On 03/29/2012 01:50 AM, Jim Palfreyman wrote:
Folks, I'm currently writing my thesis on pulsars, but I need to spend time on it rather than here. :-) But since a lot of this discussion is right at the front of my brain, here's a summary.Some pulsars "glitch" or speed up. The Vela pulsar (PSR J0835-4510) does this (this is the pulsar I've been studying) and yes these type of pulsars are bad clocks. A jump of its pulse rate of the order of 10^-6 s/s randomly every few years is not good. It does nearly settle back to its original rate after a few months. The nature of these glitches (in Vela at least) is not well understood, but three theories have been put forward: - An orbiting planet - but this has been discarded due to their irregularity. - Star quakes caused by a separation of the crust on the surface of the neutron star from its super-fluid interior. (Not very popular any more) - The effects of tiny micro vortices in the internal super-fluid. (If you can understand this paper - good luck to you!) Now faster pulsars, in particular millisecond pulsars (~700 Hz from memory is the fastest) are quite good clocks and they do rival atomic clocks. The hunt is on to find as many of these as they can, well spread across the sky, so they can look at the effects of gravitational waves on the beams of these super accurate clocks. This is one proposed method to detect gravitational waves. The main problem I see from the original suggestion is that most pulsars are quite faint and you need a very decent telescope to see individual pulses. Vela is very bright, and the 26m telescope I used can only just see the average pulse. I'm studying bright pulses and we can see those easily. So to dedicate a massive radio telescope (or two) pointing at a millisecond pulsar just so we can re-transmit it, is probably not sensible. However, studies of these remarkable pulsars is ongoing.
Hmm, wouldn't the space-located antenna have a good chance of better S/N as the antenna sees cold space and could be kept cold itself?
I was also thinking antenna size would be a limitation. Then I was thinking about what WMAP has achieved in measuring the background temperature and look back at the very early years of the universe.
Cheers, Magnus Cheers, Magnus _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
