Neutron star

Neutron stars were stars created by the collapse of much larger stars.

The Tythonians set a neutron star on a collision course with Chloris in retaliation for Lady Adrasta imprisoning Erato. After the Fourth Doctor freed him, he spun an aluminium shell around the star, allowing the Doctor to use his TARDIS's tractor beam to pull it off course and save Chloris. (TV: The Creature from the Pit)