It's a space Slinky! Hubble shows spiral stream from black hole
The magnetic field around a nearby black hole in an elliptical galaxy appears to be shaped like a helix, according to a new assemblage of 13 years worth of observations from NASA’s Hubble Space Telescope.
Oh, nevermind: there’s a massive Slinky out in space, it’s 5,000 light-years long, and even the first guy to chronicle it nearly a century ago thought it was pretty darn cool.
But American astronomer Heber Curtis was wrong, in 1918, when he described "a curious straight ray" in the Virgo cluster of galaxies, as seen from a 36-inch refracting telescope at the Lick Observatory on Mt. Hamilton, near San Jose.
Hubble is a gussied-up 2.4-meter aperture telescope that doesn’t have to contend with Earth’s distorting atmosphere, and it has been capturing images of the M87 elliptical galaxy for 13 years.
Scientists from the Space Telescope Science Institute at Johns Hopkins University took months to analyze some 400 images taken by Hubble's wide-field camera. They assembled them into what amounts to a flip-book that shows the plasma stream ejected from a mind-achingly massive black hole some 50 million light years from Earth.
The super-heated gas stream is ejected from an accretion disk that orbits the black hole, a kind of waiting room just this side of the hole’s “event horizon.” Magnetic fields around the black hole entrain some of this ionized gas and eject it in a stream.
This simplified disk-and-jet notion has been analyzed and revamped into a sophisticated model of black holes, which lie at the center of galaxies. In January, a team from University of Texas predicted the field and jets were far more warped than previously thought, shaped both by gravity and the magnetic force created by the black hole’s spin.
The Hubble imagery is the first visual evidence that the gas stream traces a helix shape.
“Past observations of black hole jets couldn't distinguish between radial motion and side-to-side motion, so they didn't provide us with detailed information of the jet's behavior," Eileen T. Meyer of the Space Telescope Science Institute said in a written statement.
Meyer and her colleagues are fascinated with one particular clump of gas, dubbed Knot B, that appears to zig-zag. Other clumps seem to loop around an invisible object. Figuring out why will help add more precision and depth to the physical model of black holes.
"The jet structure is very clumpy. Is this a ballistic effect, like cannonballs fired sequentially from a cannon?" Meyer said. "Or, is there some particularly interesting physics going on, such as a shock that is magnetically driven?"
Meyer issues a note of caution, however. This is one set of imagery from one black hole, so it’s premature to assume all of them behave the same way.
Meyer's team, which published its findings Friday in the Astrophysical Journal Letters, will be taking a look at a few more Slinkies.
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