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Thoraiya
2009-May-22, 12:16 AM
Hi all (I see I'm not the first writer to come here begging for help!) - I'm posting these questions in the interests of preventing Bad Astronomy before it can reach the shelves.

My story involves aliens who see in the gamma ray spectrum and live on a pulsar planet.

I'm having trouble getting my head around what your average day in the PSR 1257+12 system would be like.

Partially because my basic grasp of physics is defunct (what does the star
look like from the surface of the planet to a person who sees in gamma? How
does all the radiation interact with all the weird magneticky stuff that's
going on?).

Partially because I can't find the information I want in a form I can
understand.

On the one hand, I have the internet telling me that "these rocky planets
can't support life because of the radiation", with no detail about exactly how MUCH radiation and of what type (I kind of need to know this to make the aliens remotely credible).

On the other hand I have Schonfelder's "The Universe in Gamma Rays" giving me a whole bunch of mathematical equations and tables that my brain can't translate into the answers to questions like "is there daytime and nighttime", "do the planets ever pass directly through the lighthouse beams of the pulsar" etc.

Can anyone help?




Oh, and before you point me to this picture...


http://www.nasa.gov/images/content/148752main_image_feature_574_ys_4.jpg

(It's an artist's representation of the PSR 1257+12 system)

...I've seen it under attack in several places, though nobody has explained exactly why it's so terribly wrong.

*twiddles thumbs and waits hopefully for enlightenment*

PraedSt
2009-May-22, 12:43 AM
Interesting story!

No enlightenment, but this might help add to your imagination. :)

The Earth in Gamma Rays (http://www.nasa.gov/vision/earth/lookingatearth/gamma_earth.html) (NASA)


"If our eyes could see high-energy gamma rays, this is what the Earth would look like from space," said Dr. Dirk Petry of NASA Goddard Space Flight Center in Greenbelt, Md. "Other planets -- most famously, Jupiter -- have a gamma-ray glow, but they are too far away from us to image in any detail."

http://img34.imageshack.us/img34/9752/earthgamma.jpg (http://img34.imageshack.us/my.php?image=earthgamma.jpg)

Thoraiya
2009-May-22, 12:55 AM
That is so cool! Thank you, PraedSt!

PraedSt
2009-May-26, 09:54 AM
No joy yet? You could try splitting your several questions; that way you might get a better response. :)

Anyway, some amateur attempts:

1. What does the star look like from the surface of the planet to a person who sees in gamma?
Very broadly, probably the same as the Sun looks to us. A bright shiny disc. Colour will depend on the planet's atmosphere and your alien's physiology.

2. How does all the radiation interact with all the weird magneticky stuff that's going on?
The neutron star's magnetic field concentrates a lot of the radiation into the beams, that's as much as I know. And your planet's magnetic (http://en.wikipedia.org/wiki/Magnetosphere) field will likely behave just like ours.

3. no detail about exactly how MUCH radiation and of what type?
Yeah, I can't give you details, but you get electromagnetic radiation (http://en.wikipedia.org/wiki/Electromagnetic_radiation) and particle radiation (http://en.wikipedia.org/wiki/Particle_radiation) from any star. Anyway, it strikes me that you want radiation surely? Otherwise your planet will likely die.

4.is there daytime and nighttime?
Most likely, and you can simply specify 'yes'. As long as your planet's rate of rotation around its axis is different from its rate of rotation around the star, and your planet is not flipped on its side, you'll get night and day (http://en.wikipedia.org/wiki/Daytime_(astronomy)).

5. do the planets ever pass directly through the lighthouse beams of the pulsar?
Unlikely. Again, you can simply specify 'no'. Planetary orbits trace out great circles (http://en.wikipedia.org/wiki/Great_circle), and (as far as I know), the beams trace out small circles (http://en.wikipedia.org/wiki/Small_circle). These are unlikely to intersect unless your aliens are cosmically unlucky.

trinitree88
2009-May-26, 03:54 PM
Collimation factors for jets from type 2 "supes" which produce pulsars are ~ 10,000/1..John Middleditch et al....so the beams should be roughly the same order of magnitude. The pulsar should stimulate all the photoreceptors, appearing "white" to their eyes....unless they have special gamma-only receptors. You could have them have small germanium calorimetric deposits near their photoreceptors???? maybe.
First ionization energy for atoms is typically a few tens of electron volts, so a gamma ray can create a long ionizing path in living tissue, or several people in a row...not good for fragile carbon bonded lifeforms. Dissociation energy for bonds in carbon chains, and polar hydrogen bonds in protein stereochemistry are even more susceptible to radiation disruptions. You'll need to postulate a biochemical mechanism to repair tissue at an extraordinary rate, and plenty of redundant DNA to mitigate chromosal damage.
You could have them live in lead crystal houses with ~ 30 % lead, a few meters of thickness ought to cut the radiation down the way x-ray technicians do....tricky.

chornedsnorkack
2009-May-26, 04:04 PM
Does anyone even know how much pulsars radiate in directions off the beam? Earth is on the beam path of those that pulse... but are any neutron stars observable that are pulsars but have beams directed elsewhere?

PraedSt
2009-May-26, 04:29 PM
Does anyone even know how much pulsars radiate in directions off the beam? Earth is on the beam path of those that pulse... but are any neutron stars observable that are pulsars but have beams directed elsewhere?
We can only observe them because their rotating beams produce a pulsing effect. So pulsars with beams that don't sweep into our path aren't observable from Earth.

chornedsnorkack
2009-May-26, 04:34 PM
We can only observe them because their rotating beams produce a pulsing effect. So pulsars with beams that don't sweep into our path aren't observable from Earth.

In which case, they should also be neither observable from nor dangerous to their own planets.

Argos
2009-May-26, 04:50 PM
I wonder what kind of life could withstand a gamma-ray shower.

Swift
2009-May-26, 07:00 PM
I wonder what kind of life could withstand a gamma-ray shower.
In Robert L. Forward's book Dragon's Egg, the Cheela are a lifeform that lives on the surface of a neutron star, their metabolize is based on nuclear interactions (not chemical) and, IIRC, they see either x-rays or gamma rays.