How bright would Eta-Carinae supernova be?

If Eta Carinae goes supernova in our lifetime would it be bright enough to
outshine venus? Eta Carinae is more than 8,000 light-years away. Is there a
way to prediect this? I think it would be an awesome site to see, if it went
off in our lifetime.





Fee

Not precisely, but sure. eta Carinae, when it goes, will be a Type II
supernova and will brighten probably to something in the neighborhood
of absolute magnitude -18 or -19. (Maybe toward -19 since it's so big?)
That means that it would be magnitude -18 or -19 if seen from a distance
of 10 parsecs, which is about 32.6 light-years.

With all the dust it has thrown off, that should be an impressive show,
watching the light/shell expansion.

Clear Skies

Chuck Taylor
Do you observe the moon?
Try http://groups.yahoo.com/group/lunar-observing/
And the Lunar Picture of the Day http://www.lpod.org/
************************************

It will not, of course, be that close (thankfully), but about 250 times
further away. Objects that far away are about 12 magnitudes dimmer than
they would be at 10 parsecs, so that eta Carinae will have an apparent
magnitude of about -6 or -7, several times brighter than Venus.

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
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Fee Fillers wrote:
If Eta Carinae goes supernova in our lifetime would it be bright enough to
outshine venus? Eta Carinae is more than 8,000 light-years away. Is there a
way to prediect this? I think it would be an awesome site to see, if it went
off in our lifetime.

Not precisely, but sure. eta Carinae, when it goes, will be a Type II
supernova and will brighten probably to something in the neighborhood
of absolute magnitude -18 or -19. (Maybe toward -19 since it's so big?)
That means that it would be magnitude -18 or -19 if seen from a distance
of 10 parsecs, which is about 32.6 light-years.

It will not, of course, be that close (thankfully), but about 250 times
further away. Objects that far away are about 12 magnitudes dimmer than
they would be at 10 parsecs, so that eta Carinae will have an apparent
magnitude of about -6 or -7, several times brighter than Venus.

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

wow Thanks for the info. I was looking for this on google, and couldnt find
much!

Thats a day i look forward too heh

"Brian Tung" wrote in message
...
Fee Fillers wrote:
If Eta Carinae goes supernova in our lifetime would it be bright enough
to
outshine venus? Eta Carinae is more than 8,000 light-years away. Is
there a
way to prediect this? I think it would be an awesome site to see, if it
went
off in our lifetime.

Not precisely, but sure. eta Carinae, when it goes, will be a Type II
supernova and will brighten probably to something in the neighborhood
of absolute magnitude -18 or -19. (Maybe toward -19 since it's so big?)
That means that it would be magnitude -18 or -19 if seen from a distance
of 10 parsecs, which is about 32.6 light-years.

It will not, of course, be that close (thankfully), but about 250 times
further away. Objects that far away are about 12 magnitudes dimmer than
they would be at 10 parsecs, so that eta Carinae will have an apparent
magnitude of about -6 or -7, several times brighter than Venus.

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

Fee Fillers wrote:
wow Thanks for the info. I was looking for this on google, and couldnt find
much!

You can Google my web pages, but you can't Google me.

Thats a day i look forward too heh

Do you live in the southern hemisphere? The best view would be from
there (and it cannot be seen at all from north of 30 degrees north
latitude).

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

Not precisely, but sure. eta Carinae, when it goes, will be a Type II
supernova and will brighten probably to something in the neighborhood
of absolute magnitude -18 or -19. (Maybe toward -19 since it's so big?)
That means that it would be magnitude -18 or -19 if seen from a distance
of 10 parsecs, which is about 32.6 light-years.

It will not, of course, be that close (thankfully), but about 250 times
further away. Objects that far away are about 12 magnitudes dimmer than
they would be at 10 parsecs, so that eta Carinae will have an apparent
magnitude of about -6 or -7, several times brighter than Venus.


What if Eta Carinae was only as far as Vega (25 light years) and it did this?
Would it hurt life on Earth? How bright would it be?

Jim Beam

Jim Beam wrote:
What if Eta Carinae was only as far as Vega (25 light years) and it
did this? Would it hurt life on Earth? How bright would it be?

That 25 light-years works out to about 8 parsecs. The apparent magnitude
of eta Carinae would then be about -19. That's a few hundred times
brighter than the Full Moon, with all of that light squeezed into a tiny
point, too. You wouldn't be able to look at it without squinting.

As bright as it would be, however, the Sun would still shine upon the Sun
with a light 1,000 times brighter. So eta Carinae would put on a dazzling
light show, but not affect life on Earth--if only visible light were to be
considered.

However, visible light is not the only light to be considered. As it so
happens, supernovae emit a lot more high-energy radiation, relatively
speaking, than the Sun does. The Sun peaks in the visible region, but
the fusion processes bared by supernovae emit plenty of gamma rays. It
is this radiation that would do the damage, if there is damage to be done.

At that point, a lot depends on what eta Carinae is destined to do. If
it blows up as a typical (though perhaps larger than average) Type II
supernova, 8 parsecs might be *just* barely far enough to escape serious
damage (though cancer and mutations would probably make a decent living).
But eta Carinae is such an unusual case that no one feels quite certain
just what it will do, exactly.

Fortunately, it lives a lot further away than 8 parsecs, so the question
is merely academic and not an actual concern.

The Gum Nebula is the remnant of a supernova that exploded sometime in
the late Stone Age and is centered only about 1,500 light-years (about
450 parsecs) away. At that distance, a typical supernova would appear
to be about magnitude -10. What a sight that would have been--and a safe
one at that--but there was no one to record it in writing.

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

The Gum Nebula is the remnant of a supernova that exploded sometime in
the late Stone Age and is centered only about 1,500 light-years (about
450 parsecs) away. At that distance, a typical supernova would appear
to be about magnitude -10. What a sight that would have been--and a safe
one at that--but there was no one to record it in writing.

Thank you for your answer.

Are there other Gum Nebula in waiting? Is the local area so well cataloged
that we know there are no dangerous/or/close stellar explosions in our future?
How long will Eta C. stay at it's intensely bright level once blowing up?

JB

Jim Beam wrote:
Are there other Gum Nebula in waiting? Is the local area so well
cataloged that we know there are no dangerous/or/close stellar
explosions in our future? How long will Eta C. stay at it's intensely
bright level once blowing up?

It's pretty unlikely that there is a Type II supernova waiting to happen
within 10 parsecs. Within that range, there are no stars that are as
massive as is thought to be needed: about 8 solar masses and up.

That leaves Type Ia supernovae (there are Type Ib and Ic, but they are
like Type II without hydrogen lines), which require a massive white
dwarf (near the Chandrasekhar limit of 1.4 solar masses) and a companion
star that feeds it with fusible mass. There aren't any of these within
our local neighborhood either. There are white dwarfs with companions,
to be sure, but either the white dwarfs are too small, or the companions
are too far away, or both.

Within the 450 parsecs that separate us from the center of the Gum
Nebula, it's less certain. Certainly, Betelgeuse is expected to go
supernova in the astronomically near future, but it's still more than
far enough away to do no more than put up a good show. I'm sure there
are other likely candidates. Because white dwarfs are so dim, Type Ia
candidates are considerably harder to pick out at such distances.

Type II supernovae, such as eta Carinae will one day be, have light
curves that can be parametrized largely by just their mass. (Also their
composition, but to first order that shouldn't matter.) Generally, they
reach a peak after a few weeks or so, and stay fairly bright for a matter
of weeks to months. They typically remain bright longer than Type Ia
supernovae; this is because Type II supernovae still have some fusible
hydrogen and helium to illuminate. I seem to recall that the light
emitted by Type Ia supernovae are mostly because of the decay of heavier
elements synthesized during the explosion (like nickel-56).

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

What if Eta Carinae was only as far as Vega (25 light years) and it did this?
Would it hurt life on Earth? How bright would it be?

Short answer: it would be apparent magnitude -15 or so; about 10,000 times fainter
than the Sun, but brighter than the full moon. Very likely no major long-term
effects on the biosphere.

Long answer: http://stupendous.rit.edu/richmond/answers/snrisks.txt

Michael Richmond