Milky Way's Black Hole Wasn't Always Such a Wimp

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Milky Way's Black Hole Wasn't Always Such a Wimp

Posted by Soulskill on Wednesday May 30, 2012 @08:27AM from the you-wouldn't-like-me-when-i'm-angry dept.

scibri writes "Sagittarius A*, the dormant supermassive black hole that lies at the center of our galaxy, was much more active not that long ago. Astronomers using the Fermi Gamma-ray Space Telescope have picked up some faint gamma-ray signals that suggest Sagittarius A* was emitting a pair of powerful gamma-ray jets like other galactic black holes as recently as 20,000 years ago (arXiv paper). If our black hole was more active in the past, it could explain why Sagittarius A* seems to be growing about 1,000 times too slowly for it to have reached its current mass of about four million solar masses since the Galaxy formed about 13.2 billion years ago."

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dormant black hole? by ZombieBraintrust · 2012-05-30 08:38 · Score: 4, Interesting

What makes a black hole dormant? Lack of gamma ray jets... ?
1. Re:dormant black hole? by buchner.johannes · 2012-05-30 08:48 · Score: 4, Informative
  
  What makes a black hole dormant? Lack of gamma ray jets... ?
  Lack of gas and dust streaming in. The disk + torus the infalling gas produces while accreting produces all the radiation we see from black holes in active galactic nuclei (AGN). Another side effect are the jets that you can see in radio frequencies (although not in all AGN.
  There is actually a gas cloud falling in in these decades, so we might see our black hole light up. http://www.nature.com/nature/journal/v481/n7379/abs/nature10652.html
  
  --
  NB: The message above might reflect my opinion right now, but not necessarily tomorrow or next year.
2. Re:dormant black hole? by buchner.johannes · 2012-05-30 09:04 · Score: 4, Informative
  
  I'd like to know where this black hole came from. Was there some random star floating through space, which died, and then it started gobbling up everything? Including our galaxy (which will eventually fall in). Or maybe the superblackhole was a previous galaxy from ~25 billion years ago that fell into itself?
  To my knowledge it is currently unknown how those massive black holes (millions of solar masses) form originally. We know they form very early in the universe (1Gyrs after the big bang, our universe is ~14Gyrs old). Do they come from many stars? Were stars in those early times extremely massive? Is there some way of growing black holes very fast?
  Those are open questions in Astrophysics ... you are welcome to join in :)
  We know that merging galaxies should combine their black holes but also grow them (more gas infall) -- but nobody knows how two black holes merge ( https://en.wikipedia.org/wiki/Binary_black_hole#The_final-parsec_problem ).
  
  --
  NB: The message above might reflect my opinion right now, but not necessarily tomorrow or next year.
Re:Weight of a teaspoon amount by fuzzyfuzzyfungus · 2012-05-30 08:42 · Score: 4, Insightful

I get the impression that concepts like 'volume' start to get a little tricky once you pass the event horizon...
Re:Weight of a teaspoon amount by Colonel+Korn · 2012-05-30 08:49 · Score: 4, Informative

The singularity itself? A teaspoon of singularities would have infinite weight. Maybe you mean everything inside the event horizon? In that case calculate the Schwarzschild radius (2Gm/c^2) of 4 million solar masses, then get the density [4 million solar masses /(4/3 pi r^3)] and multiply by the volume of a teaspoon. I think the density of everything inside the event horizon for that big of a black hole is actually pretty low.

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"I zero-index my hamsters" - Willtor (147206)
Re:Weight of a teaspoon amount by Anonymous Coward · 2012-05-30 09:00 · Score: 5, Funny

Don't know, none of our "teaspoon on a rope" measuring devices have been successfully pulled back out past the event horizon.
On an unrelated note, we need more interns.
Asterisk by Megane · 2012-05-30 09:00 · Score: 4, Funny

It wasn't always such a wimp, but then it got caught doing steroids, so it had to have an asterisk after its name.

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#naabhaprzrag, #sverubfr-000, #agi-fcbafberq, negvpyr[pynff*=' negvpyr-ary-'] { qvfcynl: abar !vzcbegnag; }
I dare you by Anonymous Coward · 2012-05-30 09:06 · Score: 5, Funny

Oh sure, it's easy to call it a wimp from way out here on the outskirts of the galaxy. But I bet you wouldn't call it a wimp if it were right in your face!
Re:WWKKT? What would Kim K. think? by osu-neko · 2012-05-30 09:52 · Score: 5, Insightful

Is anyone else disturbed that such an incredibly major change happened only 20,000 years ago?
This could be worse than an ice age.
No. If, 20,000 years ago, it was much more active, it proves living in a galaxy with an active nucleus is not a problem. What it means is, if it becomes more active again, we don't really have anything to worry about -- we've been living with the "problem" for most of five billion years and gotten along just fine...

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"Convictions are more dangerous enemies of truth than lies."
quieted by mass by __aaltlg1547 · 2012-05-30 12:15 · Score: 4, Interesting

It was explained in my astrophysics class that when a black hole reaches a certain mass that whole stars pass inside the event horizon before being torn up by tidal force. Then the singularity no longer has a big accretion disk and the radiation emitted by infalling matter is trapped within the event horizon. So it goes quiet.