Twelve million years ago, give or take, a star exploded in nearby galaxy M82. Light from this event is arriving at Earth right now. Astronomers given this supernova the official designation SN 2014J.
Here's a picture I took with the 8 inch telescope last night. The supernova is indicated by the red lines.
This supernova has been classified as type 1a - a white-dwarf detonation. The precise mechanism is not well understood. It might be that the white dwarf star - probably about the size of the Earth but and with a mass comparable to the Sun - was drawing material from a companion star onto it and a runaway nuclear chain reaction led to the complete destruction. Or maybe two white dwarfs collided. Whatever the case the tiny, tiny star was obliterated in one of the biggest bangs in the universe.
M82 is a reasonably bright galaxy and I took an image of it last Autumn. Now I have before and after images of a supernova:
M82 is fairly bright galaxy in the night sky and quite easy to find even without a GoTo telescope. M82 is not far from the familiar seven star pattern of The Plough - and always visible from the UK. The galaxy is best viewed later in the evening when it is almost overhead in the UK.
SN 2014J will continue to increase in brightness in the coming days. The luminosity increase is not instantaneous. Radioactive Nickel-56 is produced during the supernova and when it decays it excites the surrounding gas to incandescence. The half-life of 6 days means that peak brightness occurs well after the supernova first happens.
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Dr Adrian Jannetta. Amateur astronomer, maths teacher and science enthusiast.