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Astronomers probing how black holes shape galaxy evolution

Astronomers have assembled photos to make a series of time-lapse movies showing a jet of superheated gas being ejected from a supermassive black hole.

Washington: Astronomers have assembled photos, collected from more than 13 years of observations from NASA`s Hubble Space Telescope, to make a series of time-lapse movies showing a jet of superheated gas being ejected from a supermassive black hole.

Eileen T. Meyer of the Space Telescope Science Institute in Baltimore, Maryland, said that central, supermassive black holes are a key component in all big galaxies.

She said that most of these black holes are believed to have gone through an active phase, and black-hole powered jets from this active phase play a key role in the evolution of galaxies.

Meyer asserted that by studying the details of this process in the nearest galaxy with an optical jet, they are hoping to learn more about galaxy formation and black hole physics in general.

The research team spent eight months analyzing 400 observations from Hubble`s Wide Field Planetary Camera 2 and Advanced Camera for Surveys. The observations, taken from 1995 to 2008, are of a black hole sitting in the center of a giant galaxy dubbed M87.

Meyer found evidence that suggests the jet`s spiral motion is created by a helix-shaped magnetic field surrounding the black hole. In the outer part of the M87 jet, for example, one bright gas clump, called knot B, appears to zigzag, as if it were moving along a spiral path. Several other gas clumps along the jet also appear to loop around an invisible structure.

M87 resides at the center of the neighboring Virgo cluster of roughly 2,000 galaxies, located 50 million light years away. The galaxy`s monster black hole is several billion times more massive than our sun.

The Hubble data also provided information on why the M87 jet is composed of a long string of gas blobs, which appear to brighten and dim over time.

`The jet structure is very clumpy. Is this a ballistic effect, like cannonballs fired sequentially from a cannon?` Meyer asked, `or, are there some particularly interesting physics going on, such as a shock that is magnetically driven?`

Meyer`s team found evidence for both scenarios. `We found things that move quickly,` Meyer said. `We found things that move slowly. And, we found things that are stationary. This study shows us that the clumps are very dynamic sources.`

The study has been published online in The Astrophysical Journal Letters.


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