Image credit: Max-Planck-Institut für extraterrestrische Physik (MPE)
This is a PSPC image of the Perseus region of the sky. It shows several things. One of these is Algol, known mythologically as "the Demon Star", actually an eclipsing binary system. This means that the orbits of the two main stars appear to lie almost edge on from Earth, allowing eclipses can occur. The primary star, Algol A is classified as a B star and is 3 times larger than the sun. Algol B is a G star with a cooler surface temperature than the sun. AMW 7 is a cluster of galaxies in which the hot gas is cooling and accreting onto the central dominant galaxy.
Please use the Feedback link if you have questions on ROSAT.