Radio Jets from the Milky Way’s Black Hole Could be Pointing Right at Earth

By Amber Jorgenson | January 21, 2019 5:00 pm
Sagittarius A

This image shows different views of Sagittarius A. The top two images are simulations of its scattered and unscattered light, while the bottom two show real images taken by a telescope array. (Credit: S. Issaoun, M. Mościbrodzka, Radboud University/ M. D. Johnson, CfA)

We’ve spent decades trying to decode our supermassive black hole, but crucial clues could’ve been in front of us all along.

Using an array of 13 radio telescopes, astronomers from the Max Planck Institute were able to home in on Sagittarius A* (pronounced A-star), the region that houses the Milky Way’s supermassive black hole. And once they’d cleared out the noise of scattered light that surrounds it, they found that the powerful radio emission that blasts from the black hole is coming from just a tiny area, which could be aimed right at Earth. The research was published Monday in The Astrophysical Journal and, if confirmed, could shed new light on Sgr A* and its radio jets.

Black Hole Blasts

Supermassive black holes are pretty common in our universe, sitting at the hearts of most large galaxies. Their strong gravitational fields allow them to suck in and obliterate objects that get too close to them. And while they absorb most of this celestial matter, a small fraction escapes the black hole and blasts back out into space. These emissions, known as jets, are carry abundant radio waves and travel at nearly the speed of light.

And even though we can detect some of Sgr A*’s radio emissions from Earth, studying it is easier said than done. There’s a cloud of hot gas that sits between Earth and Sgr A*. And this interstellar gas scatters the jets’ light, making it hard to pinpoint radio waves from the black hole.

Glaring Beam

But recently, a team of researchers were able to isolate this radio emission using very long baseline interferometry — a technique that combines multiple telescopes to create a massive, extremely powerful one. Using 13 radio telescopes from around the world, they removed the effects of the hot gas to get a sharper image of the jets’ emission than ever before.

They found that it’s coming from a symmetrical source, which lines up well with the “jet” theory, since they blast from black holes in opposite directions. They also discovered that the emission is much narrower than they thought. So narrow, in fact, that it’s coming at us from just one 300 millionth of a degree — suggesting that it’s aimed almost directly at Earth.

By luck of the draw, this means that we might have a direct view into one of our black hole’s defining characteristics. And don’t worry about the jet actually blasting us, because as far as we know, being in its line of sight doesn’t put us in any danger. If anything, it could allow us to study the jet in impeccable detail and shed light on Sgr A*’s mysterious nature.

Editor’s Note: An earlier version of this story incorrectly stated why light from Sagittarius A* was scattered before it reached Earth. It is scattered by interstellar gas.

CATEGORIZED UNDER: Space & Physics, top posts
MORE ABOUT: cosmology
  • B.A. Grissom

    The Damn ad covers the whole Damn article so I can’t read the Damn thing! I can only see the bottom part here.

  • B.A. Grissom

    Finally got the ad off. I think they’re not being so truthful about it being safe in the jet region because when it munches on something like a good sized star those jets are going to spew out some MAJOR radioactivity. Black holes are known for producing Gamma Particles which are very nasty to anything living. I’ve seen photos of those jets on active black holes stretching for MANY light years.

    • Richard

      The center of the Milky Way is 100,000 light years away so When it munches on a star it would take at least 100,000 years to reach us. The problem is the light from the star being munched on would reach us at the same time so I guess we wouldn’t know till it hit us. In other words let’s hope it the Milky Way didn’t munch on a star 99,999.99 years ago.

      • tstucker

        No, the galaxie is 100,00 light years across Sag A is only 25,000 light years from us.

    • Muhammad Abbass

      “Black Holes” are not even “known” to exist, they are a theory created to explain the failure of another theory and what is being observed may not be what we have hypothesised.

      • OWilson

        A mathematical postulate, along with Dark Matter, Dark Enegy and Big Bangs.

        Derived by humans, from the shadows we, the latest in a line of great apes, see on the walls of the cave, that humans are forever bound to! :)

        Mathematics is only an elegent language of description.

        Useful, but limited, and breaks down at a certain level.

    • davidsstrail

      After 25,000 light years of travel any gamma radiation is going to slam into the bubble of hot gas around the solar system and then Earth’s atmosphere. We’re completely safe.

  • Robo

    What kind of Nerd Speak is all this stuff in here?

  • Muhammad Abbass

    OK. Do the maths. The chance of this being coincidental is lower than that of life arising spontaneously.

  • Erik Bosma

    I knew this was a bad neighbourhood.

  • kfmn

    This doesn’t mean that the jet’s angular width is 1/300-millionth of a deg or that the jet’s axis is aimed to us with this precision. Actually, they restricted the viewing angle of jet-models to be <20 deg.

  • kfmn

    And, BTW, the angular diameter of the source as seen by VLBI is 120e-6 arc sec, which is 1/30-millionth, not 1/300-millionth of a degree. You have lost an order of mag.


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