Chandra Release - September 6, 2001

Visual Description: M15

An X-ray image of two objects in a globular cluster called M15 looks like an owl’s eyes, and is dominated by shades of bright purple and blue, with a bright green-yellow spot in the center.  M15 is a well-known globular cluster located in the constellation Pegasus, about 30,000 light-years away from Earth. Chandra's image of a puzzling X-ray source called 4U2127 in the globular cluster M15 shows that it is not one neutron star binary system as thought, but two neutron star binary systems. The two neutron star systems appear so close together (2.7 arcseconds) that they were indistinguishable with previous X-ray telescopes. The source could exhibit two contradictory modes of behavior since 4U2127 is not one source, but two: one whose neutron star is hidden by an accretion disk (on the left in the image), and one (right side) where occasional X-ray outbursts reveal another neutron star's surface.