# Proxima Centauri closest star. super nova

1. Jan 11, 2012

### budd

Hi clever people. much respect.
Just wondering, if our closest star went super nova. how would it affect the earth,if at all?

2. Jan 11, 2012

### Janus

Staff Emeritus
Proxima Centauri is much too small to go supernova. In fact, none of the stars in the close stellar neighborhood of the Earth are candidates for supernovae.

3. Jan 12, 2012

### Chalnoth

While this is true, I think it does pose an interesting question: just how close would a supernova have to be to have an impact on Earth?

That depends somewhat upon what kind of supernova you're talking about. But generally it has to be within a few tens of light years to have a measurable impact. So if one went off only 3-4 light years away? Yeah, that would have a pretty catastrophic impact for life on Earth. Fortunately, that won't happen.

4. Jan 12, 2012

### Chronos

It depends on the type of supernova and mass of the progenitor star. A type 1a supernova could be somewhat dangerous if it originated within about 30 light years. Fortunately very few such candidates exist [possibly Sirius B]. A type II [core collapse] supernova could be dangerous - out to maybe 100 or so light years. Fortunately, few such candidate exist. A gamma ray burster might be hazardous out to several thousand light years - but only if pointed directly at us. Also, fortunately, only one such candidate exists [eta carinae] and does not appear to be pointed our way. The long and short of it is it appears we reside in a very boring part of the universe. That may help explain why planet earth is unusually hospitable to life.

5. Jan 12, 2012

### Ryan_m_b

Staff Emeritus
About 450 million years ago the second largest mass extinction in the history of the world occured; the Ordovician-Silurian extinction event. Roughly 50% of genera became extinct. One hypothesis for why it occurred is that a gamma ray burst from a hypernova <6000ly away stripped away half of the ozone in the atmosphere exposing all life to much more UV radiation. There is no strong evidence for this hypothesis at the moment though IIRC it is consistent with the progress of the extinctions.

6. Jan 12, 2012

### Chalnoth

I think those distances are reversed, actually. Type IA supernovae release a lot more of their energy in the form of high-energy particles, which tend to do more damage.

7. Jan 12, 2012

### budd

much respect

8. Jan 12, 2012

### Chronos

Thank, Chalnoth, I had that bass ackwards. A Ia supernova could pose a threat within a couple hundred light years whereas a type II supernova would probably need to be within about 30 light years to be threatening.

9. Jan 14, 2012

10. Jan 14, 2012

### Chalnoth

True, but those don't happen often enough to really be a significant concern.

11. Jan 15, 2012

The lowest estimate of approx one per day, or thirty times per month makes getting hit by one unlikely?

The higher estimate gives us three thousand per month and thirty-six thousand per year.

So it’s actually their distance that protects us from those bursts and not their unlikelihood..

The potential one I mentioned before is close enough to cause serious damage because the part of the star that shoots out the beam is aimed in our direction and the star is close enough. So distance is no protection in that case.

Last edited by a moderator: May 5, 2017
12. Jan 15, 2012

### Chalnoth

One hundred per day in the observable universe translates to approximately one per galaxy once every 3,000,000 years or so.

So yes, sure, if you're going to take the entire observable universe into account, anything is going to look exceptionally frequent. But it is only those that happen in our relative vicinity that are ever likely to be a problem.

You still have a $1/r^2$ falloff in intensity with distance. So yes, distance is still a protection even if it happens to be pointed at us.

13. Jan 15, 2012

### cmb

What evidence is there for this? Do you have a reference to a peer reviewed journal, please?

14. Jan 15, 2012

Anything? Are you sure you want to stick with that untenable premise? After all, that would make all phenomena occuring in our universe equally probable. something that observation tells us is not true.

In any case, nothing in your statement indicated that you were limiting the rarity to individual galaxies. So I rightfully assumed that the universe was involved

Of course! Like the one under discussion which sooner or later will go off.

Really? That depends on the distance involved doesn't it?. As previously pointed out, the distance of this one would still allow devastation of the earth if it hit us head on. Or are you disagreeing with the findings as published in the March 1 issue of Astrophysical Journal and with the physicists who assert that there is indeed danger for our earth despite the distance of this star?

BTW

Rarity is irrelevant to the findings. It's like saying that people aiming rifles out of windows are rare in cities while ignoring our neighbor as he points one out his window in our direction as we speak.

15. Jan 15, 2012

### Chalnoth

Um, a few thousand light years away is within our own galaxy. And as the article itself explains, "devastation" is a bit of an overstatement. It may deplete some of our ozone layer, which won't be great, but won't be as bad as the stuff we're doing already.

So I really don't know why you went off on this long tangent about GRB's across the whole universe. They just don't matter. If a GRB just a few thousand light years away can't do much damage, then one outside our galaxy isn't going to do anything at all. It doesn't matter whether they're pointed at us or not: they may be powerful, but they aren't that powerful.

16. Jan 15, 2012

### alexg

Except we don't have a neighbor with a rifle.

17. Jan 16, 2012

### Chronos

Eta Carinae is another 'nearby' [~7000 light years] potential GRB candidate, but, its rotational axis is pointed about 45 degrees away from us. This does not guarantee any potential gamma burst would not be directed at us any more than WR 104 would be. It's like a bullet in a bonfire, no telling what direction it might go when it goes.

18. Jan 16, 2012

The analogy is simple enough.
Your inability to understand it indicates a deficiency in reasoning ability.

19. Jan 16, 2012

I never said that the ones in other galaxies can do us harm. That's STRAWMAN.
I simply responded to your comment that gamma ray bursts are rare in our universe which is false. Then I went on to prove that your assurance that we have nothing to worry about from gamma ray bursts is false as well since we are looking at a possible hit from a nearby gamma ray source.

Now you shift to minimizing danger by misrepresenting the gist what article says. That there indeed is significant danger. Which of course is totally irrelevant to your initial statement that we are safe from gamma ray sources because of their rarity. Scientific objectvity is being interfered with here.

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Last edited: Jan 16, 2012
20. Jan 16, 2012

### Ryan_m_b

Staff Emeritus
Here you go. Note that I'm not advocating this hypothesis, merely mentioning it as relevant to the thread.