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.
In many ways stars are like living beings. They’re born; they live; they die. And they even have a heartbeat. Near the end of their lifetime they begin to pulsate, increasing and decreasing their brightness by a large amount every few hundred days. Using a novel technique, astronomers have detected thousands of stellar “pulses” in the galaxy Messier 87 (M87). Their measurements offer a new way of determining a galaxy’s age.
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.