}}<ref name="Gaia3"/>
| dec = {{DEC|−16|59|56.358}}<ref name="Gaia3"/>
| appmag_v = 12.03 - 12.18<ref name=vsx/>
}}
{{Starbox character
| type = [[Astronomy:Red dwarf|red dwarf]]
| class = M4.0Ve<ref name=davison/>
| b-v = +1.811<ref name=ubv/>
| u-b = +1.430<ref name=ubv/>
| variable = [[Astronomy:Flare star|Flare star]]<ref name=gcvs/>
}}
{{Starbox astrometry
| radial_v = +28.09<ref name=rv/>
| prop_mo_ra = 1,205.074<ref name="Gaia3"/>
| prop_mo_dec = 637.547<ref name="Gaia3"/>
| parallax = 269.0573
| p_error = 0.0337
| parallax_footnote = <ref name="Gaia3"/>
| absmag_v = 14.30<ref name=davison/>
}}
{{Starbox detail
| mass = {{val|0.130|0.013}}<ref name=ad/>
| radius = {{val|0.168|0.009}}<ref name=ad/>
| temperature = {{val|3,056|60}}<ref name=ad/>
| luminosity = 0.002195<ref name=Schweitzer2019/>
| gravity = 5.20<ref name=Schweitzer2019/>
| metal_fe = {{val|−0.26|0.08}}<ref name=ad/>
| rotational_velocity = 3.40<ref name=fouque2018/>
| rotation = {{val|68.3|ul=days}}<ref name=jayasinghe/>
| age_gyr = {{val|5.0|1.0}}<ref name=ad/>
}}
{{Starbox catalog
}}
{{Starbox reference
| Simbad = V*+YZ+Cet
}}
{{Starbox end}}

'''YZ Ceti''' is a [[Astronomy:Red dwarf|red dwarf]] [[Astronomy:Star|star]] in the [[Astronomy:Constellation|constellation]] [[Astronomy:Cetus|Cetus]]. Although it is relatively close to the [[Astronomy:Sun|Sun]] at just 12 [[Light year|light year]]s, this star cannot be seen with the naked eye. It is classified as a [[Astronomy:Flare star|flare star]] that undergoes intermittent fluctuations in [[Astronomy:Luminosity|luminosity]]. YZ Ceti is about 13 percent the mass of the Sun and 17% of its radius.

This star is unusually close to [[Astronomy:Tau Ceti|Tau Ceti]], a star of spectral class G8. The two are only about 1.6 light years apart,<ref name=solstation/> a little more than a third of the distance from the Sun to the Solar System's nearest neighbor, [[Astronomy:Proxima Centauri|Proxima Centauri]].

==Variability==
[[File:YZCetLightCurve.png|thumb|left|A visual band light curve for YZ Ceti, adapted from Jayasinghe ''et al.'' (2017)<ref name=jayasinghe/>]]
YZ Ceti is a [[Astronomy:Variable star designation|variable star designation]]: the star shows occasional rapid and brief increases in brightness, sometimes reaching magnitude 12.03, caused by eruptions from the surface.  This type of variable star is known as a UV Ceti star after its first member, or more colloquially as a [[Astronomy:Flare star|flare star]].

YZ Ceti also shows small periodic variations in brightness caused by starspots or chromospheric features moving as the star rotates.  This class of variable stars are known as [[Astronomy:BY Draconis variable|BY Draconis variable]]s.<ref name=vsx/>  The periodic variations allow the rotational period of the star to be measured at 68.3 days, although modelling of its planetary system gives a rotational period for the star of 83 days.<ref name=jayasinghe/>
{{clear left}}

==Planetary system==
On 10 August 2017 three planets were announced to have been discovered around YZ Ceti and a possible fourth sub-Earth planet candidate, still needing confirmation, with 0.472±0.096 Earth masses at an orbital period of 1.04 days. The orbits of the three confirmed planets were determined to be too close to YZ Ceti to be within the star's habitable zone, with equilibrium temperatures ranging from 347–491 K (74–218&nbsp;°C; 165–424&nbsp;°F), 299–423 K (26–150&nbsp;°C; 79–302&nbsp;°F), and 260–368 K (−13–95&nbsp;°C; 8–203&nbsp;°F) for planets b, c, and d, respectively.<ref name=ad/>

An August 2018 study reexamined the discovery measurements, confirming the orbit of YZ Ceti d, but finding a possibly marginally longer orbital period of YZ Ceti b of 2.02 days rather than 1.97 days, and additionally finding that YZ Ceti c probably orbits in only 0.75 days rather than 3.06 days. If the latter is true, YZ Ceti c would have a mass of only 0.58 Earth masses and a roughly 10% chance of transiting YZ Ceti.<ref name="Robertson2018"/> However, a 2020 study did not support the latter conclusion, finding the 0.75-day period to be an alias of the true 3.06-day period. It also did not find evidence for the fourth candidate planet.<ref name="Stock2020"/>

Two 2023 studies detected bursts of radiation in [[Radio wave|radio]] wavelengths from YZ Ceti, which is likely associated with interaction of the innermost planet, YZ Ceti b, with the star as well as evidence for the presence of magnetic fields. It may be the first detection of a magnetic field generated by a terrestrial exoplanet.<ref name="Pineda2023"/><ref name="Trigilio2023"/><ref>{{Cite web |date=2023-04-10 |title=A magnetic field on a nearby Earth-sized exoplanet? |url=https://earthsky.org/space/magnetic-field-exoplanets-yz-ceti-b/ |access-date=2023-08-07 |website=earthsky.org |language=en-US}}</ref><ref>{{Cite web |last=O'Callaghan |first=Jonathan |date=7 August 2023 |title=Exoplanets Could Help Us Learn How Planets Make Magnetism |url=https://www.quantamagazine.org/exoplanets-could-help-us-learn-how-planets-make-magnetism-20230807/ |website=Quanta Magazine}}</ref>

{{OrbitboxPlanet begin
| table_ref = <ref name="Stock2020"/>
}}
{{OrbitboxPlanet
| exoplanet = b
| mass_earth = ≥{{val|0.70|0.09|0.08}}
| period = 2.02087{{±|0.00007|0.00009}}
| semimajor = 0.01634{{±|0.00035|0.00041}}
| eccentricity = {{val|0.06|0.06|0.04}}
}}
{{OrbitboxPlanet
| exoplanet = c
| mass_earth = ≥{{val|1.14|0.11|0.10}}
| period = 3.05989{{±|0.00010|0.00010}}
| semimajor = 0.02156{{±|0.00046|0.00054}}
| eccentricity = 0.00
}}
{{OrbitboxPlanet
| exoplanet = d
| mass_earth = ≥{{val|1.09|0.12|0.12}}
| period = 4.65626{{±|0.00028|0.00029}}
| semimajor = 0.02851{{±|0.00061|0.00071}}
| eccentricity = {{val|0.07|0.04|0.05}}
}}
{{Orbitbox end}}

==See also==
* [[Astronomy:List of nearest stars and brown dwarfs|List of nearest stars and brown dwarfs]]
* [[Astronomy:Tau Boötis b|Tau Boötis b]] another extra solar planet with evidence of magnetic fields
* [[Astronomy:HAT-P-11b|HAT-P-11b]] another extra solar planet with evidence of magnetic fields
* [[Astronomy:HD 209458 b|HD 209458 b]] another extra solar planet with evidence of magnetic fields

==References==
{{reflist|refs=

<ref name="Gaia3">{{cite Gaia DR3|2358524597030794112}}</ref>

<ref name=fouque2018>{{cite journal
 | title=SPIRou Input Catalogue: global properties of 440 M dwarfs observed with ESPaDOnS at CFHT
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 | volume=475 | issue=2 | pages=1960–1986 | date=April 2018
 | doi=10.1093/mnras/stx3246 | arxiv=1712.04490
 | bibcode=2018MNRAS.475.1960F }}</ref>

<ref name=vsx>{{cite journal|bibcode=2006SASS...25...47W|title=The International Variable Star Index (VSX)|journal=The Society for Astronomical Sciences 25th Annual Symposium on Telescope Science. Held May 23–25|volume=25|pages=47|last1=Watson|first1=C. L.|year=2006}}</ref>

<ref name=Schweitzer2019>{{cite journal
 | title=The CARMENES search for exoplanets around M dwarfs. Different roads to radii and masses of the target stars
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 | last2=Passegger | first2=V. M. | last3=Cifuentes | first3=C.
 | last4=Béjar | first4=Victor J. S. | last5=Cortés-Contreras | first5=M.
 | last6=Caballero | first6=José A. | last7=del Burgo | first7=Carlos
 | last8=Czesla | first8=Stefan | last9=Kürster | first9=Martin
 | last10=Montes | first10=David | last11=Zapatero-Osorio | first11=María Rosa
 | last12=Ribas | first12=Ignasi | last13=Reiners | first13=Ansgar
 | last14=Quirrenbach | first14=Andreas | last15=Amado | first15=Pedro J.
 | last16=Aceituno | first16=J. | last17=Anglada-Escudé | first17=Guillem
 | last18=Bauer | first18=Florian F. | last19=Dreizler | first19=Stefan
 | last20=Jeffers | first20=Sandra V. | last21=Guenther | first21=E. W.
 | last22=Henning | first22=Thomas K. | last23=Kaminski | first23=Adrian
 | last24=Lafarga | first24=M. | last25=Marfil | first25=E.
 | last26=Morales | first26=Juan Carlos | last27=Schmitt | first27=Jürgen H. M. M.
 | last28=Seifert | first28=Walter | last29=Solano | first29=E.
 | last30=Tabernero | first30=H. M. | last31=Zechmeister | first31=Mathias
 | journal=Astronomy & Astrophysics
 | volume=625 | id=A68 | pages=16 | date=May 2019
 | arxiv=1904.03231 | bibcode=2019A&A...625A..68S
 | doi=10.1051/0004-6361/201834965 | s2cid=102351979 }}</ref>

<ref name="Stock2020">{{cite journal|arxiv=2002.01772|doi=10.1051/0004-6361/201936732|title=The CARMENES search for exoplanets around M dwarfs|year=2020|last1=Stock|first1=S.|last2=Kemmer|first2=J.|last3=Reffert|first3=S.|last4=Trifonov|first4=T.|last5=Kaminski|first5=A.|last6=Dreizler|first6=S.|last7=Quirrenbach|first7=A.|last8=Caballero|first8=J. A.|last9=Reiners|first9=A.|last10=Jeffers|first10=S. V.|last11=Anglada-Escudé|first11=G.|last12=Ribas|first12=I.|last13=Amado|first13=P. J.|last14=Barrado|first14=D.|last15=Barnes|first15=J. R.|last16=Bauer|first16=F. F.|last17=Berdiñas|first17=Z. M.|last18=Béjar|first18=V. J. S.|last19=Coleman|first19=G. A. L.|last20=Cortés-Contreras|first20=M.|last21=Díez-Alonso|first21=E.|last22=Domínguez-Fernández|first22=A. J.|last23=Espinoza|first23=N.|last24=Haswell|first24=C. A.|last25=Hatzes|first25=A.|last26=Henning|first26=T.|last27=Jenkins|first27=J. S.|last28=Jones|first28=H. R. A.|last29=Kossakowski|first29=D.|last30=Kürster|first30=M.|journal=Astronomy & Astrophysics|volume=636|pages=A119|s2cid=211032169|display-authors=1 |bibcode=2020A&A...636A.119S}}</ref>

<ref name="Robertson2018">{{cite journal|arxiv=1808.07059|doi=10.3847/2041-8213/aadc0b|title=Aliasing in the Radial Velocities of YZ Ceti: An Ultra-short Period for YZ Ceti c?|year=2018|last1=Robertson|first1=Paul|journal=The Astrophysical Journal|volume=864|issue=2|pages=L28|s2cid=119373170 |bibcode=2018ApJ...864L..28R |doi-access=free }}</ref>

<ref name=ad>{{cite journal |doi=10.1051/0004-6361/201731581 |bibcode=2017A&A...605L..11A |arxiv=1708.03336 |title=The HARPS search for southern extra-solar planets. XLII. A system of Earth-mass planets around the nearby M dwarf YZ Ceti |journal=Astronomy & Astrophysics |volume=605 |pages=L11 |last1=Astudillo-Defru |first1=Nicola |last2=Díaz |first2=Rodrigo F. |last3=Bonfils |first3=Xavier |last4=Almenara |first4=José M. |last5=Delisle |first5=Jean-Baptiste |last6=Bouchy |first6=François |last7=Delfosse |first7=Xavier |last8=Forveille |first8=Thierry |last9=Lovis |first9=Christophe |last10=Mayor |first10=Michel |last11=Murgas |first11=Felipe |last12=Pepe |first12=Francesco |last13=Santos |first13=Nuno C. |last14=Ségransan |first14=Damien |last15=Udry |first15=Stéphane |last16=Wünsche |first16=Anaël |year=2017 |s2cid=119393757 }}</ref>

<ref name=ubv>{{cite journal|bibcode= 2010MNRAS.403.1949K |title= UBV(RI)C JHK observations of Hipparcos-selected nearby stars |journal= Monthly Notices of the Royal Astronomical Society |volume= 403 |issue= 4 |pages= 1949 |last1= Koen |first1= C |last2= Kilkenny |first2= D |last3= Van Wyk |first3= F |last4= Marang |first4= F |year= 2010 |doi= 10.1111/j.1365-2966.2009.16182.x |doi-access= free }}</ref>

<ref name=solstation>[http://www.solstation.com/stars/tau-ceti.htm Page of Tau Ceti], see the chapter of ''Closest Neighbors'', for YZ Ceti.</ref>

<ref name=davison>{{cite journal|bibcode=2015AJ....149..106D|arxiv=1501.05012|title=A 3D Search for Companions to 12 Nearby M Dwarfs|journal=The Astronomical Journal|volume=149|issue=3|pages=106|last1=Davison|first1=Cassy L|last2=White|first2=R. J|last3=Henry|first3=T. J|last4=Riedel|first4=A. R|last5=Jao|first5=W.-C|last6=Bailey|first6=J. I|last7=Quinn|first7=S. N|last8=Cantrell|first8=J. R|last9=Subasavage|first9=J. P|last10=Winters|first10=J. G|year=2015|doi=10.1088/0004-6256/149/3/106|s2cid=9719725}}</ref>

<ref name=gcvs>{{cite journal|bibcode=2009yCat....102025S|title=VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)|journal=VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S|volume=1|display-authors=0|last1=Samus|first1=N. N.|last2=Durlevich|first2=O. V.|year=2009}}</ref>

<ref name=rv>{{cite journal|bibcode=2002ApJS..141..503N|title=Radial Velocities for 889 Late-Type Stars|journal=The Astrophysical Journal Supplement Series|volume=141|issue=2|pages=503–522|last1=Nidever|first1=David L|last2=Marcy|first2=Geoffrey W|last3=Butler|first3=R. Paul|last4=Fischer|first4=Debra A|last5=Vogt|first5=Steven S|year=2002|doi=10.1086/340570|arxiv=astro-ph/0112477|s2cid=51814894}}</ref>

<ref name=jayasinghe>{{cite journal|bibcode=2017ATel10643....1J|title=ASAS-SN V-band Light Curve of Multi-Planet M-dwarf Host YZ Cet Reveals a Rotation Period of 68 Days|journal=The Astronomer's Telegram|volume=0643|last1=Jayasinghe|first1=T|last2=Stanek|first2=K. Z|last3=Kochanek|first3=C. S|last4=Holoien|first4=T. W.-S|last5=Shields|first5=J. V|last6=Thompson|first6=T. A|last7=Shappee|first7=B. J|last8=Prieto|first8=J. L|last9=Dong|first9=Subo|year=2017|page=1}}</ref>

<ref name="Pineda2023">{{cite journal |last1=Pineda |first1=J. Sebastian |last2=Villadsen |first2=Jackie |date=April 2023 |title=Coherent radio bursts from known M-dwarf planet host YZ Ceti |journal=[[Astronomy:Nature Astronomy|Nature Astronomy]] |volume=7 |issue= 5|pages=569–578 |doi=10.1038/s41550-023-01914-0 |arxiv=2304.00031 |bibcode=2023NatAs...7..569P|s2cid=257912756 }}</ref>

<ref name="Trigilio2023">{{cite arXiv |last1=Trigilio |first1=Corrado |last2=Biswas |first2=Ayan |display-authors=0 |date=May 2023 |title=Star-Planet Interaction at radio wavelengths in YZ Ceti: Inferring planetary magnetic field |eprint=2305.00809 |class=astro-ph.EP}}</ref>

}}

==External links==
* [https://web.archive.org/web/20040307062246/http://www.ari.uni-heidelberg.de/aricns/cnspages/4c00102.htm ARICNS]
{{2017 in space}}

{{nearest systems|3}}
{{Stars of Cetus}}

{{DEFAULTSORT:YZ Ceti}}
[[Category:M-type main-sequence stars]]
[[Category:Flare stars]]
[[Category:Hipparcos objects|005643]]
[[Category:Gliese and GJ objects|0054.1]]
[[Category:Objects with variable star designations|Ceti, YZ]]
[[Category:2MASS objects|J01123052-1659570]]
[[Category:Emission-line stars]]

{{Sourceattribution|YZ Ceti}}