NASA's Fermi Satellite Detects First Gamma-ray Pulsar in Another Galaxy
14 Dec 2015 16:23:31 UTC
Topic 198342
(moderation:
Quote:
The pulsar lies in the outskirts of the Tarantula Nebula in the Large Magellanic Cloud, a small galaxy that orbits our Milky Way and is located 163,000 light-years away. The Tarantula Nebula is the largest, most active and most complex star-formation region in our galactic neighborhood. It was identified as a bright source of gamma rays, the highest-energy form of light, early in the Fermi mission. Astronomers initially attributed this glow to collisions of subatomic particles accelerated in the shock waves produced by supernova explosions.
"It's now clear that a single pulsar, PSR J0540-6919, is responsible for roughly half of the gamma-ray brightness we originally thought came from the nebula," said lead scientist Pierrick Martin, an astrophysicist at the National Center for Scientific Research (CNRS) and the Research Institute in Astrophysics and Planetology in Toulouse, France. "That is a genuine surprise."
This apparently did not involve Einstein, but I have seen no mention of it here, and thought it might be of interest.
NASA's Fermi Satellite Detects First Gamma-ray Pulsar in Another
)
Not one of ours, but that's OK. :-)
These are crazy beasts. The power involved is insane and that nebula is glowing at that energy range mainly due to that single object. The age estimate ( since formation ) is a mere two thousand years. I guess the expectation is that ( eventually ) SN 1987A will appear with similar features. One reason, at least, why they are rare is that they wouldn't behave that way for long in relative terms. At that rate of energy bleed, they would settle down to a more sedate mode. So while all/most supernova generated pulsars could go through such a stage that is all too brief and most that we now see have already done that. SN 1987A could well have a gamma pulsar but ejecta is hiding the pulsatile nature thus.
Cheers, Mike.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
RE: Not one of ours, but
)
Monster indeed, you could toast a marsh mellow a light year away.. I wondered if this pulsar might have an accretion disk or some such.
A bit of searching ...
Deep view of the Large Magellanic Cloud with 6 years of Fermi-LAT observations
RE: The age estimate (
)
I wonder if there are any historical records of a bright star being visible two thousand years ago?
You more or less took the
)
You more or less took the words out of my mouth, but whatever your view on the subject, Merry Christmas.
RE: RE: The age estimate
)
You mean something very bright in the sky - perhaps even during the day - that could, for instance, serve as a direction indicator for any south bound travelers ? Naaah, no way ..... :-)))
Cheers, Mike.
( edit ) Or put another way : what is the greatest northern latitude for which the LMC could be visible ? :-)
( edit ) LMC is at 69 degrees south, Bethlehem ( to take a random example ) is at 32 degrees north. 69 + 32 = 101 > 90 by 11 degrees .... and I don't think the LMC has a proper motion to alter that very much in a few millenia. Nor will low-on-the-horizon refraction help much either. Also not polar nutation ....
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
RE: LMC is at 69 degrees
)
Ahhh... but I think you're forgetting about that 5-star post-natal clinic in Capetown that M, J and baby were attending at the time ... :-).
After all, if you find a good Doc, you will go a long way for the benefits ;-) :-).
Cheers,
Gary.
Guardian Education had the
)
Guardian Education had the same idea yesterday:
RE: RE: Not one of ours,
)
That is also interesting. It references another study ( H.E.S.S. ) that finds Tev scale photons too. However they discuss those as being, maybe, from cosmic ray interactions with nebular gas. In that case the insanely-insane per particle energies of cosmic rays ( typically protons ) as they hit the relatively lower energy gas molecules converts to photon energy.
The top end of the cosmic ray spectrum is under dispute, but per particle energies of the order of thousands of Joules are postulated. Plenty enough energy ( ~ 10^[21] eV ) in one proton to boil your cup of coffee ! Now where oh where do they come from, huh ? :-0
Cheers, Mike.
( edit ) Actually CR's are also equivalent to a bean-bag round from a shotgun.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
RE: ..... In that case the
)
Wow ! Is the Earth's magnetic field able to stop these ?
I guess it must or, we'd all be fried by now.
Bill
RE: RE: ..... In that
)
No. It doesn't. They just plow on in. The overall flux is quite low compared to other radiations. In any event the atmosphere is our shield here, CR's hit the air molecules and cause of a 'shower' of secondary particles. That mops up and diverts the energy. Like a sponge. The deeper one is in the atmosphere - the closer to sea level, or even underground/water - the less you will risk. The various neutrino experiments are sited deep underground in old mines etc, to reduce the interference to the studies from cosmic rays.
For comparison a long haul plane flight at say 35000 feet is equivalent in radiation dosage to a traditional chest x-ray.
[ These days ( say the last 20 years ) the radiation dose from medical plain films is rather lower due to sensitivity improvements in the film substrate - rare earth elements - so they can turn the tube voltage down and still get good tissue penetration and definition. ]
Cheers, Mike.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal