|(The U.S. edition had a different cover, but the article was the same)|
Read my article in the April issue of Sky & Telescope (not available online). This was the cover story in the Australian edition of the magazine.
Could the brightest sources of X-rays in our galaxy’s neighborhood be the missing chapter in a black-hole saga? Until recently, astronomers knew of only two kinds of black hole: remnants of dead stars that collapsed onto themselves, and mega-black holes — millions of times as massive as any star — sitting in the middle of galaxies, including our own. Astronomers now reckon that some of the newly discovered X-ray sources must be the missing mid-size black holes. But there’s little agreement on how rare they are, or on how they could have formed.