Tau Ceti f is a candidate
super-Earth
A super-Earth is a type of exoplanet with a mass higher than Earth, but substantially below those of the Solar System's ice giants, Uranus and Neptune, which are 14.5 and 17.1 times Earth's, respectively.
The term "super-Earth" refers only to t ...
or
mini-Neptune
A Mini-Neptune (sometimes known as a gas dwarf or transitional planet) is a planet less massive than Neptune but resembling Neptune in that it has a thick hydrogen-helium atmosphere, probably with deep layers of ice, rock or liquid oceans (made o ...
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, but a 2015 study implies that there may not be a detectable
biosignature
A biosignature (sometimes called chemical fossil or molecular fossil) is any substance – such as an element, isotope, molecule, or phenomenon – that provides scientific evidence of past or present life on a planet. Measurable ...
because it has only been in the temperate zone for less than one billion years. In 2017, it was again recovered from radial-velocity data, along with
Tau Ceti e. Despite this, it remains 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
Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmosph ...
's perihelion in the Solar System) with an orbital period of 642 days, and has a minimum mass of 3.93 Earth masses.
However, if it and its companion planets were similarly inclined to Tau Ceti's debris disk at °, f could and 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. It is estimated to be 1.81 Earth radii.
A 2021 study was unable to confirm this planet.
Habitability
As of October 2020, Tau Ceti f is considered the most potentially habitable exoplanet orbiting a Sun-like star. 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. It and its companion may suffer from a continuous bombardment of asteroids, up to 10 times higher than in the Solar System, 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.
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.
See also
*
Sub-Neptune
References
{{DEFAULTSORT:Tau Ceti f
Exoplanets discovered in 2012
Tau Ceti