The science dealing with objects and phenomena located beyond Earth. In particular, this applies to observations and data. At its core, astronomy is the physically informed cataloging and classifying of the contents of the universe in order to better understand what is out there.

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14
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4answers
347 views

How far would you need to displace your eyes to get meaningful depth perception of the stars?

The question follows from xkcd cartoon "Depth Perception (941)". I've isolated the frames that describe the concept here. In words, one could theoretically point two cameras at the sky, and ...
5
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1answer
853 views

How does the view of night sky change as the Sun orbits around the Milky Way?

I know that the Sun and hence the Solar System orbits around the galactic center of the Milky Way. Does this rotation cause any visible change in the night sky? I know that human life span is ...
2
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6answers
56 views

Amateur Stargazing (30 degrees N)

When I look at the sky I easily recognize Orion, The Big Dipper, and the North Star (in relation to the Big Dipper). Besides these (and the moon^^), what easily identifiable (unaided eye) astronomical ...
4
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5answers
1k views

Are telescopes with a concave lens useful for astronomy?

Are telescopes with a concave lens (instead of convex ones) ever useful for astronomy? And if so, where are they used? Do they ever affect resolving power?
3
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2answers
25 views

For resolving different objects, are there any alternative coefficients to the one used in the Rayleigh criterion? (which is 1.22)

http://en.wikipedia.org/wiki/Angular_resolution#Explanation It's the point where you can't distinguish between the maxima and the first minima. But could there be cases where you have a more ...
3
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2answers
104 views

Is angular resolution important when we want the spectra of an Earth-like exoplanet?

Right now, our resolution + light gathering power are still far too low to take direct images of exoplanets, so we're limited to subtracting the planet spectra from the parent star spectra when the ...
5
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1answer
1k views

Most accurate ways to find the average distance between stars in Milky way galaxy

I've already posted here on quora. But, I'm not totally sure if it's the most reasonable method. Would anyone care to elaborate on how to find the average distance between stars in a given galaxy ...
6
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3answers
2k views

What is the irregularity in Uranus' orbit that is caused by Neptune?

I carefully read the Wikipedia article Discovery of Neptune, and I don't get what the irregularity of Uranus orbit was that lead to the discovery of Neptune. Years ago, I watched some educational film ...
7
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3answers
115 views

Are there any Earth-Meteorites on Earth?

A follow-on from this question, if meteorites can come from Mars, it seems they could have come from Earth and ended up back here (though I'm guessing that to be less likely). Do we have any evidence ...
2
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1answer
129 views

Do red galaxies have red star-lit skies?

I noticed when looking at some deep space pictures, like the Sombrero Galaxy (M104) or the Hubble Deep Field (HDF), I see galaxies of various colors. Does that mean, for instance, than any inhabitant ...
5
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6answers
281 views

Are there free data available online from cosmology (or astrophysics) experiments that anyone can analyse?

One can understand a subject better in physics by trying to solve as many problems as one can from a textbook say. When it comes to experimental physics and data analysis, no book on experimental ...
6
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2answers
793 views

Are meteorites igneous, sedimentary or metamorphic rocks?

Are meteorites igneous, sedimentary or metamorphic rocks? Or do we need a new method of rock classification for them?
4
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1answer
128 views

Does the Earth help stabilize changes in the moon's obliquity as well?

We know that the moon helps stabilize changes in Earth's obliquity. But what about Earth and the moon? Are some of the obliquity-stabilizing effects (of the moon on the Earth) communicated through ...
3
votes
1answer
191 views

How do the day/night temperature variations of moons compare to those of their planets?

Does the planet's eclipse have a significant impact on the flux of light hitting the moon? Does tidal locking have any effect on the day-night difference of the planet?
11
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5answers
2k views

Anti-Matter Black Holes

Assuming for a second that there were a pocket of anti matter somewhere sufficiently large to form all the type of object we can see forming from normal matter - then one of these objects would be a ...
5
votes
3answers
1k views

Is a water world possible, and for how long could it be stable?

I have several questions regarding this topic. First, could a water world be stable for thousands of years with most of its surface remaining covered in water. What would it take for this to be ...
6
votes
2answers
250 views

If you focus in on one image, is combining two telescopes really equivalent to a larger mirror?

Have a look at this example: In addition, the Keck I and Keck II telescopes can work together as the Keck Interferometer. The 85-metre (279 ft) separation between the two telescopes gives them the ...
3
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1answer
40 views

What determines a progenitor's fate as a spiral or elliptical?

I was thinking about my answer to Are the inner planets on planar orbits because there was more dust in the inner solar system (early on in planetary accretion)? - when it occurred to me that maybe I ...
1
vote
3answers
338 views

Software for Creating Custom Star Charts?

I need to produce custom star charts for my website. I want to be able to do the following: Specify a region, maybe a constellation or just an arbitrary region Specify what appears on the chart ...
11
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5answers
8k views

Stephen Hawking says universe can create itself from nothing, but how exactly?

Stephen Hawking says in his latest book The Grand Design that, Because there is a law such as gravity, the universe can and will create itself from nothing. Is it not circular logic? I mean, how ...
4
votes
2answers
172 views

How is the shape of the universe measured by scientists?

I would like to learn how scientists go about measuring the large-scale curvature of the universe to determine if the universe is closed 'i.e. spherical', flat, or open 'i.e. saddle shaped'. My ...
5
votes
4answers
368 views

What free software is there for observing the sky (sky map software)

I used until now only stellarium.org and I'm curious if there is any other software that is better than stellarium. By better, I mean: doesn't have high system ...
4
votes
1answer
52 views

Do stars of higher metallicity have more planets in highly-inclined Pluto-like orbits?

In an answer to a previous question of mine, one that asked about the planar orbits of inner planets, I was told the following (emphasis mine): On the subject of different solar systems, I would ...
4
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1answer
184 views

How to identify the objects in an astrophoto, and what portion of the sky it covers?

Given an astrophoto with a resolution between 0.5 and 5 arcseconds per pixel, which ways exist to identify the direction of view, field of view, and objects in the picture? I believe most amateur ...
2
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1answer
20 views

What was the most distant supernova spotted by a amateur astronomer until today?

What type of commercial amateur telescope and what method (difference imaging,...) did he use for identifying the supernova?
5
votes
2answers
89 views

Which citizen-science astrophysics and astronomy projects currently exist?

Most of you probably know of Galaxy Zoo, a citizen-science project to classify galaxies with help of untrained hobby-researchers. In mathematics, the Polymath Project is well known for its success. ...
6
votes
2answers
178 views

Funding opportunities for an independent researcher

In one of my questions I asked about the career paths to become a professional astronomer. Now let's consider the next logical step. What if a person has gained his/her PhD in Astronomy and had an ...
2
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3answers
156 views

Did I see two Milky Ways next to each other?

I am from the northern hemisphere and as far as I remember, the Milky Way was "single lane", just one stripe. At least, this is what I recall the Milky Way to look like when seeing it from near ...
3
votes
1answer
20 views

Could asteroseismology have a significant potential to unravel the mechanisms of solar cycles that last thousands of years?

Could asteroseismology have a significant potential to unravel the mechanisms of solar cycles that last thousands of years? And what about solar cycles 1 billion years ago and 2 billion years ago ...
2
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1answer
124 views

Are the inner planets on planar orbits because there was more dust in the inner solar system (early on in planetary accretion)?

Question inspired by a question thread here. So when there's lots of dust in a galaxy, the galaxy tends to collapse into a spiral galaxy (to maintain angular momentum and to minimize gravitational ...
4
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2answers
200 views

Where does a star's angular momentum go as its spin slows down?

So we know that stars slow down as they age. But total angular momentum must be conserved. Where does that angular momentum go? The dissipation of Earth's tides somehow transfers Earth's angular ...
3
votes
3answers
84 views

Distribution of each element and molecule as a function of distance from the Sun and as a function of time

Are there any graphs that show the distribution of each element and molecule as a function of distance from the Sun? And maybe even the time-evolution of each distribution over the solar system's ...
4
votes
1answer
61 views

Vesta dwarf planet status

Now that we have close-up photos of Vesta, which the IAU had previously said was a candidate dwarf planet, when is the IAU going to decide the issue? Personally, Vesta doesn't look round enough to me. ...
3
votes
1answer
670 views

At what temperature does water become a liquid on Mars? On the asteroids? And in a vacuum?

I know that I can just read off the phase diagram for water (for the surface atmospheric pressure on each object). But could there possibly be some nuances that someone might miss just from viewing ...
7
votes
3answers
5k views

How fast will the sun become a red giant?

I've read many accounts of our sun's distant fate, but what I've never heard is on what time scale these events occur. For instance, when the sun runs out of hydrogen, I presume it doesn't just WHAM! ...
6
votes
3answers
1k views

Are we capable of discovering planets in the Andromeda galaxy?

I just watched this SpaceRip video on YouTube which shows pictures taken by Hubble while looking into the disk of the Andromeda galaxy to study a certain type of variable star. It occurred to me that ...
4
votes
3answers
66 views

Can the Hanbury-Brown and Twiss effect be used to measure the size of composite objects like galaxies?

I know that the Hanbury-Brown and Twiss effect can be used to measure the size of stars. Can it also be used to measure the size of galaxies?
7
votes
4answers
788 views

Names, maps for Milky Way dust clouds?

There is a nice image of the Milky Way, labeled with constellations, at 360°x45° panorama with constellations: It leads me to wonder how much we know about the Great Rift, Coalsack and other ...
5
votes
2answers
73 views

Could many widely separated space telescopes be combined for VLBI on IR/visible wavelengths?

I have read about ground-based Very Long Baseline Interferometry telescope arrays able to achieve huge resolution at IR/visible wavelengths. There are also space-ground VLBI configurations in ...
13
votes
2answers
868 views

What is the largest observed celestial body?

I'm not referring to phenomena such as galaxies or clusters but rather, what is the largest discrete celestial body that has been observed in the universe?
4
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1answer
3k views

What's the difference between a red giant and a red supergiant?

I've seen both theoretical and observational definitions of stars. For example, an AGB star is a star where two sets of nuclear reactions (helium to carbon and hydrogen to helium) are taking place in ...
9
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1answer
45 views

“Blue Bumper” Stars

I was recently overviewing various massive compact halo object studies (the Anglo-Australian MACHO collaboration and the French I/II EROS collaboration), and they frequently reference "blue bumper ...
6
votes
3answers
26 views

Would it be interesting or useful to map objects' current (predicted) locations?

Due to light travel time, we observe astronomical objects as they were in the past. If we knew objects' motion (relative to us), it seems like we could extrapolate to their present positions, but I ...
9
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2answers
3k views

How does the central peak in moon craters form?

The central peak in many of the moon's large craters are visible with a telescope and they seem a little odd to me. Can someone explain how they form.
5
votes
5answers
61 views

Which current big Earth-based telescopes are equipped with adaptive optics?

I know only that the VLT is equipped with adaptive optics (AO) to bypass atmospheric distortion. Is it the only one, or have other telescopes been build with AO in the optical and infrared spectrum?
6
votes
4answers
79 views

Does the current light pollution set a fundamental limit for the range of Earth-based telescopes?

As far as I know, all deep-sky pictures are captured with the Hubble Space Telescope. If there would be no atmospheric distortion, could we make deeper pictures in the optical spectrum with ...
4
votes
4answers
517 views

Can the Hubble telescope bring any star into focus?

Lets say I am talking about a view like this supernova - 13 billions light year away. In short can Hubble bring any star into focus in the entire universe? And if so, to what definition? I also ...
4
votes
2answers
266 views

Is the Milky Way significantly easier to see by astronauts?

On Earth the Milky Way appears very ghostly when looked at with the naked eye, somewhat easier to see when NOT looking directly at it. Is it substantially easier to see by astronauts in space or is ...
11
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1answer
2k views

How dense are nebulae?

How functionaly dense are nebulae? Are they so sparse they are only visible from an interstellar or intergalactic perspective or would you be unable to see your hand in one? Do they vary widely in ...
11
votes
3answers
310 views

Why did the ancients fail to discover that the Earth orbits the Sun?

The ancients observed that the Sun and the 'fixed' stars rotated about the Earth. They were also aware that the Earth was spherical. They performed many astronomical measurements on the planets - ...