A study of dirty white dwarfs showed that planets grow with their stars

(ORDO NEWS) — Scientists have found that planet formation in young planetary systems begins much earlier than thought, and planets grow at the same time as their star. The so-called polluted white dwarfs helped make this discovery.

The authors of the study of the oldest stars in the universe suggested that the building blocks of the planets begin to form while the young star is growing, and the planets themselves are formed only when the star reaches its final size.

However, a study by astronomers from the University of Cambridge (UK) showed that stars and their planets “grow” together.

Scientists have a fairly complete understanding of how planets form, but the question of when their formation began remains open.

To solve this problem, astronomers studied the atmospheres of white dwarfs – gradually cooling stars, already deprived of sources of thermonuclear energy.

Among them are the so-called polluted white dwarfs, whose atmosphere contains many heavy elements such as magnesium, iron and calcium.

These elements probably come from small bodies like asteroids left over from the formation of planets that crashed into stars before burning up in their atmospheres.

Therefore, spectroscopic studies of polluted white dwarfs allow us to look inside these asteroids and understand the conditions under which they were formed.

Planet formation is thought to begin in a protoplanetary disk made up mostly of hydrogen, helium, and tiny particles of ice and dust orbiting a young star.

Dust particles stick to each other, forming larger and larger bodies. Some of them continue to collide and connect, becoming planets, and some remain asteroids.

Spectroscopic observations of the atmospheres of 200 polluted white dwarfs from nearby galaxies have shown that the asteroids that crashed into them were melted.

The reason for this melting can only be attributed to very short-lived radioactive elements that existed at the earliest times of the planetary system’s life, but decayed in just a million years.

That is, if the asteroids were melted by something that existed for a very short time at the dawn of the planetary system, then the process of planet formation must also have begun shortly after the formation of the star.

The authors also believe that some planets in the solar system, such as Jupiter and Saturn, did not immediately reach the sizes that we observe now.

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