APOD: The Black Hole in the Milky Way (2012 Nov 02)

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APOD: The Black Hole in the Milky Way (2012 Nov 02)

Post by APOD Robot » Fri Nov 02, 2012 4:06 am

Image The Black Hole in the Milky Way

Explanation: At the center of our Milky Way Galaxy, a mere 27,000 light-years away, lies a black hole with 4 million times the mass of the Sun. Fondly known as Sagittarius A* (pronounced A-star), the Milky Way's black hole is fortunately mild-mannered compared to the central black holes in distant active galaxies, much more calmly consuming material around it. From time to time it does flare-up, though. A recent outburst lasting several hours is captured in this series of premier X-ray images from the orbiting Nuclear Spectroscopic Telescope Array (NuSTAR). Launched last June 13, NuSTAR is the first to provide focused views of the area surrounding Sgr A* at X-ray energies higher than those accessible to Chandra and XMM observatories. Spanning two days of NuSTAR observations, the recent flare sequence is illustrated in the panels at the far right. X-rays are generated in material heated to over 100 million degrees Celsius, accelerated to nearly the speed of light as it falls into the Miky Way's central black hole. The main inset X-ray image spans about 100 light-years. In it, the bright white region represents the hottest material closest to the black hole, while the pinkish cloud likely belongs to a nearby supernova remnant.

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Re: APOD: The Black Hole in the Milky Way (2012 Nov 02)

Post by bystander » Fri Nov 02, 2012 4:25 am

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Re: APOD: The Black Hole in the Milky Way (2012 Nov 02)

Post by henrystar » Fri Nov 02, 2012 9:38 am

In 1957 or 1958 there was an American Astronomical Society meeting in my native Toronto. I was a kid in college, deeply interested in astronomy (I am a Professor of Astronomy today). Ambartsumian, from the Soviet Union, gave a paper proposing that there was a supermassive black hole at the center (I would have said centre then) of our galaxy. I thought he was insane!

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Re: APOD: The Black Hole in the Milky Way (2012 Nov 02)

Post by Bruce Mardle » Fri Nov 02, 2012 12:01 pm

Some people -- e.g. http://en.wikipedia.org/wiki/George_Chapline -- have suggested that black holes might not exist.

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Re: APOD: The Black Hole in the Milky Way (2012 Nov 02)

Post by BDanielMayfield » Fri Nov 02, 2012 12:25 pm

Bruce Mardle wrote:Some people -- e.g. http://en.wikipedia.org/wiki/George_Chapline -- have suggested that black holes might not exist.
But, what do YOU, think Bruce? Convincing evidence (a large number of stars very rapidly orbiting something that’s so dim we can’t see it) leads this Bruce to believe in the existence of the Milky Way’s central Super-Massive Black Hole, just as I believe other things, like the fact that the sun will rise tomorrow.

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Re: APOD: The Black Hole in the Milky Way (2012 Nov 02)

Post by BDanielMayfield » Fri Nov 02, 2012 12:56 pm

However, I am open to improved explanations Bruce. Having just read your link I see that your source ain't no dummy.

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Re: APOD: The Black Hole in the Milky Way (2012 Nov 02)

Post by Keyman » Fri Nov 02, 2012 1:33 pm

Having read the Wikedpedia entry and noting this...
{Chapline} proposed that objects currently thought to be black holes are actually dark-energy stars.

This idea incorporates the 1980 proposal by Robert B. Laughlin and Chapline that the surface of a dark energy star actually represents a quantum critical transition of a superfluid vacuum.
...as a layman I have to say, 'Oh-h-h-h-h-h. Now I get it.' :?

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Re: APOD: The Black Hole in the Milky Way (2012 Nov 02)

Post by Chris Peterson » Fri Nov 02, 2012 2:03 pm

Bruce Mardle wrote:Some people -- e.g. http://en.wikipedia.org/wiki/George_Chapline -- have suggested that black holes might not exist.
True. But they are almost certainly wrong. A non-specialist who believes black holes don't exist is almost certainly taking an irrational position. Even the handful of scientists exploring alternative explanations admit that the evidence for black holes is powerful, and none of these people make the claim that they don't exist... only that they are exploring other possibilities.
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Re: APOD: The Black Hole in the Milky Way (2012 Nov 02)

Post by Boomer12k » Fri Nov 02, 2012 2:50 pm

You would have to explain to me the mechanism of a "Dark Star" that would heat material to 100 million degrees Celsius to emit X rays by said material falling into said star, when the gravity would be insufficient by definition of a "Dark Star"...also Black Holes are not just AT the center of the galaxy, and form from various methods. So, what would be the examples, and mechanisms for "Dark Stars"...or is it just a difference of opinion? I think there is a difference as one defining point of a Black Hole is...it shrinks down to a Singularity. A Star is not a singularity as far as I know.

One defining feature of a Dark Star (Newtonian Mechanics type) is that it is about (basically as I understand this concept...) 500 times the "SIZE" of the Sun, (that is RADIUS and the same density, note I did not say MASS.) see **...This would be a very large star in volume but same density and its mass spread out over the distance....does not sound logical...as mass creates gravity, and thus the material falls into itself and ignites, thus it would shrink under gravity, thus a "dark star" like this should not even ignite...thus it would still be a "bubble of hydrogen and dust" in space, and not an ignited star....A Black Hole in theory should collapse if it has the sufficient mass,...but a Dark Star is said to be STABLE and does not collapse...Therefore...the CMBH....should be a Black Hole as the Mass is 4.3 million solar masses, not the definition of a "Dark Star"....my opinion...but then they laughed at my "Number of Planets in the Galaxy" presentation too....

**---http://en.wikipedia.org/wiki/Dark_star_ ... chanics%29

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Re: APOD: The Black Hole in the Milky Way (2012 Nov 02)

Post by dship14 » Fri Nov 02, 2012 4:02 pm

Okay .... help me out, here. The flare was photographed by NuSTAR recently ... but doesn't that mean that this flare actually happened 27,000 years ago? :?:

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Re: APOD: The Black Hole in the Milky Way (2012 Nov 02)

Post by Chris Peterson » Fri Nov 02, 2012 4:24 pm

dship14 wrote:Okay .... help me out, here. The flare was photographed by NuSTAR recently ... but doesn't that mean that this flare actually happened 27,000 years ago? :?:
It generally makes more sense to treat events at large distances as happening when they are observed, since trying to extrapolate when they "really" happened based on uncertain distance measurements adds no useful information to the analysis. That is, the fact that in a sense the event happened about 27,000 years ago has no impact on anything else we can observe.
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Re: APOD: The Black Hole in the Milky Way (2012 Nov 02)

Post by BDanielMayfield » Fri Nov 02, 2012 5:37 pm

Keyman wrote:Having read the Wikedpedia entry and noting this...
{Chapline} proposed that objects currently thought to be black holes are actually dark-energy stars.

This idea incorporates the 1980 proposal by Robert B. Laughlin and Chapline that the surface of a dark energy star actually represents a quantum critical transition of a superfluid vacuum.
...as a layman I have to say, 'Oh-h-h-h-h-h. Now I get it.' :?
Yeah, 10 dimentional string theory, nothing to it, right?
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Re: APOD: The Black Hole in the Milky Way (2012 Nov 02)

Post by BDanielMayfield » Fri Nov 02, 2012 5:52 pm

Assuming that they're real, and I agree Chris, they almost certainly are, Why Is todays APOD entitled "THE Black Hole in the Milky Way" since there are likely many BH's of various masses in our galaxy. Nit picking, but it would have been more correct to have added either Central, Super-Massive or both to the title.

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Re: APOD: The Black Hole in the Milky Way (2012 Nov 02)

Post by Wadsworth » Fri Nov 02, 2012 5:55 pm

Boomer12k wrote: one defining point of a Black Hole is...it shrinks down to a Singularity. A Star is not a singularity as far as I know.
:---[===]*
I for one don't buy into the suposed singularity of black holes. But I'm no specialist.
I'm not saying they aren't real, something is definitley there, but I don't think it is a singularity.

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Re: APOD: The Black Hole in the Milky Way (2012 Nov 02)

Post by Moonlady » Fri Nov 02, 2012 6:41 pm

One day, it will be detect, a running hamster in the center makes the galaxy turning like a wheel :wink:

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Re: APOD: The Black Hole in the Milky Way (2012 Nov 02)

Post by Chris Peterson » Fri Nov 02, 2012 7:45 pm

Wadsworth wrote:
Boomer12k wrote: one defining point of a Black Hole is...it shrinks down to a Singularity. A Star is not a singularity as far as I know.
:---[===]*
I for one don't buy into the suposed singularity of black holes. But I'm no specialist.
I'm not saying they aren't real, something is definitley there, but I don't think it is a singularity.
Indeed, there may not be a singularity at the center of a black hole. That's what the math suggests, but the mathematical description of the physics involved breaks down at that point, so from a physical sense, nobody really knows what's happening once you cross the event horizon of a black hole.
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Re: APOD: The Black Hole in the Milky Way (2012 Nov 02)

Post by StarCuriousAero » Fri Nov 02, 2012 9:57 pm

So was this little flare caused by that infalling cloud of stuff I recall reading about not too long ago? A month or 2 ago maybe? I seem to recall reading something that mentioned we should be seeing a flare up at least but can't remember where I saw that.

This dark energy star theory does sound quite compelling, especially if it does indeed contribute to the unifying of quantum mechanics and general relativity as Chapline claims. Now I'm eager to read more from this guy. I think his statement saying that black holes "don't exist" is a bit misunderstood, because it seems he's just explaining what happens inside what we traditionally know as a black hole, in a way that doesn't seemingly result in a mathematical error (the singularity i.e. black hole). It's easy to see why something inexplicable within the realms of science is unsettling, it's not fair for the science community to simply accept something as strange as a black hole while ridiculing the religious for accepting an idea as strange as "God". I'm just further speculating on my own here, but if in fact he is correct about the mechanisms at play inside black holes/dark energy stars, it seems it could provide an explanation for how the big bang occurred to begin with. How exciting!

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Re: APOD: The Black Hole in the Milky Way (2012 Nov 02)

Post by bystander » Fri Nov 02, 2012 10:49 pm

StarCuriousAero wrote:So was this little flare caused by that infalling cloud of stuff I recall reading about not too long ago? A month or 2 ago maybe? I seem to recall reading something that mentioned we should be seeing a flare up at least but can't remember where I saw that.
You may be referring to the gas cloud that is infalling towards Sgr A* or perhaps the report from Chandra of the cloud of asteroids that may surround Sgr A*.
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Re: APOD: The Black Hole in the Milky Way (2012 Nov 02)

Post by henrystar » Fri Nov 02, 2012 10:58 pm

dship14 wrote:Okay .... help me out, here. The flare was photographed by NuSTAR recently ... but doesn't that mean that this flare actually happened 27,000 years ago? :?:

Sure, but the same is true for EVERYTHING at the center of the galaxy. And, we see Andromeda as it was two million years ago, not as it is today. This is tremendously handy for studying the evolution of the universe! We're also extremely lucky the universe is as transparent as it is, for the same reason. What if we'd been in the midst of a dark interstellar cloud? Yikes!

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Re: APOD: The Black Hole in the Milky Way (2012 Nov 02)

Post by flash » Fri Nov 02, 2012 11:02 pm

Wadsworth wrote:
Boomer12k wrote: one defining point of a Black Hole is...it shrinks down to a Singularity. A Star is not a singularity as far as I know.
:---[===]*
I for one don't buy into the suposed singularity of black holes. But I'm no specialist.
I'm not saying they aren't real, something is definitley there, but I don't think it is a singularity.
It seems to me that the black hole is more than the singularity: The event horizon is (should be considered) a part of the black hole and that certainly has an extent. The singulaity is merely where the mass of the black hole is concentrated (at infinite density)! The nature of the space between the singularity and the event horizon is somewhat of a mystery... Although arguments can be made that the event horizon is no more a part of the black hole than the gravity well that it causes, it seems to me a reasonable boundary, just as the chromoshere is a part of the Sun, but the corona, solar wind, and gravity well are not.

dship14

Re: APOD: The Black Hole in the Milky Way (2012 Nov 02)

Post by dship14 » Sat Nov 03, 2012 1:18 am

Moonlady wrote:One day, it will be detect, a running hamster in the center makes the galaxy turning like a wheel :wink:
Or the end of the flick "Men In Black" ... where the Milky Way galaxy is nothing but the center of some entity's marble. :lol2:

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Re: APOD: The Black Hole in the Milky Way (2012 Nov 02)

Post by saturno2 » Sat Nov 03, 2012 3:22 am

Black holes
The riddle of the Universe

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Re: APOD: The Black Hole in the Milky Way (2012 Nov 02)

Post by BillBixby » Sat Nov 03, 2012 5:48 am

In the case of NuSTAR, its state-of-the-art telescope... After all the discussion of sending a state-of-the-art camera to Mars, am I to assume this state-of-the-art telescope was state at time of launch or state a couple years prior to launch. Semantics seem relative, however I would like to know. The scope may not have to be as reliable as the camera, in the long run.

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Re: APOD: The Black Hole in the Milky Way (2012 Nov 02)

Post by Bruce Mardle » Sat Nov 03, 2012 10:25 am

BDanielMayfield wrote:But, what do YOU, think Bruce? Convincing evidence (a large number of stars very rapidly orbiting something that’s so dim we can’t see it) leads this Bruce to believe in the existence of the Milky Way’s central Super-Massive Black Hole...
Hi, other Bruce.

I think it's likely that there's something compact and massive there, but black holes (in my naive opinion) have always seems like a 'default' explanation. The argument seems to go something like: we know what 'holds up' regular matter but sometimes the pressure is too high and it collapses into white dwarf matter; we know what holds that up but sometimes the pressure is too high and it collapses into neutron star matter; we know what holds that up but sometimes the pressure is too high and... we don't know of anything that could hold that up, so we'll assume that nothing can.
A singularity has lots of problems, though.

I once attended a lecture by the head of a university's astronomy department. He said that astronomy was a very exciting field because massive changes in beliefs were relatively frequent. I kept quiet my opinion that that might be because astronomers (and cosmologists in particular) seems relatively happy to jump to conclusions!

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Re: APOD: The Black Hole in the Milky Way (2012 Nov 02)

Post by Ann » Sat Nov 03, 2012 11:52 am

Bruce Marlick wrote:
I once attended a lecture by the head of a university's astronomy department. He said that astronomy was a very exciting field because massive changes in beliefs were relatively frequent. I kept quiet my opinion that that might be because astronomers (and cosmologists in particular) seems relatively happy to jump to conclusions!
You may be right that cosmologists are happy to jump to conclusions, at least sometimes, but my personal opinion is that cosmologists have often been too happy to "anthropomorphize". That is, cosmologists, like most of the rest of us, have been happy to think that the universe should make sense in human terms. And it should, preferably, put ourselves in the center of it all.

It is a misunderstanding that cosmologists in the past clung to the belief that the Earth is flat. The roundness of the Earth was well known by astronomers of antiquity.

However, those cosmologists of yore did stick to the idea that the Earth is the center of the universe. It took a long time to discard that idea. Copernicus stated that the Earth is orbiting the Sun rather than the other way round, and was later proven to be right about that. (Technically the Sun and the Earth orbit one another, but the size of the Sun's orbit "around" the Earth is about a meter or so, so the Sun is just wagging back and forth around its own center.)

But the Sun-centered universe just meant that our own dear Sun became the center of the universe rather than the Earth. By the time it had become understood that there was a galaxy around the solar system, astronomers first believed that our solar system, and therefore the Sun, was the center of the galaxy. William Herschel, discoverer of Uranus, championed this idea. It took the studies of globular clusters by Harlow Shapley to prove that the solar system was nowhere near the center of the Milky Way. But Harlow Shapley still believed that the mysterious "spiral nebulae" that had been discovered, and that bore names like M51 and M74, were just rotating gas clouds in our own galaxy, and that the Milky Way comprised the entirety of the universe.

It took the studies of galaxies and redshifts by Edwin Hubble to prove not only that those "spiral nebulae" were galaxies of their own, independent of the Milky Way, but also that almost all of them were moving away from us. The expansion of the universe had been proved. The expansion of the universe suggested a violent birth of the universe at a moment in time in the past, but this idea sat uncomfortably with some astronomers, who preferred the unchanging "serenity of the night". So astronomers fought over whether the universe had been born violently or whether it had always existed and looked pretty much the way it does now. It took the discovery of the cosmic microwave background radiation, the echo of the Big Bang, to convince astronomers that our universe had been fundamentally different in the past.

After astronomers had become convinced that the universe had been born in the past and had been evolving ever since, the idea that the universe would reverse its expansion and fall back on itself and disappear in a "Big Crunch" became popular. This idea quickly evolved into the concept of the "Big Bounce", where the Big Crunch immediately leads to a new Big Bang, making the universe rise from the ashes like a phoenix. Astronomers diligently began searching for evidence that the universe was destined to collapse, which was of course the necessary prerequisite for a Big Bounce. The astronomical community was absolutely stunned when studies of distant supernovae appeared to prove that the universe wasn't slowing down, like it "should". It was speeding up instead.

I think I see a lot of anthropomorphism in the way cosmologists have been thinking about the universe. So far, the universe has always proved to be bigger and stranger than most cosmologists would have guessed. Perhaps it couldn't have been different. What we humans can think and imagine is limited by our human experiences.

As for black holes, there is a lot of evidence that huge gravity wells do exist. What's at the center of those enormous gravity wells is, so far, beyond the realm of science.

Personally I'm sure that many of us are doing a lot of anthropomorphizing when we think of them.

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