Cosmic Crash at Milky Way Core?

This artist’s conception shows a supermassive black hole, with millions of times the mass of our sun, buried at the heart of our Milky Way galaxy. Credit: NASA

Astronomers around the world are on a cosmic stakeout, closely watching the supermassive black holelurking at the center of our Milky Way Galaxythat is about to gobble up an incoming gas cloud.

First spotted back in 2011, the blob of gas dubbed G2 appears poised for a suicidal plunge into the maw of the supermassive black hole called Sagittarius A* (Sgr A*). A monster of a black hole, it weighs in at about four million times the mass of our sun. Although it is a gas cloud, G2 hefts about three times the mass of Earth.

Currently G2’s distance from the black hole is equal to about 200 times the distance that Earth is from the sun, and it is spiraling in fast. It is expected to make its closest approach to the cosmic predator in the next two to three months.

When that happens, astronomers eagerly anticipate capturing their first ever glimpse of how a supermassive black hole gobbles up a cosmic snack. Astrophysicists hope to better understand not only how black holes grow and evolve, but also how matter reacts to extreme gravitational fields.

“Here we have an experiment where we get a chance to see how gas falls into a black hole,” said Leo Meyer, an astronomer at the University of California, Los Angeles, who spoke at a briefing at the meeting of the American Astronomical Society in Washington, D.C.

“These are fundamental physical processes that are not well understood, and we have a unique opportunity here to learn more about them.”

Located some 26,000 light-years from Earth, the Milky Way’s central black hole is hidden from clear view by dust and gas. However, astronomers can gaze behind the veil with infrared and x-ray telescopes. So, while backyard astronomers won’t be able to catch any of the possible brightening expected to occur as the blob of gas falls in toward the black hole, professional stargazers have both ground- and space-based telescopes trained on the soon-to-be-snacking beast.

Milky Way's galactic center as imaged by the Swift X-ray Telescope. This image is a montage of all data obtained in the monitoring program from 2006-2013. Credit: NASA/Swift/N. Degenaar (Univ. of Michigan)
Milky Way’s galactic center as imaged by the Swift x-ray telescope. This image is a montage of all data obtained by the monitoring program from 2006 to 2013. Credit: NASA/Swift/N. Degenaar (University of Michigan)

NASA’s orbiting Swift X-ray telescope has monitored the impending collision on a daily basis, for example, and astronomers are expecting to see a sudden brightening when it occurs.

The big question is whether there will be any fireworks when the blob meets its demise. That’s because astronomers aren’t sure if the blog is all gas, in which case it would glow bright, or is a star enshrouded in a gas cloud, in which case it would be quite a weak show.

“I would be delighted if Sagittarius A* suddenly became 10,000 times brighter. However, it is possible that it will not react much—like a horse that won’t drink when led to water,” Jon Miller, an astronomer at the University of Michigan, said in a press statement.

“If Sagittarius A* consumes some of G2, we can learn about black holes accreting at low levels—sneaking midnight snacks.”

Fireworks or fizzle, at this point astronomers have a front-row seat to see whatever will happen. Hopes are that within the next month or so, new observations will help astronomers narrow down the potential end game for G2.

“Will there be fireworks? The clear answer has to be: maybe,” says Meyer. “But this is a unique opportunity to learn something new in astrophysics.”

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Changing Planet

Meet the Author
Andrew Fazekas, aka The Night Sky Guy, is a science writer, broadcaster, and lecturer who loves to share his passion for the wonders of the universe through all media. He is a regular contributor to National Geographic News and is the national cosmic correspondent for Canada’s Weather Network TV channel, space columnist for CBC Radio network, and a consultant for the Canadian Space Agency. As a member of the Royal Astronomical Society of Canada, Andrew has been observing the heavens from Montreal for over a quarter century and has never met a clear night sky he didn’t like.