Does anyone else feel like looking up to the night sky and finding so many satellites is cheapening the beauty of stargazing? I remember the novelty of spotting the International Space Station back in the day, but on any given night now, I’ll see so many starlink or maybe other satellites moving that it just makes me wonder what our sky is going to look like if we live another 10, 20 years, etc. I know progress is necessary and all of that, but bleh, it seems kind of the opposite of what we look up there for. It’s like the last pretty thing we hadn’t stained with visible garbage.

We know that the universe is expanding; does something that is expanding have boundaries, and can something that has boundaries be infinite?

So, what is the source of this energy? Where does it come from?

Since the energy of the universe is constantly increasing, its source cannot be within the universe—it must lie outside of it. However, energy cannot exist outside of space-time. If the source of this energy can be found neither inside nor outside the universe, one might conclude that such energy does not exist—yet we know that it do. What is your opinion on this matter?

Hi, I'm looking for astronomy books to read. I want books that actually tell me something interesting, show cool stuff. I've searched for good astronomy books, but I either get kids books or books made to make a quick buck.
If you have good suggestions let me know!

Image by xoxomarswalker on Pinterest

I'm an airline pilot and saw this from the flight deck on two separate flights. Hoping someone can help identify it.

**Sighting 1**
- Date: 19 Oct 2026
- Video recorded: approx. 18:50 UTC (21:50 local)
- Flight: Mediterranean to northern Europe
- Position when filming: over the Aegean, between Rhodes and Thessaloniki
- Lights visible on and off from there until roughly over Austria
- Altitude: FL380 (38,000 ft / approx. 11,600 m)
- Viewing direction: approx. 280°, low above the horizon – roughly 20°, but hard to judge from the flight deck
- Duration: at least 2 hours, staying in the same direction and at the same height in the sky while we covered several hundred miles

**Sighting 2**
- Date: 23 Oct 2026, same route, around the same time
- Same direction and same position in the sky
- Seen by a different captain as well

**What we saw**
- Several small points of light at the same time
- Different colours: white, yellow, green, blue-white
- Different speeds from each other
- To the naked eye, individual lights seemed to speed up, slow down and change direction
- Lights appeared and disappeared
- No navigation lights or strobes

**What we ruled out on board**
- Reflections: cockpit lighting dimmed, visible from every seat position and angle, visible with the naked eye
- Aircraft: no position or anticollision lights
- Meteors: we saw several during the flight, and they looked completely different

Video: iPhone 16 Pro Max, 4K, handheld, 5x optical zoom, so any hand movement is magnified.

Could these be satellites in a sunlit window near the horizon, or is there another explanation? If anyone can check satellite passes for that time and position, I'd really appreciate it.

Sunlight travels through space continuously, yet when astronauts look away from the Sun, the background appears almost completely black.

I understand that Earth's atmosphere scatters sunlight, which makes our sky blue.

But here's what I'm curious about: if space contains dust, gas, and billions of stars, why isn't there enough scattered light to make the sky noticeably brighter?

Is it mainly because space is so empty, or is there more to it?

I am writing a program that generates single stars. For red giants and asymptotic giant branch stars I use simple formulas, and I would like a better, citable source.

What I use now:

• Red giant branch: luminosity from the helium core mass, L ≈ 2.3 × 10⁵ × Mc⁶ (with Mc growing from 0.12 to 0.47 solar masses for low-mass stars), and a temperature that starts near 5000 K and falls by 0.06 dex per dex of luminosity.
• Mass lost on the red giant branch: up to 0.2 solar masses for low-mass stars, set as a fixed function of the phase.
• Asymptotic giant branch (low mass): L = 2000 × 10^(0.7 q), with the temperature falling from 3600 K to 2700 K, where q runs from 0 to 1 over the phase. Mira-type pulsation begins at q > 0.4, with a period from 260 to 500 days.

My questions:

1. Is there a reliable, published source that gives luminosity, temperature, radius, mass loss and pulsation period for red giants and AGB stars as functions of mass, metallicity and evolutionary phase?
2. Are simple relations like the ones above acceptable for a program like this, or are they badly wrong in some range? Which of them is the weakest?

I do not claim these formulas are correct. I would like to replace them with something I can cite.

Look at how much we've discovered just by building better telescopes and observing the universe in new ways. James Webb has shown us things we couldn't see before, and now Roman and Rubin are coming online to cover much more of the sky or watch it change over time.

But all of these instruments are still built to measure particular things: certain wavelengths, certain signals, certain physical properties. So what happens if something out there doesn't fit what we're expecting? Especially with extraterrestrial life or intelligence, which could be nothing like what we know.

Could we detect something like that without recognizing it? Could we already have observations with evidence in them that we just haven't understood yet?

I know unexpected discoveries happen all the time, and astronomers already look for oddities in their data. What I'm trying to understand is whether there's a way to deliberately improve our odds of finding something we never anticipated, instead of just hoping to stumble on it. How do astronomers actually approach that?

These are fairly edited photos I got in a Bortle 6 zone at around 2am I think.

(And no, I'm not trying to "show off" my photos/editing, I genuinely am just curious as to what might be in these photos).

The conditions were ideal to take a picture of the moon and the parlament but unfortunately didnt have the right gear for the job. Is there a way to calculate the next time it accures so i can come more prepared ?

I heard today that Quasars are used in GPS that we use almost everyday. Seems like the satellite that try to point our location, would face inaccuracy because of difference in time between the satellite and our earth. Given the earth's rotation, which makes satellite hardtime pinning the location.

So ground stations look at distant Quasars which appear fixed to us(observers) and with respect to the Quasar we define our rotation and calculate our Earth's shifting surface. This precise location is inputted by the ground stations to the satellite, which then broadcasts the data to our phones with millimeter error margin.

I'd never in a million years even would have thought about this. I mean Quasar to our mobiles, everytime we open Maps, our location is calculated with Quasar 🤯

Maybe we take so many things for granted that we miss so much. Please share your facts and thoughts on how we use space objects day to day without noticing.

Hello, I'm a 21M and I've recently discovered a passion for Astronomy and Physics. I want to pursue these two things in a community college and then onto a full time college. From what I've heard you need to have a good high school GPA, that's where the problem comes in. I wasn't the greatest in school and didn't grow up too well so I skipped a lot and learned very little. My GPA is about .72 I believe. Do I have any hope of being able to pursue these things like this? I have my high school diploma just a terrible record.

For more problems like this one check the first comment!

In our daily lives, in chemical reactions, or within isolated laboratory settings, the total amount of mass-energy never changes.

However, the density of dark energy remains constant, even as space expands. This means that as space expands, new dark energy is generated alongside the newly created space; as the universe grows, the total amount of dark energy continuously increases.

So, what is the source of this energy?

Given that the energy of the universe is constantly increasing, its source cannot lie within the universe itself—it must reside outside of it.

Is it possible, then, to transfer energy into the universe from the outside?

Does such a source—existing beyond space-time, in a realm devoid of space and time— exist?

skycharts says its either mars, uranus or jupiter. I also have no idea. Any help is appreciated:) taken on good canon camera, but terribly blurry.

So voyager 1 is currently traveling about 17km/s, and by my math that means it will travel a light year about every 17,650 years. So in a billion years, it will have gone about 56,660 light years assuming nothing obstructs it etc. I’ve heard that space is far emptier than you might even imagine, so I was wondering, do we have any estimate on the average distance you would need to travel in a perfectly straight line before a star would be directly in your path? Like, take a random line stretching 10 billion light years in any direction, do we have an estimate of how many stars that line would pass through? Of course it depends what the line passes through, galaxies, voids, etc, but I’m saying we have a line long enough to disregard that. That would give some idea of how long the spacecraft could go before colliding with a star. But I’m mostly curious about how many stars it would pass by, say within 1 AU. If you picked a random line, how many stars would you expect to pass by at a distance of 1 AU or less for every light year you travel? (A decimal of course) What I’m essentially curious about is how inconceivable is it that the Voyager 1 space craft would ever pass near a solar system suitable for civilization, but I’m also just curious about the frequency of stars in the universe as well.

I've been looking into meteor storms and I am realizing that I'm not making a connection here:

• Comet Temple-Tuttle has a 33-year period
• It leaves streams of meteoroids behind it
• The Earth passes through these streams of debris annually
• When the Earth passes through a younger stream, the meteor shower is more intense
• The Earth does not necessarily pass through each stream "in order;" rather, during intense meteor storm years, it tends to be passing through a stream that was deposited several periods ago

If the Earth is hitting these streams "out of order," why do we only pass through the dense ones on a 33-year cycle, instead of every year? For instance, we are going to pass through the 1899 meteoroid stream in 2034 -- how does this work? Are the meteoroid streams remaining fairly close to the comet itself or something, forming a cloud instead of a line?