Extreme weather cloud

An extrasolar planet about 1360 light-years away is so close to its star that it contains vaporized rocks in the cloud.

The planet WASP- 178b revolves around a young white dwarf WASP- 178 with twice the mass of the sun, and its period of revolution is as short as 3.3 days. In such a close situation, the temperature of this gaseous world is soaring. It is so hot that it is classified as "super hot Jupiter" and may be the most extreme exoplanet we know.

Professor David Sing, an astrophysicist at Johns Hopkins University, said, "We don't know much about the weather in different planetary environments. When you look at the earth, all our weather forecasts are still fine-tuned to the extent that we can measure them. However, when we reach the distant exoplanet, our prediction ability is limited, because we haven't established a general theory to explain how everything in the atmosphere is combined and how to deal with extreme states. 」

Hot Jupiter is particularly surprising and suitable for study. As the name implies, these worlds, like Jupiter, are huge gas planets; But they are also very hot, because their orbits are very close to their stars, and some period of revolution even take less than a day.

They bring some interesting phenomena: they are unlikely to be produced in the current orbit, because gravity, radiation and strong stellar winds will certainly avoid gathering gases together. However, more than 300 hot Jupiter have been discovered so far. Astronomers believe that they formed far away from the stars and gradually migrated inward.

The mass of WASP- 178b is about 0.4 times that of Jupiter, and its volume is about 0.9 times that of Jupiter. It became fanatical because of the high temperature of its star, reaching 2450 Kelvin (2 177 degrees Celsius). This temperature is the best place to observe the evaporated silicide. Theoretical research shows that SiO can be expected to be detected when the temperature exceeds 2000 Kelvin.

The following is the method of observation. This exoplanet passes between the earth and the main star. During each transit, some light from the star is absorbed by atoms in the atmosphere of exoplanets, and each element absorbs or emits radiation with different wavelengths. This means that these elements can be identified by the spectral signals received from the stars.

This signal is very short, but if many transits are superimposed, astronomers can enlarge the spectrum and get a readable signal. Using this method, we have been able to detect the evaporated metals in the atmosphere of hot Jupiter, such as titanium, iron and magnesium.

The research team led by Professor Xin of Utah Valley University and his colleague Josh Loslinger used the Hubble Space Telescope to obtain the spectrum of WASP- 178b, and found a signal different from anything seen before. According to their analysis, this signal comes from silicon and magnesium.

They wrote in the paper: "As far as we know, especially SiO has never been detected in exoplanets before. However, SiO appears in WASP- 178b, which is consistent with the theoretical expectation, because at high temperature, SiO is mainly Si. 」

WASP- 178b is the hot Jupiter in tidal locking, which is the star of all known hot Jupiter. This means that one side will always face the stars, showing an eternal day; And the other side will always turn its back on the stars, showing the eternal night. This creates an obvious temperature difference between the two hemispheres of this exoplanet, and the rotating atmosphere rotates between the two hemispheres.

On the night side of an exoplanet, it may be cold enough that steam condenses into clouds, falls deeper into the atmosphere, and then is blown back to the day side, where minerals are gasified again.

The researchers couldn't see any signs of condensation at the end line of WASP- 178b, which is the line that divides day and night. However, the results show that SiO, namely WASP-76b, may exist on other exoplanets where the terminal line is observed. If there is rock rain on the exoplanet, then this may be the place to find it.

The research results of the research team also show that our ability to spy into the mysterious atmosphere of the distant world is getting stronger and stronger. This bodes well for observing small exoplanets farther away from the stars.

Professor Loslinger said, "If we can't know what's happening on super-hot Jupiter with reliable solid observation data, we won't have a chance to know what's happening from the weak spectra obtained by observing terrestrial exoplanets. This is a test of our technology, which enables us to establish general knowledge of physical properties, such as cloud formation and atmospheric structure. 」