Jocelyn Bell
Observing > Forty years ago today, a paper came out of Cambridge University in England announcing to the world the discovery of yet another bizarre heavenly object, a mysterious "pulsing" animal found quite by surprise. We now call it a pulsar.
It was actually discovered the summer before, in July 1967, by a young postgraduate student at Cambridge, Jocelyn Bell. And as is common in the sciences it was discovered without being looked for. She and her thesis advisor had been doing radio astronomy on far more distance objects when out of nowhere popped this little throbbing goblin.
Radio astronomy uses the radio part of the electromagnetic spectrum to "see" things out there, things invisible to our eyes. While searching deep space with her radio telescope she came across a strange pulsing of radio waves coming from an unknown point in space. Like a heartbeat it was very regular, unlike a radio noise one might expect.
It was such a regular pulse that it was suggested the signals might have been from an intelligent source, perhaps an alien civilization. Tongue firmly in cheek, the strange discovery was first called LGM-1, for Little Green Men.
The humor aside, the object was a mystery. But shortly after the release of the paper, astronomers figured out what it was. It turned out that the pulsar was just another stellar object we already knew about, only seen from a different point of view. It was a neutron star. But what is that exactly, and why do some pulse?
A neutron star is the core remnant of a giant star that went boom. When a massive star dies, it blows away its outer layers in a giant explosion called a supernova. But the core implodes into a superdense ball of neutrons.
When I say superdense, I mean superdense. A cubic inch of this stuff would weigh in at 100's of millions of tons. That, my friends, is superdense!
Moreover, when one forms it spins just like the star it came from, but it spins fast. You guessed it... superfast. Like an ice skater bringing in her arms to spin faster, the neutron star, shrunk to the size of a large city, can spin fast - hundreds of times a second.
This high spun neutron star has a north pole and a south pole, the result of an intense magnetic field. It is out of these poles that radio waves spew.
This all leads us back finally to the pulsar. You might already be able to figure out what those pulses are. If the neutron star is spinning like a top but the magnetic field is slightly off axis, you can see how its radio beams could sweep out an area like the searchlights at a world premiere.
I'll use the classic lighthouse analogy as an illustration. As the beam of light from a lighthouse sweeps around and around, those on the horizon – in the line of sight – see what appears to be a regular pulse of light.
That is what a pulsar is like. It is a neutron star whose expelled radio blast is in our line of sight. We see the "pulse" each time it sweeps by. Other neutron stars could no doubt be pulsars if they would just line themselves up with us.
Once they were found, astronomers went looking for them and found them by the bucketsful.
As to Jocelyn Bell, her faculty advisor got a Nobel Prize for his work in pulsars. Jocelyn was passed over. Hmm... At any rate, her discovery of the pulsar has probably inspired many young women to take up a discipline long held captive by men. Someone say "Amen!"
Who needs a Nobel Prize, anyway.
Until next time, clear skies!
Posted by Mark Ritter at 2008.02.24 02:35 PM | Comments (0)
