# Questions tagged [planet]

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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### Easy guideline for using JPL Horizons DE431 for planets in aphelion and perihelion from 11000 BC to 16000 AD?

Can someone give me a step by step Guide how to use JPL DE431 or DE441 as a Beginner. I tried the Horizons website app and Webgeocalc but it didn't showed understandable Information. This websites ...
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### Who first observed another planet rotating?

We knew the earth rotates, but the moon is tidally locked. To tell that another planet is rotating, you have to be able to distinguish its surface (I guess?). Who first did this?
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### Project Analog Hypothetical Planet

For my story Project Analog, I was wondering if a hypothetical planet (Let's call it Suria). It has the same size and conditions as Earth with the same axis, tilt, and rotation, as well as one moon. ...
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### Maximum and minimum masses and sizes of giant planets?

What are the minimum & maximum masses and diameters of giant planets? Minimum end of the scale Earth has mass of 1 Earth mass and a mean radius of 6,371.0 kilometers, and thus a mean diameter of ...
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### How to estimate perturbations from other planets in Apsidal Precession

I am developing a fictional system which I want to calculate to as much detail as I can. Thus I have a question about astrophysics and astrophysical formulae. I know that Apsidal Precession is ...
1 vote
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### How can I calculate the geocentric longitude of Pluto in a similar way to VSOP87's algorithm?

The book "Astronomical Algorithms" teaches a way to calculate the position of any of the planets for almost any date, until you get to Pluto. To try to get around that, I attempted to ...
532 views

### Did the Late Heavy Bombardment Period Happen Because of a Stellar System Collision?

I was thinking about the impending collision between M31 and the milky way galaxy, and I've heard that since a galaxy is mostly space most of the contents of both galaxies would be just fine. Could a ...
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### Do all the planets in the universe rotate? [duplicate]

Do all the planets in the universe rotate by their own means. Do they rotate like the Earth? Are there any planets which don't rotate?
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### Why wasn't the planet Uranus recognized by ancient cultures?

Mercury, Venus, Mars, Jupiter, and Saturn have been identified by ancient astronomers as they are visible with naked eye at night. The planet Uranus, despite being visible during very clear nights, ...
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### Formation of a non-Sol Oort cloud with high mass planets

Based on recent developments in astronomy, pertaining to a greater degree of measurement, the mass of the Oort cloud around Sol is apparently only about 1.5 times the mass of earth, in contrast to ...
1 vote
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### Timelapse Video Of Motion of Mars?

I'm trying to find a timelapse video of mars moving against a fixed background of stars - could someone point me in the right direction? Thank you!
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### How can Jupiter rotate faster at the equator than at the poles (in degrees per second)?

Jupiter rotates slightly faster at the equator. If inertia is conserved as average angular momentum, what is the physical mechanism that creates a gas which is ~1% faster angular momentum at the ...
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### How can I calculate current position of planet in sky

How can I calculate current position of planet in sky from earth's point of view. I want to calculate based on given DATETIME and Location For example, if I see current position of planets on "23 ...
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### Is there a noob-friendly website/app for tracking a astronomical body's apparent movement over time?

As I walk home along my road most nights in winter, I see the Moon and one-or-more planets. Unsurprisingly, over the last 2 months, if it's been the same planet and it (and the Moon) has been in ...
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### Is Pluto still a dwarf planet?

Recent news seem to suggest that astronomers are arguing about whether Pluto should become a planet again. However, I cannot find an official source for this. Is this actually true?
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### Difference in results between JPL Horizons and cspice (rust-spice)

I am calculating the apparent planetary position of planets using the cspice library (I am specifically using rust-spice, which is a wrapper of cspice in Rust). when I calculate the same values in the ...
1 vote
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### The rocky planet sizes between the Sun and Jupiter are small, big, bigger, small, and unfinished. Is there a reason?

The rocky planet sizes between the Sun and Jupiter are small (Mercury), big (Venus), bigger (Earth), small (Mars), and unfinished (the asteroid belt). Is this just random chance or is there a theory ...
1 vote
533 views

### Can you identify this planet seen in the night sky?

I saw a very bright star in the night sky on Monday (Jan 30, 2017). The star was in the Western sky and was directly above the crescent moon. My location is Toronto, Ontario. Canada. It was about 8pm ...
1 vote
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### calculating apogee and perigee for moon and sun

The perigee does not necessarily happen when we have a full moon, using swevents we can easily determine the moon phases. Now can we use python to determine when ...
1 vote
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### On the relationship between semi-major axis and the Longitude of the Ascending Node

I noticed something looking at the Longitude of the Ascending node of various planets. Mercury: 48.331° Venus: 76.680° Mars: 49.57854° Jupiter 100.464° Saturn: 113.665° Uranus: 74.006° Neptune: 131....
1 vote
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### What would happen if a low-mass primordial black hole was captured by a brown dwarf or planet mass object?

Prompted by a recent PBS SpaceTime video The video in question discusses what would happen if a low-mass (asteroid-mass) primordial black hole were captured in the core of a Sun-like star (a so-called ...
1 vote
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### Planetary Conjunctions

Was there a conjunction between Jupiter and Mercury in 2 BC seen from Persian Gulf? Was there a conjunction between Jupiter and Venus in 4 BC seen from the Persian Gulf? If so, what day, time, and ...
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### Why is it impossible to infer the surface temperature of Venus by spectroscopy observation from earth?

It is well known that the surface temperature of the sun is determined by fitting the sunlight with the black-body spectrum. Why is this inappropriate for Venus? I have the question because of the ...
1 vote
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### Planets Named After Roman Gods, Except Earth

I’ve looked this up, but not necessarily sure the internet has the right answer. Why are the planets in our solar system named after Roman gods, except Earth, and why is only one of the nine planets ...
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### Celestial "orbits"

I heard that we're losing our moon, its slipping away from us in such tiny imperceptible steps that we don't notice any significant change even over kiloyears. The same must apply to planets, inching ...
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### Why did the dust between the planets disappear during the birth of the solar system?

I'm catching up on my childhood mistakes. One of them was the "nuclear flash", the enormous explosion when the sun ignited. Apparently, this did not happen as the ignition of the sun was a ...
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### How is a Planet's Moment of Inertia Measured Remotely?

In the July 2023 issue of Sky & Telescope there is an article titled Sights Set on Uranus. In that article the following statement is made: Since the 1930's we've suspected that Uranus and ...
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### Is there a formula for calculating surface temperature of a rocky world based on atmosphere and solar input?

For example, a thicker atmosphere would probably lead to less temperature variation . . . I assume that much is obvious. And, greenhouse gases trap heat. But when posed with a question like "...
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### Everything always looks the same

By now I have used 3 different telescopes and a pair of binoculars and no matter what I try to look at at night, whether it be stars, planets, drones, the moon or whatever, everything looks the same. ...
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### What was the definition of a planet before August 24, 2006?

In 2006, the IAU produced a definition of what it is to be a planet. This definition famously excludes Pluto, to the disarray of this small body's fans. Before this decision, what was the definition ...
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### Why does the planet Saturn have numerous (62) moons compared to the rest of the planets in the Solar System?

Saturn is a gas giant like Jupiter. It has everything from tiny moonlets less than 1 kilometer across to the enormous Titan, which is larger than the planet Mercury. Saturn has 62 moons with ...
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### How much of the surface of other planets is lit by the sun?

Since the sun is much larger than the earth, it should ideally light up a considerable portion of the earth rather than only half of it. However the sun lighting only half of the earth can be ...
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### For what period of time can planets be viewed from the North Pole as just being there?

I would like details on observations (since North Pole is not possible, approximately around the North Pole) which tell us for how long are planets visible from the North Pole? I understand that ...
1 vote
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### Potentials of space mining [closed]

I'm conducting research on the potential benefits of space mining on asteroids, like 16 Psyche. I'm hoping that those who are more knowledgeable than me can help with the following questions: Are ...
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### Would Venus have any significant effects on Earth if its orbit were entirely within the habitable zone?

If Venus was entirely inside the habitable zone, or life zone, would its proximity to the Earth provoke any remarkable changes to the Earth?
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### What celestial body (inside the solar system) has the highest flattening ratio?

As a planet, Saturn has the highest flattening(ellipticity) which is 0.09796. So, it makes Saturn with the largest equatorial bulge as a planet and as such Saturn is the flattest planet. However, I ...
221 views

### Why don't scientists believe Earth's surface water came up from the mantle?

I read, periodically, that there is more water trapped in the mantle than there is in the oceans - possibly a lot more. If so, why don't any geologists believe that Earth's surface and near-surface ...
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### Why can't a half-illuminated planet support life at all?

Here is my own translation of the Polish version of the Drake equation article in Wikipedia: (...) They must provide the right amount of heat. The smaller the star, the less heat it gives off and the ...
1 vote
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### Is the magnetic permeability (mu_0) necessary in the expression for planetary magnetic field?

To numerically analyse the Lorentz effect due to the magnetic field, say, radial component on a charge particles which of the expression would be correct, \$\{ B_r = \frac{2R}{r^3} g_1^0 \cos(\theta) \}...
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### When did Venus get as hot as it is now?

My previous question turned out to not ask the question I thought I was asking. I have read that Venus began its heating-up around 700-750 million years ago. When did the Venusian atmosphere get ...
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### When did Venus reach approximate radiation equilibrium?

I have read that Venus is roughly at radiation equilibrium - that is, heat out is approximately equal to heat in. I have also read that Venus began its heating-up around 700-750 million years ago. My ...
1 vote
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### Does the Sun have different unique orbits around barycenters?

After reading this question and seeing its image I thought about this question I'm going to publish. Does the Sun have different unique orbits around the barycenter for its multiple planets? If yes, ...
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### Moons with synchronous rotation in our solar system

Are all moons in our solar system rotating synchronously around their planet? If not, what are the criteria that some do and some don't? Many thanks for any insights!
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### When did astronomy first discover that the stars are bigger than the moon?

We take it for granted these days that the stars are bigger than the planets and the moons. But when you look at the sky, it does not appear this way. The Moon looks bigger and brighter than the stars....
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### What is the long term fate of the gas giants?

If I'm not mistaken, it is believed that the reason for such turbulent weather on the 4 outer gas giant planets is that the internal pressure is so great that it is generating heat, which is causing ...
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### If an orbit is shifting due to orbital precession, is it still a Keplerian orbit?

I was thinking about orbits a few days ago, and realized that orbits shift/precess naturally. Given that a two-body problem with a star and a planet, if the planet has an eccentric orbit that ...
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### How common for all 7 planets to be above the horizon?

I was planning for the Solar Eclipse in April 8th 2024 and noticed that at the time of totality at my location in Western NY, all 7 planets will be above the horizon. Earlier in the day it's all of ...