2
votes
3answers
97 views

Where can I find a catalog of all stars in the Milky Way?

Is there a catalog of all known stars or brightest stars in our galaxy? Preferably with some sort of galactic coordinates instead of just night sky coordinates (right ascension, etc.) I'm trying to ...
0
votes
1answer
73 views

A black “superhole” possibility?

When matter crosses the event horizon, it is easy to imagine that matter is torn apart into their individual components by tidal wave effects. Atoms would be ripped apart eventually. At one time, the ...
21
votes
6answers
396 views

How are black holes found?

Black holes have so much gravity that even light can't escape from them. If we can't see them, and the suck up all electromagnetic radiation, then how can we find them?
1
vote
0answers
79 views

In 2016, the summer solstice will coincide with a full moon. How often does this happen?

I found that the solstices work on a 400 year cycle based on this. I can't find anything similar for the lunar cycle. Is there a formula I can use to calculate the date of the full moon?
-3
votes
0answers
60 views

How many planets do on average different star types support? [closed]

I'm working on a game which takes place in space. My team and I want to create a solar system generator for the game. We have selected 8 types of stars: White dwarf Red Dwarf Binary Super Red Proto ...
1
vote
2answers
79 views

Outside of a Universe and its origin

Per the Big Bang Theory, the universe was formed from a dense singular point which existed 13 billion years ago and has been expanding ever since. This suggests that the point should have existed ...
-1
votes
1answer
47 views

Does the sun have a protective shield

Does the sun have a protective layer that at least diminishes its radiation. I know the earth's atmosphere protects us from harmful rays. But does the sun have a sort of shield as well that if removed ...
1
vote
3answers
71 views

What do we mean by space is expanding?

I know this question had often been asked on Physics.SE as well as this site but I don't get them. What do mean when we say that space is expanding? I mean that space is no physical entity that can ...
10
votes
2answers
295 views

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 ...
3
votes
2answers
66 views

Metallicity of Celestial Objects: Why “Metal = Non-metal”?

Metallicity of objects refers to the amount of chemical elements present in it other than Hydrogen and Helium. Note: The other elements may or may not be actual ...
2
votes
1answer
71 views

Is the expansion accelerating or Decelerating?

According to Hubble's Law, the farther a galaxy is, the farther it is moving away. But do we take into account the fact that we are actually looking in the past? For example, there are two galaxies A ...
7
votes
3answers
206 views

How can the 13.8 billion years old universe have a radius of 46 billion light years?

The universe is about 13.8 billion years old. Assume at the big-bang it starts from a small region and the maximum possible speed according Einstein is the speed of light how can the universe got a ...
0
votes
0answers
20 views

Coordinates of the Moon

How does one compute the right ascension and declination of the Moon at a given time (or for that matter, the altitude and azimuth)?
1
vote
2answers
52 views

Which is really larger, Big Dipper or Small Dipper, in 3D

If we take the convex hull of the 3D coordinates of the stars in Ursa Major and Ursa Minor: which hull has larger volume? This is meant semi-humorous but we might also learn some interesting points ...
0
votes
1answer
39 views

Can the Sun be used as a point source of light to achive better focus?

There's a limit to how well sunlight can be focused by a parabolic reflector or a lens because the Sun is not a point source. I wonder if the sunlight could be engineered to work as if it was (much ...
1
vote
3answers
78 views

Why can we still see 10 billion year old galaxies?

I've never fully understood why we can still see galaxies that are 10 billion light years away. The age of the universe is calculated to be 13.9 billion years old and we live on a planet that it is ...
7
votes
0answers
87 views

Dark Flow: statistical limits on existence

Dark Flow has been thrown around as a term a lot lately, especially with the latest Planck results. New Scientist reported last year that it was now statistically improbable, but the paper by Atrio ...
6
votes
2answers
60 views

Recommendation for introductory cosmology text

I am looking for recommendations for an introductory text (or texts) on cosmology on the advanced undergrad or beginning grad level. I am coming from primarily a physics undergrad background (doing ...
2
votes
1answer
62 views

Average amount of annual daylight at any place on earth

If this is the wrong group please direct me to the correct one. It seems intuitively obvious that the amount of daylight per annum should be the same for any latitude on earth. For example, 12 hours ...
9
votes
2answers
57 views

How does the evolution of a solar system not break the second law of thermodynamics?

Please forgive: I am a layman when it comes to physics and cosmology, and have tried finding an answer to this that I can understand, with no luck. As I understand it, the solar system evolved from a ...
2
votes
1answer
104 views

Black Hole / Hawking Radiation: Why only capture anti-particle?

I may have some specifics wrong here. If so, don't focus on those. Just focus on the general thrust of my question. I "understand" (cough) that particle/anti-particle pairs form spontaneously in ...
0
votes
0answers
37 views

Connection between Earth, Moon, Theia, and astroid belt?

Are there other fragments aside from the Moon that resulted from the collision of Earth and "Theia" (as it's called in recent main-stream press stories)? And if not, why not? And what happened to ...
1
vote
1answer
225 views

How big is the universe. How does it works?

I watch this movie: How big is the universe https://www.youtube.com/watch?v=b34gwCKIM50#t=50m00s I can't understand where is there triangle with 180 degrees. What exactly is this red spot on the ...
1
vote
2answers
86 views

Why do we think that there is no two-solar-mass black hole?

We think that the mass boundary between neutron stars and stellar mass black holes is around three solar masses. The maximum mass of the neutron stars now is two solar masses and we may find a 2.6 ...
1
vote
1answer
52 views

If Mars orbited the Earth how distant would it have to be to cause the same tides?

If it were possible to replace the Moon with Mars, how distant would it have to be to essentially create the same oceanic tides as the Moon currently does? Mars seems to be roughly 3 times the mass of ...
1
vote
1answer
41 views

What is $v_{GSR}$

In this paper ("The Apache Point Observatory Galactic Evolution Experiment: First Detection of High Velocity Milky Way Bar Stars") they plot and calculate $v_{GSR}$. $GSR$ stands for Galactic Standard ...
3
votes
1answer
52 views

Is there a ceiling for stable L4 or L5 masses?

L4 and L5, the Lagrange points 60 degrees leading and trailing an orbiting body, are famous for being stable. I will label the central mass S, orbiting mass J and the L4 mass T: It's said S/J ...
8
votes
3answers
345 views

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?
1
vote
2answers
32 views

Pulsars with accreting disk in binary system

Following this line, I am wondering about the following question. Accreting pulsars in binary systems are usually thought to accrete from a prograde disk, so increasing their spin in the process. ...
0
votes
1answer
59 views

Are there are any photographs online that approximate what the Milky Way looks like to the unaided eye?

I love seeing all the long-exposure photographs of the Milky Way, but I'm going to Cherry Springs State Park in Pennsylvania next month, and I'm wondering if there are any photos that approximate what ...
0
votes
1answer
43 views

Orbital Elements Transformations

I'm a third year undergrad, and for the project I'm doing this summer, I need to figure out the Earth's position and velocity from the moon's point of view. From the reading I've done, it seems like ...
2
votes
2answers
98 views

Is the Sun homogeneous?

Does the Sun have the same composition and density everywhee within it? How does it vary in other stars?
4
votes
0answers
46 views

Is it possible to have two objects moving by sum speed of light (c) in the opposite direction? [closed]

I am puzzled by this question, because by the laws between the two object the relative gravitation force should be infinite. Anyways we can take two objects where the sum of speeds are equaling c ...
4
votes
1answer
105 views

How often do stars pass close (~1ly) to the Sun?

Interstellar exchange of massive objects is difficult across several light years. But as the stars orbit the galaxy the distances between them change. I don't find data for neighbor star distances ...
2
votes
1answer
52 views

Does Tobler's First Law of Geography Apply to Star Composition?

There is a principle in Geography called Tobler's First Law of Geography which states that "Everything is related to everything else, but near things are more related than distant things." Does this ...
1
vote
0answers
119 views

How can I calculate what star was above my head when I was born? [closed]

Almost everybody knows the concept of Zodiac. But there are others. And, AFAIK, even Zodiac classification is wrong for nowadays - since the classification of the people's Zodiac Sign was developed ...
1
vote
1answer
60 views

Why do we not send diggers to Mars if we think there's underground water?

A friend of mine asked me this question: If we have a guess that there may be underground water on Mars, why do we not send rovers with diggers? I do have a few ideas, but I want alternative ...
2
votes
1answer
64 views

What is the optimal escape trajectory from near a black hole?

Consider a space ship that is being drawn closer to a black hole. The crew begins to notice the effects, and discovers that they are nearing the black hole. They then manage to halt their ...
1
vote
1answer
13 views

Term for a momentary geometric pattern formed by astronomical objects

Few days back, the Pleiades, the Sun and the Moon were forming an almost perfect equilateral triangle. Is there a term that describes such momentary geometrical patterns? ...
1
vote
0answers
84 views

How likely and severe is the threat of a gamma ray burst to earth?

In the National Geographic article: http://news.nationalgeographic.com/news/2009/04/090403-gamma-ray-extinction_2.html it is suggested that a gamma ray burst likely caused a mass extinction in earth's ...
0
votes
0answers
10 views

Any new info about solar flares hitting the Moon added by the LADEE mission?

This article from 2011 mentions simulations about the sputtering effect caused by a solar flare hitting the Moon: "We found that when this massive cloud of plasma strikes the moon, it acts like ...
2
votes
2answers
105 views

Why are spacecraft not air-launched from airplanes

I searched on the subject, thinking it could probably be cheaper to fly the spacecraft aboard a plane and then launch it from altitude. The only thing I found was this Wikipedia page, but it only ...
0
votes
2answers
44 views

What is the difference between LMC and SMC?

Apart from the obvious difference as suggested by their names that the Large Magellanic Cloud is 'larger' than the Small Magellanic Cloud, what are the other differences between them? Do give all the ...
2
votes
3answers
253 views

Did we ever actually see the earth revolving around the sun? Is the geocentric model completely disproved?

Did we ever actually see the Earth revolving around the Sun? Also, is the geocentric model completely disproved or was it sidelined because the heliocentric model made things easier to understand? ...
6
votes
1answer
54 views

Blowing up an asteroid/comet really potentially worse?

Often on television shows and in articles I see it mentioned that it'd always be bad to blow up an asteroid or comet because then the energy would just be spread out and cause even more damage. ...
1
vote
2answers
55 views

What is meant by “Radial Direction” of a galaxy?

There is a scientific journal article having a line: "In order to study the star formation scenario in the radial direction of the LMC...." What is meant by 'radial direction' of a galaxy ?
1
vote
1answer
39 views

What percentage of visual stars are actually binary stars?

I know this is such a thing as a binary star where for example two stars rotate around a central point of gravity but to the naked eye are just a star. What I do not know is how common this is ...
3
votes
2answers
426 views

How to calculate Longitude from Right Ascension?

Considering that a star of certain declination is crossing the local meridian at the observer's zenith at an unknown location on the earth. Here, the declination of the star is equal to the observer's ...
1
vote
2answers
24 views

Why the lows of the GRB 2014-04-27 in Andromeda?

The Swift gamma ray burst space telescope has measured a GRB according to the link below. But why the oscillations in the measured gamma rate? Why wasn't just an increase detected, but also as big ...
1
vote
1answer
41 views

Did the Babylonians believe in the Heliocentric version?

It's mentioned that the Babylonians decreed that there were exactly 360 days in a year. This statement was based upon the utilization of 360 as a standard (based on the sexagesimal system) i.e., they ...

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