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.
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AAVSO Light Curves
Photoelectric Photometry (PEP) Data
AAVSO Visual Data
Individual Visual Observations
AAVSO 82 Year Historical Data (Jan 23, 1921 - May 21, 2003)