Earth-like planets may be common in the universe, suggests a new UCLA study. The team of astrophysicists and geochemists presents new evidence that Earth is not unique. The study was published in the journal Science on October 18, 2019
"We have just increased the likelihood that many rocky planets will be like Earth, and there are a very large number of rocky planets in the universe," et al. by Edward Young, Professor of Geochemistry and Cosmochemistry at UCLA
Scientists led by Alexandra Doyle, a graduate student in geochemistry and astrochemistry at UCLA, have developed a new method for detailed analysis of the geochemistry of planets outside our solar system. Doyle did this by analyzing elements in asteroid rocks or rock fragments on the planet orbiting about six stars white dwarf stars.
"We study geochemistry in rocks from other stars, which is almost unheard of," Ion said, "
" It is very difficult to learn about the composition of planets outside our solar system, "says co-author Hilk Schlichting, assistant professor at UCLA in Astrophysics and Planetary Science. "We used the only possible method ̵
White dwarf stars are dense, burnt remains of normal stars. Their heavy gravitational pull causes heavy elements such as carbon, oxygen and nitrogen to sink rapidly into their interiors where heavy elements cannot be detected by telescopes. The closest studied star to white dwarf Doyle is about 200 light-years from Earth, and the farthest is 665 light-years.
"By observing these white dwarves and the elements present in their atmosphere, we observe the elements that are in the body that circled the white dwarf," Doyle said. The great gravitational pull of the white dwarf shreds the fragment of the asteroid or planet that orbits it and the material falls on the white dwarf, she said. "Observing a white dwarf is like autopsying the contents of what has stuck in its solar system."
The data analyzed by Doyle was collected by telescopes, mainly by W.M. Keck Observatory in Hawaii that space scientists have previously collected for other scientific purposes.
"If I were just looking at a white dwarf star, I'd expect to see hydrogen and helium," Doyle said. "But I see in this data other materials, such as silicon, magnesium, carbon and oxygen, a material that accumulates on white dwarfs from bodies in orbit."
When iron is oxidized, it shares its electrons with oxygen. , forming a chemical bond between them, Young said. "It's called oxidation and you can see it when the metal turns to rust," he said. "Oxygen steals electrons from iron, producing iron oxide, not iron metal. We measured the amount of iron that oxidizes in these rocks that hit the white dwarf. We studied how much metals rust. "
Rocks from Earth, Mars and elsewhere in our solar system are similar in chemical composition and contain surprisingly high levels of oxidized iron, Young said. "We measured the amount of iron that oxidizes in these rocks that hit the white dwarf," he says.
The sun is made predominantly of hydrogen, which does the opposite of oxidation – hydrogen adds electrons.
Researchers said that the oxidation of a rocky planet has a significant impact on its atmosphere, the nucleus, and the type of rocks it makes on its surface. "All the chemistry that happens on the surface of the Earth can ultimately be traced back to the oxidation state of the planet," Young says. "The fact that we have oceans and all the ingredients necessary for life can be traced to the oxidation of the planet. Rocks control chemistry. "
Until now, scientists did not know in detail whether the chemistry of rock exoplanets was similar or very different from that of Earth.
How similar are the scales analyzed by the UCLA team. to rocks from Earth and Mars?
"Very similar," Doyle said. "They are similar to Earth and Mars in terms of their oxidized iron. We find that rocks are rocks everywhere with very similar geophysics and geochemistry. "
" It's always a mystery why the rocks in our solar system are so oxidized, "Young said." It's not what you expect. The question was whether this would be true of other stars. Our study says "yes." is really good for searching for planets similar to Earth in the universe. "
White dwarf stars are a rare medium for scientists to analyze.
Researchers examined the six most common elements in the scale: iron, oxygen, silicon, magnesium. , calcium and aluminum, they used mathematical calculations and formulas because they were learning "They can study the actual rocks of white dwarfs." We can determine the geochemistry of these rocks mathematically and compare these calculations with the rocks we have from Earth and Mars, "said Doyle, whose origin is in geology and mathematics." Understanding the rocks is crucial because they reveal the geochemistry and geophysics of the planet. "
" If extraterrestrial rocks have a similar amount of oxidation as Earth, then you can conclude that the planet has similar plate tectonics and similar potential and magnetic fields like Earth, which are thought to be key ingredients in life, "Schlichting said. "This study is a leap forward so that we can draw these conclusions for bodies outside our own solar system, and it shows that it is very likely that there will be truly terrestrial analogs."
Young stated that his department employs both astrophysicists and and geochemists.  "The result," he said, "is we do true geochemistry on rocks beyond our solar system. Most astrophysicists would not think to do this, and most geochemists would never consider applying this white dwarf."
Reference: "Oxygen Beacons of Extraterrestrial Rocks: Proof of Earth as Exo-Planet Geochemistry" by Alexandra E. Doyle, Edward D. Young, Beth Kline, Ben Zuckerman and Hilke E. Schlichting, October 18, 2019, Science .
DOI: 10.1126 / science.aax3901  Co-authored by Benjamin Zuckerman, Ph.D. UCLA astronomy and Beth Klein, astronomy researcher at UCLA.
This study was funded by NASA