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Age Of Most Pulsars Is Now A Mystery
Guinnessy writes "A pulsar that has been viewed by the Very Large Array in New Mexico for the past ten years, is only 65,000 years old not 107,000 years as astronomers previously thought. The new results suggest that the main techniques that astronomers use for measuring the age of pulsars is completely wrong. There's a press release about it the NRAO's web site."
Once upon a time (well, 4 years ago), I was being trained for pulsar research. It's a topic that I still find fascinating, if even I rarely worry about things outside this solar system these days. But I have a few thoughts to offer:
It isn't as if pulsar spin-down ages have ever been that trustworthy, anyway. As far as I know, no one is putting much faith in them, beyond a factor a few. This work indicates that the spin-down ages is off from the dynamic age by a factor of 2. For astrophysics, that's bang-on (as Carl Hansen likes to say).
Basically, the weaknesses of the spin-age are pretty obvious: you assume the pulsar started spinning infinitely fast (well, obviously not) and that the field isn't decaying in time. In fact, it is known that dynamic ages are smaller than spin-down ages for older pulsars (around a million years), possibly due to field decay. (Er, "dynamic ages" has previously been determined by how far the pulsars have moved above/below the galactic disk and how fast they are moving.)
I was also a little irked by the statment that this is the first pulsar were we've been able to find the supernova remenant it is moving out of. The wording seemed to me to imply that we've never been able to associate a pulsar with a SN remenant before, but both the Veil pulsar and the Crab pulsar are clearly associated with known SN remenants. However, I don't believe that either of them is moving. (Flip side, we know exactly how old the Crab pulsar is, since the Chinese recorded the SN in 1054 AD.)
That's enough from me, for now. Other than to say that I'm kind of impressed that they did this on the VLA. It really isn't the best instrument for pulsar work. (But there aren't many radio dishes far enough north to cover the northern sky.)