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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4
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3answers
183 views

How empty of fuel are spacecraft booster rockets typically?

A recent XKCD What-if article mentions the situation where each additional kilogram of cargo to LEO requires an additional 1. 3 kilograms of fuel, which in turn requires fuel to carry ...
6
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2answers
289 views

Is dark matter really present around the sun?

Recently I read an article that there is dark matter around the sun but if it is so, than why can we see it clearly. If it is called matter than it shall show some hindrance in radiation we receive ...
2
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1answer
138 views

What is the diameter of the sun as a function of wavelength/frequency (around 10GHz)?

I have this vague recollection of being told that the diameter of the apparent surface of the sun is a function of what band you observe it in. I'm looking for a model of this that works for bands in ...
5
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3answers
171 views

Why are planetary systems so rare?

According to this site there are 258 know planetary systems and 302 planets. Mostly each of the listed system has only 1 planet of Mercury's or Mars' size, while our system has up to 8 planets. From ...
10
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2answers
402 views

Can $10^{23}$ stars be treated with methods of statistical mechanics?

Statistical mechanics is used to describe systems with large number of particles ~$10^{23}$. The observable universe contains between $10^{22}$ to $10^{24}$ stars. Can we treat those many stars as a ...
7
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1answer
1k views

What happened to Apollo's Saturn-third-stage rockets?

I read recently the original Apollo 11 press release and it mentions that the Saturn V's third stage (used for Trans-Lunar Injection) was deployed into a solar orbit of some kind: (Source: Press ...
2
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1answer
235 views

Calculating the time of dawn

Knowing that astronomical twilight (i.e. astronomical dawn) is when the sun is 18 degrees below the horizon, I am calculating the astronomical twilight time this way: ...
0
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2answers
171 views

What's the evidence supporting 1 singular Big Bang? [duplicate]

Possible Duplicate: What has been proved about the big bang, and what has not? I love to dabble with science, I'm by no means a scolar in this field. One thing that haven't seen proven yet ...
3
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1answer
99 views

How did Cook and other astronomers time the 1769 Venus transit?

The 1769 transit of Venus was observed and coordinated by over one hundred astronomers around the world. How did they measure time so accurately, key to the observations having any scientific value? I ...
0
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1answer
72 views

What does the latin letter mean in Bayer name of a star such as “$\Upsilon$ Andromedae $b$”?

What does the latin letter mean in Bayer name of a star such as the "$b$" in "$\Upsilon$ Andromedae $b$"? I tried in vain to look it up in Wikipedia or elsewhere on the Web.
1
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1answer
131 views

Is there anything special about the Sun's photosphere in terms of density?

The Earth has a definite boundary between rocky/ watery surface and gaseous atmosphere. The same cannot be said of the sun. Even though the photosphere gives an apparent "edge" to the sun via the ...
3
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2answers
146 views

Black hole Cyg X-1 doesn't seem dense enough

According to wikipedia, here are the Cygnus X-1 vital stats: Mass 14-16[7] M☉ Radius 20–22[8] R☉ A radius of 10 R☉ means a volume of 10^3 = 1000 Sols. ...
6
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1answer
76 views

Does a celestial system exhibit a collective magnetic field?

Sol exhibits a magnetic field, most of the planets in orbit around Sol exhibit a magnetic field - strong and weak both. Does the solar system as a whole exhibit a magnetic field? Does the paradigm ...
7
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2answers
362 views

How would one navigate interstellar space?

Headed out from Earth within the Solar System, Sol and Earth both may be used as reference. When traveling in interstellar space with stellar systems themselves traveling at varying velocities even ...
1
vote
1answer
89 views

Why are galactic centers always brighter than the edges?

As you can see this image http://i.stack.imgur.com/YOt8C.jpg and other galaxy images, the centers generally much brighter. Why is that? Is there a very big star? A very big gravitational field?
1
vote
2answers
130 views

Will Pluto be in the ecliptic plane when New Horizons passes by? Was this deliberate?

From the illustrations at the New Horizons website it seems that Pluto may be in or near the ecliptic plane when New Horizons passes by. Is this intentional? Of course Pluto was to move to that ...
3
votes
2answers
110 views

Cannon on spacecraft: hitting yourself

Some Soviet space stations reportedly had anti-aircraft cannons installed. Could such a cannon hit the firing space station accidentally on a subsequent orbit? The muzzle velocity of the cannon is ...
2
votes
1answer
67 views

Sunrise time across the globe?

This question is more astronomy related, I started thinking when I heard from one of my friends living in Jiamusi, that Sun rise at 02:00 and sets at 14:00, I know that this place is more near to ...
6
votes
3answers
807 views

How long was a day at the creation of earth?

Since the earth is slowing its rotation, and as far as I know, each day is 1 second longer every about 1.5 years, how long was an earth day near the formation of earth (4.5 billion years ago)? I ...
0
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0answers
56 views

How is the universe expanding? [duplicate]

Possible Duplicate: spacetime expansion and universe expansion? Is the space between planets is growing or the space between stars is growing or the space between galaxies is growing?
0
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1answer
57 views

Does water in the drain follow the distance-squared rule of force?

When I shower I notice that the soapy water spinning around the drain often takes the form of a spinning galaxy, complete with spiral arms. Does this indicate that the water's speed around the drain ...
0
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1answer
239 views

Large-Scale-Structure (LSS) and the Fingers-of-God

In the Large-Scale-Structure (LSS) artifacts named fingers-of-god are apparent in the redshift space and justified by "The large velocities that lead to this effect are associated with the ...
0
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1answer
120 views

Does diffraction contribute to the Black Drop effect?

Two reasons are given to explain the black drop effect here, but I think I came up with a third. Consider a two-dimensional cross section of the situation just after second contact and just before ...
-2
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1answer
119 views

on what fundamental force is a black hole based on?

what fundalmentel force does a black hole based on? It seems people is very unfamilar with black holes. I will take a guess, is it electromantic force? please explain.
1
vote
1answer
114 views

questions about stars clusters

I recently watched the documentary miniseries "How the Universe Works" and few things can't stop bothering me. I am not an astronomer nor a physicist so those may be dummy questions. what I get know ...
0
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2answers
376 views

speed of light,breaking the barrier

when the sound barrier is broken,a series of concentric waves of sound is produced.Does it mean when the speed of light barrier is broken,a ripple of photons are created in the space-time fabric?
2
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0answers
59 views

Could a Class A Stellar Engine Use A Brown Dwarf

Could a class A stellar engine (or maybe a class C one) be built using a brown dwarf (for argument's sake, a T-dwarf like Gliese 229B)? Would it be capable of enough thrust to move itself any ...
18
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2answers
884 views

Can a planet have a larger diameter than Jupiter?

I have heard it said that if mass were added to Jupiter, then only its mass and density would increase but the diameter would stay about the same. Is this the case for Jupiter or some property of ...
3
votes
1answer
118 views

What is the black stuff blocking our view of the milky way?

I know that it is dust blocking the light. But what is this dust made of, gases or more heavy materials. If it is gas why is it not already drawn together in nebulas?
3
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2answers
131 views

Oort cloud blocking light?

Is the Oort cloud blocking a substantial amount of light in the visual spectra, making it harder for observers seeing outside the solar system?
1
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1answer
492 views

Analogy between magnetic bottle and Van Allen's radiation belt

A magnetic bottle is an arrangement that permits to confine charged particles. Here you can find a review for charged particle rotating in a magnetic field and at the bottom of the page a description ...
4
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2answers
2k views

How could scientists know how far a star or galaxy is from us?

How do astronomers measure how far a star (or galaxy) is away from the earth? How would they know that it has taken 13 million years for light to travel in space before it reaches us?
2
votes
2answers
183 views

Was Sun a part of a binary system?

I've read that many stars and other celestial bodies are found to constitute binary systems where the two bodies spin around each other. But our Sun is one of the exceptions. Could it be possible that ...
2
votes
1answer
191 views

How many stars within 5 parsecs?

I've ran some scripts on some star catalogs, which counted the number of stars with a parallax greater than 200 mas, which should mean everything closer than 5 pc. The results are as follows: ...
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1answer
113 views

What's the amount of deviation of cellestial orbits from perfect ellipses

It's well known that the planets don't orbit the sun in perfect circles and the characteristics of the elliptical orbits which serve as better approximations to their motion have been calculated ...
9
votes
1answer
332 views

Do any naked-eye stars have planets

Are there any known exoplanets around naked-eye stars? I know that Fomalhaut has a planet, and Vega has a dust belt that may be a protoplanetary disk or even analogous to our Kuiper belt. What else is ...
17
votes
3answers
567 views

Direct observations of a black hole?

I'm not very knowledgeable about physics generally, but know that nothing can escape a black hole's gravitational pull, not even light (making them nearly invisible?). My question is: What has been ...
0
votes
1answer
595 views

Triangulation for Astronomical Distances

How can triangulation be used to calculate the approximate distance to very distant celestial bodies like stars, globular clusters, etc.? And can it be used to measure the distance to a Black Hole? ...
2
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1answer
125 views

Moons of the planets

What is the phenomena behind gas giants like Jupiter and Saturn having a large number of moons as compared to other planets. Were the present state moons a part of their parent planet long time ago ?
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0answers
24 views

Expansion of Universe [duplicate]

Possible Duplicate: Why space expansion affects matter? If the Expansion is prevalent, i.e. it is observable and true then shouldn't that result in the expansion of the Milky Way galaxy, ...
0
votes
1answer
44 views

Does an uneven and/or moving surface affect quality when using a solar filter?

I have chosen to make my own solar filter using Baader as opposed to Mylar or anything else based on these: http://physics.stackexchange.com/a/25204/6805 and ...
1
vote
1answer
144 views

Distance at which a 300m asteroid is visible

Using the best available telescopes, and assuming a typical albedo of 10%, at what distance can a 300m asteroid be seen (well enough to start plotting its course) in 1) visible and 2) infrared ...
7
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2answers
1k views

How did Halley calculate the distance to the Sun by measuring the transit of Venus?

What numbers did Halley, Cook, et al. have? What was the strategy by which they calculated the AU?
5
votes
1answer
275 views

Does a tidally locked planet have seasons?

Could a tidally locked planet have seasons? According to my understanding, a tidally locked planet rotates around itself exactly once per rotation around its sun. However, if the axis of rotation of ...
2
votes
1answer
153 views

When would the proposed black hole at the centre of Milky Way gulp in our solar system?

I've heard and read that our solar system lies near to the peripheral region of the Galaxy. Then accordingly we would have a greater probability of sustaining to eventual gulping down by the ...
29
votes
8answers
8k views

Would it matter if the Earth rotated clockwise?

In the Futurama episode "That Darn Katz!" they save the world by rotating the Earth backwards saying it shouldn't matter (which direction Earth rotates). If Earth rotated clockwise and remained in ...
2
votes
1answer
437 views

Combined Gravitational Force Vectors in a Spherical Coordinate System

Asking a question here is quite intimidating for me -- while I love Physics, my high-school understanding only allows me to go so far... I've been trying to solve this problem for the last couple of ...
0
votes
1answer
148 views

Validity Of the Drake Equation [closed]

The Drake Equation is designed to estimate the number of Planets possibly having intelligent life forms existing in our Galaxy. But I don't see how it's justified. As far as we know, Earth is the only ...
1
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0answers
231 views

How to find orbital radius of star in a binary system using redshift and orbital period data? [duplicate]

Possible Duplicate: About binary stars and calculating velocity, period and radius of their orbit I am given the non-redshifted wavelength of the EM radiation from one of the stars, the ...
1
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2answers
88 views

On constancy of cometary orbits

how are the comets able to keep to a nearly fixed orbital period, though they lose a certain amount of mass during their perihelion?