Our Sun and other stars form when a dense clump of interstellar gas and dust collapses under its own gravitational pull. When a star is born in the center of such a cloud, the remaining material forms a rotating disk around it that fuels stellar growth and often gives rise to planets.
Until then, newborn stars with this type of disk had only been observed by astronomers in our galaxy, the Milky Way.
This changed on the 29th, when researchers said they spotted such a disk around a star larger and more luminous than the Sun, located in one of our closest neighboring galaxies, the Large Magellanic Cloud.
The star, growing and accumulating material from the disk, is around 10 to 20 times more massive than the Sun and is perhaps 10,000 times more luminous.
As material is pulled by gravity toward a forming star, it flattens into a rotating disk. The newly observed disk has a diameter equivalent to 12,000 times the distance between Earth and the Sun, or approximately ten times larger than that which surrounded the Sun when it formed 4.5 billion years ago.
The star, which is also releasing a large jet of material into space, is about 160,000 light years from Earth — a light year is the distance that light travels in one year, 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 that many stars like this are being formed in the Large Magellanic Cloud and other galaxies, we have never observed a circumstellar accretion disk outside the Milky Way, largely due to a lack of technology,” she added. “Observing these disks in other galaxies is very important because it tells us how stars form in environments other than the Milky Way.”
The detection was made using the Alma telescope (Atacama Large Millimeter/submillimeter) in the Atacama Desert in Chile. Until now, circumstellar disks had only been detected about 6,500 light-years from Earth.
The Large Magellanic Cloud is considered a satellite galaxy of the Milky Way, as is the Small Magellanic Cloud. Both are smaller than our galaxy and have different galactic conditions. The Large Magellanic Cloud has less dust than the Milky Way and a lower content of what astronomers call metallic elements — those that are not hydrogen and helium.
The researchers had an unobstructed view of the star.
“The star is visible at optical wavelengths, while all known stars in the Milky Way that are similar to it — in terms of stellar mass and with an accretion disk — are hidden from optical telescopes because they are still heavily enveloped by gas and dust from which they are forming,” said McLeod.
“We suggest that the star’s optical visibility is due to the different properties of the galactic environment the star is in, 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 intrigued astronomers for decades, and so building a picture of how it happens under different physical conditions is an important and super exciting step,” said astronomer and study co-author Jonathan Henshaw of the University of Liverpool John Moores.
The disk appears to be quite stable, not fragmenting as could happen with such structures.
“We don’t know whether the disk will form planets, but it’s unlikely, given that they would have to form in the harsh environment of a star with strong radiation,” McLeod said.
The astronomer expressed hope of detecting other circumstellar disks in the Large Magellanic Cloud and perhaps the even more distant Small Magellanic Cloud. “With each of them, we will be able to learn more about star formation in different galaxies and conditions.”