Supernovae are like buses: there’s nothing for ages, then two of them turn up at once.
Earlier this month a supernova was discovered in M82, also known as the Cigar Galaxy.
Over the past couple of days, another supernova has been confirmed in M99. (M99 has already had three supernovae since its discovery in 1781. This new supernova makes the count four.)
Two stars explode in the same month? Signs and portents!
— James Hutson (@jameshutson) January 30, 2014
On the other hand, a great cosmic coincidence?
The galaxy M82 is 12 million lights years away, and M99 is 60 million. At some point, 60 million years ago, a massive star at the end of its life lost its delicate balance between the gravity from its mass and the force from its nuclear furnace, and exploded.
48 million years later, and 55 million light years away, two stars in orbit around each other were completing an eons-old dance. A large star was being stripped of gas by its white dwarf companion. The white dwarf’s mass reaches a critical limit, and explodes.
12 million years later, the light from both of these events reach us.
I like to think of it as ever expanding bubbles, as the light from both explosions moves through the universe, and intersects where (and when) we are.
Appendix: Getting Numbers
Wolfram-Alpha constantly surprises me in its power, particularly interpreting my prattlings.
And my favourite surprise: “angle between m99 and m82”