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m1omg
2008-Mar-25, 03:52 PM
Which is the nearest bin. pulsar?

Kaptain K
2008-Mar-25, 04:31 PM
Do you mean the nearest pulsar that is a member of a binary system or a binary system with two pulsars?

m1omg
2008-Mar-25, 06:18 PM
Do you mean the nearest pulsar that is a member of a binary system or a binary system with two pulsars?

I mean a pair of pulsars orbiting each other.
Thanks in advance for answers.

Kullat Nunu
2008-Mar-26, 12:25 PM
PSR J0737-3039 (http://www.jb.man.ac.uk/news/doublepulsar/), 2000 ly away. There are neutron stars in binary systems, and in some cases the companion is also a neutron star but as far as I know this is the only known double pulsar system, found in 2004.

antoniseb
2008-Mar-26, 12:26 PM
As far as I know, only two of these is known.
NASA has this (http://universe.nasa.gov/program/pulsars.html) to say.

PSR 1913+16 is about 21,000 LY
PSR J0737 is about 2000 LY

Kullat Nunu
2008-Mar-26, 12:30 PM
Only one of the neutron stars in PSR 1913+16 system is known to be a pulsar.

m1omg
2008-Mar-26, 12:40 PM
Is there a closer "common" neutron star binary?
2000 light years...does it mean that about 85 million years from now there will be another mass extintion like that at the end of the Ordovician?In one documentary that I watched it was told that even GRB 6000 ly away would almost halve the ozone layer and cause deadly NOx smog over entire planet that will cause an extreme winter and 80 percent more UV will get to the surface, and that atmosphere would take decades to recover, in effect the burt will cause mass extintion, is that accurate ?AFAIK the short duration GRBs are caused by neutron stars colliding...they are very small and massive and so they lose orbital energy in binary systems by gravitational radiation quickly.

It's one theory about the extinction at the end of Ordovician.

antoniseb
2008-Mar-26, 07:14 PM
Is there a closer "common" neutron star binary?
2000 light years...does it mean that about 85 million years from now there will be another mass extintion like that at the end of the Ordovician?

If you are worried about this pair, there are some reasons not to worry:
- in 85 million years we will probably be much further from this pair, as that is more than a third of a galactic orbit.
- short GRBs are most likely highly directional with their projected energy.

That doesn't mean that such a scenario isn't a risk in the billion year time-frame, or rule out this as the cause of the Ordovician extinction. I'd be interested in reading more about any evidence about the OE that suggests this kind of event as the cause.

m1omg
2008-Mar-26, 07:32 PM
I saw it in this documentary:
http://www.youtube.com/watch?v=iNSo4xAMLy4

antoniseb
2008-Mar-27, 05:10 PM
I saw it in this documentary

Oh yeah. I saw that one, and yes it looks like the OE was a good candidate for a GRB inspired extinction event.

m1omg
2008-Mar-27, 07:09 PM
If you are worried about this pair, there are some reasons not to worry:
- in 85 million years we will probably be much further from this pair, as that is more than a third of a galactic orbit.
- short GRBs are most likely highly directional with their projected energy.

That doesn't mean that such a scenario isn't a risk in the billion year time-frame, or rule out this as the cause of the Ordovician extinction. I'd be interested in reading more about any evidence about the OE that suggests this kind of event as the cause.

At which direction from us it's going?

Kullat Nunu
2008-Mar-27, 07:23 PM
Oh yeah. I saw that one, and yes it looks like the OE was a good candidate for a GRB inspired extinction event.

How? The Ordovician extinction event was actually a series of extinctions.

m1omg
2008-Mar-27, 07:29 PM
How? The Ordovician extinction event was actually a series of extinctions.

Watch the documentary.GRB from a distance of approx. 6000 light years would destroy half of the ozone layer and cause nitrogen dioxide to form in the air, creating a brown haze cooling the planet by blocking the sun heat and leaving it open to deadly UV rays, in effect creating a series of mass extinctions.

Do not imagine GRB as a fast and dramatic end, death would come slowly and insidiously.

Triliobites were probably gone extinct because the sea suddenly drop it's temperature and many of their larvae swam in shallow depth, in effect being killed by the UV.
The evidence points to a nearby GRB as a cause of extinctions.
As you can see with a nearby binary pulsar, you don't need a young galaxy with a lot of OB stars to have ocassional GRBs.
When these things collide, one epoch on the Earth will end, and another will begin.
Soon or late, sometimes it will happen.

Kullat Nunu
2008-Mar-27, 07:49 PM
Watch the documentary.GRB from a distance of approx. 6000 light years would destroy half of the ozone layer and cause nitrogen dioxide to form in the air, creating a brown haze cooling the planet by blocking the sun heat and leaving it open to deadly UV rays, in effect creating a series of mass extinctions.

Do not imagine GRB as a fast and dramatic end, death would come slowly and insidiously.

Triliobites were probably gone extinct because the sea suddenly drop it's temperature and many of their larvae swam in shallow depth, in effect being killed by the UV.
The evidence points to a nearby GRB as a cause of extinctions.
As you can see with a nearby binary pulsar, you don't need a young galaxy with a lot of OB stars to have ocassional GRBs.
When these things collide, one epoch on the Earth will end, and another will begin.
Soon or late, sometimes it will happen.

The Ordovician extinctions took millions of years, so a single GRB is out of question and multiple hits doesn't seem plausible. Don't forget that our own planet can be quite nasty sometimes.

m1omg
2008-Mar-28, 12:21 PM
http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=240775

read