Supernova explosions occur when massive stars run out of nuclear fuel, collapse and explode in titanic blasts visible across the cosmos. They also can be triggered when a white dwarf in a binary star system siphons off enough mass from a companion to ignite runaway nuclear fusion in its core to begin the supernova process. Both types of supernovae have been spotted in a galaxy known as NGC 5468, a spectacular face-on spiral whose orientation makes it easier to spot such exploding stars. Over the past two decades, NGC 5468, located some 130 million light years from Earth in the constellation Virgo, has hosted at least five supernovae: SN 1999cp, SN 2002cr, SN2002ed, SN2005P, and SN2018dfg.
This image, taken with the Wide Field Planetary Camera 2 on board the NASA/ESA Hubble Space Telescope, shows the galaxy NGC 6052, located around 230 million light-years away in the constellation of Hercules. It is a “new” galaxy in the process of forming, the result of a merger between two separate galaxies that were gradually drawn together by gravity.
A fossilised remnant of the early Milky Way harbouring stars of hugely different ages has been revealed by an international team of astronomers. Terzan 5 resembles a globular cluster, but is unlike any other cluster known. It contains stars remarkably similar to the most ancient stars in the Milky Way and bridges the gap in understanding between our galaxy’s past and its present.