Tau Ceti f
{{Short description|Super-Earth orbiting Tau Ceti}}
{{Infobox planet
| name = Tau Ceti f
| image =
| caption =
| extrasolarplanet = yes
| discovered = December 19, 2012
| discovery_method = Doppler spectroscopy
| semimajor = 1.334 au
| eccentricity = 0.16
| period = 1.7 y
| star = Tau Ceti
| mass = ≥3.93 M🜨
| mean_radius = ~1.81 {{Earth radius}} (estimate)
| surface_grav = ≥{{val|1.201}} g
≥{{val|11.78|ul=m/s2}}
}}Tau Ceti f is a candidate super-Earth{{Cite web|title=Exoplanet-catalog|url=https://exoplanets.nasa.gov/exoplanet-catalog/7180/tau-ceti-f/|access-date=2020-10-14|website=Exoplanet Exploration: Planets Beyond our Solar System}} or mini-Neptune orbiting Tau Ceti that was discovered in 2012 by statistical analyses of the star's variations in radial velocity, based on data obtained using HIRES, AAPS, and HARPS. It is of interest because its orbit places it in Tau Ceti's extended habitable zone,{{Cite web|title=Two Nearby Habitable Worlds? - Planetary Habitability Laboratory @ UPR Arecibo|url=http://phl.upr.edu/press-releases/twonearbyhabitableworlds|access-date=2020-10-07|website=phl.upr.edu|archive-date=2021-03-08|archive-url=https://web.archive.org/web/20210308051741/http://phl.upr.edu/press-releases/twonearbyhabitableworlds|url-status=dead}}{{Cite web|title=Four Exoplanets Detected around Nearby Star Tau Ceti {{!}} Astronomy {{!}} Sci-News.com|url=http://www.sci-news.com/astronomy/tau-ceti-exoplanets-05117.html|access-date=2020-10-07|website=Breaking Science News {{!}} Sci-News.com|language=en-US}} but a 2015 study implies that there may not be a detectable biosignature because it has only been in the temperate zone for less than one billion years.{{Cite web|last=April 2015|first=Mike Wall 24|title=Nearby Alien Planets Not So Life-Friendly After All|url=https://www.space.com/29191-exoplanets-tau-ceti-alien-life.html|access-date=2020-10-07|website=Space.com|date=24 April 2015 |language=en}}{{Cite journal |last=Pagano |first=Michael |last2=Truitt |first2=Amanda |last3=Young |first3=Patrick A. |last4=Shim |first4=Sang-Heon |date=2015-04-21 |title=THE CHEMICAL COMPOSITION OF τ CETI AND POSSIBLE EFFECTS ON TERRESTRIAL PLANETS |url=https://iopscience.iop.org/article/10.1088/0004-637X/803/2/90 |journal=The Astrophysical Journal |volume=803 |issue=2 |pages=90 |doi=10.1088/0004-637X/803/2/90 |issn=1538-4357|arxiv=1503.04189 }} In 2017, it was again recovered from radial-velocity data, along with Tau Ceti e. Despite this, it remains an unconfirmed and disputed.
Characteristics
Few properties of the planet are known other than its orbit and mass. It orbits Tau Ceti at a distance of 1.35 AU (roughly Mars's perihelion in the Solar System) with an orbital period of 642 days, and has a minimum mass of 3.93 Earth masses.{{Cite journal|last1=Feng|first1=Fabo|last2=Tuomi|first2=Mikko|last3=Jones|first3=Hugh R. A.|last4=Barnes|first4=John|last5=Anglada-Escude|first5=Guillem|last6=Vogt|first6=Steven S.|last7=Butler|first7=R. Paul|date=2017-09-05|title=Color difference makes a difference: four planet candidates around tau Ceti|journal=The Astronomical Journal|volume=154|issue=4|pages=135|doi=10.3847/1538-3881/aa83b4|arxiv=1708.02051 |bibcode=2017AJ....154..135F |issn=1538-3881|doi-access=free}} However, if it and its companion planets were similarly inclined to Tau Ceti's debris disk at {{val|35|10}}°, f could {{val|5.56|1.48|1.94}} and {{val|9.30|2.48|3.24}} Earth masses, which means it's slightly more likely to be a mini-Neptune, although the exoplanet is included in the conservative sample of potentially habitable exoplanets.{{Cite web|title=The Habitable Exoplanets Catalog - Planetary Habitability Laboratory @ UPR Arecibo|url=http://phl.upr.edu/projects/habitable-exoplanets-catalog/|access-date=2020-10-14|website=phl.upr.edu}} It is estimated to be 1.81 Earth radii.{{Cite web|title=Exoplanet-catalog|url=https://exoplanets.nasa.gov/exoplanet-catalog/7180/tau-ceti-f/|access-date=2020-10-08|website=Exoplanet Exploration: Planets Beyond our Solar System}}
A 2021 study was unable to confirm this planet.{{cite journal |last1=Cretignier |first1=Michael |last2=Dumusque |first2=Xavier |display-authors=etal |date=September 2021 |title=YARARA: Significant improvement in RV precision through post-processing of spectral time series |journal=Astronomy & Astrophysics |volume=653 |issue= |pages=A43 |doi=10.1051/0004-6361/202140986 |arxiv=2106.07301 |bibcode=2021A&A...653A..43C}}
Habitability
As of October 2020, Tau Ceti f is considered the most potentially habitable exoplanet orbiting a Sun-like star.{{Cite web|title=The Habitable Exoplanets Catalog - Planetary Habitability Laboratory @ UPR Arecibo|url=http://phl.upr.edu/projects/habitable-exoplanets-catalog/|access-date=2020-10-07|website=phl.upr.edu}} Its neighbor, Tau Ceti e, was previously regarded as a potentially habitable exoplanet in the conservative sample, but it was determined to likely be too hot to hold life, more similar to Venus.{{Cite web|title=Two Nearby Habitable Worlds? - Planetary Habitability Laboratory @ UPR Arecibo|url=https://sites.google.com/a/upr.edu/planetary-habitability-laboratory-upra/press-releases/twonearbyhabitableworlds|access-date=2020-10-08|website=sites.google.com}} It and its companion may suffer from a continuous bombardment of asteroids, up to 10 times higher than in the Solar System,{{Cite web|date=2004-07-02|title=Death Down Asteroid Alley|url=https://www.astrobio.net/meteoritescomets-and-asteroids/death-down-asteroid-alley/|access-date=2020-10-08|website=Astrobiology Magazine|language=en-US |url-status=usurped |archive-url=https://web.archive.org/web/20040829013306/http://www.astrobio.net/news/modules.php?op=modload&name=News&file=article&sid=1053&mode=thread&order=0&thold=0 |archive-date=2004-08-29}} but a conjectured (super-)Jovian planet as outlined in a 2019 Astronomy & Astrophysics paper may be shepherding the disk, as it may be as close as 3 AU and as far away as 20.{{cite journal|last1=Kervella|first1=Pierre|last2=Arenou|first2=Frédéric|last3=Mignard|first3=François|last4=Thévenin|first4=Frédéric|display-authors=2|title=Stellar and substellar companions of nearby stars from Gaia DR2|journal=Astronomy & Astrophysics|volume=623|year=2019|pages=A72|issn=0004-6361|arxiv=1811.08902 |bibcode=2019A&A...623A..72K |doi=10.1051/0004-6361/201834371|s2cid=119491061 |quote="We also detect the signature of a possible planet of a few Jovian masses orbiting τ Ceti…The observed signal could be explained for example, by a Jupiter analog orbiting at 5au."}}
Tau Ceti f has a somewhat eccentric orbit, varying from approximately 1.12 to 1.547 AU. Therefore, Tau Ceti f receives ~20.3% ± 0.41% Earth flux at apocenter and ~38.86% ± 0.796% Earth flux at pericenter, for an average of ~27.42% ± 0.562% Earth flux. Tau Ceti f has an estimated equilibrium temperature of only 190 Kelvin. If the conditions were the same as on the Earth, Tau Ceti f's average temperature would be around -50 °C. However, with a thicker atmosphere and a larger ocean, the temperature could resemble Earth's.{{Cite web|title=Open Exoplanet Catalogue - tau Ceti f|url=http://openexoplanetcatalogue.com/planet/tau%20Ceti%20f/|access-date=2020-10-08|website=openexoplanetcatalogue.com}}
See also
References
{{Reflist}}
{{Tau Ceti}}
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