Supernova

[Jumbuck]

http://news.bbc.co.uk.../sci/tech/8382348.stm

In summary: massive star (up to 40X mass of Sun), 4500 lightyears away, could become a supernova at any time

When this happens, might it be bright enough to see during daytime?

[mollykins]

eerr if i've done my maths right, no. if it is fourty times bigegr, the light wil ltravel 40 times further (i think) which would only be 324 light years.

[mollykins]

Unless light doesn't work like that.

[Jumbuck]

Erm, the light doesn't just stop, it will continue to infinity and beyond.

A comparison might be made with the supernova which give rise to the Crab Nebula. This occurred in 1054 and was definitely bright enough to be seen during the day because it was noted by Chinese and Arab astronomers. That progenitor star was probably about 10X the mass of the Sun and at a distance of 6,500 lightyears (these numbers I did get from Wikipedia), so both significantly less massive and further away.

All of which suggests, at first sight, that this impending supernova might be very bright, so I was wondering whether basing expectation solely on the numbers might be misleading.

[jake-the-peg]

I'd think so.

We're way overdue for one - there hasn't been a supernova in our galaxy since the invention of the telescope - it was Keplers supernova http://en.wikipedia.org/wiki/SN_1604 that was 20,000 light years away and reached a magnitude of -2.5 so about as bright as Venus which you can certainly see at dusk.

As the brightness decreases with the square of the distance one similar supernova would by my calculation be about -5.7 which is brighter than any star or planet but not as bright as the full moon (about -12) - this is a logarithmic scale

Eta Carinae is another candidate - this is 100 solar masses so a real bruiser and very unstable
http://en.wikipedia.org/wiki/Eta_Carinae

[Jumbuck]

Thanks jake-the-peg for that (I was too lazy to bother with the maths).

I just hope that one of them happens within my lifetime. You can bet that some religious espousers or cultists will claim it as a sign from their deity/leader.

[jake-the-peg]

THe aths isn't difficult but you have to know how - by assuming they are similar you just set the absolute magnitude to be the same for each and then the formula for appraent magnitude gives you how bright one is compared to the other.

Of course a big star like eta carinae will make a very very much bigger bang!

Yes I hope to see one in my lifetime too - it will be a very big event!

[gen2]

It is strange to think that these events have already happened. If only we had some way of knowing when, we could all be out there with a telescope for when the light eventually gets here.

[heathfield]

The planet Venus can be seen in broad daylight - if you know exactly where to look.

[mollykins]

where do you look.

[Jumbuck]

Venus is currently quite near the Sun in the sky.

If you want a good planetarium program then may I suggest Stellarium http://www.stellarium.org/ - it's a lot better than those online versions.