Chandra's view of Sagittarius A*, the Milky Way's central black hole, in 2005. (AFP/NASA-HO/File)
X-ray Echoes of a Past Outburst of Sgr A*
15 Apr 2008
In a forthcoming paper, the history of the X-ray brightness of Sgr A*, the massive black hole at the heart of our Galaxy, is derived from observations made over a 11-year period by four X-ray observatories. The results are based on X-ray line emission from molecular clouds, considered to be reflecting Sgr A*’s X-ray emission with a delay time of 300 years.
Sgr A* is a compact radio source located at the dynamical centre of our Galaxy as confirmed by, for example, its apparent motion (solely due to our own motion around the Galactic centre) and the orbits of stars close to the Galactic centre. It is generally believed to be a massive black hole of several million solar masses.
Currently, Sgr A* is observed to be in a quiescent state. Its X-ray luminosity is several orders of magnitude below that of active galactic nuclei with a comparable sized black hole. This is the case even during the known frequent flaring events of Sgr A* when the flux increases by a factor of ~10. Observed events in our Galaxy’s central region actually occurred ~26 000 years ago as we are at a distance of about 8 kpc from the Galactic centre.
Does this mean that we will begin to detect evidence of the feeding frenzy 25,700 years from now?
Wow, 26,000 light years away and we know what happened 300 years ago. Time travel is here!!!
This is my galaxie. There are many like it, but this one is mine.
(You may use it, but bus your own trays.)
If the gases illuminated when they passed near the black hole, and
If the black hole is 26,000 light years away, and
If the black hole awoke only 300 years ago, THEN
How could the brighter light from the illuminated gas have reached us by now to figure this out?
What do I know . . .I’m a only a banker.
Don’t we need to wait another 25,700 years to know what it was doing 300 years ago?
Monster black hole? 300 years ago?
I had no idea Michael Moore was that old.
Whoever wrote this is an idiot. Here’s better explanation.
The black hole is 26,000 light years away. 300 years ago plus 26,000 years, a major supernova flare occured. It ejected massive clouds of gas. Those gases took 300 years to reach the vicinity of the black hole, and the effect the black hole had on that gas is just now reaching us. All the excitement happened back when humans were still duking it out with each other over who got the best mammoth steaks.
I am confused. If it is 26,000 light years away, how do we know what happened 300 years ago????
John Wheeler not available for comment.
Wouldn’t that really be 26,300 years ago?
I’ll blame the journo for this blooper: It is impossible to determine what took place 300 years ago on an object that is 26,000 light years away.
A flare affecting something 26,000 light years away?
WOW! News travels fast.
What is the chance that clouds of gas exist between us and the supernova, with a 300-light-year added path difference compared to straight line-of-sight with the supernova? As seen by us, those clouds would be lighting up right now in the reflected light of the supernova, which may be detectable. If the clouds were large, we should see a spherical shell of illumination traversing them (at the speed of light). Parts would light up or disappear as the supernova’s light hit new patches, or traversed beyond the spatial extent of patches previously illuminated.
The Cycle of Cosmic Catastrophes:
Flood, Fire, and Famine
in the History of Civilization
by Richard Firestone,
Allen West, and