Beware the Piranha

[C1ay]

Deep in the heart of the Milky Way galaxy lurks an extraordinary black hole. Astronomers call it "supermassive." It has been feeding on the core of our galaxy so long, the hole has accumulated more than a million Suns of mass inside its pinprick belly.

 

lefthttp://hypography.com/gallery/files/9/9/8/accretiondisk_torus_thumb.jpg[/img]How do we know it's there? You can't see a black hole. It reveals itself whenever an errant star or cloud of gas meanders too close. Matter falling into the hole is ripped apart and superheated, emitting bursts of high-energy radiation just before it disappears over the event horizon. Occasionally a burp of X-rays emanates from the Milky Way's core, and astronomers check off another meal.

 

Today these burps are seldom, but among astronomers it is widely thought that the Milky Way's "monster in the middle" used to be more active--frighteningly so. Paul Martini of Ohio State University (OSU) explains: "Billions of years ago, when our galaxy was young, there was more 'food' in the core—lots more gas and stars for the black hole to consume." He believes there could have been "a real feeding frenzy" lighting up the center of the Milky Way like a beacon visible half-way across the Universe.

 

Could this be true?

 

Finding out requires traveling back in time--a trick, believe it or not, astronomers are able to perform. "By looking at galaxies billions of light years away, we can see them as they were billions of years ago," explains Martini. "This can give us a clue to the state of the Milky Way when it was young."

 

So, in an effort led by OSU astronomy graduate student Jason Eastman, Martini and colleagues used data from NASA's Chandra X-ray Observatory to examine 12 clusters of galaxies ranging in distance from 2.4 to 5.7 billion light years away. Their purpose: to learn how galactic cores change over time.

 

What they saw reminded Eastman of "piranhas in a very well-fed aquarium." Younger galaxies tended to be very active; supermassive black holes at their cores were furiously consuming matter and producing copious X-rays in the process.

 

Older galaxies, on the other hand, were relatively calm; the frenzy was subsiding. "It's not that the black holes were no longer hungry," says Eastman, "they were just running out of things to eat." The ratio of active X-ray cores in the galaxies they analyzed, younger vs. older, was about 20 to 1.

 

"The food, or fuel for a central black hole, is primarily thought to be interstellar gas," adds Martini. "It is likely that an occasional star is also swallowed, but most researchers agree that clouds of gas are the main fuel source."

 

Hence the big picture: When galaxies are young, a black hole forms at the core. Why? "Because that is the bottom of the galaxy's gravitational potential well," answers Martini. "Gas, stars, even smaller black holes will settle to the center of the galaxy over time." At first, gas is abundant, and the black hole feeds greedily, announcing itself to the cosmos via high-energy X-rays. As time passes, the core is depleted of gas and feeding subsides. By the time a galaxy is as old as the Milky Way (10+ billion years), the central black hole has grown to millions of solar masses, but only takes an occasional meal. The fish is hungry, but the water is nearly empty.

 

Source: NASA

[ishaan]

hey, can u plz tell me in detail y it is impossible to identify a black hole acc. to u??????????

[BruceLeeReborn]

Ya know what's sad? I realized there was a black hole in the middle of our galaxy when i was in 3rd grade. I saw a picture of our galaxy and thought, "Hey, it looks like soapy water going down a drain. There must be a black hole in the middle." And what do you know? There is. Why do some people ignore obvious signs such as the one I noticed, and look for comlex ones such as x-ray emissions? *Bracing self for flaming by science buff*

[coldcreation]

Hence the big picture: When galaxies are young' date=' a black hole forms at the core. Why? "Because that is the bottom of the galaxy's gravitational potential well," answers Martini.[/quote']

 

It sounds like Martini's had a few too many.

 

His comment is comparable to this: Why did the Sun form in the center of the solar system? Because it is the bottom of the gravitational potential well.

 

 

There is no black hole (supermassive or otherwise) at the center of the Galaxy (or any other galaxy).

[BruceLeeReborn]

How do you know? You can't just say that...:doh:

[coldcreation]

How do you know? You can't just say that...:doh:

 

How do we know there are no monsters in the ocean?

[C1ay]

There is no black hole (supermassive or otherwise) at the center of the Galaxy (or any other galaxy).

 

Can you prove that? Can you prove that there could never be a mass so great that it's gravity could trap light? Could you prove that photons are somehow immune from gravity?

[coldcreation]

Can you prove that? Can you prove that there could never be a mass so great that it's gravity could trap light? Could you prove that photons are somehow immune from gravity?

 

I never wrote that photons (or radiation in general) is immune from gravity. Obviously light (and radiation throughout the entire spectrum) is affected as it passes through a curved spacetime continuum (accross the vast expanse of space) or through the gravitational field of a massive body.

 

The gravitational redshift and time dilation experiments (Pound Rebka, Shapiro, etc) are good examples of how radiation is affected depending on altitude and direction of propagation in relation to the earth.

 

My point is simple, and I share Einstein's stance on the subject: There is no guarantee that matter condenses to anywhere near what would be called a singularity or black hole.

 

Pauli's exclusion principle is clear enough. As far as bosons, on the other hand, might be concerned, I have my doubts.

 

There is certainly a threshold beyond which matter (protons, neutrons, etc.) will no longer collapse (whhich is at, I suspect, neutron star density, whatever that is).

 

"Beware the Piranha." LOL

Milky Way's "monster in the middle...used to be more active--frighteningly so" LOL

"a real feeding frenzy" LOL

"piranhas in a very well-fed aquarium." LOL

"It's not that the black holes were no longer hungry," says Eastman, "they were just running out of things to eat." LOL

"astronomers check off another meal." LOL

"furiously consuming matter" LOL

"a burp of X-rays" LOL

 

 

Black hole are fun...I love them...

 

 

I think I'll go have another martini. LOL.

 

CC

[C1ay]

There is no guarantee that matter condenses to anywhere near what would be called a singularity or black hole.

 

That's right, there are no guarantees. None that support or refute the possibility for such an entity. OTOH, I don't personally believe that a black hole has to be a singularity, it only needs to have enough mass to trap light, regardless of the volume of space it occupies...

[Jay-qu]

That's right, there are no guarantees. None that support or refute the possibility for such an entity. OTOH, I don't personally believe that a black hole has to be a singularity, it only needs to have enough mass to trap light, regardless of the volume of space it occupies...

That is exactly the point I have been thinking, would all the mass of the universe be sufficient?

[coldcreation]

That is exactly the point I have been thinking, would all the mass of the universe be sufficient?

 

Are you invoking the kind of singularity that would have occurred in a big bang? If so, that is of the kind that ejects radiation rather than trapping it.

 

 

 

There is no guarantee that matter condenses to anywhere near what would be called a singularity or black hole.

 

That's right, there are no guarantees. None that support or refute the possibility for such an entity. OTOH, I don't personally believe that a black hole has to be a singularity, it only needs to have enough mass to trap light, regardless of the volume of space it occupies...

 

Do you imply there may be a spacetime wormhole, or rather, an aglomeration of highly compact material -- it would have to be primarily in bosonic form -- just inside the event horizon but not compact enough to degenerate to a singularity?

 

 

 

cc

[C1ay]

Well, any object smaller than its Schwarzschild radius is a black hole. Certainly larger quantities of mass have a larger radius than smaller. Such objects are referred to as gravitational singularities but I don't particularly believe this implies the volume of space occupied by these entities. I seem to remember that the Schwarzschild radius of the black hole at the center of the Milky Way is approximately 7.8 million km.