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.
0
votes
0answers
81 views
Mass loss rate of planetary nebulae
The “interacting wind” model of planetary nebulae is based on the idea that the white dwarf phase of stellar evolution is preceded by a red giant phase. A fast wind from the hot white dwarf overtakes ...
13
votes
1answer
383 views
What percentage of the sky is occluded by stars?
If you drew rays from the center of the earth out to infinity at every angle, what percentage of them would intersect a star?
Extra details:
Assume the rays are mathematical rays, or that they ...
4
votes
3answers
170 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 ...
5
votes
2answers
229 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
votes
1answer
104 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 ...
4
votes
3answers
150 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
votes
2answers
348 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 ...
6
votes
1answer
572 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:
I know that on ...
2
votes
1answer
148 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:
...
1
vote
2answers
126 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
votes
1answer
91 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
votes
1answer
62 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
vote
1answer
89 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
votes
2answers
140 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
votes
1answer
71 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
votes
2answers
178 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
76 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
110 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
104 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
58 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 ...
3
votes
2answers
289 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 ...
5
votes
1answer
366 views
Might a planet perform figure-8 orbits around two stars?
Might a planet perform figure-8 orbits around two stars?
I'm thinking that if the two stars were equal mass (and not orbiting each other) then a planet that were to go right between them would ...
0
votes
0answers
49 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
votes
0answers
115 views
To measure the distance to a star using spectroscopic parallax which two do you need to know? [closed]
To measure the distance to a star using spectroscopic parallax which two do you need to know?
A) Spectral type
B) Parallax angle
C) Visual or apparent magnitude
D) Mass
0
votes
1answer
53 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
votes
1answer
136 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
votes
1answer
114 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 ...
-1
votes
1answer
114 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
89 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 ...
3
votes
3answers
353 views
What makes the earth keep spinning?
I am thinking of what makes the earth keep spinning. Is there anybody here know the answer?
0
votes
2answers
220 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
votes
0answers
54 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 ...
17
votes
2answers
791 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
89 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
votes
2answers
93 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
vote
1answer
261 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
votes
2answers
428 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
141 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
153 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:
...
4
votes
5answers
6k views
Gravity on the International Space Station
We created a table in my physics class which contained the strength of gravity on different planet and objects in space. At altitude 0(earth), the gravitational strength is 100%. On the moon at ...
1
vote
1answer
71 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 ...
5
votes
1answer
172 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
431 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
267 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
votes
1answer
108 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 ?
0
votes
0answers
22 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
43 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
112 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
votes
2answers
354 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
213 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 ...
