The discovery of at least seven Earth-sized planets orbiting the same star less than 40 light-years from Earth, or 235tn miles away, in the constellation Aquarius, is big news given that they could have water on their surfaces and potentially support life. This is the first time that so many of such planets are found around the same star, according to Michaël Gillon, lead study author and astronomer at the University of Liège in Belgium.
The study was published last week in the journal Nature and the findings were also announced at a news conference at Nasa headquarters in Washington. The seven exoplanets were all found in tight formation around an ultracool dwarf star called TRAPPIST-1. The name is derived from a telescope the researchers used – TRAnsiting Planets and PlanetesImals Small Telescope.
Estimates of their mass also indicate that they are rocky planets, rather than being gaseous like Jupiter. Three planets are in the habitable zone of the star, known as TRAPPIST-1e, f and g, and may even have oceans on the surface. The researchers believe that TRAPPIST-1f in particular is the best candidate for supporting life. It is a bit cooler than Earth, but could be suitable with the right atmosphere and enough greenhouse gases. These researchers had announced the discovery of three initial planets orbiting the same star in May. The new research increased that number to seven planets total.
Amaury Triaud, one of the study authors and an astronomer at the University of Cambridge, believes the discovery is a crucial step towards finding if there is life out there. Life may begin and evolve differently on other planets, so finding the gases that indicate life is key. Thomas Zurbuchen, associate administrator of Nasa’s Science Mission Directorate, was of the view that the discovery could be a significant piece in the puzzle of finding places that are conducive to life.
The planets are so close to each other and the star that there are seven of them within a space five times smaller than the distance from Mercury to the Sun. This proximity allows the researchers to study the planets in depth as well, gaining insight about planetary systems other than our own. Starting closest to the star and moving out, the planets have respective orbits from one-and-a-half to nearly 13 Earth days. The orbit of the farthest planet is still unknown.
Based on preliminary climate modelling, the researchers believe that the three planets closest to the star may be too warm to support liquid water, while the outermost planet, TRAPPIST-1h, is probably too distant and cold to support water on the surface. But further observation is needed to know for sure.
The Hubble Space Telescope already is on the case. The still-under-construction James Webb Space Telescope will join in once it is launched next year. The Webb will search for gases that might be a byproduct of life: oxygen, ozone and methane. Over the next decade, the researchers want to define the atmosphere of each planet, as well as to determine whether they truly do have liquid water on the surface and search for signs of life.
Altogether, astronomers have confirmed close to 3,600 planets outside our solar system since the 1990s, but barely four dozen are in the potential habitable zone of their stars, and of those, just 18 are approximately the size of Earth. Although it would take us millions of years to reach this newly discovered star system, from a research perspective, it is a close opportunity and the best target to search for life beyond our solar system.
