# What would our night sky look like if the solar system was 100 light years from the centre of the Milky Way

When we look at photo's of the centre of the Milky Way, it looks extremely bright due to the concentraion of star systems...

If our solar system was only 100 light years from the centre of the Galaxy, would we still have a dark night sky?

• It's a great question. And don't forget we have our kickass supermassive black hole at the middle of our galaxy - astronomy from your 100 ly position would be fantastic! – Fattie Oct 30 '18 at 10:06
• Somewhat related. Just alter the density of stars to suit, though the stellar population in a globular cluster is also quite different. astronomy.stackexchange.com/questions/1241/… – ProfRob Oct 30 '18 at 19:13
• OP an interesting point - are you aware that, simply within our own solar system, once you get to the planets like Uranus .. it is VERY DARK. There's no real "daylight" as you and I thin of it. Our Sun becomes more like a "bright moon". (You can google any number of simulations of this example ... even if other stars were very close indeed on stellar scales ... really I think the sky would be pretty much pitch black as usual! – Fattie Nov 1 '18 at 3:04

I have tried to collate some info from various other answers.

Density of stars where we are:

# About 0.15 per cubic parsec

Density of stars "at the middle of the galaxy". Unfortunately I don't know how "100 ly" affects this. It's probably about this figure.

# About 50-100 stars per cubic parsec

So in this QA it's "about 500x as dense".

It would seem that this is in fact:

# Not very bright. About the same amount of light overall as when there's a full moon.

However the overwhelming factor is

# If one particular star was "very close" to us?

How likely would it be, in the region under discussion, that another star is "very" close to us - close enough that that one particular star is extremely bright?

# No, the stars there are not so close that you'd typically be close enough to a really bright star that it would be bright.

That seems to be the bottom line.

(There's a completely pointless, if pretty, image here showing what it's like "inside a star cluster" {where? At what depth?} here Unfortunately that image does not simply state the star density they are simulating - so it is of no help at all to this excellent QA!)

the bottom line then:

# "If our solar system was only 100 light years from the centre of the Galaxy, would we still have a dark night sky?" Answer, yes, there would just be "more stars". It would be hardly any brighter.

To improve on this answer, the next thing we need to quantify is one piece of information:

# What actually is the star density at "100 ly from the center"?

Is it 50, 100, 25, 300, 72.275 stars per cubic parsec?

I don't know.

• A fun point, would it be different (slightly? a lot?) if inside the galactic bar? IDK.
• @/fattie: thank you for this excellent and well thought out answer...of course I am disappointed that we would still have a night sky :) – Our Man in Bananas Oct 31 '18 at 11:48
• Distance to the nearest star scales as $\rho^{-1/3}$, so if the star density is 1000 times higher than our neighbourhood we should expect it to be about 1/10th of the distance to our nearest star. The same is true for the rarer bright stars; we should hence expect a Sirius-like star about 1 light-year away (hence apparent magnitude −6.46) and an Arcturus-like star about 2.5 ly away. While the night sky might still be dark, it would be pretty spectacular and some stars would likely cast faint shadows. – Anders Sandberg Oct 31 '18 at 16:44