ALMA finds newborn stars close to Milky Way’s black hole
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If you want to build a house of cards, you’d better not try it outside during a hurricane. Likewise, you would expect that it is hard for new stars to form in a violent environment. Still, ALMA has found eleven small baby stars extremely close to the huge black hole in the core of our Milky Way.
A star is born from a cool cloud of gas and dust. Because of its own gravity, the cloud slowly contracts. Eventually, a new star forms at the cloud’s center. But you don’t expect that to happen if the cloud is torn apart first.
The black hole at the core of our Milky Way galaxy is very massive. It weighs four million times as much as our Sun. As a result, it has tremendously strong gravity. The resulting tidal forces distort nearby gas clouds and rips them apart. Moreover, any material that falls into the black hole becomes very hot. It starts to emit ultraviolet light and X-rays. This energetic radiation will also try to disrupt nearby clouds of gas and dust.
A few years ago, though, astronomers found a number of massive stars close to the black hole that are just 6 million years old – pretty young for a star. So maybe the most massive clouds of gas and dust are able to withstand the violence of the black hole.
Now, ALMA has revealed an even bigger surprise. Within three light-years distance from the supermassive black hole, ALMA has found eleven low-mass baby stars. They are extremely young: a mere 6,000 years. Such low-mass stars form from smaller clumps of gas and dust. But it’s hard to understand how a small cloud can survive so close to the black hole.
Somehow, the original low-mass clouds must have started to contract and collapse, despite the black hole’s tidal forces and fierce radiation. Maybe the clouds became compressed by turbulence, or by fast-moving gas clouds that slammed into them.
It’s not yet known if the newborn low-mass stars will also be accompanied by planets. If so, however, such planets will not be very hospitable to life, because of the deadly radiation from the black hole. Luckily, our own Earth is at a safe distance: some 27,000 light-years!
The black hole at the core of our Milky Way is known as Sagittarius A*. It weighs in at four million time the mass of the Sun. It is located at a distance of 27,000 light-years, in the crowded central regions of our galaxy. Optical telescopes cannot study this region, because it is obscured by dark, absorbing clouds of dust. But at millimeter and submillimeter wavelengths, ALMA is able to peer through the dust clouds. Thanks to its high sensitivity and sharp vision, ALMA has now detected eleven low-mass protostars. Newborn stars blow away jets of gas in two opposite directions, and ALMA has detected the millimeter radiation from carbon monoxide molecules in those jets.
The discovery of the eleven low-mass protostars was done by an American-Australian team of astronomers. The leader of the team was Farhad Yusef-Zadeh. Farhad is a professor of astronomy at Northwestern University in Evanston, Illinois. For over thirty years, he has been studying the supermassive black hole in the center of our Milky Way galaxy. The new discovery has been published in The Astrophysical Journal Letters, a professional astronomy magazine.Check this in ALMA site