Tau Ceti, a nearby Sun-like star, MAY have an Earth-like planet
One of the closest Sun-like stars to us, Tau Ceti, in the constellation of Cetus the Sea Monster, MAY have a family of five Earth-like planets orbiting it, one of which MIGHT be in the star’s circumstellar habitable zone (CHZ), otherwise known as the “goldilocks zone” where it’s not too hot, not too cold, but just the right temperature for liquid water to exist.
Tau Ceti lies only 12 light years away from our solar system, which in astronomy terms is just next door. There are only 19 stars closer to the Sun, and only one of these is a Sun-like star, Alpha Centauri, which lies only 4.4 light years away.
Tau Ceti is a bit smaller than the Sun (0.8 times the Sun’s radius), is cooler (5350K compared to the Sun’s 5780K) and less luminous (0.5 times the Sun’s brightness), and so the CHZ in which the Earth-like planet MIGHT orbit is much closer to the star than the Sun’s CHZ, around half the Earth-Sun distance, approximately 75 million kilometres.
The five planets that MIGHT have been discovered are labelled Tau Ceti b, c, d, e, and f, and the Earth-like planet is the fourth from the star, e.
Why all the MAYBEs and MIGHTs? Well, that comes down to the method by which the planets were detected. They were discovered by observing the star Tau Ceti, and watching for wobbles caused by the gravitational pull of the orbiting planets. Now all five potential planets are similar in size to the Earth, between two and six times the mass of the Earth, but still are tiny compared to the star, and so the wobbles they cause the star to make are very small, almost indistinguishable from noise in the data. Further studies of the star’s wobble might show that some, none, or all of these potential planets might just be artifacts in the data.
How to find Tau Ceti in the sky
Tau Ceti is visible in the sky this month, lying low in the south around 8pm. To find it you have to star hop from the distinct constellations of Orion and Taurus to the much less obvious Cetus.
Find Orion, with the three stars of Orion’s belt pointing up and to the left to the bright star Aldebaran in Taurus. Aldebaran lies in a V-shape collection of stars called the Hyades making up Taurus’ head. This V-shape arrow points down and to the right to a bright-ish star called Menkar in Cetus, lying low in the south. Lower and to the right is the brightest star in Cetus, Diphda, and the fainter star to the left of this is Tau Ceti. Phew!