
Nearby Galaxy M82 Hosts a New Supernova - throwaway_yy2Di
http://www.slate.com/blogs/bad_astronomy/2014/01/22/kaboom_nearby_galaxy_m82_hosts_a_new_supernova.html
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splat
This supernova will be very important for figuring out what Type Ia SNe are.
As Phil Plait mentions, astronomers only know that white dwarfs are involved,
but there are several competing models as to how the white dwarf(s) explode.
One of the main ways we will be able to distinguish between these models is by
observing what the supernova looks like long after the explosion since this is
when the shock will be interacting with distant material. Because this
supernova is so close we will be able to observe it long after the explosion
and will therefore be able to observe its interactions with very distant
material.

This is important because the so-called single-degenerate model in which a red
giant dumps material onto the white dwarf is expected to produce very faint
hydrogen lines. Observing these hydrogen lines in the spectrum would be a
smoking gun for the single degenerate model. On the other hand, if they are
not observed, it would put very tight constraints on how the single degenerate
model could work.

Another reason these observations will be useful is that head-on collisions
between white dwarfs are expected to produce two separate explosions with
different velocities -- this then produces double peaks in the spectral lines
[1]. Sometimes these are hard to observe because the SNe are so far away,
however. They will be most easily observable in this SN. If they're found it
would be a smoking gun for a head-on collision between two white dwarfs.

[1] [http://arxiv.org/abs/1401.3347](http://arxiv.org/abs/1401.3347)

~~~
InclinedPlane
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.

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throwaway_yy2Di
_" Given the fact that it’s nearby, up high for so many observers, and caught
so early, this may become one of the best-observed supernovae in modern
times."_

 _" [...] But the good news is it appears to have been discovered about two
weeks before it hits peak brightness. Supernovae get brighter over time before
fading away, and this one may get as bright as 8th magnitude, which is within
range of binoculars._"

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songzme
Its very sad to think about all the aliens living in or around the M82 galaxy.
I hope they managed to invent inter-galactic space travel in time to escape to
another solar system safely. God bless them.

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

~~~
mhurron
A supernova is a big explosion, but I don't think it's quite 'galaxy
sanitizing' big.

~~~
Tossrock
An appellation reserved for gamma ray bursts (and only within the emission
cones).

~~~
gbhn
[http://what-if.xkcd.com/73/](http://what-if.xkcd.com/73/)

A nearby supernova would definitely be sterilizing to the kind of life found
on Earth, and to a lot of other imaginable forms. Of course, "nearby" in
astronomical terms is sometimes unintuitive. :-)

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nolanpro
Old news. that happend 12,000,000 years ago...

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

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mmanfrin
Man these Samsung phones just keep getting bigger and bigger.

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nmc
“ _And just to get this out of the way, we’re in no danger from this
explosion. It’s far too far away._ ”

Also, it happened 12 million years ago, so I think we are pretty safe.

~~~
gabipurcaru
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?

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sliverstorm
Surely after 12M years, the bullet will have rusted to dust in-flight? :)

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pavel_lishin
Not enough oxygen for it to rust. And even if it were, a collection of dust
traveling at bullet speeds would still probably kill you.

But worry not! A bullet fired from 12 million light years away would probably
be ablated into nothing by the interstellar dust.

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btilly
Nope.

Stop and think about the fact that starlight can travel that distance.
Therefore the accumulated dust along that path is not enough to block light.
That little dust won't stop a bullet either.

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pavel_lishin
But it's not just starlight - it's the light of a whole nova (and the
collective light of a whole galaxy.)

I can see starlight from the bottom of a pool, but the water in the pool will
still stop a bullet.

(I am not a scientist, I could be entirely wrong, but it seems like the
collective dust of 12 million light years would surely ground down a bullet,
while being intermittent enough to let starlight pass through in aggregate.)

~~~
btilly
Well let's calculate it. According to
[http://www.universetoday.com/30280/intergalactic-
space/](http://www.universetoday.com/30280/intergalactic-space/) there is
about 1 hydrogen atom per cubic meter. According to
[https://www.google.com/search?q=light+year+in+meters&ie=utf-...](https://www.google.com/search?q=light+year+in+meters&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-
US:official&client=firefox-a&channel=fflb) there are about 10^16 meters in a
light year. So 12 million light years is about 10^23 meters. Avagadro's number
is about 6 * 10^23. So a tube a square meter across is a bit under 0.2 moles
of hydrogen. According to
[http://answers.yahoo.com/question/index?qid=20080619205711AA...](http://answers.yahoo.com/question/index?qid=20080619205711AAuBH5O)
at standard air pressure a mole of hydrogen would be about 22 liters, so we're
talking about 4 liters of gas at standard pressure. Which would be about 1
square meter across, and 4 millimeters tall.

The collective dust of 12 million light years of intergalactic space does not
seem likely to grind down a bullet very much.

That said, the whole calculation is flawed because first you have to get out
of our galaxy, which is much higher density. Though that also wouldn't stop a
bullet. But then you have our atmosphere, and that most definitely _would_
destroy a bullet that tried to pass through it!

But the moral remains. Space is empty. Really empty. Unimaginably so.

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bjackman
Awesome! How often do astronomers catch supernovae like this?

~~~
InclinedPlane
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.

