2023-05-13 23:17:00
‘Mini-Neptune’, which is much larger in mass than Earth but smaller than Uranus, is a common exoplanet found in our galaxy, but relatively little has been identified as there are no similar planets in the solar system.
However, the James Webb Space Telescope (JWST) succeeded in observing the atmosphere of a mini-Neptune full of water vapor that had not been seen before, providing a clue to broaden our understanding of this.
A research team led by Dr. Eliza Kempton, an exoplanet astronomer at the University of Maryland, published the results of observing the mini-Neptune ‘GJ 1214 b’ in the scientific journal ‘Nature’.
| ▲ An artist’s rendering of GJ 1214 b, a ‘mini-Neptune’ with a vapor-filled atmosphere. |
GJ 1214 b is a large gas planet orbiting an M-type dwarf star in the constellation of Ophiuchus, about 40 light-years from Earth.
However, atmospheric observations were not possible because the entire planet was completely covered by a layer of haze or clouds.
In addition to the traditional observation method of analyzing starlight passing through the atmosphere of the GJ 1214 b planet, the research team observed the planet just before it went behind the star and immediately after it came out of the backside with the Webb Telescope’s mid-infrared ray (MIRI) instrument, creating a ‘heat map’. introduced a new method of making
The heat map revealed temperature changes between the day and night sides of the planet, giving clues to the composition of the atmosphere.
The day and night temperatures varied from 279 °C to 165 °C. This large temperature change is possible only in the atmosphere composed of heavy molecules such as water and methane, which means that the atmosphere of GJ 1214 b is not composed of light hydrogen molecules. will be.
This also indicates that GJ 1214 b may have started out in a watery state.
“If GJ 1214 b started out with a hydrogen-rich atmosphere, it would either have lost a lot of hydrogen, or it would have formed from a heavier material rich in ice or water,” Kempton said.
The temperature of GJ 1214 b is high by Earth standards, but much lower than expected, the team said. It was analyzed that this is because the planet’s atmosphere reflects much of the star’s light rather than absorbing and heating it up.
“For the past 10 years or so, the only thing we know about this planet is that it has a cloud or haze in its atmosphere,” said study co-author Dr. Robert Zelem of the Jet Propulsion Laboratory (JPL). He said it has a connotative meaning to look into the phenomenon.
The research team explained that the GJ 1214 b planet was too hot to have an ocean, but water in the form of water vapor could be the main component of its atmosphere. . GJ 1214 b currently has an orbital period of only 1.6 days.
The team notes that GJ 1214 b likely has a watery atmosphere, but methane may be a significant component, adding that further in-depth observations are needed to draw universal conclusions about mini-Neptune formation.
Science Team [email protected]
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