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To Study the Foreign World, Astronomers Look for White Dwarfs




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In searching for an Earth-like world among the stars, much of the focus is on finding planets in the habitable zone of stars, where they are at the right distance for liquid water to exist on the surface. But that is only one ingredient needed for a planet that truly resembles Earth. Other factors & lsqb; like the size & rsqb; (/ blog / small-worlds /) come into play, for example. But finer aspects are also important, such as the geological composition of a planet.

To be truly Earth-like, a planet must have a ratio of similar elements such as iron, oxygen, and carbon. This ratio affects everything from the formation of rocks and minerals to the internal composition of the planet. But studying the geology of exoplanets is beyond the capabilities of today's telescopes. We have just begun to study things like the atmosphere.

But new research has used ingenious methods to study the composition of extrasolar planets indirectly. Instead of trying to study extrasolar planets, this work looks at white dwarfs.

White dwarfs are the remnants of a Sun-like star that has collapsed due to its gravity. The gravity of white dwarfs is so strong that the heavy elements of the star sink to their core. But white dwarfs also have a thin atmosphere which can contain traces of heavier elements. These elements cannot exist in stars because they collapse into white dwarfs, so they must originate from planets and other rocky objects that fall into white dwarfs.

By studying the atmosphere of the white dwarf, we can study the ratio of the elements that exist on planets that have orbited stars. A team recently did this and looked at the ratio of the six most common elements in a rocky body: iron, oxygen, silicon, magnesium, calcium, and aluminum. Using this ratio, they created a mathematical model to determine the type of geology that the planets have.

One of the things that the team found was that these worlds would have a high ratio of iron and oxygen, similar to the composition of planets like Earth and Mars. This means that extrasolar planets may have the same composition, and are therefore geologically similar.

In other words, when we find a world the size of Earth that orbits a star like the Sun, they will most likely also have a similar geology. And that means that the chances of a truly Earth-like world are higher than we ever thought.

Reference: Alexandra E. Doyle, et al. "Lack of oxygen from extrasolar rock: Evidence of geochemistry like extrasolar planets" Science Oct 18 2019: 356-359

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In searching for an Earth-like world among the stars, much of the focus is on finding planets in the habitable zone of stars, where they are at the right distance for liquid water to exist on the surface. But that is only one ingredient needed for a planet that truly resembles Earth. Another factor [such as size](/ blog / small-worlds /) come into play, for example. But finer aspects are also important, such as the geological composition of a planet.

To be truly Earth-like, a planet must have a ratio of similar elements such as iron, oxygen, and carbon. This ratio affects everything from the formation of rocks and minerals to the internal composition of the planet. But studying the geology of exoplanets is beyond the capabilities of today's telescopes. We have just begun to study things like the atmosphere.

But new research has used ingenious methods to study the composition of extrasolar planets indirectly. Instead of trying to study extrasolar planets, this work looks at white dwarfs.

White dwarfs are the remnants of a Sun-like star that has collapsed due to its gravity. The gravity of white dwarfs is so strong that the heavy elements of the star sink to their core. But white dwarfs also have a thin atmosphere which can contain traces of heavier elements. These elements cannot exist in stars because they collapse into white dwarfs, so they must originate from planets and other rocky objects that fall into white dwarfs.

By studying the atmosphere of white dwarves, we can study the ratio of the elements that exist on planets that have orbited stars. A team recently did this and looked at the ratio of the six most common elements in a rocky body: iron, oxygen, silicon, magnesium, calcium, and aluminum. Using this ratio, they created a mathematical model to determine the type of geology that the planets have.

One of the things that the team found was that these worlds would have a high ratio of iron and oxygen, similar to the composition of planets like Earth and Mars. This means that extrasolar planets may have the same composition, and therefore are similar geologies.

In other words, when we find a world the size of Earth that orbits a star like the Sun, they will most likely also have a similar geology. And that means that the chances of a truly Earth-like world are higher than we ever thought.

Reference: Alexandra E. Doyle, et al. "Oxygen deprivation from extrasolar rocks: Evidence for the Earth-like geochemistry of extrasolar planets" Science Oct 18 2019: 356-359


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