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tkdguy

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Re: More space news!

 

might mean a magnetar

 

Well, if he does mean a Magnetar, then Phil Plait has some good articles on the burst in question - http://blogs.discovermagazine.com/badastronomy/2009/06/18/ok-so-maybe-we-can-be-a-little-frightened/#.UP6UxPI5t8E and http://www.slate.com/blogs/bad_astronomy/2012/12/27/cosmic_blast_magnetar_explosion_rocked_earth_on_december_27_2004.html

 

"... See, the magnetic field is coupled to the crust of the neutron star. The crust is extremely rigid and under vast pressure from the gravity of the star. If the crust cracks — a starquake, if you will — the energy released makes the strongest earthquake ever recorded on our planet look like a friendly pat on the back. I once calculated the strength of such a starquake, and it would register as magnitude 32 on the Richter scale. This ultraviolent blast shakes the magnetic field of the star, which in turn reacts by slamming around subatomic particles… the bottom line is that such an event can trigger a phenomenal release of X-ray energy from the star. And by "phenomenal" I mean "pants-wetting terrifying".

 

 

In December 2004, the magnetar SGR 1806-20 underwent such a starquake. In one-tenth of a second the subsequent blast released something like 2 times 1046 ergs of energy — equal to about 50 trillion times the Sun’s output during that same period."

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Re: More space news!

 

Well, if he does mean a Magnetar, then Phil Plait has some good articles on the burst in question - http://blogs.discovermagazine.com/badastronomy/2009/06/18/ok-so-maybe-we-can-be-a-little-frightened/#.UP6UxPI5t8E and http://www.slate.com/blogs/bad_astronomy/2012/12/27/cosmic_blast_magnetar_explosion_rocked_earth_on_december_27_2004.html

 

"... See, the magnetic field is coupled to the crust of the neutron star. The crust is extremely rigid and under vast pressure from the gravity of the star. If the crust cracks — a starquake, if you will — the energy released makes the strongest earthquake ever recorded on our planet look like a friendly pat on the back. I once calculated the strength of such a starquake, and it would register as magnitude 32 on the Richter scale. This ultraviolent blast shakes the magnetic field of the star, which in turn reacts by slamming around subatomic particles… the bottom line is that such an event can trigger a phenomenal release of X-ray energy from the star. And by "phenomenal" I mean "pants-wetting terrifying".

 

 

In December 2004, the magnetar SGR 1806-20 underwent such a starquake. In one-tenth of a second the subsequent blast released something like 2 times 1046 ergs of energy — equal to about 50 trillion times the Sun’s output during that same period."

 

I wonder if there were any life-sustaining planets near enough to it to have been damaged / sterilized. Also, there is a typo in one of the articles:

 

it would register as magnitude 32 on the Richter scale

 

The quake itself would have registered as 23 on the Richter scale
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Re: More space news!

 

There was a talk about neutron stars here last week, and this event was specifically mentioned. The gamma-ray flash overloaded every detector we have. And the reflection of the gamma-ray flash off the Moon was detected, which is quite something considering how lousy a gamma-ray reflector it is.

 

Damage to nearby planets ... considering the numbers of planets that Kepler is finding, the answer for that is probably yes. OTOH, the flash is so brief it would only zap one face of any planet, so the back face (from the point of view of the blast) would escape direct irradiation. Figuring out what you'd need to do to sterilize a planet in a single burst like that is hard; frankly, unless the thing is really on top of you (so that the planet is all but vaporized by the radiation, which I am not sure can be done) I'd be surprised if it could zap an entire planet in one shot. Depends on the actual details of the emission and a few other things that aren't well known.

 

That magnetar is rather closer to the Galactic Center than we are, so that part of the Galaxy has already been zapped well by a number of objects. Since mass is flowing slowly toward the center, the high-mass star population is larger there and always has been, and things that go bang violently tend to come from high-mass stars. Type Ia supernovae are an important exception to that.

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Re: More space news!

 

Stars sometimes do bad things for life, so living near them increases the risk. Increased size also makes it more likely for bad things to happen, and happen sooner. Living near one is pretty much mandatory. But living near many large, older stars is just asking for it. And as oen approaches the galactic center, age and size increase.

 

I've also heard that the metallicity of the star & it's planets impacts the chance of life.

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Re: More space news!

 

There's no doubt that you get more star formation where there is more matter, and matter does pile up near the Galactic Center. And more nastiness comes from very high mass stars than anything else. I have read suggestions that the central parts of the Galactic Disk may be uninhabitable in the long term because of such things, though the focus was on the central black hole and episodes of AGN activity by that.

 

It was found fairly early in the planet-search racket that stars with planets tend to be more metal-rich than average, but there has been a planet found orbiting a star in a globular cluster (which are old and metal-poor) so that can't be an absolute effect. There has also been some speculation about stars which have or used to have planets have had their surface compositions altered by accretion of planetary material. That's possible but hard to do; stars are just so much more massive than planets that making a detectable change in stellar composition is nigh on impossible. The easiest thing to change is perhaps the lithium abundance, because solar-type stars do destroy the lithium in their envelopes during their main sequence phase, and the spectroscopy of lithium is such that even just an Earth's share of Li can make an observable difference.

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Re: More space news!

 

All Galaxy News' date=' keeping you up to date on the Milky Way since 1.2 billion ABB (after big bang)![/quote']

 

No' date=' you're thinking of GNR -- "Galaxy News Radio! We're Radio Free Wasteland, and we're here for [i']you[/i]!"
Brought to you by the Deep Space Network
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Re: More space news!

 

What's AGN?

 

Prolly active galactic nucleus.

 

Sorry, forgot that AGN wasn't quite a mainstream term. Yes, AGN = Active Galactic Nuclei. When the central black hole is accreting mass at a large enough rate so it has a big accretion disk around, big enough to make for large X-ray and gamma-ray fluxes, ejection of strong jets out the poles of the disk, and so on. Seyfert galaxies, BL Lac objects ("blazars"), and quasars are all AGNs seen at different levels of mass accretion rate and different angles.

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