(IAAC) Keep an eye on Rho Cassiopeiae

-----Original Message-----

Message: 1
From: Dennis Miller
Date: Fri, 24 Jan 2003 22:25:42 EST


Keep an eye on Cassiopeia -- it contains a naked-eye star that may
brighten and dim dramatically in the coming months. That was the
message at a Tuesday press conference at the American Astronomical
Society meeting in Seattle. Alex J. R. Lobel and Andrea Dupree
(Harvard-Smithsonian Center for Astrophysics) both reported observations
of the active hypergiant star Rho Cassiopeiae, which is visible to
the naked eye at magnitude 4.5...

According to Lobel and Dupree, the star has had a chaotic recent 
past. In 1946 astronomers watched it fade to 6th magnitude and cool
from 7,000 degrees to 3,000 degrees Kelvin, changing from spectral
type F to M...

Then in 2000 astronomers caught Rho Cas acting up again. It brightened
by 20 percent (0.2 magnitude), then dimmed by about two magnitudes
while again cooling by more than 3,000 degrees K.

This time astronomers were better prepared to study what was going 
on. The star turned out to be having the largest stellar mass ejection
ever recorded...

It wouldn't take many such ejections to have life-altering effects on 
the star. Its behavior may hold the answer to one of astronomy's
lingering questions -- why are there no stars more luminous than a
million Suns?

"Maybe these mass losses constrain the luminosity," suggests Dupree...

It also seems to have an encore planned. The telltale spectral changes
that it showed before its 2000 events have showed up again, only this 
time they are happening much faster. While Rho Cas isn't expected to
change much in coming days, "We are looking at months rather than
years,"  says Dupree...

Dennis Miller

> http://SkyandTelescope.com/news/current/article_842_1.asp

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