Astronomy Stack Exchange
Astronomy Stack Exchange

Most Popular

more tags
1500 questions
21
votes
1 answer

Dark Matter Particle Candidates

Dark matter appears to dominate the matter component of the universe as compared to luminous, or baryonic, matter. Though it does not interact electromagnetically (it doesn't absorb, scatter, or emit photons), there is an ever-increasing mountain of…
astromax
  • 5,973
  • 23
  • 45
21
votes
2 answers

Space expansion in layman terms

So far I got to understand the expansion of space is not to be understood as stars drifting further apart through space. There's something more fundamental - e.g. you can't simply measure speed of it, nor tell where the center of the universe (the…
SF.
  • 6,259
  • 2
  • 26
  • 53
21
votes
2 answers

Was Earth closer to Europa on 1983-11-25 or 1985-07-22?

xkcd #2003: gives a humorous line of succession to the United States presidency. The comic's title text, found by hovering over the comic, states that a tie is broken by whoever was closest to the surface of Europa when they were born. The only…
BeseechLoveVeil
  • 211
  • 1
  • 3
21
votes
5 answers

Does the Sun belong to a constellation?

Each new star we find is generally considered to be part of the constellation it is nearest to. Our Sun is obviously a star, just much closer. Is our Sun part of any constellation? If so, which constellation is it a part of?
user96
21
votes
4 answers

In a planetary system close to the galactic core, would it be possible to see the supermassive black hole?

I understand that radiation on planets near the galaxy’s center make life on these planets nearly impossible, and that one cannot truly “see” a black hole. However, if you could stand on the surface of a planet that orbits a star close to or within…
BeccaLew
21
votes
5 answers

How was Trappist-1 discovered?

I was going through all the questions in this community related to TRAPPIST-1 in order to know how planets TRAPPIST-1b to TRAPPIST-1h were discovered, but there aren't any. How were they discovered?
Hammad Nasir
  • 321
  • 2
  • 9
21
votes
5 answers

What does forward modeling mean?

In my research on exoplanets, I have heard many people talk "forward modeling of exoplanet atmospheres". I don't know what the "forward" means in "forward modeling" and how it compares with "reverse modeling", if that's even a thing. What is…
NeutronStar
  • 2,663
  • 1
  • 19
  • 33
21
votes
2 answers

Near-Earth supernova

There are 51 stars within 17 light years of the Earth (source). If one of these stars was to become a supernova, how would they effect the Earth?
Larian LeQuella
  • 1,484
  • 1
  • 13
  • 24
21
votes
3 answers

Will Saturn's rings become a moon?

Planets form from disks of matter orbiting around a star; some moons form from disks of matter orbiting planets. If this were going to happen around Saturn, approximately how much time would it take?
Eduardo Serra
  • 2,695
  • 17
  • 38
21
votes
1 answer

How can I collimate a dobsonian telescope with a laser collimator?

I've had a dobsonian telescope for a while now, but I've never been able to collimate it. I thought I had it collimated once, but when I looked through it the star didn't look right, it looked kind of like a round disc with a hole in the middle. I…
Wipqozn
  • 315
  • 1
  • 2
  • 8
21
votes
2 answers

Are there any galaxies which fell out of sight horizon due to cosmic expansion?

If farthest galaxies run away from us with acceleration making them exceed speed of light, we should expect them to disappear from sky among time with increasing quantity. Did we observe this? Can we indicate next galaxies to eliminate and their…
Waldemar Gałęzinowski
  • 351
  • 1
  • 4
21
votes
2 answers

How bright would the sun appear from the hypothetical Planet Nine proposed by Caltech?

Theoretical Planet Nine, proposed by Caltech's Mike Brown and Konstantin Batygin, is said to have a 15-20 thousand year orbit. Approximately how bright would the sun appear from Planet Nine aphelion and perihelion?
joseph.hainline
  • 1,556
  • 12
  • 21
21
votes
4 answers

Why are orbits elliptical instead of circular?

Why do planets rotate around a star in a specific elliptical orbit with the star at one of it's foci? Why isn't the orbit a circle?
Devgeet Patel
  • 1,064
  • 1
  • 9
  • 12
21
votes
2 answers

Hypothetical trans-Neptunian planets orbiting the Sun

The planet HD 106906 b was found at 650 AU from its home star, a star not so different from the Sun. Fomalhaut b is also a young planet that is orbiting very far away from its star. These two planets were discovered mainly because they are young…
Victor Stafusa - BozoNaCadeia
  • 1,064
  • 6
  • 19
21
votes
3 answers

How has the Earth's orbit changed over hundreds of millions or billion of years?

First, I know that modeling orbital mechanics of 8 planets is hard, but there are some theories out there, for example, Jupiter is thought to have moved in towards the sun then started moving away. Article and Uranus and Neptune may have switched…
userLTK
  • 24,019
  • 1
  • 46
  • 82
1 2 3
…
99 100