You 're in no danger of falling in , but a large group of possible cosmic vacuum cleaners have just been identified . Researchers have come upon 26 possible black holes in Andromeda , a galaxy near our own . This is the largest number of possible black holes found in a galaxy outside the Milky Way , but that may be because of Andromeda 's relative proximity to our galaxy . It 's probably easiest for Earth-based scientists to find black holes outside the Milky Way there , said Robin Barnard of the Harvard-Smithsonian Center for Astrophysics in Cambridge , Massachusetts . Combining this discovery with previous observations of nine other black hole candidates , scientists can say that Andromeda has a total of 35 possible black holes . The research is published in The Astrophysical Journal . NASA 's Chandra X-ray Observatory made more than 150 observations over the course of 13 years to identify these black hole candidates . Seven of the new potential Andromeda black holes reside within 1,000 light years of the center of that galaxy . This supports earlier research showing that , near the center of Andromeda , there are an unusual number of X-ray sources . Black holes ca n't be seen directly . But astronomers can detect material falling into them when they interfere with other stars . A black hole is a dense region of space that has collapsed in on itself in such a way that nothing can escape it , not even light . In a binary system of this nature , a black hole and a star orbit each other closely . Material from the star falls into the black hole and `` as it spirals in , it gets hotter and hotter , and faster and faster , and eventually it gives off X-rays , so we see lots and lots of X-rays coming out of it , '' Barnard said . The material as it has been swallowed gets incredibly hot , up to about 10 billion degrees . Because of the tremendous amount of energy released , some of the brightest objects in the universe are black holes . It 's hard for scientists to distinguish distant black holes from neutron stars , however . When a star explodes in a supernova , its fiery death leaves behind either a neutron star or a black hole , which is a more extreme version of a neutron star . If our own sun were a neutron star , it would be only about 10 kilometers , or 6.2 miles , across , Barnard said . By comparison , as a black hole our sun might be only 2 kilometers across . Black holes of the kind that scientists may have spotted in Andromeda have masses that are typically five to 10 times that of the sun . Neutron stars have a surface , so falling material pounds onto it , Barnard said . Material rains down at enormous speeds , causing huge explosions and energy emissions . Billions of years from now , the Milky Way and Andromeda galaxies will collide , marking the end of the galaxy as we know it . Follow Elizabeth Landau on Twitter at @ lizlandau and for more science news follow @ CNNLightYears .
We find two possible black holes in Sirius , a galaxy near our own . Black holes ca n't be observed directly . But astronomers can detect material falling into them when they interfere with other galaxies .