[ncmncm]

A galaxy is really a pretty dangerous place for organic life.

One supermassive black hole merger in the same or nearby galaxy, a biggish black hole merger within 10,000 light years, a magnetar hiccup within 500 ly, or a workaday supernova 5 ly off might be enough to sterilize a whole solar system. There is no guessing how many times life has been wiped clean that way.

The sooner our descendants can get the hell out of the galaxy, the better.

[brabel]

I think we are in a relatively safe corner of the galaxy though... IIRC there's no cosmical existential threat we know of within the next billion years or so, and the kind of cataclism you're talking about would be the kind of thing we should already be able to predict millions of years in advance.

[ncmncm]

Sol orbits the galaxy independently of all other bodies. We don't know where most of the magnetars are, never mind their orbits, which are anyway unpredictable. (The nearest we know of is ~5kly? away. Or more, or less.) We don't know where any but two of the black holes are, although there must be a billion or more. Less than ten million years ago we flew into a dust cloud left over from a recent supernova.

We could have been in sterilization range of a magnetar dozens or hundreds of times since life evolved, so we're just lucky none erupted when we were. The core supermassive black hole blew somehow just 100Mya, fortunately pointed somewhere else.

The only safe-ish corner is very far from everything else, and off-axis from the central black hole. We are deep in the thick soup.

[Thiez]

And what exactly would our hypothetical descendents do there, in the middle of nowhere with no star, no planets, and no energy?

[jeremyjh]

There are stars that are far from everything else and off-axis. There are even stars that get ejected from the galaxy all-together.

[ncmncm]

Yes, one of those last would be a good choice, if we could get to one.

But I don't expect our distant descendants to be dependent on starlight. A nice Kuiper Belt and Oort Cloud are good to stay in for access to building material and fusion fuel, but the most valuable resource, otherwise, will be abundant free cold.

Planets, as such, and sunshine are for the extremest primitives. Nobody advanced would want to be closer to the sun than, say, Neptune.

[GoblinSlayer]

We are in the galactic habitable zone.

[ncmncm]

There is no such thing as a "galactic habitable zone" defined or meaningful.

There is a an obviously uninhabitable zone close to the core black hole, and uncountable similar zones elsewhere, but Sol could move into one of the latter at any time. And, distant events could wipe us out, anyplace else, with decreasing probability as the density of other stars in the immediate neighborhood decreases.

All we can say is that we have not entered any uninhabitable zones in the last billion years or so, i.e. five orbits, and not been blasted too badly from a distance, likewise. Milder events could wipe out everything but deep-sea microbes, which at this late date might not leave time to evolve intelligent life again.

Lots of galaxies have heavy star-forming going on in the rim, with increased risk of supernovas. I don't know if we know whether ours is among those. (I doubt we can tell. Such regions are identified by high UV flux, but UV is blocked by dust, which is plentiful.) But otherwise, farther from the core is generally safer.

[GoblinSlayer]

Habitable in a sense that we can stay away from the active star formation zones for a long time. Assuming those zones are deadly.

[ncmncm]

You can see active star formation zones with the naked eye from Earth's surface. Star formation is happening literally all around us.

Star formation zones are very far from the most deadly places in the galaxy, or even in our neighborhood.