[net.astro] StarDate: September 17 Discovery of the Ghoul Star

dipper@utastro.UUCP (Debbie Byrd) (09/17/85)

A star called Algol can be seen with the naked eye to fade periodically
in brightness.  More about this star -- when we come back.

September 17  Discovery of the Ghoul Star

On today's date in the year 1764, the German astronomer John Goodricke
was born.  At the age of 18, he determined regular intervals of
brightening and fading in a star -- the star known to the ancients as
the Ghoul Star.

Today we call this ghoul star Algol.  Algol is an amazing star because
it really does fade in brightness at regular intervals of about three
days.  It stays faded for about 10 hours, and then slowly brightens
again.  This entire process, by the way, is visible to the naked eye --
and can be seen if you carefully compare the brightness of Algol to
nearby stars.

John Goodricke died at the age of 21 -- just three years after his
study of Algol.  But he was the first to suggest that this star is
really two stars -- and that its fading brightness is caused by a
partial eclipse of one star by the other.  We call stars like Algol
"eclipsing binaries." They are accidents of our particular vantagepoint
in space -- in other words, we only see Algol fade because because the
eclipse occurs along our line of sight from Earth.

To the ancients, the ghoul star Algol was one of the most dangerous and
unfortunate stars in the heavens.  It represented the head of Medusa --
a monster who had snakes in place of hair.

With the aid of a star chart, you can get to know Algol -- and watch
its changing brightness.  The star is located in the constellation
Perseus -- now visible in the northeast each evening.


Script by Deborah Byrd.

(c) Copyright 1984, 1985 McDonald Observatory, University of Texas at Austin