The temperature of TRAPPIST-1 b, one of the seven planets in the TRAPPIST-1 planetary system about 40 light-years away from Earth, was measured using thermal energy emitted in the form of infrared rays.
This is the first time capturing light from an exoplanet that is small in size and not as hot as a rocky planet in the solar system, confirming that exoplanets orbiting M-type dwarf stars such as TRAPPIST-1 are habitable. presented as an important step forward.
According to the National Aeronautics and Space Administration (NASA), an international research team led by astrophysicist Dr. Thomas Green of the ‘Ames Research Center’ measured the temperature of TRAPPIST-1 b using the Mid-Infrared Instrument (MIRI) of the James Webb Space Telescope (JWST). The results were published in the scientific journal Nature.
| ▲ A rendering of Trappist-1 b. |
The face temperature of the planet has been measured to be around 500 Kelvin (450 °F), indicating that it cannot have an atmosphere.
Trappist-1 is an ultracold red dwarf (M-type dwarf) with only 9% of the mass of the sun, and is known to have seven planets at a distance from the sun to Mercury. All of these planets are about the same size as Earth, and six are rocky.
Trappist-1 b, which rotates in the innermost part, is exposed to light four times the solar energy received by the Earth as it orbits less than 1/100 of the distance between the Sun and the Earth with a cycle of 1.51 days. Although it is not within the habitable zone, it became an observation target because it could obtain information about the situation of other planets or M-type dwarfs in the TRAPPIST-1 planetary system.
M-type dwarfs are 10 times more likely to contain rocky planets than there are 10 times more sun-like stars in our galaxy. However, these stars are known to be very active in their youth, destroying the atmospheres of nearby planets with flares and X-rays that burst out with large amounts of energy.
Previous observations with the Hubble and Spitzer Space Telescopes have not found atmospheric evidence, but they cannot be ruled out.
The research team measured the temperature of the planet as a way to resolve this uncertainty.
Trappist-1 b is a synchronously rotating planet with only one side always facing the star due to the tidal force, so if there is an atmosphere, heat circulates and the temperature of the other side will be lower than when it is not.
The research team used ‘secondary eclipse photometry’ technology, which measures the change in light with MIRI when TRAPPIST-1 b orbits behind the star instead of in front of it.
Although TRAPPIST-1 b does not emit visible light, it emits infrared light, so the temperature was calculated using the infrared light emitted by the planet by subtracting the stellar light during the second solar eclipse from the total infrared light of the star and planet.
The star was more than 1,000 times brighter than the planet, and the change in brightness was within 0.1%. It is said that no telescope before the Webb telescope has been able to capture it.
The research team observed the second solar eclipse five times, and as a result of examining various scenarios according to temperature through computer models, they came to the conclusion that it matched almost perfectly with the rocky body without an atmosphere.
“This is the first time that we have captured the heat emitted by a rocky planet that is not very hot, and it is a really important step forward in the discovery of exoplanets,” said the research team.
Science Team [email protected]
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