(dr) NASA/JPL-Caltech/R. Hurt (IPAC)
Tail of the exoplanet WASP-69 b
The enormous structure, which is made of gas escaping from the exoplanet’s atmosphere, is being blown by stellar winds like a giant “wind sleeve”.
Astronomers discovered that the exoplanet WASP-69 b has a long tail, which stays 44 times larger than Earth when this world approaches its star. This large structure is formed by the gas that comes out of the exoplanet’s atmosphere, pushed by the stellar winds of the star it orbits.
According to , WASP-69 b, found 160 light years away, is a gas giant similar in size to Jupiter, but much less massive. It orbits very close to its star, taking just 3.9 Earth days to complete one revolution.
The planet was discovered in 2014 and, at that time, the scientific community had already realized that, every second, the exoplanet lost around 200 thousand tons of its helium and hydrogen atmosphere. This rate suggests that the exoplanet must have already lost the equivalent of seven times the mass of our planet during its seven billion years of existence.
After analyzing the exoplanet with the WM Keck observatory on Maunakea, Hawaii, scientists collected several precise measurements that allowed them to discover that WASP-69 b has a tail almost 560 thousand kilometers long.
The structure is formed when stellar winds push gas away from the planet, creating a kind of “path”. Stellar winds are similar to the wind from our Sun, that is, a flow of electrically charged particles constantly fired by the star.
Not case of WASP-69 b, the tail would disappear if the star stopped releasing winds, because without these emissions, the escape of gases would occur in a symmetrical and spherical manner.
This peculiar feature of the exoplanet could help astronomers better understand how gas giants form and evolve over time, as these worlds represent a good opportunity for scientists to study stellar winds from the “tail” created by interactions with the atmosphere.
The findings were published in Astronomy and Astrophysics.
