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Milky Way's Black Hole a Gamma Source?
eldavojohn writes "A paper recently accepted for publication (preprint here) proposes a sound explanation for the source of the gamma rays that permeate our galaxy. The Milky Way's central object Sagittarius A*, widely believed to be a supermassive black hole, is now suspected to be the source. To test this theory, two scientists created a computer model to track the protons, flung outward with energies up to 100 TeV by the intense magnetic fields near the event horizon, as they make a random walk through the plasma environment. It can take thousands of years for them to travel 10 light-years from the black hole, where they collide with lower-energy protons to form pions. These decay into gamma radiation emanating from a torus-shaped region around the central object."
"The Milky Way's central object Sagittarius A* [CC], widely believed to be a supermassive black hole, is now suspected to be the source."
Would that make it an "A-Hole" ?????
Agent K: A *person* is smart. People are dumb, stupid, panicky animals, and you know it.
Long Shot is ready for departure
I wonder if that means that life is only possible near the outer arms of the galaxy? If you assume that gamma rays are a point source in the middle of our galaxy, what sort of radiation levels are you going to see closer to the center?
You're thinking of microwave radiation.
- None can love freedom heartily, but good men; the rest love not freedom, but license. -- John Milton
The world's burning. Moped Jesus spotted on I50. Details at 11.
The summary makes it sound as though this is an explanation for the DIFFUSE gamma-ray emission seen in our Galaxy. This is not the case, the paper only discuss a source of gamma-rays observed to be spatially coincident with the Galactic center. Gamma-ray telescopes do not have high angular resolution so there is a possibility that the gamma-rays are not actually coming from the Galactic center in the first place. Finally this is not a new proposal. Proton acceleration near black holes is quite commonly discussed and accepted. Furthermore photo-pion production is a well known process that has been well measured in the lab. I think the real meat of this paper is that they are suggesting observations of emission associated with the black hole that we have observed gravitationally for a while now. This is the big news, not that the gamma-rays in our galaxy have been explained, not that protons make pions which decay into gamma-rays.
Tardigrades [aka Water Bears], which live everywhere on this planet Earth, can...
1) resist storage in liquid nitrogen
2) survive in contact with mineral acids, organic solvents, and boiling water
3) survive in a a vacuum and under high pressure
4) withstand ionizing radiation of over 600,000 roentgens (500 roentgens would be fatal to a human)
While this probably is an accurate translation, GP has a point. A lot of science can seem rather ad hoc at times. Before we had discovered all the planets, scientists noted that the orbits of the known planets were not quite what they should be. Instead of declare that newton's theory of gravity was wrong, they theorized that there was an unknown planet. After doing some calculations, they determined where this planet had to be, looked up at the sky, and found Neptune.
Similarly, when cosmologists look at the apparent rate of expansion of the universe (and how that rate has changed over time), they get that if their model of the way things work (general relativity) is correct, then their estimates of the mass in the universe based on empirical observation cannot possibly be right. Instead of abandoning relativity and leaving a void in its place, they say, "This will work of there is a large amount of matter that we can't observe. Dark matter!" Of course, this doesn't resolve everything, and we need various other adjustments (like dark energy, or physical constants that aren't constant) which look like kludges, but which have predictive power and are the best answers we've got.
Do we "know" this is correct? Of course not! We don't even know that the next time we drop an apple, it will fall to the floor. Science is a process, though, and it isn't productive to dismiss the theories of today before we've seen the observations of tomorrow.
We know a lot more than you give us credit for, perhaps you need to read a little deeper, try Relativity by Albert Einstein. AE just made up stuff because observations didn't fit Newtons proven model. So he just made up some equations to match the observations. But alas his made up equations didn't correctly model acceleration or gravity, so he made up GR.
GR is a very accurate theory, and there is experimental evidence of it. The two most famous are the perihelion precession of Mercury, and stars visible near the eclipsed sun. Of course being semi-interested in Cosmology/Astrophysics you would already know that.
Stuff like Dark Matter that just doesn't get made up, it falls out naturally when equations which are shown to work in one situation are shown to fail in another. DM vs GR for example. There's a lot of guess work as to what DM is, but that's where life gets interesting, we don't know what it is. We know 'something' is there, we just don't know what the something is. DM isn't a convenience item, its a wart, because without the wart GR which is shown to work in other cases could be used to correctly model galactic motion.
If someone is passing you on the right, you are an asshole for driving in the wrong lane.
"Do discoveries like this mean anything at this time considering there's no way to prove any of it?"
There is no way in science to PROVE ANYTHING. All one can do is disprove a theory you can never prove a theory to be true. This is a very basic part of how science works
A theory is a good theory if it is predictive and makes good predictions and it is disprovable and it has not been disproved. But a theory can't be proven to be true.
Have you ever read Wittgenstein? Goggle the name. He wrote, long before the 1960's a question "Have I ever been to the moon?" He argued that while he thought he'd never been there and knew of no one who had he could not prove he's never been to the moon and further that such proof was impossible. Proof is very different from being very, very certain. He goes on to explain the difference and what can and can not be proven. Some things can never be proven not matter what you do
In science all you can be is "very certain" but must always be open to being proven wrong. For example we think and are very certain that light follows the inverse square law but can you prove that it ALWAYS does? It only takes one exception to disprove the theory but a trillion observations would not prove it true.
Well now I'm thinking of heating up a frozen BBQ sandwich. Thanks.
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