Rho Cassiopeiae - Observation

Observation

The Bayer designation for this star was established in 1603 as part of the Uranometria, a star catalog produced by Johann Bayer. The star catalog by John Flamsteed published in 1712, which orders the stars in each constellation by their right ascension, gave this star the Flamsteed designation 7 Cassiopeiae.

Rho Cassiopeiae is somewhat unstable in its luminosity. Its apparent magnitude is currently about 4.5. In 1946 it dimmed to 6th magnitude and cooled approximately 4000 Kelvin, before returning to its previous brightness. A similar eruption was recorded in 1893, suggesting that it undergoes these eruptions approximately once every 50 years. This happened again in 2000–2001, when it produced one of the largest outbursts known, ejecting approximately 10,000 Earth masses, or about 3% of a solar mass. During the summer of 2000 it was observed (by the William Herschel Telescope) to have cooled from 7,000 to 4,000 Kelvin in the course of a few months.

These observations have also shown evidence that Rho Cassiopeiae may have already become a supernova (though the light from the explosion has not yet reached us), or will in the near future, because it has consumed most of its nuclear fuel. Assuming its eruptions have continued to occur at the same rate as those observed recently, the star will have lost approximately 20 solar masses over 10,000 years.