First Look at a Black Hole’s Feast

A true heart of darkness lies at the center of our galaxy: Sagittarius A* (pronounced “A-star”) is a supermassive black hole with the mass of four million suns packed into an area only as wide as the distance between Earth and the Sun. Itself invisible to direct observation, Sgr A* makes its presence known through its effect on nearby stars, sending them hurtling through space in complex orbits at speeds upwards of 600 miles a second. And it emits a dull but steady glow in x-ray radiation, the last cries of its most recent meals. Gas, dust, stars… solar systems… anything in Sgr A*’s vicinity will be drawn inexorably towards it, getting stretched, shredded and ultimately absorbed (for lack of a better term) by the dark behemoth, just adding to its mass and further strengthening its gravitational pull.

Now, for the first time, a team of researchers led by Reinhard Genzel from the Max-Planck Institute for Extraterrestrial Physics in Germany will have a chance to watch a supermassive black hole’s repast take place.

A cloud of cool ionized gas has been spotted rapidly approaching the accretion disk of Sgr A*, picked out within several years’ worth of observations made with the European Southern Observatory’s Very Large Telescope array located in the high, dry mountains of Chile’s Atacama Desert.

These images taken over the last decade using the NACO instrument on ESO’s Very Large Telescope show the motion of a cloud of gas that is falling towards the supermassive black hole at the center of the Milky Way. (ESO/MPE)

The cloud, estimated to be three times the mass of Earth, has already begun to break apart due to the powerful tidal forces created by Sgr A*’s gravity. These will only intensify as the cloud moves closer to the black hole, eventually ripping it apart entirely and creating shockwaves of energy and radiation flares.

Of course, this is exactly what researchers are hoping for.

This will be the first time that the feeding process of a supermassive black hole will be witnessed from start to finish. There is still much to be learned about the enigmatic curiosities that reside at the centers of many galaxies, and witnessing Sgr A*’s latest meal will help increase our working knowledge of SMBHs, and black holes in general.

“The idea of an astronaut close to a black hole being stretched out to resemble spaghetti is familiar from science fiction. But we can now see this happening for real to the newly discovered cloud. It is not going to survive the experience,” said Stefan Gillessen, the lead author of the paper.

“It’s very exciting,” he added.

It’s estimated that the entire process could take up to a decade to unfold, with the gas cloud encountering Sgr A*’s event horizon in 2013.

The video above takes us on an amazing flight into the heart of the Milky Way beginning at our planet’s location within an outlying arm and zooming all the way to where Sgr A* resides. Inside the galactic hub we can see massive stars orbiting an invisible yet undeniably massive point, and the hazy cloud of gas that’s destined for dinner is circled in white, showing its locations from 2002 until now.

It’s only a matter of time before it succumbs to the black hole’s embrace. And when it does, our telescopes will be watching.

The next two years will be very interesting and should provide us with extremely valuable information on the behaviour of matter around such remarkable massive objects.”

– Reinhard Genzel, team leader

The team’s paper was published today in this week’s issue of the journal Nature. Read more on the ESO press release here.

Video credit: ESO/MPE/Nick Risinger ( Emerson/Digitized Sky Survey 2 Music: xxx

15 Replies to “First Look at a Black Hole’s Feast”

  1. arXiv

    And here is the paper from the preprint server.

    Yeah, this is exciting news! In 2013 all available telescopes observing any part of the electromagnetic spectrum will be watching. Tons of data waiting to be examined. A lot to learn! Great. Let’s have some fun. 🙂

  2. The black hole Sgr A* is about 6 million kilometers in radius. So it is only several times the radius of the sun.


      1. The Schwarzschild radius is r = 2GM/c^2. To compute the Schwarzschild radius for a solar mass we use

        G = 6.67×10{-11}m^3/kg-s^2
        M = 1.99×10^{30}kg
        c = 3×10^8m/s

        2GM/c^2 = 2×6.67×10^{-11}x1.99×10^{30}/9×10^{16}m

        = 2.94×10^3m, or 2.94km. This is about double what I have logged away in memory. However, for a black hole with 4 million solar masses then M — > 4×10^6 times M = 1.8×10^7km or 11.8 million kilometers.

        By way of comparison the orbit of Earth is about 1.5×10^8km and Mercury is about 5.8×10^7km. The solar radius is about 7×10^5km. I think the radius I had memorized was in miles for 1km =~ .6 miles and so 2.94km is 1.76 miles. This is changed some if the black hole is rotating, where the Schwarzschild radius at the equator actually decreases. However, the static limit which defines the frame dragging ergosphere is equal to the Schwarzschild radius.


      2. You can take the radius r = 3km (approximate) for our sun and easily see that for some of these SMBH behemoths that are 10 billion solar masses, such as in M87, that their horizon scales to 30 billion km or nearly 10 times the radius of the solar system. If you use the formula for the lifetime of a black hole due to Hawking quantum radiance it will exist for 10^{110} years. Curiously though, I find black holes which are a billion billion time smaller than a proton to be the most interesting. There the black hole is a quantum field and the foundations of physics are most evident.


    1. I have been investigating this particular point for a while, and have found half a dozen different answers as to the size of Sgr A*, ranging from the distance from the Sun to Mercury, to within Pluto’s orbit, to 1 to 2 AUs in diameter. I’m not sure if it has been nailed down yet, although to get the density needed to cause all this ruckus it would definitely have to be rather compact.

    1. The excitement doesn’t stop in a very long time if you go by relativity, where the event will be observed by myriad observers as the light spreads out into the universe.

      However if you pick one reference frame you can only count the event once. Astronomers have wisely adopted the local relativistic frame.

      I think they had to, or the cosmologists wouldn’t have played nice. =D

    — James Ph. Kotsybar

    Mysteriously cloaked, obscure despite
    Interior illuminating glare,
    Long veiled by your own dusty lace-curtain,
    Kept hidden, locked within your gallery,
    You work continuously through the night.

    We speculate about what goes on there
    And, though still not absolutely certain,
    Your close companions that we’ve seen scurry

    Give us reason for darkest suspicion
    About the nature of your deepest part,
    Long overlooked, seething with sedition,
    And we believe we’ve glimpsed rapacious art.
    X-rays show what other light can’t impart:
    Young stars conceal a black hole at your heart.

  4. It is astonishing to me that such dramatic motion, from such distance, can be visible to us, as seen in the clip above, even though of time-lapse sequence. And in viewing it, there is a sense of awe in contemplating what spectacles of mass, energy and force may actually be taking place there, behind the dusty stellar veils (in focused lens of crystal clarity of the minds eye), through majestic movements of time, and overwhelming scales of space, in the fantastic environment surrounding these mighty dark-Engines cloaked in intriguing galactic mystery.

    My compliments on the writing of this piece: It was a pleasure to read.

  5. Nice article!

    ultimately absorbed (for lack of a better term)

    How about “black holed”?

    OB nitpick:

    with the gas cloud encountering Sgr A*’s event horizon in 2013.

    Actually most of the cloud will survive the event (see the simulations in Spectrum7Prism link) and will not eventually encounter the horizon.

    The article made a good job on circling the “swallowed whole” metaphor though.

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