, <\/em>changes our understanding of how planetary systems formed, potentially solving a major puzzle in astronomy.<\/p>\nWhat can white dwarfs tell us about the formation of early planets?<\/h3>\n \u201cWe have a pretty good idea of how planets form, but one outstanding question we\u2019ve had is when they form: does planet formation start early, when the parent star is still growing, or millions of years later?\u201d said Dr Amy Bonsor from Cambridge\u2019s Institute of Astronomy, the study\u2019s first author.<\/p>\n
To answer this question, Bonsor and her colleagues studied the atmospheres of white dwarf stars \u2013 the ancient, faint remnants of stars like our Sun \u2013 to investigate the building blocks of planet formation. The study also involved researchers from the University of Oxford, the Ludwig-Maximilians-Universit\u00e4t in Munich, the University of Groningen, and the Max Planck Institute for Solar System Research, Gottingen.<\/p>\n
\u201cSome white dwarfs are amazing laboratories, because their thin atmospheres are almost like celestial graveyards,\u201d Bonsor explained.<\/p>\n
Normally, the interiors of planets are out of reach of telescopes. But a special class of white dwarfs \u2013 known as \u2018polluted\u2019 systems \u2013 have heavy elements such as magnesium, iron, and calcium in their normally clean atmospheres.<\/p>\n
These elements must have come from small bodies like asteroids left over from planet formation, which crashed into the white dwarfs and burned up in their atmospheres. As a result, spectroscopic observations of polluted white dwarfs can probe the interiors of those torn-apart asteroids, giving astronomers direct insight into the conditions in which they formed.<\/p>\n
Planet formation is believed to begin in a protoplanetary disc \u2013 made primarily of hydrogen, helium, and tiny particles of ice and dust \u2013 orbiting a young star. According to the current leading theory on how planets form, the dust particles stick to each other, eventually forming larger and larger solid bodies. Some of these larger bodies will continue to accrete, becoming planets, and some remain as asteroids, like those that crashed into the white dwarfs in the current study.<\/p>\n
The differentiation process<\/h3>\n The researchers analysed spectroscopic observations from the atmospheres of 200 polluted white dwarfs from nearby galaxies. According to their analysis, the mixture of elements seen in the atmospheres of these white dwarfs can only be explained if many of the original asteroids had once melted, which caused heavy iron to sink to the core while the lighter elements floated on the surface.<\/p>\n
This process, known as differentiation, is what caused the Earth to have an iron-rich core.<\/p>\n
Bonsor stated: \u201cThe cause of the melting can only be attributed to very short-lived radioactive elements, which existed in the earliest stages of the planetary system but decay away in just a million years.<\/p>\n
\u201cIn other words, if these asteroids were melted by something which only exists for a very brief time at the dawn of the planetary system, then the process of planet formation must kick off very quickly.\u201d<\/p>\n
The study suggests that the early-formation picture is likely to be correct, meaning that Jupiter and Saturn had plenty of time to grow to their current sizes.<\/p>\n
\u201cOur study complements a growing consensus in the field that planet formation got going early, with the first bodies forming concurrently with the star,\u201d Bonsor concluded.<\/p>\n
\u201cAnalyses of polluted white dwarfs tell us that this radioactive melting process is a potentially ubiquitous mechanism affecting the formation of all extrasolar planets.<\/p>\n
\u201cThis is just the beginning \u2013 every time we find a 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 must have been when it formed its iron core. It\u2019s amazing that we\u2019re able to probe processes like this in exoplanetary systems.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"
A team of astronomers has found that planet formation in our young solar system started much earlier than previously thought.<\/p>\n","protected":false},"author":22,"featured_media":27314,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"categories":[771],"tags":[818,3477],"acf":[],"yoast_head":"\n
Study of white dwarfs reveals interesting facts about planet formation<\/title>\n \n \n \n \n \n \n \n \n \n \n \n \n\t \n\t \n\t \n \n \n \n \n \n\t \n\t \n\t \n