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Sagittarius A*: NASA's Chandra Finds Milky Way's Black Hole May be Grazing on Asteroids
Sagittarius A*

  • A new study suggests mysterious X-ray flares caught by Chandra may be asteroids falling into the Milky Way's giant black hole.

  • These flares have been seen during periodic observations over several years and happen about once every day.

  • If confirmed, this result may mean that there is a cloud around the black hole containing hundreds of trillions of asteroids and comets.

This image from NASA's Chandra X-ray Observatory shows the center of our Galaxy, with a supermassive black hole known as Sagittarius A* (Sgr A* for short) in the center. Using intermittent observations over several years, Chandra has detected X-ray flares about once a day from Sgr A*. The flares have also been seen in infrared data from ESO's Very Large Telescope in Chile.

A new study provides a possible explanation for the mysterious flares. The suggestion is that there is a cloud around Sgr A* containing hundreds of trillions of asteroids and comets, which have been stripped from their parent stars. The panel on the left is an image containing nearly a million seconds of Chandra observing of the region around the black hole, with red representing low-energy X-rays, green as medium-energy X-rays, and blue being the highest.

An asteroid that undergoes a close encounter with another object, such as a star or planet, can be thrown into an orbit headed towards Sgr A*, as seen in a series of artist's illustrations beginning with the top-right panel. If the asteroid passes within about 100 million miles of the black hole, roughly the distance between the Earth and the Sun, it would be torn into pieces by the tidal forces from the black hole (middle-right panel).

These fragments would then be vaporized by friction as they pass through the hot, thin gas flowing onto Sgr A*, similar to a meteor heating up and glowing as it falls through Earth's atmosphere. A flare is produced (bottom-right panel) and eventually the remains of the asteroid are swallowed by the black hole.

Another solar system analogy for this type of event has recently been reported. About once every three days a comet is destroyed when it flies into the hot atmosphere of the Sun. So, despite the significant differences in the two environments, the destruction rate of comets and asteroids by the Sun and Sgr A* may be similar.

Very long observations of Sgr A* will be made with Chandra later in 2012 that will give valuable new information about the frequency and brightness of flares and should help to test the model proposed here to explain them. This work has the potential to understand the ability of asteroids and planets to form in the harsh environment of Sgr A*.

Fast Facts for Sagittarius A*:
Credit  X-ray: NASA/CXC/MIT/F. Baganoff et al.; Illustrations: NASA/CXC/M.Weiss
Release Date  February 8, 2012
Scale  Image is 15 arcmin across (20 light years)
Category  Black Holes, Milky Way Galaxy
Coordinates (J2000)  RA 17h 45m 40s | Dec -29° 00´ 28.00"
Constellation  Sagittarius
Observation Date  43 pointings from 21 Sep 1999 to 18 May 2009
Observation Time  278 hours (11 days 14 hours)
Obs. ID  242, 1561, 2943, 2951-2954, 3392, 3393, 3549, 3663, 3665, 4683, 4684, 5360, 5950-5954, 6113, 6363, 6639, 6640-6646, 7554-7759, 9169-9174, 10556
Instrument  ACIS
Also Known As Galactic Center
References K. Zubovas et al., 2012, MNRAS, in press; arXiv:1110.6872
Distance Estimate  About 26,000 light years
distance arrow
Visitor Comments (12)

(part 2) My impression: The region around Sagittarius A (further refered as "SA" is milky way`s central black hole) flashing up again and again (by matter falling into it). Other- obviously large- stars AROUND have strong activity fluctuations under its influence. Esp. the star right above SA is already loosing much of izs mass,and a long tail of gases leads towards SA In one moment this star seems even split into two/ into half and reunites again after. . At the end of the clip just another star suddenly appears resp shines up right in the image...

Posted by helmut on Thursday, 10.11.12 @ 16:45pm

I just discovered this side. Great work!! Especially that video here made by Chandra form the galactic center ( Sagit. A). What it shows says much. But- it would be kind, if any of you NASA expert would make a comment on it what he/she believes this video actually shows.! read ff2

Posted by helmut on Thursday, 10.11.12 @ 16:44pm

Dear Massimo Calvani,
Thanks very much for your comment. I am aware that the work of Kostic et al. is referenced by Zubovas et al. I will email you with some suggestions for further recognition of the work by Kostic et al.
-P.Edmonds, CXC

Posted by P. Edmonds on Tuesday, 02.14.12 @ 10:11am

Dear kiyohisa,
There will be material - mainly hot gas - around the outside of the event horizon. This will eventually pass over the event horizon, never to be seen again, unless some process like a wind or a jet ejects it. I do not believe that secret passages (like wormholes) are generally being invoked by researchers to understand material falling onto black holes.
-P.Edmonds, CXC

Posted by P. Edmonds on Tuesday, 02.14.12 @ 10:07am

Dear Mike Delaney,
Thankfully, the Earth is not being drawn towards Sgr A*. There are *much* stronger sources of gravity, such as the Sun and the Moon.
-P.Edmonds, CXC

Posted by P. Edmonds on Tuesday, 02.14.12 @ 10:05am

Dear Mike Delaney,
It's believed that black holes can radiate in a process called Hawking radiation, although this is believed to take an extremely long time for astrophysical black holes.
-P.Edmonds, CXC

Posted by P. Edmonds on Tuesday, 02.14.12 @ 10:02am

Dear Wilhelm Koen,
Good comment - the authors estimate that about 10% of the rest mass of the asteroid will be converted into energy, although all of this might not go into X-rays.
-P.Edmonds, CXC

Posted by P. Edmonds on Tuesday, 02.14.12 @ 09:57am


Is this E(X-Ray)=m(Asteroid)xc²?

Posted by Wilhelm Koen on Saturday, 02.11.12 @ 23:32pm

All is not lost. Even if we have not observed any, Black holes can dissipate on their own.
Some tornadoes don't reach ground, they just disappear on their own into the atmosphere.

Posted by Mike Delaney on Friday, 02.10.12 @ 21:59pm

How quickly are we (earth) being drawn toward sag A? Can we estimate how long it will take us to be drawn into it?

Posted by Mike Delaney on Friday, 02.10.12 @ 19:17pm

Will the circumference of the black hole have "the dust which is not absorbed in the center" around?
Or is there "a secret passage" in a law of the physics?
Still mystery many "black holes"
NASA expects discovery to surprise people of the world from now on.

Posted by kiyohisa tanada on Friday, 02.10.12 @ 06:45am

This scenario was discussed already by Dr. Uros Kostic (Faculty of Mathematics and Physics, University of Ljubljana,)in his PhD Thesis, and published in A&A in 2008-2009.
As far as I know, this is the FIRST suggestion that SgrA* flares might be due to accretion and tidal disruption of asteroids and comets.

Posted by Massimo Calvani on Friday, 02.10.12 @ 05:36am

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