Proxima Centauri closest star. super nova

[budd]

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

 

[Janus]

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.

 

[Chalnoth]

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.

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.

 

[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.

 

[Ryan_m_b]

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.

 

[Chalnoth]

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.

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.

 

[budd]

Thank you for your replies.

much respect

 

[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.
Re: http://stupendous.rit.edu/richmond/answers/snrisks.txt

 

[Radrook]

'Death Star' Gamma-Ray Gun Pointed Straight at Earth
http://www.nature.com/news/2008/080306/full/news.2008.653.html

Not so unlikely as the article above points out. In fact, we might just be looking down the barrel of a gamma ray burst "cannon" about to go off.

 

[Chalnoth]

Not so unlikely as the article above points out. In fact, we might just be looking down the barrel of a gamma ray burst "cannon" about to go off.

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

 

[Radrook]

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

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

4. How often do Gamma-ray bursts occur?
Based on almost 30 years of observing gamma-ray bursts, we now think that on average there is one gamma-ray burst per day somewhere in the Universe. However, recent developments in the study of gamma-ray bursts (see below) indicate that the true number of these events may be 100 times larger. This means that we only see one out of every 100 gamma-ray bursts.
http://users.obs.carnegiescience.edu/eberger/faq.html

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.

 

[Chalnoth]

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 per5 year.

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

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.

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 as it is in these others.

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.

 

[cmb]

There is no strong evidence for this hypothesis at the moment though IIRC it is consistent with the progress of the extinctions.

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

 

[Radrook]

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.

Anything? Are you sure you want to stick with that untenable premise? After all, that would make all phenomena occurring 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

But it is only those that happen in our relative vicinity that are ever likely to be a problem.

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

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.

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?

Real Death Star Could Strike Earth
Short fuse
The pinwheel, named WR 104, was discovered eight years ago in the constellation Sagittarius. It rotates in a circle "every eight months, keeping precise time like a jewel in a cosmic clock," Tuthill said.

Both the massive stars in WR 104 will one day explode as supernovae. However, one of the pair is a highly unstable star known as a Wolf-Rayet, the last known stable phase in the life of these massive stars right before a supernova.
"Wolf-Rayet stars are regarded by astronomers as ticking bombs," Tuthill explained. The 'fuse' for this star "is now very short — to an astronomer — and it may explode any time within the next few hundred thousand years."
When the Wolf-Rayet goes supernova, "it could emit an intense beam of gamma rays coming our way," Tuthill said. "If such a 'gamma ray burst' happens, we really do not want Earth to be in the way."
Since the initial blast would travel at the speed of light, there would be no warning of its arrival.


Firing line
Gamma ray bursts are the most powerful explosions known in the universe. They can loose as much energy as our sun during its entire 10 billion year lifetime in anywhere from milliseconds to a minute or more.
The spooky thing about this pinwheel is that it appears to be a nearly perfect spiral to us, according to new images taken with the Keck Telescope in Hawaii. "It could only appear like that if we are looking nearly exactly down on the axis of the binary system," Tuthill said.

Unfortunately for us, gamma ray bursts seem to be shot right along the axis of systems. In essence, if this pinwheel ever releases a gamma ray burst, our planet might be in the firing line.
"This is the first object that we know of that might release a gamma ray burst at us," said astrophysicist Adrian Melott at the University of Kansas in Lawrence, who did not participate in this study. "And it's close enough to do some damage."

This pinwheel is about 8,000 light years away, roughly a quarter of the way to the center of the Milky Way Galaxy. While this might seem far, "earlier research has suggested that a gamma ray burst — if we are unfortunate enough to be caught in the beam — could be harmful to life on Earth out to these distances," Tuthill said.

What might happen
Although the pinwheel can't blast Earth apart like the Death Star from Star Wars — at least not from 8,000 light years away — it could still cause mass extinction or possibly even threaten life as we know it on our planet.
Gamma rays would not penetrate Earth's atmosphere well to burn the ground, but they would chemically damage the stratosphere. Melott estimates that if WR 104 were to hit us with a burst 10 seconds or so long, its gamma rays could deplete about 25 percent of the world's ozone layer, which protects us from damaging ultraviolet rays. In comparison, the recent human-caused thinning of the ozone layer, creating "holes" over the polar regions, have only been depletions of about 3 to 4 percent, he explained.
"So that would be very bad," Melott told SPACE.com. "You'd see extinctions...

http://www.space.com/5081-real-death-star-strike-earth.html

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.

 

[Chalnoth]

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?

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.

 

[alexg]

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.

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

 

[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.

 

[Radrook]

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

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

 

[Radrook]

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.

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.

'Death Star' found pointing at Earth
Star-system explosion could threaten life on Earth.


Katharine Sanderson


The clear dust spiral shows that a beam from this star would be aimed at Earth.Courtesy of the researchers
Astronomers have spotted a binary star system that could collapse to produce a massive gamma-ray burst at any point during the next few hundred thousand years — and it is pointing at Earth.


The binary star system WR 104, some 8,000 light-years from Earth in the Sagittarius constellation, is made up of two stars that complete an orbit of one another every 8 months. Both stars are massive and have strong solar winds that spew out material, resulting in a spiralling trail of hot gas and dust.


Peter Tuthill at the University of Sydney in Australia and his colleagues watched WR 104 for 6 years, during which time they saw 10 full orbits and captured them on camera using the Keck telescopes on Mauna Kea, Hawaii. The research is published in the Astrophysical Journal1.


The resulting pictures show the spiralling dust in all its glory, and reveal a potentially devastating fact: Earth looks down the axis of the system. “It is pointing at us within a range of about 0–16º,” says Tuthill, who estimates it is most likely 12º off-centre. “It would take on a different appearance, looking foreshortened, if we were looking at it from a wider angle.”


The massive stars are certain to explode, and soon, astronomically speaking. The question is whether this will happen in a supernova that bursts in all directions, spreading out the damage, or whether the stars are spinning fast enough for this explosion to be directed in a gamma-ray burst. If so, the angle of the system means that we are in the firing line for one half of the burst jet.


It is unclear how direct the burst would have to be to have an effect, says Tuthill. It has been variously postulated that a burst angle of 2–20º might put us outside the danger zone, but Tuthill says that even a miss of 12º would be dangerous for life on Earth.
Caught in the beam


A mass-extinction event on Earth some 450 million years ago might have been triggered by a gamma-ray burst. Adrian Melott at the University of Kansas in Lawrence, who suggested this in 2003, says that the new observations of WR 104 are big news because this is the first candidate system spotted that could produce a similar Earth-walloping gamma-ray burst in the future. “If it were a full gamma-ray burst and we were caught in the beam, the effects would be pretty severe,” says Melott. “My guess is that there would be a lot of death from it, rather like a small-scale nuclear war.”


A gamma-ray beam might not kill us all immediately. First there would be a bright flash, possibly blinding people, says Melott, then after a few hours the effects would begin in earnest.


The gamma rays would break up molecules in the atmosphere, producing particular oxides of nitrogen that would start to eat up the ozone layer after a few hours, says Melott. Within a few days a quarter of the ozone layer would be destroyed, he suggests.


The ozone destruction would allow through enough ultraviolet light to cause severe radiation damage to plants and people. The nitrogen oxides would also cause acid rain that could kill off plants and algae.
http://www.nature.com/news/2008/080306/full/news.2008.653.html

[/QUOTE]

 

[Ryan_m_b]

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

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

 

[cmb]

Thanks. (Nice that it is a 'free download' too!)