WASHINGTON – Our sun and other stars formed when dense clumps of interstellar gas and dust collapsed under their own gravitational pull. Once a star is born at the center of the cloud, the remaining material forms a rotating disk around it that supports the star’s growth and often gives birth to planets.
These newborn stars with stellar disks were observed by astronomers only in our Milky Way galaxy – until now. But researchers said Wednesday that they have seen such a disk around a star larger and brighter than the sun in one of our closest neighboring galaxies, the Large Magellanic Cloud.
The star, which is growing and gathering material from the surrounding disk, is about 10 to 20 times more massive than the sun and perhaps 10,000 times brighter.
As material is pulled by gravity towards a forming star, it flattens into a rotating disk. The newly observed disk has a diameter about 12,000 times the distance from Earth to the Sun, or about 10 times larger than the disk that circled the Sun when it formed about 4.5 billion years ago.
The star, which also releases large jets of material into space, is about 160,000 light years from Earth. A light year is the distance light travels in a year, 5.9 trillion miles (9.5 trillion km).
“This is very exciting,” said astronomer Anna McLeod of Durham University in England, lead author of the study published in the journal Nature.
“While we know many stars like this form in the Large Magellanic Cloud and other galaxies, we have never observed circumstellar accretion disks outside the Milky Way, largely due to a lack of technology. Observing these disks in other galaxies is very important. is important because it tells us about how stars form in different environments than the Milky Way,” added McLeod.
The detection was made using the Atacama Large Millimeter/submillimeter Array (ALMA) telescope in the Atacama Desert, Chile. Until now, circumstellar disks have only been detected within about 6,500 light years from Earth.
The Large Magellanic Cloud is considered a satellite galaxy of the vast Milky Way, as is another galaxy called the Small Magellanic Cloud. Both are smaller than our galaxy and offer different galactic conditions. The Large Magellanic Cloud has less dust than the Milky Way and a smaller content of what astronomers call metallic elements – other than hydrogen and helium.
The researchers enjoyed an unobstructed view of the stars.
“This star is visible at optical wavelengths, whereas all stars like this in the Milky Way – in terms of stellar mass and having an accretion disk – are hidden from optical telescopes because they are still heavily covered by gas. and the dust that is the source of its formation,” said McLeod.
“We suggest that the optically visible stars are caused by differences in the nature of the galactic environment in which the stars reside compared to the Milky Way.”
Massive stars form more quickly and have shorter lives than less massive stars like the Sun.
“The formation of high-mass stars has puzzled astronomers for decades, so building a picture of how this occurs under different physical conditions is an important and very exciting step,” said astronomer and study co-author Jonathan Henshaw of Liverpool John Moores University.
The disk appears to be quite stable, not fragmented as can occur in such structures.
“We don’t know whether the disk will ever form a planet, but this is unlikely given that the disk would have to form in a hostile environment such as a star with strong radiation,” McLeod said.
McLeod expressed hope of detecting other circumstellar disks in the Large Magellanic Cloud and perhaps in the more distant Small Magellanic Cloud.
“With each galaxy, we will be able to learn more about star formation in different galaxies and conditions,” McLeod said.
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