[GTSVA]

"Brad Schaefer: For all we know, Betelgeuse has just gone supernova. Betelgeuse is about a thousand light years away. So if Betelgeuse has gone supernova anytime in the last thousand years, the light of this supernova explosion could be speeding to us even as we speak – maybe it will arrive tonight – and suddenly Betelgeuse will flash into being brighter than a million full moons in the sky – all up above us. It would be a spectacular sight."

Okay...I don't doubt anymore.

[High Max]

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[Aardwolf]

Did you miss the part where it would kill everything on the side of the planet facing it?

[High Max]

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[IceFire]

Did you miss the part where it would kill everything on the side of the planet facing it?

Extremely unlikely.  Supernova's have been witnessed in past history...its rare but not completely unheard of.

[High Max]

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[FUBAR-BDHR]

You would need a very young huge star going nova and creating a super massive black hole like in the center of a galaxy to get a gamma ray burst.  Think the term for that is hypernova.  They only occur in star nurseries.

Has anyone thought of what having several months of near daylight would do to plant life especially crops?

[MP-Ryan]

Has anyone thought of what having several months of near daylight would do to plant life especially crops?

Not much.  Total daylight is only responsible for so much.  Climate, soil conditions, and moisture are all big factors for plants.

[Solatar]

If I understand correctly, it wouldn't be entirely daylight all the time or anything. The Earth would still rotate, so sections of the planet that wouldn't be able to see Betelgeuse wouldn't be affected at that time, and the light would likely be a very bright harvest moon brightness, not another sun.

[FUBAR-BDHR]

Seems like a lot of crops only ripen in the dark though.  Peppers, tomatoes, etc.  Not sure about the science of it but it sure seems that way.   

[Aardwolf]

Eh... maybe the person I talked to misheard the figure. It's possible he gave me the outlook for a 40-lya supernova, and not a 400.

[watsisname]

A supernova of Betelgeuse wouldn't be bright enough to turn night into day, though it would be plainly visible in the daytime.  I'd think the effect on plantlife would be minimal at best.  As for possible hypernova, the rotation axis isn't aimed at us so we're not at risk from that either.  Sorry to the doomsday aficionados. 

[GTSVA]

Like Eta Carinae. o.O

[Mika]

"Brad Schaefer: For all we know, Betelgeuse has just gone supernova. Betelgeuse is about a thousand light years away. So if Betelgeuse has gone supernova anytime in the last thousand years, the light of this supernova explosion could be speeding to us even as we speak – maybe it will arrive tonight – and suddenly Betelgeuse will flash into being brighter than a million full moons in the sky – all up above us. It would be a spectacular sight."

I wish they would be more careful with the terms when they say something like that. There are pretty good reasons why Scientists should use words like irradiance, radiance and radiant intensity and especially NOT to use the damn "intensity" in their papers (it's almost always wrong). Brighter with respect to what? For the general audience, "brightness" is also a physical term, but with a totally different meaning: http://en.wikipedia.org/wiki/Brightness
Yes, if all the light comes from a point (distant star), the relative radiance between moon and star gone supernova is definetely high, but since it is almost a point source, it doesn't have surface area to provide high amount of power.

This all comes back to question how much EM radiation does the supernova release. SN1006 (class 1a) blew up 7200 lightyears back, and the result was that it was visible, about the size of Venus and one quarter of the brightness of the moon. Betelgeuse is 640 lightyears away, so a factor of ten less for distance equals factor of 100 for the area. So about hundred times brighter than the moon, if it has approximately the same amount of energy. I need to check the former irradiance number and how close it is to this estimation.

How much brighter is 100 times more brighter illumination than the moon?
http://en.wikipedia.org/wiki/Daylight

It is about the illumination under a storm cloud during midday. It is hard to believe one could damage eyes with that amount of power.

There are some differences between classes 1 and 2, and I think 1a would be the most dangerous. I'll let the astronomers do the classification stuff, just tell me the estimate of the released electromagnetical radiation.

Mika

[watsisname]

Astronomy babble time.

Betelgeuse would be a type II supernova (core collapse of a massive star).  Type Ia supernovae involve the collapse of a binary white dwarf when it reaches ~1.4 solar masses (through accumulating matter from the partner star).

Type Ia's are very consistent in their brightness since it's pretty much always the same thing blowing up every time.  They have a peak absolute magnitude of ~-19.5.  As for Betelgeuse, it depends on what variety of SNII is goes off as (I'm not sure).  There's P and L type, P meaning the intensity plateau's after the peak, while L has a linear decline.  SNII-P can have a wide range of peak brightnesses, while SNII-L are usually ~2.5 magnitudes fainter than Ia's, which would be -17. 

If we assume Betelgeuse goes off with peak absolute magnitude -17, and it's distance is 640LY = 196 parsec, then:
m_v - M_v = -5 + 5log₁₀(d)
m_v - (-17) = -5 + 5log₁₀(196)
m_v = ~-10.5, which is slightly less than the full moon in apparent brightness.  But since it will be a point source it will appear quite intense.

[Black Wolf]

Has anyone thought of what having several months of near daylight would do to plant life especially crops?

It would screw them completely. Lots of plants, including plenty of commercial crops rely on the length of the day/night cycle to tell them the season, and thus when to move between phases of growth, and they're surprisingly precise about it (i.e. to the minute accuracy). Fortunately, as has ben pointed out, this isn't what we're going to have.

Yeah, they say that the gamma ray burst that would do that to Earth is so unlikely that it has a very small chance of ever happening during the entire 10 billion year life time of the earth. Of course there is a theory that a gamma ray burst was responsible for a mass extinction that occured about a few hundred million years ago. I think it was one of the first mass extinctions and the most devastating one.

It's closer to 4 billion years of life on Earth, for starters, (The whole planet's only been here 4.5, give or take) and the event you're thinking of (Ordovician-Silurian around 450 odd mya) was only the first one if you want to think about in the old "Big Five" mentality. We don't know an awful lot abut the really early earth, but the likelihood is that mass extinction evens had been going on for almost the entire time life's been here - hell, in all likelihood life has been sent entirely extinct and re-evolved multiple times, especially if you accept the light carbon they found in the Jack Hills diamonds last year as evidence for life (That would mean we had life less than 300 million years after Earth formed, suggesting it's more or less inevitable whenever there's somewhere it'll form, making extinction and re-evolution far more likely). Even if you want to wait until we have a better idea of what's going on, then the first (and by far the most severe) confirmed mass extinction happened around 2 billion years ago when photosynthetic micro-organisms started polluting the atmosphere with oxygen and killed off almost the entire (at the time anareobic) ecosystem. Even in terms of the big five, the Permian Triassic has the O-S beat for severity.

And, at least vaguely on topic, the idea that it was a gamma ray event has no real evidence to support it - it was just a computer model that said it was possible. There're much more plausible explanations that have actual geological evidence backing them up, specifically that a continental landmass was sitting over the south pole while a massive ice age event was occuring, which sucked up a lot of water, destroyed almost all shallow marine habitats by dropping sea levels way down (possibly all the way to the continental shelf margins at times) and then flooding them again during interglacials, over and over again. It's important to note that defining an extinction event is based on marine life, and that, at the time, life on land was very restricted, so changes in the marine environment are what matter.

[Mika]

Seeing that it would be a Class II supernova with two magnitudes less of optical power, I would approximately get about the same number using both the radiometric powers and historical information of supernovas.

It would most likely cause lasting after images if viewed for a long period, but not serious kind of damage. There could be some amount of iris adapting diameter to decrease the amount of light, but this is contestable since the rest of the sky is almost black.

Long time since I have last seen the apparent brightness formula, could've been 7 years ago.

[watsisname]

(Editted to be less confusing) I understand that with a lightsource viewed at infinity (like in the case of a star), the light entering the eye is focused to a point on the retina.  But does the angular size of the source factor in at all for how damaging it is to the eye?  I.e, would looking at the sun be any more or less damaging if it were instead a pointsource of the same magnitude?

[Mika]

You are basically talking about things that are related to the optical energy conservation law (called optical invariant or etendue). If you are looking at a point source, the image of this point would be imaged as a perfect point if the lens was perfect. When you extend the source slightly and would consider two points, the two points will always be separated by some distance governed by magnification if the imaging would otherwise remain constant. In principle, there will always be some infinitesimal difference between these two points if the imaging was perfect. Well, that's the theoretical stuff of imaging. And everybody knows, in theory practise and theory don't differ, but in practise they do.

I'll post some more stuff here tomorrow, as there is a party I need to attend.

[Mika]

Continuing the post before

Unfortunately, perfect point to pont imaging does not exist. This is because one would need to collect the whole inpinging wavefront in order to get a perfect point image, but this would require infinitely large aperture (ouch). The minimum achievable spot size is given by the Airy radius, which in turn depends on the lens F/number.

With F/8 (2 mm iris diameter), the spot size is of order 4 µm (Airy radius). So the image of the point will be spread over this area. Now, if one looks at the larger object, there will be some overlapping energy on this spot (human eye "pixel size" is about 2.5 µm). However, when one looks at the whole situation, I think that the amount of energy that the is spread over the other pixels due to diffraction is actually regained by the diffraction effects on those other pixels. So, even a point source can damage your eye (as evidenced by the lasers). So what happens when you increase the size of the source? You simply destroy larger area of the retina. Would this answer your question?

Another thing to note is that those rods and cones don't see Apparent Brightnesses or Watts, they are mainly photon counters. So to damage the retina, one has to fire enough photons in small enough area to cause damage. Only those photons that arrive on your 2mm diameter iris from the distance of 640 lightyears count.