Question about the Andromeda galaxy

[Junghalli]

In a discussion on another message board somebody commented that he remembered something about the Andromeda galaxy having a higher level of X-rays or background radiation than our own.

This may be somewhat relevant for my SF (if it impacts the likelyhood that advanced life may develop there) and something I'm personally curious about anyway. Google hasn't been able to turn up anything about it. Can anybody confirm or deny that this is in fact true?

[Temujin]

In the Star Trek franchise, increasing levels of radiation were driving the Kelvans (TOS - "By Any Other Name") to seek greener pastures. This could be a brain bug from there as I've heard of it as well, but never confirmed from an official scientific source.

[Jeremy]

Tangentially, in Larry Niven's Known Space, the core stars of the galaxy begin a cascading chain of novas, sending out a wall of space death.

Is this remotely possible?

[Samuel]

Tangentially, in Larry Niven's Known Space, the core stars of the galaxy begin a cascading chain of novas, sending out a wall of space death.

Is this remotely possible?

Probably not (Not an astrophysicist). Novas occur when a star runs out of fuel (well, fuel it can fuse to get enough energy), collapses inward and then explodes out.

If a Nova was close and strong enough to affect neighboring stars, it would have the problem of only hitting one side.

[Temujin]

Tangentially, in Larry Niven's Known Space, the core stars of the galaxy begin a cascading chain of novas, sending out a wall of space death.

Is this remotely possible?

Probably not (Not an astrophysicist). Novas occur when a star runs out of fuel (well, fuel it can fuse to get enough energy), collapses inward and then explodes out.

If a Nova was close and strong enough to affect neighboring stars, it would have the problem of only hitting one side.

I think that's another brain bug. I remember I used to hear that a lot from less reputable sources years ago. Essentially, the idea is that gamma rays from the supernova would have some sort of an effect on nearby stars causing them to go supernova prematurely (I don't recall what the time frame was supposed to be or how it was supposed to work); thus creating a cascade effect of supernovae across a galaxy.

Of course how it was supposed to magically work when a supernova is tied to a star's mass, and hence fuel, is beyond me; especially since it was supposed to affect stars not normally capable of going supernova.

Additionally, it ignores the obvious fact that the galaxies would have all undergone a chain reaction and blown themselves apart billions of years ago.

[Ariphaos]

Andromeda is a bit brighter than the Milky Way, but I thought it was actually rather low in the x ray spectrum?

[Temujin]

That's the case as I understand it. I believe there are a few bright point sources of x-rays, but not overall high levels.

[starslayer]

Is this remotely possible?

Sweet Jesus no. I like Niven as an author, but nothing of the sort could ever remotely happen. While it is true that if you greatly perturb of star, it will either collapse or blow up, for a supernova to perturb a star that greatly requires that said star basically be at ground zero, and even then, it's really only likely to give it a nice big shove out of the system.

Essentially, the idea is that gamma rays from the supernova would have some sort of an effect on nearby stars causing them to go supernova prematurely (I don't recall what the time frame was supposed to be or how it was supposed to work); thus creating a cascade effect of supernovae across a galaxy.

That was the proposed mechanism? That kind of disturbance is in the "wouldn't even scratch the paint" category when put to a star. If the gamma ray flux was large enough, the star would temporarily expand as the outer atmosphere heated up, and it would have a slightly stronger solar wind for a while, but the atmosphere would cool down soon enough, and it would be back to business as usual.

As for your point about supernovae being tied to stellar mass, that's only strictly true for a purely internally driven one; as I mentioned above, if you greatly perturb a star very quickly, the star will either collapse or blow up. IOW, if throw the right stuff at a star, it will go supernova. To get our Sun to blow itself to pieces, for instance, throw a white dwarf or something similar at it.

[Temujin]

Thinking back some more, one of the ideas related to gamma rays causing a supernova was that a hyper advanced race could fire what was essentially a gamma ray laser at a star to induce a premature supernova. This was to be done from their home system, and hence the thought was that they could causally wipe us out with little effort if they wanted to.

That was my point about stellar mass; while I can't recall the exact mechanism, it caused a techno babble / magic reaction causing stars like our Sun to go supernova for no other reason than being hit by some concentrated gamma rays from across light years of space.

[starslayer]

Thinking back some more, one of the ideas related to gamma rays causing a supernova was that a hyper advanced race could fire what was essentially a gamma ray laser at a star to induce a premature supernova. This was to be done from their home system, and hence the thought was that they could causally wipe us out with little effort if they wanted to.

That's all kinds of stupid. Just point the laser straight at us; even the most radiation-hardened settlement is going to be rather crispy under anything close to the gamma ray flux needed to do something like that (and by "close", I mean within at least ten orders of magnitude at a guess).

If you were to construct such a laser and point it at a star, it would indeed explode; once the outer layers are blown off, the star's inner reaches will expand violently until equilibrium is reached. Because the change is so quick, though, the remaining mass (which will still be the lion's share of the star's mass) simply can't lose enough energy to remain bound in a stable star, so it all goes kablooie. And that's if you turned off the laser once Step 1 was complete - if you kept it on (likely), the star goes... even more kablooie, so not much of a change. Also, this requires so much energy (you're taking the Death Star to a star, in effect) that any planets in the system are going to be absolutely fried, and completely destroyed as well (there's no goddamn way you're focusing gamma rays to simply a stellar diameter over interstellar distances; QED and Maxwell's equations won't allow it). So this kind of a laser is some really gigantic overkill, if you ask me.

[Temujin]

Yeah, its all kinds of stupid. I was a kid when I first read about it in the 1980s, and even then I was picking it apart. But I kept seeing in various works, so at the time the meme must have been pretty prevalent in certain circles.

[Sriad]

Yeah, its all kinds of stupid. I was a kid when I first read about it in the 1980s, and even then I was picking it apart. But I kept seeing in various works, so at the time the meme must have been pretty prevalent in certain circles.

It's just one of those low-sci-IQ things that goes around building on itself. Along with the "We have enough nukes to destroy Earth/planets aren't that hard to destroy" thing, you've got "stars blow up by themselves ALL THE TIME, so it wouldn't be too hard to touch one off early", because that's how conventional explosives work!