We get less than 35 centimeters of rain a year in Colorado, which is less than the U.S. average. It's not raining molten rocks.
It's not possible for a lot of exoplanets. Clouds made of molten rock can be seen on some alien worlds that are very close to their host stars.
WeTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkiaTrademarkia If we observe a star while an exoplanet is passing directly in front of it, then some of the starlight goes through the planet's upper atmosphere on its way to us. We can detect what is in the planet's atmosphere by taking a spectrum at that time.
The minerals in most planets are silicates. The silicates rise up in the atmosphere if the planet is sufficiently hot. They form droplets which form clouds. That is what happens on Earth with water. It is the same idea with more heat.
When we look at the star's spectrum, we see less light in certain colors because the clouds absorb light at specific colors.
This has been done for many exoplanets, but the problem is figuring out what the temperatures are. The silicates will rain out if the planet is too cold. If it's too hot, the silicates don't form clouds. There are different temperatures where you would expect to see these clouds.
A team of astronomer looked at the range limits to see if they could be found. They looked at the sky from 2003 to 2020 with the help of a space telescope. They looked at brown dwarfs, objects more massive than planets but without enough mass to ignite hydrogen fusion in their cores, which is rare. These objects are plentiful and can be found in the right temperature range. They have atmospheres that are very similar to massive exoplanets, so they can be used as stand-ins.
They found a lot of spectrum in the archive. Low-mass stars or young brown dwarfs still seething with the heat of their formation are what are known as late M type objects. Sixty-nine of the brown dwarfs were cooler L-class.
They were able to organize the spectrum by temperature. The silicate clouds begin to show up in objects L2 or later, which is cooler than 1,690 C. The silicates don't form clouds if it's hotter than this. The silicates rain out in L8 where the temperature is 1,070 C. These are indicators of the range of clouds that can form.
Even where the temperatures are right for clouds, in some objects no one is seen. It is not clear why, but it could be due to weather. The clouds absorb certain colors of light and that changes the colors we see. Taking images through different filters can be used to identify objects that can't be photographed.
The brown dwarf's brightness changes over time. The brown dwarfs had the strongest absorption from silicate clouds. I think the clouds are patchy, and holes between them would allow light from deeper inside the brown dwarf to escape. We can see different amounts of light when the object is moving. I think it is logical.
All of this helps us understand hot exoplanets. There are small rocky worlds around faint red dwarfs and huge gas giants with tens of times the mass of Jupiter. It's possible to mix and match all sorts of situations for these planets. Understanding any of them leads to understanding all of them, just like studying wind patterns on Jupiter and the ice caps of Mars and cratering on Mercury tell us more about how our own planet was born and changed with time.
We do that so we can look inside. Studying everything else in the Universe is important in understanding ourselves.
All Rights Reserved © 2024
