Celestial body that orbits following an elliptical path around a star or stellar remnant.

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Are Uranus and Neptune too big for their location?

So I was watching some TV, and I heard Dr. Plait mention that the planets Uranus and Neptune are too big to be located so far out in our solar system. Now, I heard his explanation on the show as to ...
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292 views

Would a rocky planet orbiting so close to a very hot star eventually vaporize?

I was thinking about the physics behind a hypothetical scenario where a planet the size and the mass of the Earth is orbiting so close to a very hot star and what the long-term fate of such a planet ...
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139 views

How scientists could say that such meteorite comes from Mars

How could scientists affirm that a meteorite comes from Mars and not from another source ? This is a probability or an absolute certainty ? How much percent ?
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530 views

What would the collision between a (large) solid planet and a gas giant be like?

Assuming a Jupiter-like planet and an Earth-like planet (Except, say... half the mass of Jupiter), what would happen when the two collide? For clarification: What would the actual collision be like? ...
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If it was possible to dig a hole that went from one side of the Earth to the other…

...And you jumped in. What would happen when you got to the middle of the Earth? Would you gradually slow down, until you got to the middle and once you were in middle would every direction feel like ...
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Are there planets that do not rotate on their axis?

I was reading a thread about how a pendulum would be affected if the Earth did not rotate and Larian's answer made me wonder if all planets rotate necessarily due to physics. So that's the question: ...
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What are the prerequisites for considering any other planet to be habitable?

Well, there is a measure of how a planet could be considered like Earth, called Planetary habitability. Based on this measure, what are the prerequisites needed to consider a planet to be a habitable ...
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22 views

Ring height stats?

I'm working on a basic simulation system which will include planets with rings, I want to create dust and asteroids within a 3D ring but I'm struggling to find any stats on the sort of height ranges a ...
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Biggest crater in the Solar System

It seems that the biggest crater in the Solar System is Borealis Basin on Mars. The Wikipedia entry and this piece of news say it has been formed by an impact with a body of around 1600 - ...
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What causes the orbital eccentricity?

I found some websites trying to attribute this to the external other forces affecting the 2 body problem to follow an elliptical rather than a circular orbit, but I am not convinced though. I think ...
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How do you explain Kepler's third law in general terms without complex math?

I understand the first law-elliptical orbits, and the second-equal area in same time, but I need help with the third one. Note that I am not in an AP course or taking calculus at the moment so simple ...
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How do the Planets and Sun get their initial spin?

How do the Planets and Sun get their initial rotation? Why do Venus and Mercury rotate so slowly compared to other planets? Why does Venus rotate in a different direction to Mercury, Earth and Mars? ...
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Are planetary orbits measured from the Sun's surface or centre?

I would imagine planetary orbits are measured from the Sun's centre and not its surface. Is that true? I can't find anywhere that actually states this.
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How big (compared to our moon) would Saturn look from Titan's surface?

How large in the night sky would Saturn look from Titan's surface? I believe they are tidally locked.
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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 ...
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229 views

Why do the terrestrial planets have many of the same gases in their atmospheres?

While the gases are present in very different abundances, and the atmospheres have very different pressures, Earth, Mars and Venus all have a similar cast of gases: nitrogen, argon, CO2, others in ...
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What if the Moon was 100x more massive: Binary planets?

I was reading a couple of Earth-Moon related questions (Mars just collided with Earth! A question of eccentricity, Could the earth have another moon?) and they got me thinking about planet-moon ...
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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, ...
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What would happen if the polar ice caps of Mars melted?

My dad told me that Mars' polar ice caps are made of H2O and CO2. If they melt, would it add an atmosphere to Mars and allow life?
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For observing planets what kind of telescope offers the best view?

I've heard that using a refractor is better than a reflector when it comes to planets to best reproduce their colors. But perhaps other factors can weight in too? For example, do you want a slow or ...
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481 views

Can a planet form before the parent star ignites?

I'm unable to find an answer to my questions via my searches. This questions pertains to the timeline of a star system creation. My question: During the creation of a star system, can satellite ...
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78 views

Is a rogue 'exoplanet' classed as a exoplanet?

Given that the term planet strictly (according to the IAU) refers to a body around the sun, rogue planets can't be called that, so I assume they must be called rogue exoplanets? But do they even ...
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Why does Jupiter emit more energy than it receives?

I hear that Jupiter and Saturn emit more energy than they receive from the Sun. This excess energy is supposedly due to contraction. Is this accepted as fact (or is it controversial)? Does this ...
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How does the atmospheric UVB attenuation of terrestrial planets compare?

On Earth, UVB (280nm - 315nm or 320nm depending on the source) undergoes extensive attenuation through the atmosphere, when observed at the planet's surface, as illustrated below: Image source ...
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Rocky Planet in the center of System [duplicate]

We all know that mostly stars are at the center of planetary systems, but is it possible that instead of a star there was a rocky planet in the center with stars (and other planets and moons) orbiting ...
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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, ...
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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 ...
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Earliest terrestrial planet?

If I've understood correctly, the heavier elements needed for terrestrial planets such as iron can only form in supernova. If that is indeed true, how long since the beginning of the universe would ...
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232 views

Will Neptune change Pluto's orbit some day?

My seven-year-old son loves astronomy-- so much so that we read space books before bed time. One of our books talks about Pluto's orbit crossing over Neptune's orbit and will be (or is) closer to the ...
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Is it possible to determine astronomically/astrophysically whether other planets have ever encountered polarity reversal?

We know of geomagnetic flip in Earth's history by studying geologic data. Given other planets in the system also possess a magnetic field leads to the assumption that such polarity reversal may not be ...
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Are there Trojan family or Hilda family satellites locked in Earth's orbit?

Jupiter has many Trojan asteroids located at Lagrangian points L4 and L5 and Hilda asteroids dispersed between points L3, L4, and L5. Does the Earth have similar satellites? If so, how many?
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What colour would the sky of a high-oxygen, high-argon, high-water vapour atmosphere be?

Although this is a hypothetical, I think it is nevertheless a legitimate physics problem. I would very much appreciate any answers you can give. What colour would the sky be, both at daytime and at ...
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Falling through the rotating Earth

Suppose you were standing on the rotating Earth (not necessarily Equator or the poles) and suddenly your body lost the ability to avoid effortlessly passing through solid rock. Because the earth's ...
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How plausible is a subsurface ocean on Pluto?

According to this article on physorg.com, it's likely that Pluto has a subsurface ocean of liquid water. It suggests that the ocean would be about 165 km deep, under an equally deep crust of solid ...
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Why aren't there any clear planets/ stars?

Most gases are clear. So why are there not any planets or stars that are more or less clear in color? I suspect this question may be extremely stupid.
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How does one calculate where the “surface” of a gas-giant would be?

Okay, so Jupiter, Saturn, et. al are gas giants. I understand that they have large gassy atmospheres, which, due to the pressure would eventually become more and more dense as one approaches the ...
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339 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 ...
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What coordinate system is used to describe planets positions in the universe?

How are planets positions described in the space and in respect to what? For example is Sun the origo and right now at this moment Earth has [coord_X, coord_Y, coord_Z]? or maybe [lng, lat]? ...
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What structural or chemical mechanism results in Saturn having a density less than that of water?

According to NASA’s Saturn fact sheet, Saturn has a density considerably less than water and the lowest density of the major planets. What compositional and/or structural mechanisms are theorised to ...
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Are there any models for distribution of asteroid sizes in a belt?

Question: Is there any function that can describe the distribution* of asteroid diameters expected within an*' asteroid belt? *: distribution as frequency of occurrence within the asteroid belt or ...
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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, ...
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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 ...
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Binary Star system with one star stationary?

Can a Binary Star system be possible where in one star is stationary and the other star revolves around it? (Just like a planet revolving a star. i.e planets in the system and the star revolving ...
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What is the general relativity explanation for why objects at the center of the Earth are weightless?

The idea that as you move through the earth you get a symmetric cancelling of gravitational acceleration which approaches zero acceleration due to gravity at the center of the earth makes a lot of ...
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Does the Earth actually rotate around the sun? [duplicate]

Why does one say that the Earth rotates around the sun? There should be no preferred reference frame and from an observer on the sun, the sun will rotate around the Earth.
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What sustains the rotation of earth's core (faster than surface)?

I recently read that the earth's core rotates faster than the surface. Well, firstly, it's easier to digest the concept of planetary bodies, stars, galaxies in rotation and/or orbital motion. But, ...
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Are “broken” planets possible in the real world?

In the Star Wars universe, there are mentioned (or rather shown) two planets that had some kind of great explosion in their history. First is Peragus, with its exposed core, that partially exploded ...
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Transit of Mercury: how did he see it?

On November 7, 1631 Pierre Gassendi saw the transit of Mercury across the face of the Sun. How did he see it? I mean what instrument was used to reduce the apparent brightness of the Sun?
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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 ...
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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 ...