Slashdot Mirror
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.
This space unintentionally left blank.
so at 4 million solar masses how much would a teaspoon of that stuff weigh?
Is that +/- the 27.000 years that light would have to travel in order for us to observe the jets stopping?
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!
Is anyone else disturbed that such an incredibly major change happened only 20,000 years ago?
This could be worse than an ice age.
(-1: Post disagrees with my already-settled worldview) is not a valid mod option.
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."
What does 20000 years ago mean, given that there 26000 is a light-year distance between us an Sagittarius A*?
Is that 20000 + 26000 = 46000 years, since otherwise we would still see the jets for the next 6000 years?
What does 20000 years ago mean, given that there is a 26000 light-year distance between us an Sagittarius A*?
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.
Ph'nglui mglw'nafh Cthulhu R'lyeh wgah'nagl fhtagn.
In the land of the blind, the one-eyed man is king.
http://www.google.com/search?q=galactic+superwave+theory
One example:
http://www.etheric.com/LaViolette/Predict.html
"Subsequent concurrence (1998): In 1988, when presented with Dr. LaViolette's Galactic explosion hypothesis, astronomer Mark Morris dismissed the idea as having no merit. However, in 1998 after ten years of observation, Morris was quoted as saying that the center of our Galaxy explodes about every 10,000 years with these events each lasting 100 years or so."
Imagine if you were to go outside one night and the sky suddenly lit up as bright as day and stayed that way for 100 years!
Maybe matter falls towards the galactic core, but interacts with the core to produce shock waves that push it away again, to form some sort of resonant process that happens every 10,000 years?
A 21st century issue: the irony of technologies of abundance in the hands of those still thinking in terms of scarcity.
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.
Surely he would have un-invented chads while he was there?
And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.
If two black holes happens to be near each others, will they collide?
Or will one of the black hole swallow the other?
Will the bigger black hole swallowing up the smaller one, or will it be the reverse, the little guy biting chunks out of its bigger counterpart?
And when two black holes interact with each others, what will happen to the dimensions?
Will it create enough disruptions to the dimensions in the vicinity that temporary additional dimensions pop up here and there?
Muchas Gracias, Señor Edward Snowden !
The singularity (theorized to be) at the center of a black hole is a mathematical point in space/time, and so of infinite density. As we "step back" from the singularity, the average density of the matter/energy racing by quickly decreases, and would depend on how much crap is accreating during the measurement. Once we're within the outer (Schwarzschild) horizon, we (again, theoretically) speed up beyond the speed of light, only to find things getting really backed up close in. We hit the inner (Cauchy) horizon, which I'll naively label a standing "shock wave", and go subluminal the rest of the way in. Calculating the density at that "shock wave" might be an interesting exercise for a post-grad/doc.
The singularity would hold the vast majority of the mass within the event horizon, and thus when deposited in your teaspoon (or hell, on the tip of a pin) would weigh in at 4 million solar masses. Your question works better when scooping up a bit of a white dwarf or neutron star, two stellar remnants that are in fact solid at their surfaces.
white dwarf: 4.95 metric tons (5.4 short tons)/teaspoon
neutron star: 18.3 metric tons (20.1 short tons, near the surface)/teaspoon
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.
Much as the primordial gas cloud of our solar system created enough density at the center to light up as a star, the much more massive cloud of material that is our galaxy was likely to collect a clump at/near the center that would pass the Schwartzchild limit and collapse as a black hole. It might not have had all that much time to shine like a star before collapsing, or it may have been a number of stars merging within the crowded galactic core. After the collapse, those stars that were about to merely merge with the center mass instead were instead ripped into a huge accreation disc, and feed the powerful polar jets we used to call quasars
I haven't read Susskind yet, but I have read General Relativity by Dirac.
According to Dirac's, the singularity will never actually occur because of time and space dilation. The stellar matter will accelerate towards the singularity but never actually reach it. And never is an appropriate term since according to Hawking the black holes have a finite lifetime and will eventually evaporate according to Quantum Mechanics.
Will get to Susskind as soon as I finish a couple of Penrose books.
If someone is passing you on the right, you are an asshole for driving in the wrong lane.
Wouldn't it be ironic what we call Black Holes are really Wormholes...
Unless there is some unknown thing about the radiation stopping that allowed civilization to develop.
Like a lower rate of mutations allowing humanity to become genetically stable.
Sounds like a good Sci-Fi premise.