Some 45 light years from Earth, the galaxy NGC 4051 was discovered in the constellation Ursa Major by John Herschel in 1788. It is part of a spiral-rich subset of the Virgo supercluster of galaxies that includes the Milky Way. Classified as a Seyfert galaxy, NGC 4051 hosts a supermassive black hole in its core with 1.7 million times the mass of the Sun. Multiple supernovae blasts have been observed in the galaxy over the past several decades, the first in 1983 and the most recent in 2010 when the core of a massive star that had already lost its outer layers of hydrogen and helium exploded in a type 1c supernova. Such explosions are sometimes referred to as stripped core-collapse supernovae. This beautifully rendered view of NGC 4051 was captured by the Hubble Space Telescope.
Some supernovae have a reserve tank of radioactive cobalt-57 fuel that cuts in and powers their explosions for three times longer than astronomers had previously thought. The discovery by Australian and US researchers gives important new clues about the causes of Type Ia supernovae, which astronomers use to measure vast distances across the universe.
Two astronomy students from Leiden University have mapped the entire Milky Way Galaxy in dwarf stars for the first time. They show that there are a total of 58 billion dwarf stars, of which seven percent reside in the outer regions of our galaxy. This result is the most comprehensive model ever for the distribution of these stars.
This Hubble image is of the peculiar galaxy NGC 1487, lying about 30 million light-years away. We are witnessing the possible merger of several dwarf galaxies into a new single galaxy. Its appearance is dominated by large areas of bright blue stars, illuminating the patches of gas that gave them life. This burst of star formation may well have been triggered by the merger.