r/askastronomy

I know that if you go stand at the north pole in the summer, the sun never sets and in the winter it never rises, but at some point it has to switch.

Is the equinox just the only day the sun sets?

Or does it start getting like one hour of night, then two, then three (as it goes to fall) until its fully night, so the equinox is when its 50/50 day and night?

Our radio and TV signals have already created a growing bubble of artificial emissions around Earth. But if humanity vanished, that bubble would keep traveling outward at the speed of light.

Would an alien civilization millions of light-years away still be able to detect evidence that we once existed?

And what would last longer: our radio signals, satellites, spacecraft, or the physical traces of civilization on Earth?

How long do you think our technological footprint would remain detectable?

I’ve been wondering how many people actually keep track of things like target, integration time, settings, conditions, what went wrong and what they want to change next time.

Do you use a notebook, spreadsheet, AstroBin, phone notes, or just rely on the Seestar app/files?

I recently made a more structured system for myself, but I’m curious what other Seestar users actually find worth recording.

This is a history of cosmology/astronomy question.

I am curious about how recently the cosmological view that the stars are fixed in some sort of firmament persisted.

My uninformed guess is that the firmament view held sway until either parallax measurements were capable of telling us that different stars were at different distances (so mid to late 19th century?), or parallax was at least capable of telling us the minimum distance to stars was so great that they had to be objects as bright as our sun (early 19th century?). But I am just guessing. Perhaps there were reasonably persuasive arguments against a celestial sphere or firmament that didn't depend on fine parallax measurements.

I believe the idea that the stars are objects like our sun has been around much longer, but I'm asking when the, if not consensus view changed, but when the generally accepted view among astronomers shifted way from a celestial sphere or firmament.

If there are any books or papers describing this history, I would welcome pointers to it.

I have a F8 560mm lens available, is it possible to photograph Andromeda with a shorter exposure, or manually correcting the tripod?

I've seen posts where the exposure is like 2 hours long so I don't know if it can be done manually

I'm trying to understand why space travelers age slower. Sorry if I described the question in a bit messy.

If a planet is away from earth, let's say 10 light years away, it means that if you travel at speed of light, it will take 10 years to get there, so the distance between earth and that planet is 10 light years.

A starship with a crew of astronauts, when they reach that planet and return to earth, everyone on earth is 20 years older, but the crew members will probably only older far less than 20 years(according to scientists).

But how? If the total distance between earth and the planet is a fixed distance (10 light years away), doesn't it means the crew on that starship also need 10 years to get there, they start from earth at speed of light, it should take them 10 year to get there? So they should experience 10 years to get there and 10 years to back to earth, everyone on that ship should age also 20 years?
If they age only 2 years for example (I am not scientist just random number), doesn't that means they only traveled total distance of 2 light years ?
Even if time slow down at speed of light, the speed is same, isn't the distance is still 10 light years (10 x speed of light)?

If distance = speed x time

The distance doesn't change, the speed doesn't change(light speed which is maximum in universe in theory), then you still need 10 years to get there unless...distance changed?

Do the crew members also experience 10 years in time but only "2 years biologically"? Or do they only experience 2 years time?

Edit:

Not sure if I got this right. I have read all replies and came to a conclusion: the distance is different from 2 perspectives.

So now I wonder...

If some aliens see us earth 100 light years away, they decide to fly to earth at light speed, from their perspective, the distance between is nearly 0, takes almost 0 time to arrive earth, but for earth people, we see them in a telescope, they are coming "slowly" closer everyday, and scientists predict they will arrive in 100 years.

The question is... from earths perspective, by the time they arrived we have already passed 100 years, but to them is almost instantaneous, so what do they see when they arrived? Earth after 100 years or The same Earth they see in a telescope when they leave their planet since they take almost no time to arrive?

Hey everyone! I'm a recent CS grad who happens to love stargazing, and I'm considering building a stargazing app, but before I sink a few months into it, I wanted to check if this is actually something the community would find useful (or if it's already been solved better by something out there).

Some feature ideas so far:

• Real-time sky conditions for a location (cloud cover, light pollution, moon phase) at that time or in the near future
• Point your phone at the sky to identify stars, planets, and constellations
• Alerts for upcoming events worth watching (meteor showers, visible planets, ISS passes, etc.) in your vicinity
• Maybe a social-media-esque feature where you can post pictures you've taken (kinda like this subreddit)

A few questions if you have a minute:

1. Do you already use an app like this? If so, which one, and what does it get wrong or leave out?
2. Of the features above, which would actually get you to open the app regularly vs. which feel like nice-to-haves?
3. Is there anything that consistently annoys you about existing stargazing apps (ads, inaccurate data, clunky UI, paywalls, etc.)?

Ignore the circumstances that would lead to this configuration, but could there be a binary system with both a star and a black hole at its center, with at least one exoplanet in a stable orbit around them?

Is there any other configuration that would work? Are there black holes small enough to orbit stars?

Guys i found this video on facebook, you can see at the edge of the sun how the flairs rises and fall, and was wondering like due to the huge size of the sun, these flairs must be really really fast to rise and fall in a few seconds... so anyone knows how fast are these?