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Virtual Telescope Zooms In On Milky Way Black Hole
FiReaNGeL writes "An international team has obtained the closest views ever of what is believed to be a super-massive black hole at the center of the Milky Way galaxy. The astronomers used radio dishes in Hawaii, Arizona and California to create a virtual telescope more than 2,800 miles across that is capable of seeing details more than 1,000 times finer than the Hubble Space Telescope. The target of the observations was the source known as Sagittarius A* ("A-star"), long thought to mark the position of a black hole whose mass is 4 million times greater than the sun. Though Sagittarius A* was discovered 30 years ago, the new observations for the first time have an angular resolution, or ability to observe small details, that is matched to the size of the event horizon."
Thats your basic Beowulf cluster of telescopes.
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An international team has obtained the closest views ever of what is believed to be a super-massive black hole at the center of the Milky Way galaxy.
*Zoom Out*... "Is that?.. It.. it.. it's Oprah eating a klondike bar. Sorry folks, our mistake."
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The milky way is our galaxy.
Also, 2 different brands of chocolate bar.
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"a virtual telescope more than 2,800 miles across that is capable of seeing details more than 1,000 times finer than the Hubble Space Telescope"
- ok, but HST is an optical telescope, not "radio dish".
Can we stop saying "virtual telescopes" and start using the proper grown up terms? Interferometry and Aperture Synthesis aren't hard to understand. It's a pet peeve of mine, and slashdotters should be of a level of intelligence that they can understand this stuff.
http://en.wikipedia.org/wiki/Astronomical_interferometer
http://en.wikipedia.org/wiki/Aperture_synthesis
Yes you get the same angular resolution as a much larger telescope (one as big as the distance between the telescopes), which is why you do it. However it's important to note that you you don't increase the amount of radiation you're collecting - it's still just the sum of the telescopes you're using.
I'll try to put it simply. Let's use optical telescopes as a familiar example. (In practice optical interferometry is much harder than radio astronomy, but I digress). The larger the diameter of the mirror (or lens) the more light we collect, and the smaller an object we can look at with reasonable detail (There is a physical relationship between the diameter of the telescope and the smallest thing you can resolve with it). We could space multiple telescopes a good distance apart and increase how small a piece of the sky we can look at in detail. The detail we could now resolve depends on the distance between the telescopes. However we're still only collecting as much light in total as the sum of the light collected by each scope. So even though we can look at a much smaller part of the sky, we won't be able to brighten up the image as much as if we had the larger telescope. It's still worth doing and it still yields discoveries, but it's not the same as having a massive telescope.
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the moon and various satellites spin around the earth
the earth and various other planetary objects spins around our sun
our sun spins around a giant black hole
what does the giant black hole spin around?
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Here is the actual negative surrounded by brackets:
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Nope. Gravitic force gets weaker the further you get from the mass exerting it.
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Sagittarius A* ? :)
Dijkstra's Scorpio is better
Ok ok, I'm not a space nerd!
As a physicist, I sometimes wish I could hear the words 'supermassive black hole' in a professional context without immediately thinking of that catchy song from their new album.
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Pics or it didn't happen
Oh, we have lots of pretty pictures (of colorful surrounding gas). We just don't have enough picture details to determine what it is, that is happening.
What we could really use, like out of a science fiction story, is to stumble upon an ancient astronomer's time-lapse photo project. About 10-20 million years should be sufficient. But in case our stumbling plan fails, how would like to go down in history, sayyyy in 10-20 million years from now, as the guy who got the ball rolling?
with the gravitational pull it would look like:
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http://dictionary.reference.com/search?q=expanding
To determine that something is expanding you must first know its dimensions. Since we don't know the dimensions of the universe, we can't really tell if it is expanding or not. There is movement within the observed portion of the universe that is compatible with the concept of an expanding universe.
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Apologies, it was a straight copy and paste of the title. Luckily, I posted them in Chrome, so you may sue Google if you have suffered any permanent injuries as they hold all the rights :).
Indeed the European Space Agency has had such a project for years: a space optical interferometer named Darwin, with an additional twist: by using descructive interferometry instead of constructive one, they intend to switch off a star in the center of the field of view, to see the planets around (these ones being way darker you wouldn't detect them otherwise), analyse the molecules in them etc. Needless to say, this project is still in its early phases, but indeed appears, with a schedule, in ESA's plans. http://en.wikipedia.org/wiki/Darwin_(ESA)
Herve S.
Hmm..... Near the "A-Star"?
Does this mean that in the center of our galaxy is the biggest "A-Hole" in our galaxy?
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General relativity makes no predictions about what is happening at the center of black holes - there is a singularity in the equations there. Worse, in general relativity singularities are (probably) never "naked" - if you go in to see what is happening you can never come back out, or send a signal back out, to tell us about it.
But, yet, the gravity of the black hole, as experienced outside, does increase with time as things get sucked in.
There is an accretion disk around the event horizon, where things (dust, gas) are orbiting around at nearly the speed of light. As these things rub together, and as new stuff gets added, there is lots of energy to be detected far away - especially in jets of very hot matter out of the poles.
The event horizon itself, for a black hole of this size, is not detectable. (Very small black holes should glow with Hawking radiation.)
Also, the expansion takes the form of things moving away from each other, not themselves getting bigger. Black holes don't suck things in anymore than the Earth sucks in the moon. If you get close enough, yeah, you'll fall in. But it's not like water going down a drain, or a vacuum. There are black holes in the center of the galaxy that are frighteningly huge, millions of solar masses... that aren't gobbling up stars. While their gravity is strong, the distances involved quickly makes the pull very weak. That and there are other objects pulling in every other direction.
Interesting side bit - Small black holes evaporate over time. Virtual particles pop outside the event horizon and sometimes escape, becoming real. Over enough time the black hole fizzles away. How that works exactly you'd have to ask Hawking.
Any physicists on hand to clarify/correct? /long fascinated by black holes
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If you had an array of Hubble sized telescopes in space and could put them whatever distance you'd like from each other, what sort of results could you get?
That is basically the Space Interferometry Mission (SIM), which alas has had funding troubles recently. The component telescopes are not the size of the Hubble, but the idea is exactly as you suggest. One thing you could do with this is detect Earth sized planets in a solar system like ours out to a reasonable distance.
By definition, the event horizon is the area surrounding a black hole inside which the escape velocity exceeds the speed of light, therefore you can't see anything beyond it. You're probably thinking of the accretion disk.
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No. You have distance, rate of change of distance (speed) and rate of change of speed (acceleration). Gravity provides an acceleration, which is dependent on distance (meaning that you have a rate of change of acceleration due to gravity, which is what makes orbital calculations tricky). If two objects are moving away from each other, they have an initial speed. Gravity will be applying a force on them, which will be decreasing their speed, but their distance will keep increasing. As the distance increases, the effect of gravity decreases (it's proportional to the inverse of the square of the distance). As such, objects can continue to move away from each other (i.e. the volume encompassed by the distance between them will expand) without any reduction in gravity. The question is whether the initial impulse was enough to allow them to keep moving away from each other (continual expansion theory) or whether they will eventually start moving back towards each other and then collapse (big crunch theory).
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If you'd replace the sun with a black hole of the same mass, the earth would remain on the same orbit as it does now. A black hole doesn't pull any harder than another object of the same mass.
It's only when you get close that things start to change. Gravity is zero if you're 3km from the center of the sun, but with its black hole replacement, it would be impossible even for light to get away from it.
Right here folks: http://web.mit.edu/newsoffice/2008/blackhole-view-0903.html
Sagittarius A* - Previous location of the Large Hadron Collider
Here, actually.
thought that was ( * )
Technically I think the gravitational field would be more accurately represented as:
( o )
but the gravity can also distort the frame of reference
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