Scrutable

Probably not. But it is behaving rather oddly.

https://www.nationalgeographic.com/scie ... JdVsPQtTNs

<quickly Googles how far away Betelgeuse is and will it annihilate us when it goes> No? Fine.

That would be way cool.

Martin Y wrote: ↑

Sat Dec 28, 2019 9:12 pm

<quickly Googles how far away Betelgeuse is and will it annihilate us when it goes> No? Fine.

That would be way cool.

National Geographic wrote:600 light-years away

Maybe it exploded 599 years and 362 days ago so we get a fantastic New Year's display.

How long would the debris take to get to us though?

Brightonian wrote: ↑

Sat Dec 28, 2019 9:49 pm

Martin Y wrote: ↑

Sat Dec 28, 2019 9:12 pm

<quickly Googles how far away Betelgeuse is and will it annihilate us when it goes> No? Fine.

That would be way cool.

National Geographic wrote:600 light-years away

Maybe it exploded 599 years and 362 days ago so we get a fantastic New Year's display.

How long would the debris take to get to us though?

National Geographic wrote:Astronomers calculate that it’ll take about six million years for the shock wave and any cold, diffuse debris to reach the solar system

Brightonian wrote: ↑

Sat Dec 28, 2019 9:49 pm

Martin Y wrote: ↑

Sat Dec 28, 2019 9:12 pm

<quickly Googles how far away Betelgeuse is and will it annihilate us when it goes> No? Fine.

That would be way cool.

National Geographic wrote:600 light-years away

Maybe it exploded 599 years and 362 days ago so we get a fantastic New Year's display.

How long would the debris take to get to us though?

Depends what sort of debris.
Neutrinos may actually reach us before the first visible indication - they are produced in the core and are effectively unimpeded before leaving Betelgeuse, Although they don't travel at the speed of light itself, some of them will be travelling so close to the speed of light that they won't be overtaken by the first EM radiation.

The first EM radiation to be detected is likely to be gamma rays - as those wavelengths can escape while the visible light is still being blocked by the material in the outer layers of the star.

I'm not sure how long it will take for any high energy Cosmic Rays generated in the supernova to reach us - it feels likely to me that determining that would be one of the key scientific discoveries to be made.

In terms of significant amounts of 'matter', the Crab Nebula is the expanding remnant of a Supernova that occurred almost 1000 years ago (in 1054), and the nebula is about 5 1/2 light years across.
Another supernova remnant is the Veil nebula, which is estimated to have happened about 21,000 years ago - and that is 'only' 65 Light years across - so any material reaching us from about 600* light years away is unlikely.

Do we have estimates for supernovae frequency in our galaxy?

Two per century according to this

A supernova you can see with the naked eye would be amazing. Hope it does go.

Martin Y wrote: ↑

Sat Dec 28, 2019 9:12 pm

<quickly Googles how far away Betelgeuse is and will it annihilate us when it goes> No? Fine.

That would be way cool.

This is what happens when a supernova is a bit closer:
http://www.astronomy.com/magazine/2019/ ... ected-life

It would not be way cool because it would likely eliminate lots of potential sites for extra terrestrial life, causing millions of souls to cry out in anguish and reducing our chances of making contact with them.

plodder wrote: ↑

Thu Jan 02, 2020 10:34 am

It would not be way cool because it would likely eliminate lots of potential sites for extra terrestrial life, causing millions of souls to cry out in anguish and reducing our chances of making contact with them.

It's very unlikely that there's any life there. It's only 10 million years old, which is too short a time for planets to form. It doesn't have any known ones.

By the way, orangutans had already diverged from the other great apes when Betelgeuse formed.

But presumably the shock wave would cause chaos outside the embryonic Betelgeuse system?

plodder wrote: ↑

Thu Jan 02, 2020 11:06 am

But presumably the shock wave would cause chaos outside the embryonic Betelgeuse system?

As above, the crab nebula is 5.5 light years across after 1000 years, the same* distance as alpha centauri is from us. And the shock there is probably pretty weak by now - a sphere 5.5 light years in diameter is big. If the entire mass of Betelgeuse was spread out over that, the density would be 3 10^-16g/m³, which is not that much, even in terms of 0.005c shock hitting something like the Earth's atmosphere. The mass in a shock would be only about kind of density at that distance (mass is concentrated in the shock, but not all the mass of the star would be ejected. These probably very roughly cancel out). Even if you put all the mass of Betelgeuse into a shock 1m thick, it'd come out to only a few g/m³ in the shock.

In any case, Betelgeuse has an absolute motion of 30km/s, and is already creating a (much weaker) bow shock in the ISM and gravitational effects that could disturb planetary systems it passed near. It was born in the Orion Molecular Cloud, but is now one corner of Orion.

*Astronomical precision says that things within a factor of two or so are basically the same.

The light could be worse than the shock at that distance, I suspect, but I haven't actually calculated that.

dyqik wrote: ↑

Thu Jan 02, 2020 11:41 am

The light could be worse than the shock at that distance, I suspect, but I haven't actually calculated that.

A nearby SNova's gamma ray burst is likely to have an effect on any nearby planets' surface (and atmosphere) - but I'm not sure how long these last, so it may only bake one hemisphere if it only lasts a matter of minutes or hours.

High energy cosmic rays are likely to increase the number of radioactive elements in the atmosphere, but that may well lead to an evolutionary burst.

dyqik wrote: ↑

Thu Jan 02, 2020 11:41 am

The light could be worse than the shock at that distance, I suspect, but I haven't actually calculated that.

The article I linked to above says that anything closer than about 30 light years "would induce a mass extinction from radiation destroying the ozone layer, allowing lots of ultraviolet radiation through". Well, that's what it would do to Earth; you'd need to assume there'd be planets close to Betelgeuse which have ozone layers (which they would probably need to have otherwise the UV from their own suns would break down any even slightly interesting molecules and you'd never get life).

Gfamily wrote: ↑

Thu Jan 02, 2020 12:20 pm

dyqik wrote: ↑

Thu Jan 02, 2020 11:41 am

The light could be worse than the shock at that distance, I suspect, but I haven't actually calculated that.

A nearby SNova's gamma ray burst is likely to have an effect on any nearby planets' surface (and atmosphere) - but I'm not sure how long these last, so it may only bake one hemisphere if it only lasts a matter of minutes or hours.

High energy cosmic rays are likely to increase the number of radioactive elements in the atmosphere, but that may well lead to an evolutionary burst.

The article I linked to above says that a supernova about 50 parsecs away 2.6 million years ago may have increased the flux of muons, which would have a) led to more cloud-to-ground lightning, causing forests to burn and be replaced by grassland and b) irradiated about 1 km of ocean so that it "contributed to a newly documented marine megafaunal extinction at that time."

See also https://phys.org/news/2018-12-supernova ... -dawn.html and https://phys.org/news/2017-05-distance- ... earth.html and

I'm puzzled by the more lightning thing. Presumably charge accumulates in the air due to wind sweeping charge off the earth?
That would be due to weather, which is relatively unaffected by cosmic rays.
The rays would provide more ionised pathways, but with no more charge available to kick off the lightning bolts, perhaps you would just have a lot more weedy bolts, and rather less powerful ones?

rockdoctor wrote: ↑

Thu Jan 02, 2020 3:10 pm

I'm puzzled by the more lightning thing. Presumably charge accumulates in the air due to wind sweeping charge off the earth?
That would be due to weather, which is relatively unaffected by cosmic rays.
The rays would provide more ionised pathways, but with no more charge available to kick off the lightning bolts, perhaps you would just have a lot more weedy bolts, and rather less powerful ones?

Particles knocking together in tall convective systems is what generates the charge. That's why you can get lightning storms above volcanic eruptions and, as we're seeing in Australia, bushfires. I think you are correct that more and less energetic bolts would result from more ionised trails.
ETA actually as there would be also be more ionised pathways within the clouds themselves, one could argue that there might be increased within-cloud lightning as well, sapping the energy otherwise available for cloud to ground strikes. It's a bit handwavy.

Convection in clouds causes charge separation (AIUI). The effects of the muons is to produce mini tracks of ionisation that can allow the charges to reconnect to the ground.

Mine is also handwavy

From cosmic explosions to terrestrial fires? in the arXiv. (ETA: it's not obvious that their model is an more complicated than "cosmic rays might cause the initial ionization which leads to a lightning strike therefore more cosmic rays means more lightning" - nothing about each strike being proportionally weaker. But apparently there was an increase in wildfire frequency which otherwise goes unexplained. Bear in mind this in is arXiv where you can say whatever you like, it's not exactly peer-reviewed.)

See also Supernovae in the neighbourhood in Nature.

If most lightning discharges between cloud tops and cloud bases then ionization tracks could allow a large increase in ground strikes without any increase in total lightning energy, I suppose.

What a very interesting article, thanks!

I was under the impression that Eta Carinae is the visible star closest to actually blowing.

my nephew is working on the SNO+ experiment for his PhD and one of the nice effects of that is that it'll give some early warning of an impending supernova, so that telescopes can be pointed in that direction for when the light hits.

El Pollo Diablo wrote: ↑

Mon Jan 13, 2020 11:52 am

my nephew is working on the SNO+ experiment for his PhD and one of the nice effects of that is that it'll give some early warning of an impending supernova, so that telescopes can be pointed in that direction for when the light hits.

Ace. I would dearly, dearly love to see a home galaxy supernova. Kepler's Star (1604) is the last visible from Earth, 500 years ago. 2 subsequent supernovae (last 1600s, late 1800s) were obscured by galactic dust. We're well overdue.

ETA it appears that Cassiopeia A - the c1680 supernova - may have been catalogued by Flamsteed as 3 Cassiopeaie, but he had no idea it was unusual and it was only third magnitude - the supernova is 11,000 LY away.