To Babylon 5 fans, Epsilon Eridani is (will be?) the home to our “last, best hope for peace”. To some loosely versed in Star Trek lore, it is credited as being the star orbited by the planet Vulcan (although somewhat more officially, Vulcan is placed in the 40 Eridani star system). To astronomers, it is a very Sun-like star some 10.5 light years away, which may be the home of two (or more) planets. And now it appears it is something of a younger version of our own solar system.
The star has long been of interest to astronomers as the possible location of exoplanets, and in 1987, it appeared as if a Jupiter-sized planet had been discovered orbiting Epsilon Eridani at roughly seven times the distance of the Earth from the Sun, and with an orbital period of some 7 terrestrial years. Initially called Epsilon Eridani b, the planet has been strongly contested over the decades for assorted reasons – even though in 2016 it was granted a formal name: AEgir (sic).
Observations of the system also revealed that the star appears to be surrounded by a cometary ring, somewhat akin to out own Kuiper Belt, and in 2008, the Spitzer Space Telescope revealed that the Epsilon Eridani system may have two major asteroid belts. the first of which correlates to the position of the asteroid belt in our own system, and the second, much broader and denser belt lying roughly at the same distance from the star as orbit of Uranus around the Sun.
Like Epsilon Eridani’s planets, the existence of the debris material surrounding the star as two distinct asteroid belts has been contested.Because the Spitzer data failed to indicate a clearly defined band of “warm material” of gas and dust within each of the rings, it has been hypothesised that rather than being two individual belts, they might actually mark the inner and outer boundaries of a single accretion disk.
The difference here is important. If the debris exists as to separate rings of material, it raises the prospect that there are planetary bodies orbiting Epsilon Eridani which may have both helped order the rings and remove debris from the space between them. If there is only one extended accretion disk around the star, it reduces the potential for planets having formed. Now the results of a 2-year study, published in the April edition of Astronomical Journal, sheds new light not only on the asteroid belts, but on the Epislon Eridani system as a whole.
The study, led by Kate Su, an Associate Astronomer with the Steward Observatory at the University of Arizona, used data gathered during a 2015 observation of Epsilon Eridani by the remarkable Stratospheric Observatory For Infrared Astronomy (SOFIA) observation platform developed by NASA and the German Aerospace Centre, DLR. This is a specially modified 747 jet aircraft designed to carry out extended studies of celestial targets.
Operating at almost 14 kilometres (45,000 ft) altitude, SOFIA flies well above the major distorting effects of Earth’s atmosphere, allowing it to use a 2.5 metre optical telescope with 3 times the resolution power of Spitzer, together with an ultra-sensitive infra-red imaging system called FORCAST, the Faint Object infraRed CAmera for the SOFIA Telescope, to observe targets.
Su and her team used the data gathered by SOFIA’s 2015 observations of Epsilon Eridani, coupled with the Spitzer data and the results of other ground-based observations of the star to build a series of computer models of the system. The results of the models tend to very much confirm that Epsilon Eridani does have two asteroid belts, each with its own distinct “warm band”, and that there could be at least three Jupiter-sized planets within the system helping to organise the rings.
Not only that, but the study suggest that the Epsilon Eiridani system might be directly comparable to our own as it was not long after the inner planets formed. If this is the case, the study of Epsilon Eridani could help astronomers gain greater insights into the history of our own Solar System.