A STAR PREPARES TO BLOW ITS TOP
Keep an eye on Cassiopeia -- it contains a naked-eye star that may
brighten and dim dramatically in the coming months. That was the
at a Tuesday press conference at the American Astronomical Society
in Seattle. Alex J. R. Lobel and Andrea Dupree (Harvard-Smithsonian
for Astrophysics) both reported observations of the active hypergiant
Rho Cassiopeiae, which is visible to the naked eye at magnitude
According to Lobel and Dupree, the star has had a chaotic recent
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
Then in 2000 astronomers caught Rho Cas acting up again. It
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
star turned out to be having the largest stellar mass ejection ever
It wouldn't take many such ejections to have life-altering effects on
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
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
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,"