Rho Cas (type semiregular) is a hypergiant star and one of the most luminous stars in our galaxy. Eruptions on these very rare, very massive stars produce huge mass ejections evidenced by dramatic spectral changes and optical dimming (an ejection in 2000 amounted to 10,000 Earths worth of material and caused a ~1.5-magnitude drop in visual brightness). Understanding hypergiants can help answer fundamental questions related to maximum stellar mass limits.
Astronomers are anticipating possible major activity in rho Cas over the next few months. Spectra of rho Cas show that its hydrogen lines have brightened, which indicates the probable onset of an eruption leading to mass ejection and consequent optical fading. This pattern was seen in the last months of 2000, and astronomers feel that the eruption projected for the coming months may be stronger than the 2000 one.
These chart links are obsolete (11/2013); create charts using VSP at http://www.aavso.org/vsp
The Rho Cas spectrum was taken by Maurice Gavin with his WPO spectrograph [dispersion = 3.24A/pixel] in 60s exposure via a 30cm Meade LX200 and Starlight Xpress MX9 CCD on 2003 July 7. It covers a 1100A swathe at the red end of the spectrum from 5900A [left] - 7000A [right] and currently shows no evidence of either emission in lines like H-alpha or broad absorption bands of TiO etc.
The Rho Cas spectrum closely resembles nearby alpha Cas [type K0] included - the two consecutive exposures #1,#2 of Rho Cas show a near perfectmatch. More spectra at http://home.freeuk.com/m.gavin/gensp18.htm
Spectrum by Doug West. Click image to enlarge.
AAVSO Light Curves
Photoelectric Photometry (PEP) Data
AAVSO Visual Data
Individual Visual Observations
AAVSO 82 Year Historical Data (Jan 23, 1921 - May 21, 2003)