The end of the world isn't nigh

[robagar]

Luckily, Eta Carinae is not aimed at us...

THE THREAT TO LIFE FROM ETA CARINAE AND
GAMMA-RAY BURSTS

Arnon Dar, A. DeRujula

Abstract
Eta Carinae - a large blue variable star in the Carina constellation, more than 100 times as massive and 5 million times as radiant as the Sun - is the most massive and luminous star known in our galaxy[1]. Eta Carinae is rapidly boiling matter off its surface; at any time
its core could collapse into a black hole, which may result in a giant supernova and a gamma-ray burst (GRB) [2]. If pointing in our direction, a GRB from Eta Carinae, - only D ~ 2 kpc away - would devastate life on Earth. Auspiciously, recent observations indicate that the gamma-rays in GRBs are narrowly beamed in cones along the rotational axis of the progenitor star [3,4]. In the case of Eta Carinae the GRBs will not point to us, but will be ravaging to life on planets in our galaxy that happen to lie within the two beaming cones. The mean rate of massive life extinctions by jets from GRBs, per lifesupporting planet in galaxies like ours, is once in 100 million years, comparable to the rate observed in our planet [5].

The full text is here (pdf), describing the effects on Earth if we were in the way (equivalent to 1 kiloton TNT going off per square km in the facing hemisphere - don't read before going to bed)

[freespace]

See, astronomy can save lives :-) If we can recognise the signs of such supernova events, we can prepare our underground bunkers and giant tinfoil hats properly :-)

[bojan]

It is not aimed directly, but not too far away either (have a look at homunculus shape... it is about 15~20 degrees away from aiming directly at us).. it all depends on how narrow that beam will be, and what amount energy will be packed in the blast.

[bojan]

Upps, I missed by 10 degrees (after reading the article) :-)
I feel better now :-)

[bojan]

BTW, the mass extinctions caused by GRB's are only one of the plausible explanations for "big silence"...

[jjjnettie (Jeanette)]

We won't need a GRB to wipe out life on Earth, we're doing the job quite nicely ourselves.

[Argonavis (William)]

Originally Posted by jjjnettie

We won't need a GRB to wipe out life on Earth, we're doing the job quite nicely ourselves.

There is evidence that life arose on Earth some 4 GY ago, fairly early in the Earth's history. There is no evidence that I can see of life being wiped out in any collective sense either now or in the future.

Seems to be doing rather nicely, actually.

We often forget that the overwhelming bulk of life on Earth, both in numbers and organic bulk, is unicellular. It has to represent 99.99% of life on Earth. Always has been and probably always will be. Those bacteriums know a thing or two about survival. Us macro beings just come and go in mere flickers of time.

It is not only astronomy that makes us humble to how insignificant we are, biology does the same.

[xelasnave]

Originally Posted by bojan

BTW, the mass extinctions caused by GRB's are only one of the plausible explanations for "big silence"...

Well they did not get me .
I read an interesting article on possible effects on evolution (short of extinction ).
Thanks Rob for the link.
alex