Recent research suggest that more than half the stars we know about exist in multiple star systems, with a large fraction of these being 2 star, or binary systems. These systems are held together by gravity, and are important as their masses can be determined from observations of their orbits. By extrapolating these results, the masses of single stars can then be estimated.

SS433 is a binary star system which consists of a massive, hot star and
a compact object (a small, dense object at the end of a starʼs life,
such as a neutron star or black hole), orbiting around a common centre
of mass. As material falls from the star to the compact object, a disk forms, and jets of material are ejected at 90 degrees to the disc.

In this activity you will calculate the red and blue shifts of these jets and work out how long it takes them to reach the edge of the supernova remnant, W50.

• Course Leader: Sarah Roberts