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From: dipper@utastro.UUCP (Debbie Byrd)
Newsgroups: net.astro
Subject: StarDate: November 19 Millisecond Pulsars
Message-ID: <805@utastro.UUCP>
Date: Mon, 19-Nov-84 02:00:29 EST
Article-I.D.: utastro.805
Posted: Mon Nov 19 02:00:29 1984
Date-Received: Wed, 21-Nov-84 05:09:08 EST
Organization: UTexas Astronomy Dept., Austin, Texas
Lines: 39

Astronomers know at least one star that may spin on its axis some 640
times per second.  More on millisecond pulsars -- right after this.

November 19  Millisecond Pulsars

Pulsars were discovered in 1967.  A pulsar is like a lighthouse star
that emits a discreet pulse of radio energy from a spot, or pair of
spots, on its surface.  So each time a pulsar spins, we on Earth see a
pulse of radio energy.

Most pulsars pulse once every fraction of a second -- or once every few
seconds -- but two pulsars have been found that pulse hundreds of times
in a single second.  These objects -- which then would be spinning
around hundreds of times each second -- are known as millisecond
pulsars.

The first millisecond pulsar was found only a few years ago, in 1982.
The second one was found the following year.  Like other pulsars, these
objects are believed to be neutron stars -- incredibly dense stars
formed in supernova explosions.  As material blows outward from a
supernova, the core of the star is crushed inward to an extreme density
-- and a neutron star is made.

The problem with millisecond pulsars -- which again pulse hundreds of
times each second -- and therefore are thought to spin around hundreds
of times in a single second -- is that they may be accountable only if
they lie in double star systems.  Material from a companion to the
neutron stars may be causing these stars to speed up their spins -- but
if that's the case, then how did the companion survive the
indescribable violence of a supernova explosion -- which gave birth to
the pulsar in the first place?

The answers aren't all in -- but the millisecond pulsars are a new
mystery for astronomers to think about.


Script by Deborah Byrd.

(c) Copyright 1983, 1984 McDonald Observatory, University of Texas at Austin