Two months after the failure of a fourth gyroscope shut it down, and 3 weeks after a shuttle crew paid it a service call, the Hubble Space Telescope is back in business.
Using a sensitive, new X-ray telescope, astronomers have identified the origin of the high-energy part of the X-ray background and found that supermassive black holes at the cores of galaxies are far more numerous than visible-light surveys indicate.
Two new studies suggest that galaxies may be surrounded by vast halos of
dark matter extending at least 1.5 million light-years from each galaxy's
center.