What would happen if a close star like Sirius went supernova?

Question

All the recorded supernova have been many 1000's of light years away while Sirius is only 9 light years away! The sun is unlikely to explode so nothing to worry about on that score

Answer 1

Although the effect on current stars in the vicinity of a supernova would be disastrous, as heavier elements are produced very rapidly in supernovae, the effect on the prospects for life on planets orbiting the stars that are yet to form in the vicinity would be beneficial in the long-term in that the interstellar material in the region would be enriched with a high proportion of metals (by which astronomers mean elements heavier than helium).

Only metal-rich stars have terrestrial planets (if they consist entirely of hydrogen and helium, then all they can produce is gas giants like Jupiter) and the development of life depends on an abundance of carbon (or silicon, possiby) to form organic compounds like amino acids, which are the building blocks of cells.

This is how we come to have terrestrial planets around Sol and life on this one. There was a supernova explosion nearby and we inherited. Sol is a Population I star that only came into being 4.5 billion years ago. The universe is 13.7 billion years old and in the preceding 9.2 billion years a much higher proportion of stars (Population III and Population II stars) were large ones, and went supernova as a consequence, and created a legacy of metals from which Sol (and other stars with terrestrial planets) have since benefitted.

The most likely nearby star to go supernova is Betelgeuse, the red supergiant in the constellation Orion, 427 light years away from us. Its diameter is 650 times that of the Sun, if it were to be put in our Solar System in place of the Sun, its outer surface would extend to the orbit of Jupiter (that's big!)

Wikipedia say the following about that concrete possibility:

Astronomers predict that Betelgeuse will ultimately undergo a type II supernova explosion although it is possible that the mass is low enough for Betelgeuse to leave a rare oxygen-neon white dwarf.

Opinions are divided as to the likely timescale for this event. Some regard the star's current variability as suggesting that it is already in the carbon burning phase of its life cycle, and will therefore undergo a supernova explosion at some time in the next thousand years or so.

Skeptics dispute this contention and regard the star as being likely to survive much longer. There is a consensus that such a supernova would be a spectacular astronomical event, but would not — being so distant — represent any significant threat to life on Earth.

Even so, Betelgeuse would brighten at least 10,000 times as a supernova, causing it to shine with the luminosity of a crescent Moon. Some sources predict a maximum apparent magnitude equal to about that of the full Moon (mv = -12.5).

This would likely last for several months. It would look like a brilliant point, the brightness of a full Moon with the color of an incandescent bulb at night, and easily visible in daylight. After that period it would gradually diminish until after some months or years it would disappear from naked eye view.

Then Orion's left shoulder would vanish for a time until, in a few centuries, a splendid nebula would develop. However, if Betelgeuse's axis (one of its poles) is pointed towards Earth there would be tangible effects here. A shower of gamma rays and other cosmic particles would be directed at Earth.

There would be spectacular aurorae and possibly a measurable diminution of the ozone layer with consequent adverse radiation effects on life. In such an orientation towards the solar system it would also appear many times brighter than if its axis were pointed away.

AFTERMATH OF A SUPERNOVA

The supernova of 1054 AD has left behind the Crab Nebula (M1 in the constellation Taurus). See what that looks like, less than a 1,000 years after the supernova explosion, in the link below. To get a general idea of what Betelgeuse going supernova would leave behind.

The nebula was first observed in 1731 by John Bevis. It is the remnant of a supernova that was recorded by Chinese and Arab astronomers in 1054. Located at a distance of about 6,300 light years (2 kpc) from Earth, the nebula has a diameter of 11 ly (3.4 pc) and is expanding at a rate of about 1,500 kilometres per second.

The nebula contains a pulsar in its centre which rotates thirty times per second, emitting pulses of radiation from gamma rays to radio waves. The nebula was the first astronomical object identified with a historical supernova explosion.

The fact that the force of the explosion has produced a nebula 11 light years across within 1,000 years of that explosion does rather suggest that stars in the immediate vicinity of a supernova will never be the same again! In the case of Sirius A that would be Sirius B, its companion white dwarf, 20 AU away and Procyon, 5.24 light years away. But Sol would not be far behind, as it is not much further away than Procyon,

Answer 2

If Sirius was mass enough (say 8 times the mass of the sun) to go SN it would be a type 2. A supernova release about 10^42 Joules as radiation in The initial burst. (which is about 10000th of the total energy!) At 9 Light years this would result in a burst of about 10^25 Joules per square metre over a few seconds. This would be REALLY BAD!

The first thing you would see is the entire sky go really bright blue, this would be followed by the loss of you retina and death. One side of the earth's entire atmosphere would be stripped off in a fairly short period of time. After that things would go down hill!

Interestingly Sirius is a binary and it's secondary is a white dwarf. It is likely that when Sirius enters the giant branch there will be some mass transfer between the two whihc might be enough for the seconadry to undergo a type 1a supernova.

Answer 3

Sirius Supernova

Answer 4

The idea that Betelguese is the most likely star to go supernova is incorrect. There are others far more likely to become a type 2a supernova, like "The Garnet Star" Mu Cephei, a more massive red supergiant closer to it's end. Eta Carinae is thought to be so unstable it may explode at any time. And there are several Type 1a candidates, the nearest being IK Pegasi B.

Answer 5

Sirius is 8.8 lightyears away. If a star at that distance were to explode as a supernova, the gamma radiation would fry us 8.8 years later, and, perhaps two years after that, the shockwave would hit. The total amount of material in the shell would probably amount to a bit over one solar mass. If it were expanding at 0.8c, it would carry about 2.5E+12 Joules to every square meter of normal surface as it passed through the solar system.

Answer 6

As others have said it’s really unlikely because Sirius isn't big enough to go supernova - but if it did happen we wouldn’t survive.

Firstly there would be massive amount of radiation… & if somehow you survived that by escaping the Earth - then there would be a powerful shock wave that would apparently hit the Earth about two years later...you see, no chance of survival!

PS Thanks for giving a previous (rather sarky) reply 'the Best Answer’ :)

Answer 7

Sirius is about 2 Sun Masses so its core can't get hot enough to fuse carbon and oxygen to neon and magnesium and further to form an iron core. So it cannot explode as SNII. The distance between Sirus A and B never goes below 8 AU so even when Sirius reaches AGB they won't be nearer than about 6AU. At such distance the white dwarf cannot acrete significant amount of matter from its partner so won't be able to get above Chandrasekar limit.

Answer 8

Actually there may be a bit of worry. The intense radiation from the supernove may be enough to seriously damage if not destroy our ozone layer, rendering us unprotected from the sun's radiation. This would be bad for us, all that ultraviolet getting through. We'd have to live in shelters until the ozone was replenished, which could take a while.

Answer 9

The caption tells part of the story. You have to click the links for the whole story. Briefly, if a white dwarf is part of a binary system, gas from a companion star can accumulate on the surface of the white dwarf until enough is there to form a critical mass, and the hydrogen on the surface fuses into helium in an enormous detonation across the entire surface of the star.

Answer 10

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