Most Popular
1500 questions
18
votes
1 answer
"Who saw" the binary neutron star merger first? What was the sequence of events? (GRB/GW170817)
I'm trying to read Multi-messenger Observations of a Binary Neutron Star Merger the "cast of thousands" OPEN Access ApJ letter 848:L12 (59pp), 2017 October 20 https://doi.org/10.3847/2041-8213/aa91c9 and get a feeling for the sequence of events that…
uhoh
- 31,151
- 9
- 89
- 293
18
votes
5 answers
How can the universe be infinite?
I've heard from renowned astrophysicists that we don't yet know whether or not the Universe is infinite. How is that possible regarding the big bang theory is accepted (as they all do)? Are they referring to the existence of other Universes when…
harogaston
- 1,037
- 1
- 8
- 21
18
votes
2 answers
Why do stars appear to twinkle?
Sometimes at night you will look up to the stars and they will appear to twinkle, getting brighter and darker in bursts.
Why does this happen? Is this because of our atmosphere? Would they twinkle if you were just in space? How about looking from…
user96
18
votes
3 answers
What is the difference between asteroids, comets and meteors?
Some celestial objects seem to be referred to as asteroids, some as comets, and some as meteors or meteorites.
What is the distinction between all of these different objects? Are any of them the same?
user96
18
votes
2 answers
Understanding The Turnover Point of Angular Diameter Distance
I am trying to get a better understanding of cosmological distances, in particular the angular diameter distance which I have also seen referred to as angular size distance.
What I am looking for is a more detailed explanation of why the angular…
Michael
- 183
- 1
- 4
18
votes
4 answers
Did the earth form outside the solar system?
Why isn't it possible that the earth formed outside the solar system and got attracted later by the Sun?
I just need arguments to defeat this hypothesis.
Señor ABƵ
- 181
- 1
- 3
18
votes
2 answers
Why haven't Earth and Venus got any tiny moons? Or have they?
Why haven't some meteoroids gotten caught in Earth's or Venus' orbit?
AFAIK most meteors are tiny fragments from comets. Shouldn't some comet tail sometime have passed Earth orbit at velocities suitable for our planet to capture such fragements? And…
LocalFluff
- 11,383
- 4
- 31
- 73
18
votes
1 answer
Why does the moon sometimes appear giant and a orange red color near the horizon?
I've read various ideas about why the moon looks larger on the horizon. The most reasonable one in my opinion is that it is due to how our brain calculates (perceives) distance, with objects high above the horizon being generally further away than…
Larian LeQuella
- 1,484
- 1
- 13
- 24
18
votes
4 answers
Why is liquid water considered a requirement for life?
I`ve heard about different extremofiles living on earth. Is water a requirement for life because we have not seen life survive on earth without it, is it a chemical reason which makes life without water seem impossible? Could life exist with water,…
bogen
- 2,356
- 2
- 18
- 32
18
votes
2 answers
Could the 9th planet be virtual?
Astronomers recently claim that there is evidence for a 9th planet. As far as I understood it, this is mainly based on coinciding orbital parameters of a few Kuiper belt objects.
Could the 9th planet be a virtual planet? I mean this in the sense…
engineer
- 283
- 1
- 2
- 8
18
votes
3 answers
How do we know the big bang didn't happen in an existing universe?
I understand the evidence for the big bang (expansion, background radiation, etc), but how do we know that it was the start of the universe? Why couldn't it have occurred in an existing, but very sparsely populated universe?
SArcher
- 289
- 1
- 4
18
votes
4 answers
Are there ways other than the collapse of a star which have been observed to form black holes?
Every time I hear about a black hole, it's always in conjunction with the collapse of a star. Have any other processes been observed to create a black hole?
user19
18
votes
2 answers
How long should it take for us to observationally determine if Caltech's Planet Nine is really there?
Caltech just released a report that says there is possibly a large (10 earth mass) planet in a remote orbit (10 - 20 thousand year) that explains a lot of observations of Kuiper Belt objects. How long could it take for this to be confirmed or…
joseph.hainline
- 1,556
- 12
- 21
18
votes
1 answer
Have we ever observed a body, such as a large asteroid, "hitting" the Sun?
Some other SE questions about launching ICBM's into the sun got me wondering whether we have ever observed an object on a path that intersected with the Sun? How close did it get?
rolfedh
- 283
- 1
- 5
18
votes
1 answer
Our galaxy, the Milky Way, forms part of a galaxy group called The Local Group. What are the parameters that dictate what a galaxy group is?
Are there different classifications or just the one? How does our galaxy group compare with others?
Eduardo Serra
- 2,695
- 17
- 38