December 6, 2022

Study of ‘polluted’ white dwarfs finds that stars plus planets grow together

The study suggests that the particular early-formation picture is likely to be correct, meaning that Jupiter and Saturn had plenty of time to grow to their current sizes

A team of astronomers have found that planet development in our young solar system started much earlier than previously thought, with the building blocks associated with planets growing at the same time as their parent star.

A study of some of the oldest stars in the universe suggests that the building blocks of planets like Jupiter and Saturn begin to form while a new star is growing. It had been thought that planets only form every star has reached the final size, but brand new results, published in the journal  Nature Astronomy , suggests that stars and planets “ grow up” together.

The research, directed by the University of Cambridge, changes our understanding of how  planetary systems , including our own solar program, formed, potentially solving a major puzzle in astronomy.

“ We have a pretty good idea of how planets type, but one outstanding question we’ve had is whenever they form: does  earth formation   start early, when the  parent star   is still growing, or millions of yrs later? ” said Dr . Amy Bonsor from Cambridge’s Institute of Astronomy, the study’s first author.

To attempt to answer this particular question, Bonsor and the girl colleagues studied the atmospheres of white dwarf stars— the ancient, faint remnants of stars like the sun— to investigate the building blocks associated with planet formation. The study also involved researchers from the College of Oxford, the Ludwig-Maximilians-Universitä t in Munich, the particular University of Groningen as well as the Max Planck Institute meant for solar system Research, Gottingen.

“ A few white dwarfs are amazing laboratories, because their thin atmospheres are almost like celestial graveyards, ” said Bonsor.

Normally, the interiors of planets are out of reach of telescopes. But a unique class of white dwarfs— known as “ polluted” systems— have  heavy elements   such as magnesium, iron, and calcium within their normally clean atmospheres.

These elements should have come from small bodies like asteroids left over from planet formation, which crashed in to the white dwarfs and burnt up in their atmospheres. Consequently, spectroscopic observations of contaminated white dwarfs can probe the interiors of those torn-apart asteroids, giving astronomers direct insight into the conditions by which they formed.

Planet formation is thought to begin in a protoplanetary disk— made primarily of hydrogen, helium, and tiny particles of ices and dust— orbiting a young star. Based on the current leading theory about how planets form, the  dust particles   stick to each other, eventually developing larger and larger strong bodies. Some of these larger bodies will continue to accrete, becoming planets, and some remain because asteroids, like those that damaged into the white dwarfs in the current study.

The particular researchers analyzed  spectroscopic observations   from your atmospheres of 200 polluted white dwarfs from nearby galaxies. According to their analysis, the mixture of elements observed in the atmospheres of these white dwarfs can only be described if many of the original asteroids had once melted, which caused heavy iron in order to sink to the core as the lighter elements floated on the surface. This process, known as differentiation, is exactly what caused the Earth to have an iron-rich core.

“ The cause of the melting can simply be attributed to very unsuccsefflull radioactive elements, which existed in the earliest stages from the planetary system but corrosion away in just a million yrs, ” said Bonsor. “ In other words, if these asteroids were melted by something which only exists for a extremely brief time at the daybreak of the planetary system, then your process of planet formation should kick off very quickly. ”

The study suggests that the particular early-formation picture is likely to be appropriate, meaning that Jupiter and Saturn had plenty of time to grow to their current sizes.

“ Our study suits a growing consensus in the field that will planet formation got heading early, with the first physiques forming concurrently with the celebrity, ” said Bonsor. “ Analyses of polluted  white dwarfs   tell us that this radioactive melting process is a potentially ubiquitous mechanism affecting the development of all extrasolar planets.

“ This is only the beginning— every time we find a brand new white dwarf, we can gather more evidence and learn more about how planets form. We can trace elements like nickel and chromium and say how big an asteroid should have been when it formed the iron core. It’s incredible that we’re able to übung processes like this in exoplanetary systems. ”

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