January/February 2004 Table of Contents
courtesy of A Lobel.
eruption in 1946 of mighty Rho Cassiopeiae put the astronomy community
on guard, and recent, exciting changes in the star may portend something
big and explosive for it in the near future.
goes without a proper name, but recently the 17th brightest star
of the northern constellation Cassiopeiae is drawing the attention
of amateur and professional astronomers worldwide. In the spring
of 2000 Rho Cassiopeiae, or r Cas, brightened up to magnitude 4.0,
then dimmed to an astonishing 5.3 over the next half year, while
changing its usual yellowish-white color to the red-orange glare
of Betelgeuse (a Orionis). Such a rapid, extraordinary change was
also observed for the star in 1946, bringing it to the attention
of astronomers everywhere.
types of variable stars are known to change their visual brightness
in a rather predictable way—stars such as Mira (o Ceti) and
Algol (b Persei). And the R Coronae Borealis stars can suddenly
dim by several magnitudes; they are much fainter and less intrinsically
luminous than r Cas, however.
shining at about half a million times the Sun’s luminosity,
Queen r Cas is known to be one of the most luminous, cool stars
of our Galaxy. Tucked away in the Orion spiral arm of the Galaxy,
at an approximate distance of ten thousand light-years, it is possibly
the most distant star with a surface temperature comparable to that
of our Sun that can easily be observed with the unaided eye.
you enjoyed this excerpt from a feature article and would
like to receive our bi-monthly Mercury magazine, we invite you to
join the ASP and receive
6 issues a year.