Milky Way Black Hole Could Reignite

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.

Comments

Protect yourself

[Beavertank]

Remember kids, just like government mind control rays the gamma ray bursts generated by our galaxy's black hole center can be blocked by a tin foil hat.

You may want a tin foil codpiece, too.

Eye muss bee knew hear

[sm62704]

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)

Re:Eye muss bee knew hear

[Dan East]

"The way the black hole could turn into a quasar is for the galaxy to collide with another galaxy."

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.

Re:Eye muss bee knew hear

[DirkGently]

Because black holes can only "eat" so fast.

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.

Re:Eye muss bee knew hear

[A nonymous Coward]

Nothing to see here (and if it happened, nobody to see it) Move along, move along.

Re:Eye muss bee knew hear

[IndustrialComplex]

Massive relativistic death lasers? Concertgoers bouncing against each other to near the speed of light?

It isn't a galactic collision. It's just the reunion tour for Disaster Area.

I am building a ringworld

[RichMan]

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)

Okay, so this isn't relevant to my day-to-day life

[mmell]

but it is intriguing. I'm always impressed when scientists come forward and admit that they've found something they didn't expect. It validates the scientific method and the people who apply it to research - whether it be mathematics, anthropology, physics, cosmology, . . .

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?

20 to 40%? Reignite?

[Gat0r30y]

From TFA it seems like somewhere between 20-40% of galaxies surveyed have active nuclei, but how do they know they reignited?

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. How could it be verified that despite the lack of a recent collision with another galaxy, these particular phenomenon were at some point dormant like ours, then reignited? How are they supporting this claim that these galactic nuclei must have spontaneously rekindled vs. they have been winding down from a collision very far in the past?

There's just one problem: Astronomers have found quasarlike centers--called active galactic nuclei (AGN)--in some relatively nearby galaxies, which should be far too old to generate such energies. So they should be too old for this sort of behavior, but how are they verifying the time since the last collision? Another possibility is that these galaxies had a collision more recently right?

Re:20 to 40%? Reignite?

[HTH NE1]

How could it be verified that despite the lack of a recent collision with another galaxy, these particular phenomenon were at some point dormant like ours, then reignited? By the velocity vectors of surrounding matter affected by the blast? A collision would give the local matter directionality whereas a spontaneous reignition would send matter out in all directions uniformly.

Haven't you watched CSI: Stellar Cartography Unit?

The galactic core could be exploding?

[meringuoid]

... Well, shit. I'd nearly saved up enough to buy a General Products hull, and now it seems they've shut up shop and left town.

No evidence for "re-ignition"

[random coward]

Quick summary of TFA: Scientists observe that the black holes at the center of galaxies were Quasars on far away galaxies. The one at the center of the Milky Way and other nerby galaxies were observed to not be Quasars. So they theorised that the black holes initially are quasars after galaxy formation, and they run out of fuel. New observations show that nearby galaxies do in fact have quasars. A scientist conjectured that it re-ignited. Better conjecture may be that the fuel source of those blackhole-quasars is more variable than previously thought.

Feed Me

[iamlucky13]

For a black hole to be active, it needs stuff falling into it...gas, dust, stars if you're unlucky. The stuff heats up to an extraordinary temperature due to friction as it falls in. To be hazardous at our distance of 25,000 light-years from the galactic center, it has to be quite a bit of matter falling in for a harmful intensity of radiation.

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.

Re:oblig.

[infonography]

Worst. Trek. Movie. Ever. Don't be so hasty, there are plans for many more....