by Sarah Scoles



You've heard it a billion times: Don't go near the supermassive black hole. You'll shoot your eye out have your entire body stretched into spaghetti-thinness like Mike Teavee post-Television Room. And the same is true for molecular gas that would like to turn itself into stars.

Please don't forget the lessons I have taught you (Credit: Willy Wonka and the Chocolate Factory)Generally, if you are a cloud of molecular gas with ambition to become something more, you'd be well-advised to steer clear of shearing gravitational fields, such as those surrounding the most dense and extreme objects in the universe. Duh.

Or maybe not?

Observations from the new ALMA (Atacama Large Millimeter Array) telescope and CARMA (Combined Array for Research in Millimeter-wave Astronomy) show that fetal stars are gestating while snuggled up against Sagittarius A*, the black hole at the center of the Milky Way, which is a respectable 4 million times the mass of our Sun.

Scientists believed that stars could not form so close to such a massive object, as the effects of its gravity should prevent clouds of molecular gas -- the combined egg/sperm that leads to star formation -- from collapsing under their own gravity to form self-adhesive spheres of plasma.

The data

They believed it was impossible, at least, until they made a detailed map of the millimeter-wave photons coming from right around Sagittarius A*. In this map, they saw the characteristic signal of the compound SiO -- the aptly named silicon monoxide. And the SiO was clumped together in clumps. Eleven distinct and identifiable clumps. They look like and move like this:

Silicon monoxide clumps 1-11 are labeled in this map of the galactic center. Some of the clumps were even lucky enough to have their velocities measured, which is what the plots artistically surrounding the map show (Yusef-Zadeh, et al., 2013)Scientists see SiO where protostars -- objects that are not yet stars but are well on their way -- are shooting "I'm here!" jets into space. The protostars' energy excites the molecules and make them glow at specific wavelengths.

When the astronomers saw the SiO evidence that protostellar jets, and thus protostars, were forming so close to a supermassive black hole, they thought, "Huh?" and then decided to try to answer that question before publishing a paper and then publish a paper with the answer.

The conclusions

For any star -- whether it's next to a supermassive black hole or not -- to form, a cloud of molecular gas has to collapse and become denser and denser and hotter and hotter until it is dense and hot enough to hold itself together and begin nuclear fusion.

Near a supermassive black hole, astronomers thought the shearing gravitation -- tidal forces -- would prevent molecular gas from collapsing, because the gravitational effect of the black hole would always be more than the gravitational effects of molecules on each other.

But when actual empirical evidence contradicts what you made up in your head and on paper/hard drive, you have to adjust what's in your head, because those protostars are way too far away to be adjusted in a reasonable amount of time, and also you'll shoot your eye out.

In their paper (cited below), the researchers put forth two explanations:

Clump-clump collisions: Small clumps of gas were able to form, and then they accidentally hit each other and stuck together, and as more and more clumps stuck to them, they became massive enough for their internal gravity to take over. The problem with this idea is that it requires 60 individual initial clumps. UV compression: There's a significant UV radiation field around Sagittarius A*. The radiation causes pressure, which can cause compression, which can cause clumps of gas to collapse. The only problem with this explanation is that it takes 50,000 straight years of UV compression to give a clump the kind of mass and collapse that allow its own gravity to win.

So there are problems with both models. There are problems with most models.

Not that dapper Harry Stiles of One Direction is a model, but, you know, you get my point. My point being that Photoshop is amazing and scientific models, like models of teenage popstardom, are rarely perfect.But at least they came up with some ideas, and they (or other teams) can investigate clump-clump collision and UV compression in other situations and on hellasupercomputers to see if tweaking the terms leads to scientific expectations that better match scientific data.

While they do that, you can think about how

these protostars formed in the past 100,000-1,000,000 years. Whenever I hear numbers like that in astronomy, it makes me sit up and hit my head on something and listen. Because in terms of the universe, 100,000 years ago might as well be right now. I mean, dude, Homo sapiens existed then.

Whenever I hear numbers like that in astronomy, it makes me sit up and hit my head on something and listen. Because in terms of the universe, 100,000 years ago might as well be right now. I mean, dude, Homo sapiens existed then. they are big! One is more than 30 times more massive than the Sun is.

One is more than 30 times more massive than the Sun is. they are bright! One is more than 40,000 times more luminous than the Sun is.

One is more than 40,000 times more luminous than the Sun is. they are hanging out around a gigantic pit of superdense nothingness that has ripped spacetime. If only they could speak, they could tell us what this black hole has been doing while the modern hominid species has been flitting about planet Earth. But they can't. So we'll just have to keep doing science.

F. Yusef-Zadeh, M. Royster, M. Wardle, R. Arendt, H. Bushouse, D. C. Lis, M. W. Pound, D. A. Roberts, B. Whitney, & A. Wootten (2013). ALMA Observations of the Galactic Center: SiO Outflows and High Mass Star Formation near Sgr A* The Astrophysical Journal Letters arXiv: 1303.3403v1