Tonight's Sky
Sun
Sun
Moon
Moon
Mercury
Mercury
Venus
Venus
Mars
Mars
Jupiter
Jupiter
Saturn
Saturn

Tonight's Sky — Change location

OR

Searching...

Tonight's Sky — Select location

Tonight's Sky — Enter coordinates

° '
° '

Chandra helps confirm evidence of jet in Milky Way’s black hole

Astronomers have finally identified a jet of high-energy particles in Sagittarius A*.
RELATED TOPICS: BLACK HOLES | MILKY WAY
Sagittarius A*, the supermassive black hole at the center of the Milky Way.
Composite image of Sagittarius A* (Sgr A*), the supermassive black hole at the center of the Milky Way.
X-ray: NASA/CXC/UCLA/Z. Li et al; Radio: NRAO/VLA
Astronomers have long sought strong evidence that Sagittarius A* (Sgr A*), the supermassive black hole at the center of the Milky Way, is producing a jet of high-energy particles. Finally, they have found it in new results from NASA’s Chandra X-ray Observatory and the National Science Foundation’s Very Large Array (VLA) radio telescope.

Previous studies, using a variety of telescopes, suggested there was a jet, but these reports, including the orientation of the suspected jets, often contradicted each other and were not considered definitive.

“For decades, astronomers have looked for a jet associated with the Milky Way’s black hole. Our new observations make the strongest case yet for such a jet,” said Zhiyuan Li of Nanjing University in China.

Scientists have found jets of high-energy particles throughout the universe on large and small scales. They are produced by young stars and by black holes a thousand times larger than the Milky Way’s black hole. They play important roles in transporting energy away from the central object and, on a galactic scale, in regulating the rate of formation of new stars.

“We were very eager to find a jet from Sgr A* because it tells us the direction of the black hole’s spin axis. This gives us important clues about the growth history of the black hole,” said Mark Morris from the University of California, Los Angeles.

The study shows that the spin axis of Sgr A* is pointing in one direction, parallel to the rotation axis of the Milky Way, which indicates to astronomers that gas and dust have migrated steadily into Sgr A* over the past 10 billion years. If the Milky Way had collided with large galaxies in the recent past and their central black holes had merged with Sgr A*, the jet could point in any direction.

The jet appears to be running into gas near Sgr A*, producing X-rays detected by Chandra and radio emission observed by the VLA. The two key pieces of evidence for the jet are a straight line of X-ray-emitting gas that points toward Sgr A* and a shock front — similar to a sonic boom — seen in radio data, where the jet appears to be striking the gas. Additionally, the energy signature, or spectrum, in X-rays of Sgr A* resembles that of jets coming from supermassive black holes in other galaxies.

Scientists think jets are produced when some material falling toward the black hole is redirected outward. Since Sgr A* is presently known to be consuming very little material, it is not surprising that the jet appears weak. A jet in the opposite direction is not visible, possibly because of gas or dust blocking the line of sight from Earth or a lack of material to fuel the jet.

The region around Sgr A* is faint, which means the black hole has been quiet in the past few hundred years. However, a separate Chandra study announced last month shows that it was at least a million times brighter before then.

“We know this giant black hole has been much more active at consuming material in the past,” said Frederick K. Baganoff from the Massachusetts Institute of Technology in Cambridge. “When it stirs again, the jet may brighten dramatically.”

Astronomers have suggested the giant bubbles of high-energy particles extending out from the Milky Way and detected by NASA’s Fermi Gamma Ray Telescope in 2008 are caused by jets from Sgr A* that are aligned with the rotation axis of the galaxy. The latest results from Chandra support this explanation.

The supermassive black hole at the center of the Milky Way is about 4 million times more massive than our Sun and lies about 26,000 light-years from Earth. The Chandra observations in this study were taken between September 1999 and March 2011, with a total exposure of about 17 days.
0

JOIN THE DISCUSSION

Read and share your comments on this article
Comment on this article
Want to leave a comment?
Only registered members of Astronomy.com are allowed to comment on this article. Registration is FREE and only takes a couple minutes.

Login or Register now.
0 comments
ADVERTISEMENT

FREE EMAIL NEWSLETTER

Receive news, sky-event information, observing tips, and more from Astronomy's weekly email newsletter.

ADVERTISEMENT
ADVERTISEMENT
BoxProductcovernov

Click here to receive a FREE e-Guide exclusively from Astronomy magazine.

Find us on Facebook

Loading...