Expert: James Gort - 7/29/2011

Question
Hi James,
I'm a bit confused whther pulsars can be seen with the naked eye or not. This site says no http://answers.yahoo.com/question/index?qid=20090909210825AA76nBs
This site says "External viewers see pulses of radiation whenever this region above the the magnetic pole is visible"
http://imagine.gsfc.nasa.gov/docs/science/know_l2/pulsars.html

Answer
Hi H.M.,

No known pulsars can be seen with the naked eye. But, of course, they can be "seen" from earth - with telescopes.  As the sites you listed say, most pulsars are much brighter in the radio or even gamma regions of the spectrum, with less energy in the optical regime. But a good telescope will show at least one - the Crab Nebula's central star (in Taurus) - about 16th magnitude. But even if you saw it, the star wouldn't appear to be a pulsar, since its period is so fast - 33 milliseconds. Your eye/brain has something called "persistence of vision", which means that a fast on/off cycle would appear as continuously on.

A good (but somewhat dated) review of optical pulsars is found at http://www.eso.org/sci/publications/messenger/archive/no.99-mar00/messenger-no99.

Hope that helps.

Prof. James Gort