2023 Author: Bryan Walter | [email protected]. Last modified: 2023-05-21 22:24
TRAPPIST-1 and its exoplanets as seen by the artist
For the first time, an international team of astronomers has studied the atmosphere of two exoplanets, similar in size to Earth. Thanks to the Hubble telescope, scientists have found that most likely the gas envelopes of the planets are not similar to the hydrogen-helium atmospheres of the giant planets. This increases the chances that the TRAPPIST-1 planets have habitable conditions. The study is published in the journal Nature, briefly reported in a press release from the space observatory.
In order to get the opportunity to study the composition of the atmospheres, astronomers used the event of a double transit of exoplanets TRAPPIST-1b and 1c against the background of the central star of the system. This happened on May 4, 2016. The transit of each of the planets separately lasts 36 and 42 minutes, and planet 1c appeared on the disk of the star 12 minutes earlier than 1b.
The authors compared the change in the star's spectrum during transit with several possible models of the exoplanet's atmosphere. In particular, a helium-hydrogen atmosphere devoid of clouds was excluded with a confidence level of 10 sigma. At the same time, the absence of pronounced absorption lines in the spectrum does not allow making any specific assumptions about the composition of the planet. Thus, observations do not exclude an atmosphere from water vapor or a hydrogen atmosphere with a dense layer of clouds.
The TRAPPIST-1 system is located 40 light years from Earth. In its center is a cold star, 12 times less than the mass of the Sun. Scientists have recently discovered that three exoplanets are orbiting around it. For two planets, the sidereal period is one and a half and 2.4 days, respectively, and for the third, less studied, it is in the interval from 4.5 to 73 days.
Earlier, similar observations were made for the exoplanet Gliese 1214 b, a super-earth located near a red dwarf. Its mass is about 6.5 times that of the Earth, it is located 40 light years from the Sun.