A hypothetical image of the “mini-Neptune” and its surroundings. Image: Retrieved from NASA
Astronomers have observed for the first time that two exoplanets in the universe are gradually losing their outer atmospheres and will become “super-Earths”. The study also found that the gas near the planet escaped in a different direction than the expert’s analysis, and the researchers said that it is still being clarified.
Researchers have discovered two “mini-Neptunes” that are losing their atmospheres from the Hubble Space Telescope. One is the planet HD 63433c around the star HD 63433 in the constellation Gemini, 73 light-years away from Earth; the other is the planet TOI-560b around the star TOI-560 in the constellation Hydra, 103 light-years away from Earth. The researchers published this in The Astronomical Journal on February 1.
Baked by stellar radiation, the atmospheres of the two planets are volatilizing, like water vapor from a pot of boiling water, according to a NASA press release. Observational data show that the hydrogen gas near HD 63433c is escaping at a speed of 50 kilometers per second; while the helium gas near TOI-560b is escaping at a speed of 20 kilometers per second, the main researcher, Caltech graduate Michael Zhang told This means that this is because the gravity of the mini-Neptunes is difficult to retain the high-speed moving gas, and it also means that the two mini-Neptunes will become two super-Earths.
In addition, the study also unexpectedly found that the gas escaping from TOI-560b was flowing to its star TOI-560, contrary to scientists’ previous judgments, which had previously been believed that the escaped atmospheres of planets would move away from their stars.
In October 1995, two Swiss scientists announced the first discovery of an exoplanet and named it 51 Pegasus, which shocked the astronomical world. Scientists have discovered thousands of planets so far, and divide the planets with rocky surfaces into two categories. The first is “mini-Neptune”, which is 1.6 to 1.75 times the size of Earth; the second is “super-Earth”. “(super-Earth), its mass is higher than that of Earth, but much lower than that of the solar system’s ice giants Uranus and Neptune, which are 14.5 and 17 times that of Earth, respectively.
Heather Knutson, a professor at the California Institute of Technology, said that exoplanets that have been studied for a long time have learned to expect the unexpected. The researchers point out that more observations are still needed to clarify whether the escape of the atmosphere to the star is a general rule or an occasional event.
