Celestia Forums

Just for fun, has any one tried to figure out what the force of the blast wave from a typical super nova explosion would be at the distance of the earth (1AU)?

Yes. Planet go *poof*

OK. I guess you want more than that .

For starters, remember you have a supergiant exploding, so they're already about 2-5 AU in radius. So the Earth would be well inside that, unless you meant 1 AU from the surface. And given that it's a supergiant, if you're 1 AU from the surface then you're vapour anyway.

But even if you're like, 100 AU from it, when it blows the planet's a goner. You've got a sustained luminosity of about 10 billion Sols for a couple of weeks when it goes supernova - it's not instant - so the planet's going to get blasted away in the torrent of radiation (and even after a few weeks the luminosity is still millions of Sols). I calculated this all out for a brown dwarf orbiting Antares at a distance of 2000 AU and the system was toast even out there. And when the actual blast wave hits (I've just been talking about the increased luminosity so far, not the physical blastwave of material blown out from the star), you're going to get the equivalent of several megatons equivalent of TNT hitting per square metre of area of planet.

And then over the next few years you'll sterilise everything for several cubic parses around the supernova.

So they're not fun to be around .

Well i guess that blows out (no pun intended) my theory of riding out the initial blast, and I doubt that an planet short of another dead star would be afford you any protection from the blast

Just for my peace of mind, would someone be able to tell me how far away the nearest *potential* supernova candidate is from Earth (excluding Sol of course)

Would that be Betelgeuse?

julesstoop wrote:Would that be Betelgeuse?

I think so. Betelgeuse is 427 ly from Sol, Antares is about 600 ly. Though I think Antares is more likely to blow before Betelgeuse?

The fun part is one of those might already have exploded, but we don't know about it yet because of the lightspeed travel time .

Last that I read was the if Betelgeuse exploded it should not be a life threatening event for earth. However for a few weeks after the initial explosion the luminosity from the explosion would be about the equivalent of a full moon.

Wikipedia has a decent article about the subject of Betelgeuse going supernova and the possible effects on our little world.

Here's quite a good page about it also...
http://www.astro.uiuc.edu/~kaler/sow/st ... candidates

BTW: Has anyone read "Inconstant Moon" by Larry Niven???

Not me.

Do we know wether Betelgeuse's or Antare's poles are directed towards earth or not?

Also, a few thousand years after either goes supernova, will the shockwave itself, when it reaches Earth, have any effect on Earth or the rest of the solar system, or will it be too weak by then?

PlutonianEmpire wrote:Not me.

Do we know wether Betelgeuse's or Antare's poles are directed towards earth or not?

Also, a few thousand years after either goes supernova, will the shockwave itself, when it reaches Earth, have any effect on Earth or the rest of the solar system, or will it be too weak by then?

The shockwave itself won't have an effect out here, no.

I remember seeing a a small animation of Betelgeuse rotating once. The pole (axis of rotation) clearly wasn't pointed in our direction.

I guess my next question in as ?€?what if?€

According to several sources I've just consulted, including one on the NASA website, Betelgeuse is at least 20 times as massive as our sun, and has more than enough current mass to explode in a hypernova explosion resulting in a Black Hole, not a neutron star. One has only to type "Betelgeuse" and "Black Hole" in Google, and you will get dozens of hits suggesting that this is the fate of the star. If true, then it will broadcast a gamma ray burst when it blows, which will certainly affect Earth's atmosphere and/or ozone layer when it hits us.

What is annoying is that this is in direct conflict with dozens of other sites that claim Betelgeuse will explode as a supernova and result in a neutron star, not a black hole.

Since it is a MASSIVE star, I had always presumed it would end as a Black Hole.

I wish Astronomers would make up their minds. Betelgeuse is not confusing. It is BIG star. It is either big enough to result in a Black Hole, ... or it is not! Which is it?????



Frank

fsgregs wrote:I wish Astronomers would make up their minds. Betelgeuse is not confusing. It is BIG star. It is either big enough to result in a Black Hole, ... or it is not! Which is it?????

Welcome to Science.

Depends what stellar models you use, I guess. And we probably don't know which ones are accurate til we actually see it happen.

fsgregs wrote:If true, then it will broadcast a gamma ray burst when it blows, which will certainly affect Earth's atmosphere and/or ozone layer when it hits us.

I believe that only happens if the stars axial tilt points one of it's poles at us. Other wise, we're pretty safe, i think.

PlutonianEmpire wrote:Also, a few thousand years after either goes supernova, will the shockwave itself, when it reaches Earth, have any effect on Earth or the rest of the solar system, or will it be too weak by then?

This is an unfortunate myth that the media have propagated... A supernova would not actually have a shock wave, because a shock wave is something that propagates through a medium surrounding an object that undergoes an explosion or other upheaval. When a bomb goes off in the atmosphere, it pushes out on the air around it and creates an expanding pressure wave of superheated air that's responsible for most of the damage it causes. When an earthquake happens, it sends a shock wave out through the ground. But space is a vacuum. Aside from a very tenuous interstellar medium, there's nothing to transmit the physical force of the explosion.

So there are only two things from a supernova that could affect you. One is the radiation it gives off, whether the EM radiation propagating at lightspeed or the particle radiation propagating at a high sublight velocity. The other is the expanding cloud of matter expelled from it. It's wrong to call that a "shock wave" because the material itself is expanding outward to fill vacuum, while a shock wave is a compression expanding through a pre-existing material. And that cloud will expand very slowly (compared to the speed of light) to form a nebula, and will soon become too diffuse to make a difference. In the case of, say, the Crab Nebula, the material expelled from the supernova has only travelled a maximum of 5.5 light-years from the star in the 275 years since the supernova. (Of course the supernova actually happened 6300 years before we saw it, but we're only seeing the nebula as it looked 6300 years ago, so it cancels out.)

So don't think in terms of "shock waves." That's just one of the countless bad-astronomy myths that Hollywood has propagated. The real hazard is radiation.

But, Christopher, supernovae *do* cause shock waves. Most supernovae happen in clouds of gas and dust that are still in the process of condencing into stars (most supernovae are relatively young, high-mass stars). While those shock waves may not generate as dense a fluctuation as what happens in the Earth's atmosphere, they are enough to cause more stars to start condending out of the higher density clouds that are produced in those waves.

...and don't forget "gravitational waves" being emitted from an exploding supernova. They may also be viewed as shock waves. I am sure you all know that several sophisticated detectors for gravitational shock waves are installed on our planet, waiting impatiently for a signal ...

Bye Fridger

selden wrote:But, Christopher, supernovae *do* cause shock waves. Most supernovae happen in clouds of gas and dust that are still in the process of condencing into stars (most supernovae are relatively young, high-mass stars). While those shock waves may not generate as dense a fluctuation as what happens in the Earth's atmosphere, they are enough to cause more stars to start condending out of the higher density clouds that are produced in those waves.

I always figured that those "shock waves" were what I was referring to as the "blast wave" in my first post on this thread - the outer layers blown out by the star. They have physical density, so they would interact with matter around them (be it gas, dust, planets, whatever). When I calculated it out, this ejected material is what would be slamming into an orbiting planet's surface with the equivalent force of several megatons of TNT per square meter.

That's almost unimaginable. Imagine a force that is many thousand times more powerful than the Hiroshima nuke being unleashed on every square metre of the planet's surface that faced the star!! It's mind-boggling!