r/astrophysics

Hello fellow astrophysicists! I am currently applying to Spain for an exchange semester, and I only have extracurriculars left to take.

I was browsing through classes and an Extragalactic Astrophysics class caught my attention; it’s always been a special interest of mine. The class recommends basic knowledge of astrophysics.

I’ve only taken physics, calculus, and chemistry courses… So I don’t know if it would be a mistake to take this course. Please be completely honest with me, will this class be terrible for my GPA or will I be able to handle it?

Okay so I had a random shower thought the other day and wasn't really sure where to ask but what happens to a compass in space? Does it still point north or does it just keep spinning or does the earths magnetic field mess with it?

I had a shower thought the other day. Since supermassive black holes exist at the center of galaxies, could there be an "ultra" supermassive black hole at the center of the universe?

If something like that isn't possible, why not?

I'm curious to know what you guys think. It might be a dumb question but I figured I would ask anyways and maybe learn something new!

Hello, I am trying to estimate how many unborn human lives a single second of delay in universal colonisation costs.
To get an accurate value, I need to know how many stars fall beyond the Cosmological Event Horizon (where they become unreachable from Earth at the speed of light).

I could not find a source on this value. I could get an estimate by calculating the difference between the volume of the sphere encompased by the horizon and the sphere encompased by the horizon - radius velocity/one second. This would give me the average number of stars in the sliver of volume that would move beyond the horizon in the span of a single second.

But this would not account for the distribution of stars in our "local" space. Like, I heard we are somewhere in the Great Universal void (the Boyes void?). So the star density could be far lower if the horizon edge passes through this or some other void. Or far greater if it passes through the dense regions.

I will estimate it roughly if I have to, but if the astronomers already did the calculations better, I would love to have the results. Surely some astronomer calculated this right? I could not find it googling.

What would happen if space had air?

Would the Earth burn up from friction? Would astronauts be able to be without spacesuits? Would Earth veer off course from the friction? What will happen to the debris spinning around Earth? Will they fly away? Will they be knocked back into Earth's atmosphere? What will happen to other planets? Will Mercury just burn up as well? Could we even go to space anymore because of friction?

Ok that's about it (maybe)😁

edit: to clarify air as in the gaseous mixture that is earth's atmosphere

Edit2: thanks for all the cool replies!! Thank you for trying to answer all my Saturday morning questions lol

Just a thought I had today…..the supermassive black holes that are at the center of galaxies……did those originate from stars or was the “BigBang” event soo massive and powerful that black holes were formed/created instantly?

So i've just started freshmen year in a quantum computing degree do u think i will get enough physics to major later in astrophysics knowing that this degree is more computer science heavy than physics