Astronomers have discovered thousands of planets orbiting stars in our galaxy, known as outer planets. However, it is difficult to know exactly what it is made of or whether it resembles Earth.
To try to figure it out, said astronomer Si Shu of the US National Science Foundation’s (NSF) National Research Laboratory for Infrared Optical Astronomy. NOIRLab) with geologist Keith Buterka, of California State University, he studied the atmosphere of what is known as Polluted white dwarf stars.
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These are the dense, crumbling cores of previously normal stars, such as the Sun, that contain material that were once planets, asteroids, or other rocky bodies that orbited the star in the distant past, but at some point fell. in the white dwarf and “pollution” its atmosphere.
By looking for elements that can’t be found naturally in the white dwarf’s atmosphere (i.e. anything other than hydrogen and helium), scientists can figure out what rocky planetary bodies that fell on the star were made of.
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Buterka and Shaw observed 23 contaminated white dwarfs, about 650 light-years from the sun, where elements such as calcium, silicon, magnesium and iron were precisely detected, thanks to observations made at the WM Keck Observatory in Hawaii. Hubble Space Telescope and other observatories. A study published in the journal Nature Communications.
The scientists then used the abundant measurements of those elements to reconstruct the minerals and rocks they might form. They found that these white dwarfs have a much wider range of compositions than any of the inner planets in our solar system, indicating that their planets have a variety of rock types.
In fact, some of the compositions are so unusual that researchers have had to come up with new names (such as “pyroxenite quartz” and “periclase donets”) to classify the new types of rocks previously found on those planets.
“While some exoplanets that have orbited polluted white dwarfs in the past look similar to Earth, most have rock types that are alien to our solar system,” Xu said. “They have no direct counterparts in it.”
Buterka described some characteristics of this new type of rock that once formed distant rocky bodies: “Some types of rocks that we see from white dwarf data will dissolve more water than rocks on Earth and could affect the way oceans develop, and he explained, “Some types of rocks will dissolve more water than rocks on Earth,” he explained. Rocks can melt at much lower temperatures and produce a crust thicker than rocks on Earth, and some types of rocks can be weaker, which may facilitate the evolution of plate tectonics.”
Previous studies of contaminated white dwarfs have found elements from rocky bodies, such as calcium, aluminum, and lithium. However, Butyrka and Shaw explained that these are minor elements (which usually make up a small part of terrestrial rock) and measurements of major elements (which make up a large part of terrestrial rock), especially silicon, are really necessary to know what kinds of rocks were on those planets.
Moreover, Buterka and Shaw claim that the high levels of magnesium and low levels of silicon measured in the atmospheres of white dwarfs indicate that the rocky debris detected likely came from the planets’ interior, from the mantle, rather than from their crust.
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Some previous studies of polluted white dwarfs had predicted the presence of continental crust on rocky planets that once orbited those stars, but Shaw and Buterka found no evidence of crustal rock.
However, the observations do not completely rule out the presence of continental crust of planets or other types of crust. “We think there are rocks in the Earth’s crust, and we can’t see them, probably because they occur in a very small, immeasurable fraction, compared to the mass of other planetary components, such as the core and mantle,” Buterka explained. .
According to Xu, the pair of astronomer and geologist was the key to unraveling the secrets hidden in the white dwarf’s polluted atmosphere. “I met Keith Buterka at a conference and was excited to help me understand the systems I was observing. He taught me geology, taught me astronomy, and figured out how to understand these mysterious exoplanet systems.”
With information from NOIRLab
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