If I was on a earthlike planet in a sunlike solar system that was near the Milky Way’s galactic core, what would the night sky look like?
Say I am staring toward the massive black hole at the center at midnight. Would it be possible to see the black hole as a disk if we were close enough while our sun orbits the black hole?
On the other hand, if I’m looking in the sky in the opposite direction of the black hole and the sun, there would be a much higher number of stars and higher luminosity than our sky back here on earth. So, how much more brighter would the midnight sky be?
There are thousands of stars within a few light years of the galactic center. For comparison, there are only 9 stars within 10 light years of the solar system. There are also over one hundred massive stars from a recent burst of star formation, which are over a million times brighter than the sun.
You might therefore expect to see huge numbers of stars in the sky, but this isn’t the case. The massive stars are so bright they would wash out the fainter ones. An OB star would appear as bright as the sun from a distance of about 15 light years, and they would on average be much closer than this. There are also large amounts of gas and dust in the vicinity, so I’d expect the entire sky to be lit up.
If you were close enough to the supermassive black hole, you’d see it as a black disc. There would be a strong gravitational lensing effect. However, it’s probably obscured by it’s accretion disc. As gas falls into it, it is compressed and heated.
I’ve seen speculation that intelligent life couldn’t evolve around stars close to the galactic centre because star density means that the average time between gamma ray extinction events is too low. So given that FTL travel is impossible, no being will ever see the sky from any star near the galactic centre.
If a sky shines white, but no intelligent being can ever see it even in theory, is it still white?
In terms of stellar densities, perhaps not a whole lot different than it would like from deep within a globular cluster.
[ol]
[li]In the solar neighborhood we average about one star per cubic parsec.[/li][li]At the core, (around 100 parsecs from the center) about 100 per cubic parsec.[/li][li]Inside a globular cluster: 100 or 1000 stars per cubic parsec.[/ol][/li]Illustration: The night sky from inside a globular cluster
In principle, you could have a star close enough to the central black hole that you’d see a black disk in the sky, and that distance would still be far enough out that you wouldn’t be killed by the tidal forces. In practice, though, there’s a whole lot of junk going on that close, and so far as we can tell, no stars.
I think you underestimate people’s ability to populate the entire galaxy even without FTL travel. People won’t be taking a day trip in and out for the view, but a suitably expansionist space-faring people would have no trouble populating most of the core in a relatively short time, even if they needed to evolve somewhere else.
I agree with what you say, but bear in mind just what a challenging environment this would be; any of the short-lived stars there could explode as a supernova at any moment, and periodically one or other of the stars closest to the supermassive black hole might get ripped apart in a phenomenal burst of debris. These waves of detructive radiation would arrive at the speed of light, so you’d have to keep a close eye on every star there to predict if and when it would blow.
I suspect that a suitably advanced civilisation could pobably thrive in such an environment, but it would have to be prepared to withdraw all its vunerable components into radiation-proof shelters on a periodic basis. Such a civilisation would probably be very different to our own.
Some interesting animations and images of the galactic centre here. http://www.mpe.mpg.de/ir/GC/index.php
The central black hole itself would look interesting too; if it isn’t surrounded by a glowing accretion disk, it might only be visible by the concentric rings of optically distorted background stars that surround it- and I think you’d have to get relatively close to see them…
Well, ok, the view AND the panini. We’re serving the best TurkeyClubCranberrySauce Panini anywhere near the Core. But I’d suggest making it a day trip, because you’ll never get to sleep with all this light.
