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Milky Way Black Hole Could Reignite
Posted by
kdawson
on Thu Apr 10, 2008 10:26 AM
from the tinfoil-umbrellas-might-help dept.
from the tinfoil-umbrellas-might-help dept.
sciencehabit sends us to Sciencemag.org for an account of a survey of nearby galaxies that points to the possibility that once-quiescent galactic nuclei could wake up and become active again. If the Milky Way's dormant black hole should become active, it could be bad news for life on Earth (and elsewhere in the neighborhood). The paper (PDF) is up on the arXiv.
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The Milky Way's Black Hole Is Not So Quiescent 152 comments
esocid writes in with a followup to the recent discussion about the possibility that our galaxy's central black hole could reignite. "Using NASA, Japanese, and European X-ray satellites, a team of Japanese astronomers has discovered that Sagittarius A* let loose a powerful flare three centuries before the time at which we are observing it (i.e., 26,000 years in the past). X-ray pulses emanating from just outside the black hole take 300 years to traverse the distance between the central black hole and a large cloud known as Sagittarius B2, so the cloud responds to events that occurred 300 years earlier. 'By observing how this cloud lit up and faded over 10 years, we could trace back the black hole's activity 300 years ago,' says team member Katsuji Koyama of Kyoto University. 'The black hole was a million times brighter three centuries ago.'"
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Protect yourself (Score:5, Funny)
You may want a tin foil codpiece, too.
oblig. (Score:3, Funny)
Re:oblig. (Score:5, Funny)
Parent
Eye muss bee knew hear (Score:4, Informative)
I don't think we have anything to worry about. Nothing to see here (and if it happened, nobody to see it)
Re:Eye muss bee knew hear (Score:5, Informative)
That's not what the article says:
It's not understood what is causing the black holes to become newly active, because in most cases there is no evidence of collisions or mergers.
Parent
It's not just definite, it's *in*definite. (Score:2)
Re: (Score:3, Insightful)
> turn into a quasar is for the galaxy to collide with another galaxy.
You didn't RTFA very well. The point is that they have found galaxies whose black holes have reignited without there being any evidence of a collision.
Re:Eye muss bee knew hear (Score:5, Interesting)
As matter accelerates and gets closer and closer to the event horizon, particles begin bouncing into each other, like outside that one Who concert. Except in this case, instead of being crushed to death (as those concert-goers), centripetal force slings matter towards the poles of the hole with enough energy to achieve escape velocity. This creates a massive beam of ultra-high energy particles that would be very bad for your health. Well, two beams (one "up" and one "down"), but you get the idea.
Parent
Soo close (Score:2)
Re:Eye muss bee knew hear (Score:5, Funny)
It isn't a galactic collision. It's just the reunion tour for Disaster Area.
Parent
Speaking as user Slartibartfast... (Score:2)
Reading comprehension requires practice (Score:2)
Actually, the main message I get from the article is how complex the universe is, and how little is known, even by the most knowledgeable, about how these mechanisms work.
Re: (Score:2)
Re:Eye muss bee knew hear (Score:4, Funny)
Parent
Feed Me (Score:4, Informative)
Our galaxy's black hole, Sagittarius-A, is not considered active, although it does have some weak emissions, primarily at harmless infrared and radio wavelengths consistent with a very small accretion disc. The nearest star to the black hole is estimated to be about 70 times as far away from it as it would need to be for the gravitational forces to remove significant amounts of material from the star. It also has an orbital period of 15 years, so it would take a long time and a significant perturbance to fall significantly close. It doesn't seem likely at all that it would become active in the foreseeable future.
Parent
Re: (Score:3, Informative)
Darn, and I never EVER rtfa, but the summary made it necessary. So for my fellow slashdotters who hate to RTFA, what they mean by "reignite" is to turn into a quasar. The way the black hole could turn into a quasar is for the galaxy to collide with another galaxy.
I don't think we have anything to worry about. Nothing to see here (and if it happened, nobody to see it)
Obviously there is something to see here. Us. Our sun was a member of a galaxy that was absorbed by the Milky Way. The evidence is in the fact that we do not orbit the center of this galaxy in the plane of its arms, but rather perform a wave-like motion alternatively above and below the center plane, passing through the plane in between peaks. A galactic collision could produce the effect noted in TFA, while simultaneously increasing interstellar gas and dust cloud densities, protecting the outer stars fro
I am building a ringworld (Score:4, Funny)
Step 1:
- invent scrith
Step 2:
- build Ringworld
Step 3:
- profit (sell real estate)
Re: (Score:3, Interesting)
So massive core explosions delivering a huge radiation wave are expected. Step 1: - invent scrith Step 2: - build Ringworld Step 3: - profit (sell real estate)
Dear Sir and/or Madam:
Good Day. My name is Jack Brennan. You may call me Brennan-monster. I am writing on behalf of my Protector brethern. This letter constitutes a cease and desist notice. You have been publishing our trade secret, that is, our business plan. Please remove said plan from you website at once or face litigation.
Sincerely yours, Jack Brennan
Re: (Score:2)
Re: (Score:3, Funny)
I am civilised, after all. I'm a Belter, not a lawyer.
Jack Brennan.
Re: (Score:2, Interesting)
Okay, so this isn't relevant to my day-to-day life (Score:3, Insightful)
SO - not unlike the assertion (for example) that there's a large asteroid with Earth's name on it, this research seems to indicate that perhaps we should start studying this phenomenon now even if there's nothing we can do about it now. After all, much of our modern technology was understood to be impossible/impractical as little as a century ago; if we start looking now, perhaps we can devise a mechanism for the preservation of our species before we need it. Then again, when has humanity ever shown that much foresight?
Re:Okay, so this isn't relevant to my day-to-day l (Score:2)
Re: (Score:2, Interesting)
You DO know that such collisions involve one particle with high velocity impacting a particle at rest (relatively speaking) with respect to the earth, making the collision products scatter like billiard balls after a good break and thus taking them away from the planet in short order? As opposed to colliding two streams with o
Re: (Score:3, Interesting)
It seems to me that a significant fraction of the collisions would produce particle showers pointed towards the ground. Even if 99% of the "evil bits" have momenta that don't allow them to settle into the earth, there's still a lot of evil bits (produced by incident particles with energies 10^4-10^6 times more energy than the LHC) over the last 4+ billion years that haven't des
Oh noes! (Score:2, Funny)
Quick, invade something, anything!
Re: (Score:2)
20 to 40%? Reignite? (Score:5, Insightful)
Re:20 to 40%? Reignite? (Score:4, Informative)
Haven't you watched CSI: Stellar Cartography Unit?
Parent
The galactic core could be exploding? (Score:5, Funny)
Still not getting it ... (Score:2)
So, a quasar is an energetic black hole? Or it's kinda like a black hole, but different, and with more spinning and less dark?
What is the black hole "doing" when it's not spraying high energy particles every where? What happens to turn a black hole into a quasar short of two colliding galaxies? We're now sure that there is a black hole in the center of all-if-not-most galaxies seems to be implied by thi
Re: (Score:3, Informative)
Quasars are an effect created by the supermassive black holes at the centre of each galaxy, these black holes consume tremendous amounts of mater (something like 10 sun masses a year) the more solar masses they consume the brighter they are. Obviously there is only so much material than can be pulled in by the supermassive black hole, eventually all the material is either ejected as high intensity engery (the quaser pulses we can observe) or consumed by the black hole.
The scary part (Score:2)
The night sky would be pretty though.
maybe it already has (Score:3, Insightful)
Re: (Score:3, Insightful)
No evidence for "re-ignition" (Score:4, Informative)
Re: (Score:2)
Black hole eats everything in easy reach, goes dormant. New source of fuel builds up in the neighborhood, black hole starts eating again, and the galaxy "reignites".
Axis of Rotation (Score:2, Interesting)
Re: (Score:3, Interesting)
Re: (Score:2, Informative)
Space as we know it.. (Score:2)
Here's a theory (Score:3)
We detect the presence of black holes at galactic centers by observing the stars whirling around said galactic center at high rates of speed, right? All those stars whirling around have mass, therefore, gravity. Other stars moving around, maybe not as near to the galactic center, also have gravity. All this movement and such may attract, due to gravitational pull, a cloud of gas somewhere nearby. Slowly it gets pulled by the stars' gravity, until it gets into the gravitational pull of the black hole. Quasar'd!
Just you wait... (Score:2)
Re: (Score:2)
Nope. That's entirely speculation. We do not know the transverse velocity of the Andromeda galaxy, only the velocity along the line of sight. No way to tell if it's going to hit or not.
What to do? (Score:2)
stranger than fiction? (Score:2)
It seems like I read a sci-fi short story along these lines. Only I don't think it was a "black hole reignition". It was a "sun-like" object, only on a much larger scale. Scientists had verified it's existence and determined that, coincidentally, the first light from that object would soon reach earth (I don't know how they discovered it before the light from it reached us, but that's beside the point). Anyway, everyone's watching waiting to see this amazing new thing when it appears ... and it burns ev
The ORI are coming and need the black hole to powe (Score:2)
Re: (Score:2)
And it may have already happened, so go ahead and have that extra dessert.
-science nerd, dessert lover
Wrong. We are ~26,000 LYs from the galactic core. (Score:2)
Re: (Score:2)