Questions on astronomical objects orbiting a star massive enough to be rounded, not massive enough to cause fusion, and which have cleared its orbit of planetesimals.

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0answers
32 views

Weird light in the sky, curious as to what it is [on hold]

One night (a couple days ago) I looked out my bedroom window and saw a red light. It was fairly big but obviously not close to the window. It was moving, back and fourth between the distance of a ...
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1answer
31 views

A question about the distribution of mass among the planets in the Solar System

Is it coïncidence that the mass of a planet has about its maximum in the middle planets (Jupiter), while the mass of the closest and furthest planets has a minimum (Mercury and Pluto)?
6
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1answer
179 views

Why are Saturn bands much fainter than Jupiter's?

The atmospheric composition of both planets are very similar. Then why are Jupiter's bands more visible (North and South equatorial belt, etc.): Whilst Saturn's are not: (except for the storm of ...
0
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2answers
61 views

Kepler's second law of motion

Planets sweeps out equal areas in equal times. Is the area being calculated here the area of a triangle? You draw a straight line from the center of the sun to the earth at point A. The Earth moves ...
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2answers
64 views

Can a tidally-locked planet maintain an obliquity

If a planet is tidally-locked, can it have an obliquity? e.g. the Earth's rotation is being slowed by tidal forces. A long way in the future it will be tidally locked. As it slows, will the ...
5
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1answer
82 views

Do other planets with a magnetic field also have two Van Allen belts?

On Jupiter and Saturn, aurora is seen around the planet's poles, so that implies that there must be a kind of magnetic field around those planets. Perhaps even the moon Europa could have a magnetic ...
0
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1answer
48 views

Would we be able to feel the acceleration of a planet with a highly eccentric orbit?

Even though our Earth moves on average 67,000 miles per hour around the Sun, we cannot feel its movement since its speed is fairly constant. More precisely, its change in speed is very low and our ...
1
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1answer
89 views

Which lens and magnification is best to see planets?

I just bought a Celestron Travel Scope 70 and it comes with a 20mm and a 10mm eyepiece. I get a good view of the Moon but I am not able to see Jupiter, Saturn or Mars as expected. I read about the ...
0
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2answers
74 views

Does the retrograde movement affect the true angular distance between 2 planets?

I need to calculate the relative angular path between two planets in the geocentric view or in other words the number of degrees of a circle one planet travels away from another planet around the ...
3
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2answers
296 views

Could the earth become a star if more mass was added?

I've heard that the only difference between a star and a planet is mass, meaning that if planets accredited enough mass they would too become stars. Does this mean that the star started off as a ...
3
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1answer
74 views

Star formation: When a nebula collapses, is it only the gasses that form the star?

A nebula is made of dust (elements heavier than He and H) and gas (H and He). Stars are made when nebulae's collapse and hydrogen begins to fuse. 99% of nebula material goes into making the star. The ...
15
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2answers
4k views

Why do the planets orbit in the same direction?

Theoretically, planets would have an approximately equal chance of going one way in their orbit or another but in reality, this is not the case (at least in our solar system). Why is this?
3
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1answer
75 views

Why the light curve goes down when the planet is behind the star?

There is a video explaing the transiting exoplanet light curve — https://www.youtube.com/watch?v=RrusIZaWDW8 It is clear to my why the curve goes down when the planet is between the observer and the ...
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1answer
55 views

Distance and orbital period for terrestrial binary planets

This article, http://phys.org/news/2014-12-binary-terrestrial-planets.html, suggests binary planets could orbit each other at a distance of only three planet radii. For two earth-like planets, that is ...
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0answers
22 views

What are the requirements to become a planet? [duplicate]

A planet is taught to us (at primary school) as a ball of rock that orbits around the Sun and is similar to our own planet, Earth (in as a ball of rock). But of course, humans have to be more specific ...
5
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1answer
95 views

Would a viewer see Earth from the rim of Shackleton Crater?

I've been researching this but so far have not found an answer. If you were standing on the top of the rim of Shackleton Crater at the lunar south pole, would you be able to see any of Earth? I can't ...
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2answers
100 views

Could this three moons system be stable?

In my fictional world I have selected all parameters to maximize the Hills Sphere of my planet. The planet has three times Earth's mass and it is located in 2 AU from its star that's 1.4 times more ...
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0answers
31 views

Question on retrograde motion [duplicate]

I am a beginner Does planets exhibit retrograde motion (eg Mercury and Venus) only because of earth rotation? Or is there any other reason? Please clarify
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2answers
122 views

If the planets only attract, then how can they stay in their orbit?

Gravity is related to mass, and gravity is an attracting force on every body. Then what happens when bodies only attract each other..without repulsion they may strike the sun. I think there must be a ...
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0answers
54 views

Have any co-orbital exoplanet pairs been discovered (and not subsequently retracted)?

For this question, I think a good working definition of co-orbital configuration would be two bodies orbiting around a third much larger body in a 1:1 resonance and where neither mass is negligible. ...
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1answer
86 views

Can a gas giant be hollow?

Let's think of Saturn, because of its density. Can there be a place near the center of the planet where the gravity upwards is more than towards the center, and with an atmosphere that is more ...
6
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2answers
215 views

Confirm: We can only notice planets if their orbit passes in front of their star and our view

If we can tell a planet exists by the dimming of the brightness of a star when it passes in front of our view of the star does that mean we cannot see a planet if it does not cross in front of our ...
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1answer
60 views

What causes celestial bodies to move like they do from Earth's surface?

As you probably know, the planets have pretty predictable orbits around the sun but what exactly causes the complex movement of celestial bodies in the sky from Earth's surface? Mars is an excellent ...
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2answers
2k views

Could the 9th planet be virtual?

Astronomers recently claim that there is evidence for a 9th planet. As far as I understood it, this is mainly based on coinciding orbital parameters of a few Kuiper belt objects. Could the 9th planet ...
6
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2answers
157 views

What's the name for [the other kind of planet] in a binary star system?

This XKCD what-if talks about rainbows on planets in a binary star system. It points out that there are two types: circumbinary planets, where the planet orbits far from and around both stars [...
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0answers
39 views

How much heat emanates from the planets after formation?

The 2nd answer to this question by MBR got me thinking about this. Is there some general guideline for residual heat a planet should emit, say 4.5 billion years after formation. I'm defining heat ...
3
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1answer
331 views

Which is the largest planet ever observed?

I don't know much about planets outside our solar system. Do we even know the limit of the size of how large a planet or satellite can be? The largest planet I know of is Jupiter, but could there be ...
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2answers
70 views

How does large body gravity affect planet formation?

If Jupiter's gravity is what kept the asteroid belt from forming a planet, then why didn't the sun's gravity keep the inner planets from forming?
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2answers
103 views

What is the effect of the axial precession on the orientation of the planet's orbits?

I am working on an online application to visualize the positions of the planets and to calculate their ephemerides (you find it here, but it is not complete yet). I do not have much knowledge in ...
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0answers
5 views

DUT time offsets to UTC [duplicate]

Astronomic observations in geodesy. It is well understood that sun and star positions may be expressed in Greenwich hour angle and declination. Or Right Ascension Declination. And may be published ...
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1answer
97 views

Does earth have retrograde motion?

I am a beginner. Please let me know whether earth has retrograde motion If it does not, let me know the reason
5
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3answers
260 views

Why do the gas giants in the Solar System have comparatively large orbits compared to the inner planets?

Ever since I observed the depictions of the Solar System, I was obsessed with the question of why the gas giants (outer planets) have very large orbits, compared to the planets that are closer to the ...
0
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1answer
92 views

How to calculate a planet's apparent size when the planet is viewed from a moon in orbit around it?

Specifically in this case, how large would Jupiter be seen in the Io's sky in comparison to the moon in the Earth's sky? How to calculate this? Also, if somebody knows any online software which lets ...
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2answers
175 views

What is the fifth moon-like object I saw around jupiter through my telescope?

Tonight while observing Jupiter I was able to see a five (what looked like) moons. I have observed Jupiter often before and only been able to make out the four galilean moons. It's my understanding ...
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2answers
99 views

Retrograde motion of planets: reason and time?

I am a beginner. I'd like to understand how planets (except Sun and Moon) exhibit retrograde motion. When does the retrograde motion start for a planet (eg Mars) and how long (time limit) planets ...
10
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1answer
1k views

Can dark matter be found in the shape of planets, galaxies etc.?

If dark matter has gravity just like normal matter, does that mean it can also form planets, solar systems and so on? Any answer will be appreciated.
27
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3answers
6k views

Did I see another planet?

A couple days ago, I zoomed in with my 30x optical zoom camera, and after some exposure adjustments, a bright star in the night sky turned into this: Are those other planets or other stars? Or is ...
4
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4answers
190 views

Which Planet/Star is it?

I live in north India. About 24° latitude. I can see a very Bright star in sky. Its towards east and high up. Is it Venus , Jupiter, star or anything else? Its not Sirius. I used Orion belt for that. ...
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1answer
103 views

Why are planets round?

I was studying our solar system and all celestial objects are depicted as round objects, including black holes.. worm holes as hollow cylinders as a pathway across two universes.. even the galaxy is ...
0
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1answer
67 views

Is it possible to know if a planet is located in the Habitable Zone knowing it's properties?

Is there an equation that can give me the possibile distance of the planet from his star knowing planet's temperature (or other datas)? I found this method for calculating the Habitable Zone but it'...
2
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1answer
63 views

Can we apply Kepler's law of planetary motion to the moons motion around the earth?

I have been trying to understand Kepler's law of planetary motion for a while. So I was thinking, if it would even apply to the moon orbiting around the earth. Does the moon too orbit in an ellipse ...
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2answers
182 views

Why is the universe full of spinning objects?

Almost all celestial objects are rotating in some way about their axes. Why is this and should we expect the rotation to slow as the universe ages?
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0answers
24 views

Convergence of galaxies [duplicate]

What would happen to Earth and other planets after about millions of years at the time of convergence of milky way galaxy with andromeda galaxy? (Supposing the planets and the sun are still there and ...
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2answers
138 views

Color of planets

I am developing an astronomy software and need to know the color of each planet in the Solar System, when observed with the naked eye. I cannot find that information after googling for a while. Is ...
7
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2answers
271 views

Who gets to name Planet Nine if it is confirmed?

According to Wikipedia, "On 20 January 2016, researchers Konstantin Batygin and Michael E. Brown at Caltech announced calculation-based evidence of a massive ninth planet in the Solar System." If ...
3
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2answers
122 views

What planets and moons have we seeded with life (if any)?

Which planets and moons have we accidentally (or purposely) seeded with life? I would expect this to be any planet or moon we have sent an unsterilized (or not fully sterilized) lander to, or crashed ...
5
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2answers
290 views

Does natural satellite(s) of a planet affects its orbital velocity around a star?

Please excuse me for a lay question. As we know, to calculate the orbital velocity, we take the mass of the orbiting body, the mass of the body being orbited and the distance between the two bodies ...
2
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2answers
129 views

Could gravity waves be used to confirm the existence of a ninth planet?

Shortly after the news of the discovery of gravity waves, my physics professor explained the significance of the discovery by comparing it to a medical X-ray machine. He said that gravity waves can be ...
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4answers
132 views

What planet is better than earth to infer solar system configuration?

The mankind had to work some centuries to infer the real configuration of solar system, starting from greeks, Ptolemeus, until Copernicus, Galilei, Kepler, Newton etc. Is there any planet where we ...
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0answers
47 views

Is Planet Nine shepherding the Kuiper Belt?

Is it possible Planet Nine is shepherding the Kuiper Belt similar to the way Jupiter shepherds the asteroid belt? I understand that very little is actually known about Planet Nine at this point, but ...