How Big Is a Neutron Star Compared to New York City? A neutron star is the compact, collapsed remnant of a star after a supernova. By stellar standards, they're tiny. As you can see from this image provided by NASA, a neutron star can be as small as ten to fifteen miles across.Link -via Gizmodo Comments (7) Commenting is closed. Click here to view up to the first 100 of this post's 7 comments