GALACTIC BLACK HOLE
Image: NASA, /CXC, MIT, F.K.Baganoff et al
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Researchers are closing in on ironclad evidence for the black hole believed to lurk at the center of our Milky Way galaxy.
Astronomers used a "virtual" telescope spanning more than 2,800 miles (4,500 km) to home in on Sagittarius A* ("A-star"), the light source believed to mark the location of a black hole four million times as massive as the sun.
They were able to resolve Sagittarius A* to within 37 microarcseconds, the width of a baseball on the moon as seen from Earth. Based on the size of the light-emitting region, they believe it is offset from the exact location of the black hole, which pulls gas and dust into a disk swirling around it that gives off light.
Instead, they speculate that Sagittarius A* is either high-speed gas on one side of the rotating accretion disk or a jet of matter being ejected from around the black hole.
The case for a black hole was already "pretty solid," says study author Shepherd Doeleman, an astrophysicist at the Massachusetts Institute of Technology's Haystack Observatory. "We're now able to get information that is really on the same size scale as where we think all the action is happening in the galactic black hole."
Prior observations of the presumed black hole were obscured by surrounding gas and dust that reflect longer wavelength radio waves.
To pierce the haze, Doeleman and his colleagues used special equipment to link up four radio telescopes—one each in Arizona and California and two in Hawaii—in a technique called very long baseline interferometry. The resolving power of such a virtual telescope grows with the size of the telescope array. The joint telescopes allowed them to scan radio signals as short as 0.05 inch (1.3 millimeters) in wavelength, in the microwave range, capable of penetrating the cloud.
The researchers found that Sagittarius A* measured about 30 million miles (50 million kilometers) across, or one third the average distance between the sun and Earth. Researchers would like to observe light coming from around the black hole event horizon—the boundary past which not even light can escape the concentrated pull of gravity.
Distortion of space and time around the event horizon is believed to make the event horizon appear larger than its true diameter and—in this case—larger than the features the group resolved, Doeleman says. He says the group hopes to increase the power of the telescope array even more to look for a predicted "shadow" in front of the black hole, which would provide concrete proof of its existence.
Another coup would be measuring the black hole's rate of spin, its other basic property besides mass and something that researchers have never observed directly before either. It's exciting, Doeleman says, that "now we can start asking these questions."
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9 Comments
Add CommentThe title should have been "Continent-Wide Radio Telescope Brings Black Hole Into Focus" and the immediate following paragraphs should have first dealt with how it was done THEN the resolution and other stuff could be revealed. It's 'space-time' not 'space and time'. Sheesh! Then there's "...Doeleman says." back to back with "He says..." All this poor writing really ruins the reporting. Nobody seems to care, there at Sci Am anymore. I hope somebody will take the helm and bring Sci Am back. Who knows...maybe all the poor stuff is being squirted online. Maybe the actual publication is still neat and sharp. I hope so.
Reply | Report Abuse | Link to this"They were able to resolve Sagittarius A* to within 37 microarcseconds, the width of a baseball on the moon as seen from Earth. "
Reply | Report Abuse | Link to thisSorry, but this doesn't make any sense... do you mean they were able to magnify it to the same size as the moon as seen from earth with a resolution equivalent to a baseball (as soon on the moon)? Of course, that's far better resolution than the human eye gets so even if that IS what you are saying, it isn't a very helpful image analogy....
"the width of a baseball on the moon as seen from Earth. "
Reply | Report Abuse | Link to thisThink of a Cone that starts at your eye and extends out into space. At the distance of the moon this cone has the same diameter as a baseball. As it travels farther out into space it gets bigger and bigger. This would be like being able to see a football stadium on Jupiter (remeber the big red spot can hold 10 Earths).
The descriptor "galactic" is a necessary part of the title. The article is about the black hole thought to inhabit the center of our galaxy. You can see the difference this one word makes when you add it to an internet search of the terms "black hole".
Reply | Report Abuse | Link to thisI also disagree with your point about the structure of the article. I think your suggestion is putting the cart before the horse.
I may also add that I found you response to this article humorous. Here is a report of "a black hole four million times as massive as the sun" and your response is to quibble over title and layout and then make wild inferences about Scientific America as a journalistic institution. The possible size of this thing, the nature of a black hole (which I think excuses slipping "and" between space-time, as their relation breaks down in black holes, one of the many reasons they're so fascinating), and the possibility of further insight into our relatively immediate surroundings within our lifetimes seem not to have made as much of an impact as the "squirters" at SciAm might have hoped for! Why care to report at all if your effort is only met with rambling commentary?
Thank you Scientific America!
for more than ten years now, i have advocated for twin platforms to be inserted into the L4 and L5 nodes fore and aft of the earth in our orbit... similar to the STEREO solar observation project of recent years, except pointed away from the sun rather than toward. By means of this extremely -long-baseline (~1.7 AU) integrated with earth-based observations, this LaGrange Array (uber-binoculars) would have spectacular visual acuity. Although the cost of a stripped down project such as this would be meager (by mega-project standards) and there are chip-speed/frequency issues that constrain present viable observational wavelengths, this still seems highly attractive in terms of the new science it could generate. Sigh.
Reply | Report Abuse | Link to thisI only hope a project like this is deployed within my lifetime - i am terribly curious what we will discover, as Black-Holes, Quasars and other high-energy objects seem perfect for high-resolution, low-gathering investigative tools such as what i propose.
this report is nonsense: go here for details:
Reply | Report Abuse | Link to thiswww.sjcrothers.plasmaresources.com/Reynolds.pdf
http://www.thunderbolts.info/thunderblogs/archives/guests08/080907_gst_cro_bhf.htm
xxx
Reply | Report Abuse | Link to thisInteresting article indeed. This black hole is predicted to exist in our Milky Way as well, fascinating and scary. Performing all the different measurements on this black hole will prove to be challenging but exciting as well. They will be measuring the rate of the spin of the black hole, and because it has never been observed directly I wonder what the turnout of this will be? Sagittarius A measures close to 30 million miles across, this is big. How will this black hole change our views on our Milky Way?
Reply | Report Abuse | Link to thisThis article is interesting. I twould be great if scientists can see the existence of the black hole using radio telescopes. This proyect seems an interesant proyect, but my question would be if they are able to prove the existence of this black hole, what is their final goal. During a long time scientists claim that there are matter going around in the universe, but they dont' provide an exact information about the matter of this fact, so we are given proofs of the existencial life of the matter, but we are not given the exact tools to figure out the importance about proyects like this mentioned in the article.
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