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The Milky Way's Black Hole Is Not So Quiescent
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.'"
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)
That's a bit of a confusing sentence but I think I understand. What they really meant to say is that if Sagittarius A's flare produces a 26,000 Hz tone, it
will interfere with GT&T's subspace carrier signal and allow you to send free messages to the gamma quadrant.
How bright is a million times brighter than black?
In theory, practice and theory are the same. In practice, they're not.
Warning: that expression does not quite meant what it seems to. The "timeline" under discussion here is from our point of view as light from that area arrives here, after about 26,000 years. On the other hand, that doesn't quite mean that the events actually happened "26,300 years ago" -- there's no good global notion of time that is applicable here.
The black hole was a million times brighter three centuries ago.
We are talking of a BLACK hole here, correct ?
In Larry Niven's old Known Space story "At the Core" (collected in Neutron Star , he conjectures that because the stars at the core are so close together, one supernova-ing could cause a chain reaction that would bring killing radiation to all reaches of the galaxy. What do astrophysicists today think of this possibility? All the hype now seems to be on black holes.
'The black hole was a million times brighter three centuries ago.'
What is it about this phrase I just can't wrap my mind around? Black hole...Brighter?
Damn global warming!
Already posted a few days ago.
Prov 9:8 Do not rebuke mockers or they will hate you; rebuke the wise and they will love you.
I suspect this mostly happens when normal or superdense (neutronic) matter nears and passes the event horizon. The bigger/better question is: Any estimate on the amount of matter ingested to produce the fireworks? How many solar masses? Just what is going on around that drainhole?
To all those confused about black holes being bright - you need to learn the "two things rule" proposed by a colleague of mine - it runs like this:
There are two things you need to know about black holes: They're not black, and they're not holes.
There are two things you need to know about parallel universes: They're not parallel, and they're not universes.
There are two things you need to know about the big bang: It wasn't big and it didn't bang.
Sadly it extends way beyond just physics, but it does give an insight into why physicists have trouble communicating with the public - names come from the very early days of an idea and as often as not end up being misnomers.
In the original subject, IRTFA and came to some stupid conclusions. Blame having a bubble in my eye and being stoned on endorphins from the pain in my neck and back from holding my head down.
Anyway, I didn't say that we're safe because the black hole is fifty thousand light years away and if it started spewing radiation, whatever was left of humanity (whether already wiped out, anything like ourselves, or what we may have evolved into would see the result.
However, the thing could have exploded fifty thousand years ago, and there's no way anybody could tell. Its radiation could reach us tomorrow.
However, I'm still more scared of being squished by an SUV than from the black hole. Hell, an asteroid strike is probably more likely.
-mcgrew
mcgrew's razor: Never attribute to stupidity that which can be explained by greedy self-interest
There are two things you need to know about the two things rule: It covers more than two things, and it is not a rule.
We Didn't Start the Fire...
Anything within the event horizon of the hole, by definition, cannot escape to the outside universe again. But that doesn't mean that matter OUTSIDE the horizon, falling into the hole, doesn't get heated up unbelievably hot and radiate like hell.
I suppose you could make a pedantic argument that it isn't the hole glowing, it's the matter falling into it, but it's certainly the hole which causes it.
26,000 years? Isn't this equal to the Mayan Calendar that predicts the end of time in 2012?
I always find the idea of the time/distance involved to be amazing, and it really kinds of gives you a good perspective on how big things are (small you are). Like a friend who pointed out that the half moon you could see in the sky was because of the shadow _of the earth_. That's just crazy talk, and even more interesting as it sinks in.
This type of thing though is interesting in how it may have already reignited. Maybe just this morning, maybe 20000 years ago. We have no idea, it's not as easy as just looking out a telescope to know. Perhaps massive waves of radiation or solar flares or cosmic rays have been headed to the earth for thousands of years and we could all die tonight, or maybe it'll happen tomorrow and our great^10 grandchildren will be the ones to see it happen. I'm rambling, sorry about that. Too much afternoon coffee.
I will shred my adversaries. Pull their eyes out just enough to turn them towards their mewing, mutilated faces. Illyria
And the similar hypothesis about the layer of enriched iridium in rocks formed at the boundary between Cretaceous and those of the Tertiary periods and the associated extinction event ... 65.5 million years ago.
Could that suggest an alternative to the "impact from an asteroid or comet" hypothesis? Could this actually be the observance of a 100 million year "or so" natural galactic cycle?
If that is indeed the case, we should expect our local galactic black hole to go "milky white" in 15 to 35 million years or so.
Keep your sunglasses handy!
BTW, if you couldn't already tell ... IANAAP and IANAPG
... oy. Why choose a word that means both "being at rest; quiet; still; inactive or motionless" and "Having the power or quality of acting; causing change; communicating action or motion; acting" for the news headline? (Dictionary.com Definitions)
Eviscerati.Org: All Hail the Eviscerati
"let loose a powerful flare"...
"26,000 Hz tone"...
Sounds like the Brown Note...
Move all sig!
I really like the fact that this one thread contains more friends and fans than any other i ever read.
Its a worthy subject and article.
Hivemind harvest in progress..
My Open Letter to the Universe: .Knock and it shall be opened-Seek and ye shall find.. I ask for winning numbers on next lottery ticket purchase. Although I am solvent, I need to help family members. Would like for my #s as purchased to be selected. Thanks for previous favors granted too. I am at peace & wish to share good fortune that comes my way. TRY YOUR OWN OPEN LETTER TO THE UNIVERSE!!
That point prompted me to add that simply because Sagittarius-A was more active 26,300 years ago than it currently is, does not put it on equal footing with the distant galaxies that have supposedly re-activated after maturity. The last discussion was focused heavily on possible threats to earth if Sagittarius-A should do the same.
In fact, we know that the level of activity 26,300 years ago was no indicator of the safety of the earth from a dramatic re-start like the last discussion covered, because there were people around 300 years ago who not only were not visibly affected by it, but apparently didn't even see it, or at least left no records if they did.
...are rarely correct. For instance, when i first read this:
has discovered that Sagittarius A* let loose a powerful flare three centuries before the time at which we are observing it
it looked like this:
has discovered that Sagittarius A** let loose a powerful fart three centuries before the time at which we are observing it
Well, according to MY astrophysicists, the thing was fine until Hotblack Desiato crashed his damn stunt ship into it.
From the Title:The Milky Way's Black Hole Is Not So Quiescent
;-)
If it's not so Quiescent, then perhaps it is Resplendent, or perhaps Exultant or maybe even Transcendent.
20>PRINT "HELLO, COWARD!"
RUN
Don't look now, but some Japanese scientists are doing what the late Albert Einstein said was impossible. Albert claimed that man was forever a prisoner on this planet by saying that faster than light travel was somehow 'impossible'. Now comes some scientists with no religion to save who claim that the central singularity in our galaxy did some feeding only three hundred years ago. That is what the PhysOrg.com artical claimed. The artical did not claim the event was 26 thousand plus three hundred years ago! It claimed that the large 'jet' was produced just three hundred years ago. That is how the abstract reads, sports fans.
Watch, the 'correctors' will now jump out of the woodwork and go apoplectic on cue.
True but not really relevant. Unless the readership of Slashdot is wider than I'm aware of the only frame of reference of relevance is that of the Earth. Hence that is the only frame you need to concern yourself with is that one.
Remember that the Earth frame is arbitrary. Although relativity stipulates that there is no privileged frame, strictly speaking there is only one intertial frame which is at rest with respect to the cosmic microwave background radiation; if the Earth were at rest in it then we would see a sky with a uniform temperature in all directions. Instead we can observe a dipole moment in the sky's CMB spectrum consistent with motion at 380 km/s toward the direction of Virgo. The inertial frame of the black hole would also be worthy of consideration. But of course this is all just Slashdot nitpicking, you do your calculations in the Earth's frame because you want your result to come out in Earth proper time, and realistically this means you don't do anything different.
Not actually true: they are larger at those relative speeds but are certainly present and noticeable at far lower velocities e.g. atomic clocks on Concord, GR corrections to GPS satellite clocks etc.
Those effects are negligible with this level of approximation. Basically everything can be considered to be at rest; you guys are making this way harder than it is. This is a simple problem of geometric optics. We're seeing this glowing cloud, with a region 10 light years across, brightening and darkening within the space of 5 light years. That's very hard to explain as anything other than a light echo from a source nearby that must have been bright, and small, and rapidly varying in brightness. And look, there's this supermassive black hole sitting here 300 light years away. You don't have to be Einstein to figure this one out.
The star V838 Mon is a good example of a light echo. This star emitted a huge flash in 2002 that made it the brightest star in the galaxy for a couple months. Then it dimmed to a normal brightness. Once it did, starting in mid-late 2002, we started to see a huge reflection of the flash begin to expand out from the star as it lit up the gas and dust in the vicinity. At any given time we see a glowing sheet of gas shaped like a paraboloid open towards us with the star at its focus, and every year this paraboloid gets bigger. Now that it's 2008 this thing has become a Firefox logo 12 light years wide that continues to expand outward in all directions at the speed of light.
Actually, it's not a completely new piece of information that the Black Hole at the center of our Galaxy - or its immediate surroundings, if you want to be nitpicky - was much more active
some 300+ years ago. See http://www.esa.int/SPECIALS/Integral/SEMSKPO3E4E_0.html
28 January 2005
The centre of our galaxy has been known for years to host a black hole, a 'super-massive' yet very quiet one.
New observations with Integral, ESA's gamma-ray observatory, have now revealed that 350 years ago the black hole was much more active, releasing a million times more energy than at present. Scientists expect that it will become active again in the future.
But it seems the authors of the current scientific publication missed the earlier result.
'By observing how Sagittarian-cluster inhabitants rolled their saucer windows down, then up, while accelerating and grimacing amidst shrill cries of "the smeller's the feller!", we could trace back the black hole's activity 300 years ago,'
...make a joke around that Red Dwarf quote about black holes and grit?