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Milky Way's Black Hole Wasn't Always Such a Wimp
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."
What makes a black hole dormant? Lack of gamma ray jets... ?
Just more evidence that eating turkey makes you sleepy. It would appear that our galaxy's super massive black hole ate too much space turkey, and now it is having a nice long nap.
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I get the impression that concepts like 'volume' start to get a little tricky once you pass the event horizon...
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.
"I zero-index my hamsters" - Willtor (147206)
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.
It wasn't always such a wimp, but then it got caught doing steroids, so it had to have an asterisk after its name.
#naabhaprzrag, #sverubfr-000, #agi-fcbafberq, negvpyr[pynff*=' negvpyr-ary-'] { qvfcynl: abar !vzcbegnag; }
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!
> The singularity itself? A teaspoon of singularities would have infinite weight.
No, it wouldn't. Black holes have a finite weight.
> The singularity itself? A teaspoon of singularities would have infinite weight.
No, it wouldn't. Black holes have a finite weight.
Singularities consume no space, so you can fit an infinite number of finite weight singularities in a teaspoon. Hence infinite weight
Your mass/volume ratio is way off, though the other three are correct. It should be...
mass / volume = 1.155 * 10^6 kg/m^3
1 tsp = 4.929 * 10^-6 m^3
1 tsp of Sagittarius A* = 5.693 kg
So, it's pretty heavy, but eg. neutron stars are far, far heavier. This black hole is far denser than the sun, which has about 6.94 g per tsp.
> The singularity itself? A teaspoon of singularities would have infinite weight.
No, it wouldn't. Black holes have a finite weight.
Right, but an infinite number of singularities will fit in a teaspoon (or any volume, for that matter).
"Convictions are more dangerous enemies of truth than lies."
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...
"Convictions are more dangerous enemies of truth than lies."
Al Gore went back in time 20,000 years (and you thought he only invented the Internet) to begin the process of Galactic Cooling so counteract the effects of Global Warming.
Wolfram Alpha disagrees with both of you. It gives the result as 1.1 kg.
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.
We now have evidence that gamma rays influence climate
Speaking of incomplete data - No, we have evidence that gamma rays leave a vapour trail in a cloud chamber since that's how we detect them in an atom smasher. A few people have taken this fact and speculated that gamma rays affect the climate by seeding clouds, there are even a couple of books about the idea. Only problem is, their speculation does not not fit everyone else's observations. However you will find the 'Iris theory' presented as fact in the opinion pages of the wall street journal. Why? - Because on top of their complete lack of evidence, the people pushing this idea just happen to think it 'proves' Earth's climate is self regulating so we don't have to worry about regulating our emmissions.
And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.
http://www.wolframalpha.com/input/?i=Schwarzschild+radius+of+4+million+solar+mass+ = 7 million miles
http://www.wolframalpha.com/input/?i=Sagittarius++A*+radius = 13 million miles
Seems Sag A* radius is based on observed angular size of the radio source.
From the view of an outside observer, the larger (greater mass) black hole will appear to draw the smaller one in. In reality, they're drawn to each other, and eventually merge, like two drops of water meeting on a window pane. The singularities become one. Simulations suggest that the merger will radiate massive quantities of energy in the form of gravity waves, a major ringing of the bell.
The ringing quickly dies down, and the only evidence of the merger being 1) the changed direction of movement relative to other nearby objects and 2) major disruptions of whatever was orbiting the two holes, from stars down to the accreation disc gas.