Last week, scientists announced the discovery of a remarkable three potential habitable exoplanets orbiting around the ultracool dwarf star TRAPPIST-1, an alien planetary system just 40 light-years away from us.
It was incredibly huge and important announcement due the proximity of the system to Earth, when you consider that the most habitable exoplanet found so far beyond our solar system is located 1400 light years away. But I’m afraid we are rushing to conclusions much too fast!
First, let’s recap: on May 2, Michaël Gillon, an astronomer at the University of Liège in Belgium, announced the discovery of three planets orbiting TRAPPIST-1, a tiny, cold stars located just 40 light years away from us.
TRAPPIST-1 is much fainter than our sun, its 2,000 times less bright and a bit less than half as warm as the sun. TRAPPIST-1 is also too small, barely larger than Jupiter, about one-twelfth the sun’s mass, and less than 0.125 the sun’s width.
So, its really tiny, but stars like TRAPPIST-1 are actually very common in our galaxy, making up about 15% of the stars near the sun.
It was really unexpected to see three planets around this ultra cool star, astronomers say. Actually, it was the first time that distant planets have been found around such star. But a bigger surprise was the three planets are most likely all inside the classical habitable zone — the area around a star where planets have surfaces warm enough to have liquid water.
The kind of planets we’ve found are very exciting from the perspective of searching for life in the universe beyond Earth,
study co-author Adam Burgasser said then.
TRAPPIST-1’s trio planets are: TRAPPIST-1b and TRAPPIST-1c having orbital periods of 1.51 days and 2.42 days, respectively, and the third planet, TRAPPIST-1d, has a less well determined period in the range 4.5 to 72.8-days.
With such short orbital periods, the planets are between 20 and 100 times closer to their star than the Earth to the Sun,
Their radius are: 1.113, 1.049 and 1.163 Earth’s radius, so you can see, they are veritable Earth-sized planet. Due to their location near to the dwarf stars, scientists estimated that they are lying within the star’s habitable zone, as I mentioned above.
We can tell if the planets are probably rocky, or rich in ice like the moons of Jupiter, or rich in metal like Mercury, either way, exciting scientific adventures are now beginning.
lead author Michaël Gillon said then.
New hope?A new study, uploaded on arxiv servers, questions the habitability of these planets. Astronomers used ESA’s X-ray space observatory XMM-Newton to study TRAPPIST-1 and thus to measure the X-ray luminosity of the star, estimate its EUV(extreme-ultraviolet) luminosity, and hence consider the effects of XUV (xrays and EUV) irradiation on the Earth-sized exoplanets.
TRAPPIST-1 planetary system Analyse
It is well known that an important factor influencing the evolution of planetary atmospheres and their habitability is the X-ray and extreme-ultraviolet (EUV) radiation emitted by their parent stars (together often termed XUV radiation).
The long term effects of XUV irradiation on the habitability of terrestrial planets are complex and uncertain, and while some planets might be rendered uninhabitable through atmospheric stripping, others may become habitable through the removal of a massive primary atmosphere of H/He.
Scientists’ spectral analysis and X-ray luminosities show that TRAPPIST-1 is a relatively strong coronal X-ray source, with a similar luminosity to that of the quiet Sun despite its much lower bolometric luminosity. So, what is that mean?
The relatively close-in Earth-sized planets, which span the classical habitable zone of the star, are subject to sufficient X-ray and EUV irradiation to significantly alter their primary and perhaps secondary atmospheres. Such high-energy irradiation make the exoplanets less habitable, even entirely uninhabitable.
The things are really bad on TRAPPIST 1-b and TRAPPIST 1-c, but maybe TRAPPIST 1-d is too far to be affected by these strong x-ray emissions. We don’t know yet. But if TRAPPIST 1-d is far enough then its predisposed to frost, temperature can dip as low as -200°C, similar to planets in our solar system beyond Mars.
said R. Louden, not implied in the study.
Though, TRAPPIST 1 is still a fascinating system, scientists remarked:
Either way, the small size and low temperature of the star, and the proximity of the system to Earth, provide by far the best opportunity to date to study the atmospheres of cool, Earth-sized exoplanets.
Given all these data, the question is are these planets habitable? Personally, I don’t think so, but maybe I’m wrong. Maybe the forthcoming James Webb Space Telescope could help scientists to further analyze the atmospheres of those planets and investigate for sure if they’re habitable.