And, most importantly, do astronomers have a complete picture as to how stars and planets form, and are able to maintain such a beautiful, cohesive balance amidst the apparent chaos of the Universe?<\/p>
Astronomers now estimate that for every star we see in the night sky, there is at least one exoplanet<\/a> in orbit around it, a fact that has key implications for the search for life beyond Earth, as well as our knowledge of stellar and planetary formation.<\/p> Claire Davies is a lecturer in physics and astronomy at the University of Exeter in the UK who uses some of the highest-resolution observing facilities on Earth to study how stars and their planets form.<\/p> We asked her to answer some of the most frequently-asked questions about the formation of stars and the planets that orbit them.<\/p> The process of stars forming starts with an initial collapse of material in a molecular cloud, trigged by gravity<\/a>, and ends when hydrogen fusion ignites in the star\u2019s core.<\/p> How long this process lasts depends on the mass of the star.<\/p> Stars like the Sun take a few tens of millions of years to form, while higher-mass stars are formed much more quickly and lower-mass stars take much longer.<\/p> Regardless of the mass, the process of stars forming is rapid in proportion to a star\u2019s lifetime.<\/p> If you condensed the lifetime of a star down to the lifetime of a typical human, the formation process would only take around three months!<\/p> Our Solar System\u2019s planets<\/a>, and most extra-solar planets that have so far been discovered, are \u2018first generation\u2019 planets: they formed from the same collapsing material as the star.<\/p> During collapse, there is a battle between gravity and rotation, which results in the formation of a circumstellar disc.<\/p> The material in these discs is what collapses or coalesces further to form planets.<\/p> It ultimately depends on the lifetime of its disc.<\/p> We see some protostars in very young star-forming regions which lack discs.<\/p> However, we aren\u2019t yet able to investigate whether planets have already formed around these stars or whether the disc dispersed before they had time to.<\/p> Just because planets form in orbit around a star doesn\u2019t always mean they\u2019ll stay there either.<\/p> In long-lived discs, planets may interact with neighbouring disc material, resulting in an orbital tug-of-war.<\/p> Planets may drift inwards onto increasingly shorter orbits and some of these may end up being engulfed by their star.<\/p> Others may encounter more massive protoplanets during their migration through the disc and be thrown out of their system altogether.<\/p> Protoplanetary discs appear dark in images taken in visible light because they block out light from their host stars.<\/p> To peer inside, astronomers use instruments that are sensitive to longer wavelengths of light.<\/p> I\u2019m interested in the inner regions of discs, where temperatures reach up to 1,000\u02da Celsius or so.<\/p>5 key questions about how stars and planets form<\/strong><\/h2>
How long does it take to form a star?<\/strong><\/h3>
![\"Illustration](\"https:\/\/c02.purpledshub.com\/uploads\/sites\/48\/2023\/03\/gas-cloud-star-disc-planets-3192324.jpeg\")
Do planets form at the same time as stars?<\/strong><\/h3>
![\"Illustration](\"https:\/\/c02.purpledshub.com\/uploads\/sites\/48\/2023\/03\/solar-system-planets-3265c46.jpg\")
Do all stars form planets?<\/strong><\/h3>
![\"An](\"https:\/\/c02.purpledshub.com\/uploads\/sites\/48\/2019\/10\/HL-Tauri-ESO-48646f6-e1572265503357.jpg\")
How do astronomers peer inside protoplanetary discs?<\/strong><\/h3>
![\"Illustration](\"https:\/\/c02.purpledshub.com\/uploads\/sites\/48\/2023\/02\/protoplanetary-disc-561ccd7.jpg\")
![\"Exoplanet](\"https:\/\/c02.purpledshub.com\/uploads\/sites\/48\/2020\/11\/Exoplanet-TOI-849b-6ccf50f.jpg\")