Most Popular
1500 questions
17
votes
1 answer
How many arms does the Milky Way galaxy have?
How many arms does the Milky Way galaxy have and how is it determined?
Vincent Ashley
- 357
- 2
- 5
16
votes
4 answers
How do scientists determine the age of stars?
I was Googling about the oldest galaxies in the Universe. Everywhere is written that their age is known by the light. Referring to this line "Since light travels at a set speed, if you look at a star ten light years away, you're really seeing what…
SpringLearner
- 635
- 5
- 15
16
votes
3 answers
Calculate Distance To Stars
I was just watching a lecture from Carl Sagan. He talked about figuring out the distance to the stars; it got me interested in learning more about the subject.
As far as I know, the Inverse square law and parallax can be used. Can anyone expand on…
apxcode
- 459
- 2
- 16
16
votes
2 answers
Does Ceres have an exosphere similar to the Moon?
Thinking about the question and answers for Does the Moon have any oxygen in its atmosphere? begs the question, despite being considerably smaller than the Moon and further away from the sun, does Ceres have a similar atmosphere as the Moon?
user8
16
votes
5 answers
Why are all quasars so far away?
Why are all quasars so far away?
If the universe is homogeneous, we should expect to have a homogeneous distribution of quasars, but all of then seem to be far away from Earth. Why is that?
Carlos
- 493
- 3
- 7
16
votes
1 answer
Do planetary rings have geometric bounds?
Are there any bounds on where a planetary ring can form and maintain orbit relative to the planet?
Do they have to be in a circular equatorial orbit?
Is there a min or max altitude, say with respect to the Roche limit, geosynchronous orbit, or other…
Travis Christian
- 263
- 1
- 5
16
votes
4 answers
What is Gravitational Lensing?
What is the effect known as gravitational lensing? How does it work? What objects would be able to cause this effect?
damned truths
- 1,003
- 8
- 22
16
votes
3 answers
How do we know dark matter/dark energy exists?
I've never quite understood the theory behind why dark matter and dark energy exist. I know it has something to do with gravitational pull being stronger than what we calculate it SHOULD be, could someone explain this in more detail?
Rich
- 609
- 4
- 14
16
votes
10 answers
Is Pluto still a dwarf planet?
Recent news seem to suggest that astronomers are arguing about whether Pluto should become a planet again.
However, I cannot find an official source for this. Is this actually true?
user2539
- 185
- 1
- 3
16
votes
1 answer
What is the difference between Sphere of Influence and Hill sphere?
Wikipedia's definition of Hill sphere is:
An astronomical body's Hill sphere is the region in which it dominates the attraction of satellites. To be retained by a planet, a moon must have an orbit that lies within the planet's Hill sphere.
And…
sampathsris
- 657
- 5
- 18
16
votes
1 answer
How do large solar flares compare to flares on other stars?
Solar flares are violent releases of solar magnetic energy. Other stars are also known to have magnetic fields, in some cases much stronger than the Sun. How do the largest stellar flares compare to the largest solar flares in terms of energy…
ehsteve
- 1,164
- 8
- 14
16
votes
1 answer
Can we see the Big Bang happen if we look far enough?
The observable universe is constantly expanding as more light from the Big Bang reaches us. This light has been travelling for billions of years, so we are looking at the universe as it was a few billion years ago. This being said, would it be…
Nirvik Baruah
- 614
- 5
- 10
16
votes
3 answers
Aren't there more naked-eye-visible stars in the Milky Way plane?
Most stars which are visible to the naked eye are within 1,000 light years. The Sun is inside the Orion arm which has a diameter of about 3,500 light years. Thus, all stars (with very few exceptions) we can see unaided are inside the Orion arm and…
LocalFluff
- 11,383
- 4
- 31
- 73
16
votes
9 answers
Why is it ok for people to be saying that dark matter makes up x amount of the universe when we don't know what it is?
It strikes me as contradictory that the scientific community will say that we don't know what dark matter is, but be happy to state things like "dark matter makes up about 85% of the cosmos" (source: phys.org)
Is there something wrong with the way…
Zinn
- 397
- 2
- 10
16
votes
1 answer
How are we observing the newly discovered "dark galaxy" J0613+52, if it has no stars and is so far away from other galaxies?
I just came across a New York Times article talking about a newly found Low Surface Brightness (LSB) galaxy (also called “ultra-diffuse galaxies” or “dark galaxies”). The new galaxy, J0613+52, was accidentally discovered using the Green Bank…
Curious Layman
- 876
- 6
- 19