Interesting Outburst

A couple nights ago IY Ursa Majoris (IY UMa) went into outburst. This is one of those rare eclipsing CVs that astronomers really like to get data on, because with an eclipse you can tell the period of the system as the components orbit around each other.In a CV binary, one star is a white dwarf: a collapsed star of approximately one solar mass in the volume of the Earth. The other star is a red dwarf rather like our Sun, but redder and less massive.The red dwarf and the white dwarf orbit each other once every few hours: they are so close together that the average CV system would fit comfortably into our Sun. The red star in a CV is so close to the white dwarf that it becomes tidally distorted --- gas is stripped off the red star and falls towards the white dwarf. The infalling gas forms a disc -- an accretion disc -- with the white dwarf at its center. The gas in the disc spirals down towards the white dwarf, radiating its gravitational potential energy away as it goes. The accretion disc usually outshines both the red star and the white dwarf in visible ...