56 Ursae Majoris is dying. The star has completed the prime stage of life. Now, it’s going through some changes. It’s puffed up to giant proportions. Eventually, it will shed its outer layers, leaving only its hot, dense core — a white dwarf.
A companion star has already expired. And its death might have had a big impact on 56 Ursae Majoris — 56 UMa for short — in more ways than one.
A recent study says the companion might be a neutron star — a corpse that’s even smaller and denser than a white dwarf. It formed when the star exploded as a supernova, a hundred thousand years ago. The star’s outer layers were blasted into space at a few percent of the speed of light.
Today, the stars are separated by about 23 times the distance from Earth to the Sun. At the time of the blast, though, they probably were closer. So the supernova shockwave could have stripped away some of the surviving star’s outer layers. The explosion also created a rich brew of chemical elements. Some of those may have been embedded in the surviving star — perhaps explaining some odd chemistry seen today.
The supernova also could have blown away the material around the stars, creating an empty “bubble.”
A neutron star isn’t the only possible explanation for the companion to 56 UMa — but it might be the best one.
Under dark skies, 56 UMa is just visible to the unaided eye. It’s in the east at nightfall, to the right of the bowl of the Big Dipper.
Script by Damond Benningfield