Celestial body that orbits following an elliptical path around a star or stellar remnant.
5
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6answers
707 views
Why is the universe so organized?
If you think about the Big Bang and the flow of matter in all directions, you would think, how unorganized would this universe be? No matter how long it would take. The idea that matter or most of it ...
5
votes
6answers
549 views
Why does the earth rotate? [duplicate]
Possible Duplicate:
Why does every thing spin?
So why would the earth, or any planet for that matter, rotate along an axis? I know of no force which could come into play here, so i assume ...
5
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3answers
3k views
What is the official difference between a planet and a dwarf planet?
I'm trying to understand how objects are classified as planets, moons, or dwarf planets. Can someone please explain the differences between them? I'm really curious about why Pluto is a dwarf planet, ...
5
votes
1answer
6k views
Is the moon a planet?
Can our moon qualify as a planet? With regard or without regard to the exact definition of the planet, can the moon be considered as planet as Mercury, Venus and Earth etc. not as the satellite of the ...
5
votes
3answers
233 views
Why is the surface of Venus so hot?
Whenever I have seen Venus described, its high surface temperature is attributed to an intense greenhouse effect. This seems to make sense, as its atmosphere is roughly 96% CO2. But on Earth, the ...
5
votes
2answers
36 views
Does Mercury have a balmy spot?
From Wikipedia:
Although the daylight temperature at the surface of Mercury is generally extremely high, observations strongly suggest that ice exists on Mercury.
Does that mean there could be a ...
5
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2answers
211 views
What is the largest sphere of liquid water that could exist in space held together under it's own gravity? [duplicate]
What is the largest theoretical sphere of liquid water that could exist in space held together under it's own gravity? I've always wondered if a planet the size of earth could exist as a single volume ...
5
votes
1answer
385 views
How do astronomers measure the distance of the planets from its star?
I know they have accurate means of measuring the distance of the planets in the Solar System from the Sun. I'm skeptical how can they use the same tools or techniques for other systems so far away as ...
5
votes
1answer
991 views
How do we know the temperature on the planets?
I was watching a show and they were saying that the temperature of Pluto (I know it is not a planet) is about -300 degrees. I know that depends where in the orbit Pluto is, but how do we determine ...
5
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3answers
117 views
What does a planet look like in the infrared?
I've been trying to find a good source for what the planets look like in the infrared, specifically if viewed as a point source. I've been working with a low resolution telescope that senses in the ...
5
votes
3answers
495 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 ...
5
votes
5answers
310 views
Computing Planetary Positions
Shortly, I will be beginning my third year at University in Computer Science, I am a software developer and I will be required to work on a final year project.
My idea for my final year project is ...
5
votes
3answers
270 views
the collision of Phobos
Mars has two moons: Phobos and Deimos. Both are irregular and are believed to have been captured from the nearby asteroid belt.
Phobos always shows the same face to Mars because of tidal forces ...
5
votes
1answer
581 views
How do we determine what distant planets, stars etc are made of?
I remember this being covered somewhat back in school and I have casually read about it. I know it involves inferring from spectral analysis what physical properties an object may have right?
Though ...
5
votes
1answer
60 views
Do all known planets and moons have magnetic field?
In this Wikipedia article it is stated, that magnetic field of Earth is caused by currents in her core. The same origin is for Jupiter magnetic field.
For Moon (article) there is a magnetic field, ...
5
votes
1answer
226 views
Determining Average Tidal Effects
Maximum tidal heights vary widely across the globe, from 16 m in the Bay of Fundy to mere centimeters elsewhere. These variations are due to coastline and shoreline differences. This makes it ...
5
votes
1answer
83 views
Convert latitude of lowest altitude to argument of perigee?
I am designing an orbit around Mercury. I know the values I want for the semi-major axis, eccentricity, inclination, and RAAN. I want the altitude of closest approach (periapse) to occur at ...
4
votes
6answers
142 views
What possible science could we do during the 2012 Venus transit? [closed]
I had previously asked about how useful everyday solar physics data is to other astronomers ... But about a year from now, we will have another Venus transit, where Venus will pass between the sun and ...
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 ...
4
votes
2answers
283 views
What does the phrase “limb of the earth” or “atmospheric limb” mean?
What does the term limb of the earth (see this question, for example) or atmospheric limb mean? The phrase strikes me as very odd, since earth is nearly spherical. Do other planets with atmospheres ...
4
votes
3answers
419 views
How to concisely explain apparent retrograde motions of planets?
Some planetary orbits occasionally can appear to move backwards to an observer on the Earth?
Does anyone know concise, clear, web-based visualizations, animations or tutorials that clearly show how ...
4
votes
1answer
480 views
What would happen to Earth if Saturn were to exit the Solar System?
Suppose Saturn simply vanished. How would that affect the rest of the Solar System, specifically Earth?
4
votes
1answer
45 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.
...
4
votes
2answers
157 views
How could Horrocks have measured the AU?
I have always understood that the great historical significance of the transits of Venus, and the reason for the expeditions mounted to observe it, were that, by observing it simultaneously from two ...
4
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2answers
556 views
Lowest gravity on Earth's surface?
I am trying to determine which on Earth's surface has the lowest gravity. Googling is not finding anything concrete. My natural inclination would be to think of Mount Chimborazo in Ecuador, being on ...
4
votes
2answers
114 views
What is the mass distribution within the sun?
Jupiter is roughly 1/1000 the total mass of the sun. To get some idea of what effect Jupiter's gravity may have on the sun I'd like to know the approximate mass distribution of the sun. (i.e) the ...
4
votes
3answers
65 views
Length of day of a gas giant
How can the rotational speed, or the length of a day be determined or estimated in a planet which is composed entirely of non homogeneous fluids? There must be internal forces (pressure gradients, ...
4
votes
1answer
92 views
Direction of planetary tilt
I am building a 3d solar system simulation using WebGL and have come across the problem of establishing the direction of tilt of the various planets. No I know the tilt of the planets in degrees what ...
4
votes
1answer
493 views
Finding the position of a planet between two other planets of known mass and distance
Here is the question:
A planet with mass $m$ and a second with mass $M$ are separated by a
distance $d$. A third planet with mass $m_3$ happens to be midway
between $M$ and $m$. Where could ...
4
votes
1answer
44 views
What planets are visible to the naked eye from Mars?
Here on Earth we are blessed with being able to see some other planets, Mars & Venus etc, with the naked eye on a fairly regular basis thanks to the distance between the planets.
What about from ...
4
votes
1answer
132 views
What day/night cycles, climate and seasons would experience Alpha Centauri Bb inhabitants?
Alpha Centauri Bb is an exoplanet orbiting Alpha Centauri B. It is asserted that given the close distance to the star the planet should be tidally locked.
The orbiting period of the planet is about ...
4
votes
2answers
28 views
Lumped circuit model of Earth and Sun as a thermal system
I want to design a thermal model of the Sun heating up the Earth. The circuit below is my own design (I don't know if there is a better way to model it. If there is, please tell me.). I want to ...
4
votes
1answer
187 views
Does the Moon's orbital inclination follow the wobble in the Earth's rotation?
As the Earth wobbles during rotation, does the higher gravity at the equator tend to pull the moon toward an equatorial orbit even as the earth does that thousands of years wobble cycle? It would ...
4
votes
0answers
63 views
Atmospheric Circulation
What is the simplest simulatable model giving our rotating earth its 3 circulation cells (Hadley, Ferrel, Polar)?
The model should also show 1 circulation cell if the earth's rotation were stopped (or ...
4
votes
0answers
85 views
Hemispheric dichotomy of Mars and unstable spin axis
Is the following explanation plausible? Can you spot any flaws?
Mars doesn't have a large moon to stabilise its axis of rotation. At some point early in its formation its axis might have been ...
4
votes
0answers
35 views
Are there certain alignments in planetary orbits that create interesting effects in the moons or planets?
We have some interesting examples such as Mercury's perihelion
The planet Mercury is especially susceptible to Jupiter's influence
because of a small celestial coincidence: Mercury's perihelion, ...
3
votes
2answers
247 views
2012: Is there some astronomical event happening?
The news media has publicized that 2012 is the end of the Mayan calendar, and that all the planets will be aligned. Is there any truth to this?
3
votes
3answers
531 views
How do the Planets and Sun get their initial rotation?
How do the Planets and Sun get their initial rotation?
Why do Venus and Mercury rotate so slowly compared to other planets and why does Venus rotate in a different direction to Mercury, Earth and ...
3
votes
2answers
37 views
How could they tell things weigh a sixth of their “Earth weight” on the moon?
I frequently keep hearing stuff about "gravity on the moon is only a sixth of that as Earth's" and "of course you'll weigh more on Jupiter". I do know the relative sizes of those bodies allow for ...
3
votes
1answer
94 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?
3
votes
3answers
185 views
Does Kepler's law only apply to planets?
Does Kepler's law only apply to planets? If so why doesn't it apply to other objects undergoing circular motion?
By Kepler's law I'm referring to $T^2 \propto r^3$
3
votes
1answer
83 views
What is the maximum mass of planet HD 40307 g
Recently discovered planet HD 40307g around HD40307 Star system is claiming that its inside a habitual zone of a solar system. Besides It has water where life could be evolved.
I tried to calculate ...
3
votes
2answers
132 views
Could a planet sized bubble of breatheable atmostphere exist?
I'm reading a book (Sun of Suns by Karl Schroeder) that the main location is a planet called Virga, which contains air, water, and floating chunks of rock, and has no or a very small amount of ...
3
votes
1answer
135 views
Keeping air in a well
Let's say I've got an Earth-like planet with no atmosphere: it's just a barren ball of rock. I want to live there, but I don't like domes, so instead I'm just going to dig a big hole and let gravity ...
3
votes
1answer
96 views
Link between Earth and Mars
I am trying to the calculate the link budget for link between a ground station on Earth (with a particular latitude and longitude) and a rover at a particular location on the surface of Mars, either ...
3
votes
1answer
70 views
Does the Earth have a semi-solid body at its core because of lower pressure at the center of the Earth?
I have read that the Earth has a semi-solid iron body at its core, even though that object is surrounded by liquid magma.... I'm wondering if this is because of a pressure (and resulting temperature) ...
3
votes
1answer
13 views
For the long-term evolution of atmosphere/orbit, when is perihelion more important than mean distance?
When we want to figure out the long-term evolution of a planet's atmosphere/orbit, when is perihelion more important than mean distance?
E.g. some processes (like Jeans Escape and escape of ...
3
votes
1answer
58 views
Cassini: What information could be gained from the 2017 impact with Saturn?
First of all:
Will Cassini be operational in 2017 (pending no unforeseen equipment failures)?
Power
Communications
...
What information could we gain?
Properties of Saturn
How to build more ...
3
votes
1answer
130 views
Earth-Moon orbiting each other after being engulfed by Red Giant
Recently some exoplanets were discovered which are thought to be the leftover cores of giant planets that had survived a star becoming a Red Giant and then shrinking back to a subdwarf.
If giant ...
3
votes
0answers
25 views
The collision of Phobos [duplicate]
Possible Duplicate:
the collision of Phobos
Mars has two moons: Phobos and Deimos. Both are irregular and are believed to have been captured from the nearby asteroid belt.
Phobos always ...
