Which Camera when Betelgeuse Blows?

Robin Guymer · Jan 25, 2020

If you have been reading the news you will know about the exciting prospect of Betelgeuse going supernova anytime soon (within the next 100,000 years) due to it’s sudden dimming. Hopefully Ford Prefect and Zaphod Beeblebrox have already moved on. So are you going to capture those photons that have travelled 642.5 light years on your favourite film, or are you going to let them just bounce off your sensor glass and escape back home?

Supernovas are only seen rarely and last time in 1604 there were no cameras. So this could be the first time in the history of mankind and even in the history of the universe, that supernova photons, can be embedded onto film and captured for all time sake (with some good archiving processes).

I have my favourite night sky camera ready being the Nikon FE with the Series E 50mm F1.8 having captured some nice shots of the Milky Way and a meteor burst. These exposures average around 3 to 5 minutes depending on what film I use. So I am prepared for Betelgeuse - how about you?

Which camera and film do you have in your kit that is up to the task of capturing the first supernova photons on film that strike our little planet?

(and chill - it’s just a fun thread!)

ced · Jan 27, 2020

I'll be hiding behind my kitty...

jim10219 · Jan 27, 2020

Film doesn't capture photons. The photons excite the silver halide particles and converts them to metallic silver. The photon then bounces off into space to continue it's journey.

Beyond that, the photons hitting your camera didn't come from Betelgeuse. They came from the atoms in the air particles in our atmosphere. The photon hits an atom, excites it, and causes the atom to eject another photon while absorbing that one. Look up the Three Polarizer Paradox for some interesting applications of this.

reddesert · Jan 31, 2020

Photons from a star entering earth's atmosphere can scatter off atoms in the atmosphere and be redirected, although it is even more likely that they will be refracted slightly by variations in the the density of air - this refraction by turbulence is what makes stars twinkle and blurs the images we see through ground based telescopes.

The fraction of photons that are actually absorbed and re-emitted is low, except at particular wavelengths of absorption bands - the opacity of the atmosphere is high at these wavelengths (like absorption by ozone, molecular oxygen, CO2, and so on). When a photon is absorbed and re-emitted, it usually comes out isotropically, meaning it doesn't have a memory of what direction it came from. When you look up and see a star, you are seeing photons that actually came from the star, after glancing scatters off turbulence in the Earth's atmosphere.

Photons of identical state are indistinguishable anyway, so trying to ask the question of whether a photon is "the same" after it underwent an interaction like scattering is a bit fruitless.

Betelgeuse is cool, but I feel compelled to nitpick that astronomers photograph supernovae in other galaxies all the time. The last naked eye visible supernova was SN 1987A in the Large Magellanic Cloud, a satellite galaxy of the Milky Way. But it was only naked eye visible at dark sites in the Southern Hemisphere, so many of us didn't get a chance. If/when Betelgeuse explodes (and as the OP says, it could be some thousands of years from now), it will be the first SN visible in our own galaxy known since 1604, and it will be hard to miss.

jim10219 · Jan 31, 2020

reddesert said:
Photons from a star entering earth's atmosphere can scatter off atoms in the atmosphere and be redirected, although it is even more likely that they will be refracted slightly by variations in the the density of air - this refraction by turbulence is what makes stars twinkle and blurs the images we see through ground based telescopes.

The fraction of photons that are actually absorbed and re-emitted is low, except at particular wavelengths of absorption bands - the opacity of the atmosphere is high at these wavelengths (like absorption by ozone, molecular oxygen, CO2, and so on). When a photon is absorbed and re-emitted, it usually comes out isotropically, meaning it doesn't have a memory of what direction it came from. When you look up and see a star, you are seeing photons that actually came from the star, after glancing scatters off turbulence in the Earth's atmosphere.

Photons of identical state are indistinguishable anyway, so trying to ask the question of whether a photon is "the same" after it underwent an interaction like scattering is a bit fruitless.

Betelgeuse is cool, but I feel compelled to nitpick that astronomers photograph supernovae in other galaxies all the time. The last naked eye visible supernova was SN 1987A in the Large Magellanic Cloud, a satellite galaxy of the Milky Way. But it was only naked eye visible at dark sites in the Southern Hemisphere, so many of us didn't get a chance. If/when Betelgeuse explodes (and as the OP says, it could be some thousands of years from now), it will be the first SN visible in our own galaxy known since 1604, and it will be hard to miss.

I stand corrected. Thank you for that explanation.

Fraunhofer · Jan 31, 2020

You really would want a "camera" sensitive to neutrinos, since they might arrive days before the main event. NB, in the main event 99% of energy released is in the form of neutrinos. Neutrino "cameras" are true ULF, the biggest one which could create an actual image is Super-K and the "format" is about 50 by 50 meters. This one has taken a picture of the Sun using neutrinos, see here https://apod.nasa.gov/apod/ap980605.html

Which Camera when Betelgeuse Blows?

Robin Guymer

ced

jim10219

reddesert

jim10219

Fraunhofer

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