The densest galaxy in the nearby Universe may be this galaxy known as M60-UCD1. It is located near a massive elliptical galaxy called M60, about 54 million light years from Earth. Packed with an extraordinary number of stars, M60-UCD1 is an “ultra-compact dwarf galaxy”. It was discovered with the Hubble Space Telescope and follow-up observations were done with the Chandra X-ray Observatory and ground-based optical telescopes. It is the most luminous known galaxy of its type and one of the most massive, weighing 200 million times more than our Sun.
This composite image shows the region near M60. Data from the Chandra X-ray Observatory are pink and data from the Hubble Space Telescope are red, green and blue. The Chandra image shows hot gas and double stars containing black holes and neutron stars and the Hubble image reveals stars in M60 at the right edge of the frame.
This image of the supernova remnant Cassiopeia A combines some of the first X-ray data collected by the Imaging X-ray Polarimetry Explorer (magenta) with high-energy X-ray data from the Chandra X-Ray Observatory blue). IPXE is a collaboration between NASA and the Italian Space Agency. Studying the polarization of X-rays reveals the physics of objects and can provide insights into the high-temperature environments where they were created.
This image combines data from four space telescopes to create a multi-wavelength view of all that remains of RCW 86, the oldest documented example of a supernova. Chinese astronomers witnessed the event in A. D. 185, recording a “guest star” that remained in the sky for eight months. X-ray images from NASA’s Chandra X-ray Observatory and the European Space Agency’s XMM-Newton Observatory were combined to form the blue and green colors in the image. The X-rays show the interstellar gas that has been heated to millions of degrees by the passage of the shock wave from the supernova. Infrared data from NASA’s Spitzer Space Telescope and WISE, the Wide-Field Infrared Survey Explorer, shown in yellow and red, reveal dust radiating at a temperature of several hundred degrees below zero, warm by comparison to normal dust in our Milky Way galaxy.
Astronomers were able to determine from the X-ray and Infrared data that the cause of the explosion was a Type 1a supernova. In a Type 1a supernova an otherwise-stable white dwarf or dead star is pushed beyond the brink of stability when a companion star dumps material onto it.
Scientists also used the data to solve another mystery surrounding the remnant: how it got to be so large in such a short amount of time. By blowing away wind prior to exploding, the white dwarf was able to clear out a huge cavity, a region of very low-density surrounding the system. The explosion into this cavity was able to expand much faster than it otherwise would have. This is the first time that this type of cavity has been verified around a white dwarf system prior to explosion. Scientists say the results may have significant implications for theories of white-dwarf binary systems and Type Ia supernovae.
RCW 86 is approximately 8,000 light-years away. At about 85 light-years in diameter, it occupies a region of the sky in the southern constellation of Circinus that covers slightly more of the sky than the full moon.