Nearby Galaxy M82 Hosts a New Supernova

My understanding is that there are three competing theories which have the strongest claim on explaining Type Ia supernovae. The classic theory is that a non-white dwarf companion star feeds material onto a white dwarf, which increases its mass. This kicks off a complicated chain of events, some of which may occur over timescales of a thousand years, ultimately culminating in the initiation of fusion reactions (initially Carbon, then Oxygen) in the core of the white dwarf. The fusion reactions release heat, but because the white dwarf is already under electron degeneracy conditions it is unable to increase pressure and expand to moderate the fusion reactions, so instead they are caught in a very strong positive feedback loop. In a matter of seconds the fusion reactions consume all of the Carbon in the star and then begin consuming the Oxygen in the inner core, this process releases more than enough energy to completely unbind the star gravitationally, the star explodes in a supernova. Alternately, it's also possible that a white dwarf star could have more than enough mass to undergo a Type Ia explosion but is kept in check by rapid spinning. As the star ages and the spinning slows down it crosses a boundary where the above events occur. Or, two white dwarfs could instead merge with each other.

It's actually likely, in my opinion, that all three models contribute to Type Ia events in nature, but it's currently unknown which variety is the most common cause of such supernovae.

You mean another galaxy, assuming the supernova would create inhospitable conditions throughout all of M82.

It may be sad for any aliens living around the star itself and nearby solar systems. The rest of the galaxy won't feel a thing.

This is not the 'Star Trek' movie where, for some weird reason I'll never understand, a supernova was a catastrophic event, for civilizations with FTL travel.

If our own sun turned into a supernova (not possible btw), the nearby star wouldn't even see that for about 4 years, best case. And that would be just the radiation, matter would take hundreds, if not thousands of years to get there. So it is not like they wouldn't have any warning.

And that's for the closest star.

On the contrary, if you consider that supernovae make our version of life possible, maybe life will happen someday at M82 because of this explosion.

We are all supernova dust, after all.

OP should have appended [-11,997,986] to the title

(11,997,987 BCE)

It doesn't really make sense to talk about points in time in reference frames other than ours.

Heh. It depends on how you interpret relativity I think.

People always say this sort of thing when talking about distant events, it's not actually true.

When we're talking about long distances then the relativity of simultaneity comes into play strongly. There is no universal ordering of events, there is a substantial degree of relativity to ordering of events that are separated by great distances. And, in fact, the only hard boundaries on this ordering are the "light cones" connecting events. In one reference frame the M82 supernova could have happened 12 million years ago, in another reference frame it could have happened a year ago, or two years ago, or even 20 million years ago. In the reference frame of any neutrinos that happened to have been created in the supernova it would have occurred mere seconds or hours before the first light reached Earth.

How is this an argument? If I shoot a bullet from a very distant planet and it will reach Earth after 12M years, will you be safe if it came directly towards you?

Unfortunately there is no inverse square law for time, only for distance. So if it is large enough, regardless of how long it takes to get to us, we'd be just as toasted. You get sun burns when you are out too long, even though that was so like 8 minutes ago. :-)

That said, it also means we can probably skip that half of galaxy M82 in our search of extraterrestrial intelligence. For the planets that were within a few light years of the supernova, they probably lost anything that wasn't bolted down in terms of atmospheric gases :-).

How long ago it happened is irrelevant. It really is just the distance that is keeping us safe.

How often do they catch supernovae in general? Really often apparently: http://www.cbat.eps.harvard.edu/lists/Supernovae.html

If you mean like the 8th magnitude that this article says it could reach, then the last one to come close (and surpass it by far) was 1987A (http://en.wikipedia.org/wiki/SN_1987A) at 4.5 magnitude (I remember hearing about that when I was a kid). 1972E was 8.5. 1954A was 9.8. 1937C was 8.4. 1895B is listed as 8.0. 1885A at 5.8. There are some negative magnitude ones listed at the end of the list (1006, 1054, 1572, 1604) which were within the Milky Way. (There are wikipedia articles about those supernovae and older ones as well.)

Fairly often. There are a couple ways that supernovae get spotted. Sometimes an amateur astronomer will find a supernova, there are lots of folks who actually do this as a hobby and surprisingly it's something that such folks can actually be fairly productive about, but it requires a lot of work. Also, there are various ongoing sky surveys of various sorts including asteroid detection programs which typically pick up supernova at a fairly regular rate merely due to being able to observe a huge number of galaxies in any given night (since supernovae are typically bright for periods of many days to weeks). Additionally, we've deployed a variety of satellites that have "transient detectors" designed to look for the signs of gamma ray bursts but also capable of detecting ordinary supernovae, sometimes.

For example, in 2013 over 230 supernovae were discovered. And currently there are about 3 dozen active supernovae that can be viewed with a telescope, but most of them are fairly dim in very distant galaxies and would require a fairly sizable telescope to be able to see (~300mm aperture or so). The M82 supernova is the only one that is currently visible with an ordinary backyard telescope or binoculars.