NASA discovers seven exoplanets around dwarf star TRAPPIST-1

In a much-anticipated news conference held on Wednesday, NASA announced the discovery of seven planetary bodies in the TRAPPIST- 1 system. TRAPPIST-1 is a small, faint star found in the Aquarius constellation, situated approximately 40 light years away from us! In itself not terribly exciting – we discover news stars all the time – but it is what they found around it that made this an unprecedented discovery. Using the Spitzer Space Telescope, an infrared space telescope launched by NASA in 2003, scientists discovered a system of seven rocky planets closely orbiting TRAPPIST-1, all in close size to Earth, which – scientists suspect may be warm enough to harbor liquid water on their surface. The discovery was published on the same day in the journal Nature. [1]

TRAPPIST-1 system and our own solar system


TRAPPIST-1 was named after a Belgian-operated telescope in Chile (Transiting Planets and Planetesimals Small Telescope) that discovered the first three exoplanets in 2016. The remainder was discovered by NASA’s Spitzer Space Telescope early this year, assisted by several ground-based telescopes.

This is the first time that so many terrestrial planets have been found in the same system, all within a close range to the star: within 1.5 and 20-day orbit. All of these planets lie so close to their star that, relatively, they could all fit inside Mercury’s orbit. If TRAPPIST-1 was anything like our Sun, these exoplanets would all be subjected to burning temperatures, in an everlasting inferno – thus, no water, no life.

TRAPPIST-1, however, is not quite like our Sun: it is a dwarf star, only slightly larger the Jupiter. It also falls in the category of ultra-cool dwarf stars. So cool, in fact, that even planets orbiting very close to it could possibly harbor water in a liquid form, under the right atmospheric conditions. And three of those planets (E -G) firmly lie within this “habitable zone”. A measure of their densities also indicates that all of the planets orbiting TRAPPIST-1 are likely to be rocky – just like Earth. [1]

Image result for TRAPPIST 1 habitable zone telegraph

TRAPPIST-1 habitable zone

Thomas Zurburchen, the associate administrator of NASA’s Science Mission Directorate, commented: “This discovery could be a significant piece in the puzzle of finding habitable environments, places that are conducive to life. Answering the question ‘are we alone?’ is a top science priority and finding so many planets like these for the first time in the habitable zone is a remarkable step forward toward that goal.” [3]

This is a monumental step in spatial exploration: it suggests that the occurrence of systems where rocky planets similar to Earth would lie in the habitable zone is much higher than we previously thought! [1] Further observations of this system will enable scientists to determine the planet’s atmospheric composition  – a key factor in assessing their habitability. The launch of the James Webb Space Telescope, scheduled for 2018, could be significant in providing such further observations. Its’ much greater sensitivity will enable us to study the planet’s atmospheric composition in great detail, and detect chemical fingerprints for compounds like water, methane, oxygen, ozone; as well as analysing their surface temperature and pressure systems. [2]



[1] Bolmont et al. (2017) Water loss from terrestrial planets orbiting ultracool dwarfs: implications for the planets of TRAPPIST-1.  MNRAS 464, 3728–3741

[2] Snellen (2017) Astronomy: Earth’s seven sisters. Nature 542; 421-23



All images above: NASA


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