# 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.

49 questions with no upvoted or accepted answers
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### How was the axial tilt of planets measured?

https://en.wikipedia.org/wiki/Axial_tilt#Solar_System_bodies gives the axial tilt of all planets with two decimal precision, but how and when were they measured so precisely ? I guess it's "easy&...
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### Can mean motion resonances make orbits more unstable rather than more stable?

This paper on closely packed orbit simulation seems to suggest that having the planets in first and second order resonances decreases the time till orbits cross each other. I'd got the impression that ...
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### Kepler - Creating the Ellipse (Astronomia Nova)

In Chapter 58 in Astronomia Nova, Kepler made his final step to finally create the ellipse (for the orbit of planets) http://science.larouchepac.com/kepler/newastronomy/part4/58/index.html In the ...
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### Calculating the radial tidal amplitude on a planet from the fluid Love numbers

How do you calculate tidal amplitudes from the fluid Love numbers? In my course on planetary physics I saw an approximate expression for the displacement from equilibrium tide: \Big|\frac{V_T}{g}\...
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### Why do degenerate objects get hotter as more mass is added?

After reading this question, I decided to post a question about degeneracy. I've seen simulations on large, $15\text{+ }M_J$ objects that are accreting mass. They do not grow in radius, instead they ...
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### Help identifying a very slow-moving object during meteor shower photography

I just wonder if anyone could shed any light on this puzzle. Two nights ago whilst I was out photographing the Lyrids meteor shower from the UK something else showed up on my images when I checked ...
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### How to distinguish primary hosts (stars) and orbiting satellites (planets) and tertiary bodies (moons) by their mass and trajectory?

Suppose one has run a gravitational simulation of N bodies (has the mass, vector positions, vector velocities, etc for each body), but knows nothing a priori about ...
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### What is the theoretical maximum variability a pulsating red giant can have such that a habitable planet can stay habitable for long periods of time?

I was reading about red giants and came across this statement: Some research suggests that, during the evolution of a 1 M☉ star along the red-giant branch, it could harbor a habitable zone for ...
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### New method for exoplanet detection based on iridescence?

Could it be possible to detect exoplanets that have an abundance of iridescent minerals by analyzing their star's spectra over time as the angle in observation would lead to changes in absorbed ...
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### Simulating oceans and ice sheets on other planets or moons?

From my friends in geosciences I learned a lot about General Circulation Models (GCMs) (for Earth's atmosphere and oceans). I also learned about ice sheet models for floating ice (like sea ice or ...
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### How quickly do planetary rings form?

Just a very general question, but I haven't seen this discussed elsewhere. If a moon gets busted up for some reason, say a collision with another moon, and is at the right orbital distance from its ...
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### Average effect of a planet on a comet

I'm considering a problem involving star S, planet A, and a comet B. The orbits of the planet and comet are eccentric, with eccentricities $e_A$ and $e_B$. I'm trying to calculate the average change ...
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### Intrasolar planetary surface temperature change divergence from Earth

Considering the vast amount of insulating gas emitted by human activity on Earth without a coincident release on all other planets in the solar system as well as the phenomenon that planets in a solar ...
1answer
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### Are the planets Mercury, Saturn, Uranus and Neptune losing mass?

My understanding is that Venus, Earth, Mars, and Jupiter are all losing mass due to their gravity, temperature, and the solar wind. But what about Mercury, Saturn, Uranus, and Neptune? Mercury has a ...
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### Frequency of planet masses in any given star system?

This question is a follow-up to the expected distribution of planet masses in a given system. I am wondering, what is the distribution of various planet masses in any given system? I am expecting a ...
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### Precision of orbital period of exoplanets vs solar system planets (Extrasolar Planets Encyclopedia)

I noticed that the Extrasolar Planets Encyclopedia lists the orbital period of L 98-59 b in days to 7 decimal places. Can astronomers really measure orbital period of exoplanets to greater precision ...
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### Would Atlas Pro's prediction about the color of plant in Kepler-186F work as a biosignature to search for life?

The Atlas Pro video that prompted this question is this. Tl;dr: it is argued that due to the different spectrum of radiation emitted by Kepler-186 and what is known about the evolution of ...
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### Regarding core fragmentation of a gas giant in the envelope of a red giant

We know that large gas giants, such as Jupiter, have degenerate cores. Let's say there is a hot Jupiter ($5M_J$) that orbits an F-type star. When the star expands into a red giant, the hot Jupiter's ...
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### How big can an object get before its core becomes degenerate?

I am wondering, what is the most massive object we know of that does not have a degenerate core, and what is the least massive object that does have a degenerate code? We know that Jupiter has a core ...
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### Abundance of penitente ice formations in the solar system

When researching for my question on extraterresitral snow, I learned about a rare snow formation called penitente which seems to be found on various (dwarf) planets, like Earth, Mars, and Pluto. ...
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### How to calculate the limb darkening $\mu$ value

I am reading about limb darkening and I am very confused how to find the value of $\mu$. It states it can be found by $\mu = \cos(\gamma)$, but I am lost how $\gamma$ is found, or what it represents. ...
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### How to find the temperature of a planet accounting for the atmosphere?

Recently, I started writing a program to generate star systems, and I need a formula to find the approximate surface temperature of a planet. I know of several formulas for this, for example this one ...
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### Software apps for calculating distances between planets

Are there somewhere any software apps for calculating distances between any planets in our solar system?
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### Do retrograde spin-orbit resonances exist?

The end state of rotation of an initially fast-spinning prograde terrestrial planet (in the absence of additional forcings such as "thermal tides" in an atmosphere, e.g. Venus) is a spin-...
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### Identify moving object in the sky at night?

Last night in the Carribean, I was looking at the sky at about 8PM EST, and I noticed this really tiny object moving pretty fast from left to right, just between the two stars in the photo. It's very ...
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### Calculating the position angle of the moon (the rolling back and forth)

I have been watching the the NASA Moon Phases Video of the year 2020. Pretty much everything makes sense and I know how to calculate it including the moon phases, declination, azimuth, apogee and ...
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### What is the radial dependence of the density of Jupiter or Saturn?

Can anyone point me to the reference where I can find the density of Jupiter or Saturn as a function of the distance from its center?
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### Frequency of Earth type cores?

I've read many interesting threads concerning the composition of different planet cores in the solar system while trying to see if this question has already been asked. It appears as if Earth is ...
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### Why does the axial tilt & the rotation speed of Saturn & Jupiter vary so much?

I have seen Jupiter and its 4 largest moons in a telescope, several times. The moons are always aligned in a line. This is fine. Very interesting. But.. in case of Saturn, not only that we can see its ...
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### How to calculate the orbits of Neptune and Pluto based on the orbits of Uranus and Neptune respectively?

I get the below from Neptune and Pluto. In 1821, Alexis Bouvard published astronomical tables of the orbit of Neptune's neighbour Uranus.[22] Subsequent observations revealed substantial deviations ...
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### The path of the planets on the celestial sphere

I know that planets have a "wandering" movement on the celestial sphere. I also know that their period around the Sun vary largely as compared with the period of the Earth (one sidereal year), ...
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### When does oscillation of interplanetary plasma occurs?

When does oscillation of interplanetary plasma occur? When and what are the reasons of the excitation of this plasma that makes it oscillate? Does it oscillate when is not excited? Can extremely ...
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### 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 ...
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### Will a solidifying core inside a planet affect its appearance?

In this question it is said that Mars once had a liquid core that solidified. If the liquid has a smaller density than the solid, will this affect the outer parts of the planets? For example, if the ...
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### How likely are triple planet systems?

Is it likely to ever discover three planets of similar mass revolving around a common barycenter, or would such a system be too unstable? Such triple planet system would look like a triangle once in a ...
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### North Stars of each Solar system planet?

What are the North Stars of each individual body points too? E.g. Earth points to Polaris. Mars points to Deneb/Alpha Cygni. What about Sun, Mercury, Venus, Moon, Jupiter, Saturn, Uranus, Neptune, ...
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### Do the orbits of planets change? Where is the data for this?

Everything in the space is moving all the time. Do the orbit of major Solar Systems planets, Mercury to Saturn change? Just like Moon's orbit around Earth changes. How often, how small or big is the ...
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### Equilibrium Temperature for Extremely Cold Planets: Incorporating the CMB and Intrinsic Radiation

I want to check if I'm doing this right. I'm computing the equilibrium temperature for planets where the CMB and/or the planet's intrinsic radiation (as in weakly radiating jovians) matters. I start ...
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### Positions of planets before Christ?

All the solar system simulations I've come across showing the positions of planets only show the positions in a certain time period, at beginning of the first millenium the earliest. There was just ...
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### Is there a useful measure of how "life-dominated" a planet is?

If life exists on Mars or Venus, then in contrast to life on Earth, it must be "just scraping by". I can imagine a few ways to quantify this: Life on Mars or Venus is hard to detect -- any ...
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### Historic observational data - position of the planets

Is there an online source where historic observational data regarding the position of the planets can be found? I was always intrigued by the fact that Neptune was mathematically predicted before it ...
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### To show perihelion precession motion of Mercury in Python with matplotlib

I'm trying to make it more general code so I can trace even a parabola or hyperbola for $e=1, E=0$ and $e>1, E>0$ respectively. And after achieving that general code I want to make the same code ...
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### What is the most mass that matter likely to form?

If we plot graph between accumulate of forming mass (y-axis) and mass (x-axis), where is the maximum ? There is a story how I get this question. It start when I think about question "Is our sun is ...
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### Celestron NexStar 130 SLT Computerized Telescope GoTo Not Accurate

I am trying to use a Celestron NexStar 130 SLT Computerized Telescope, but I am not able to use the GoTo function. I do the three start alignment, it confirms matches, I make sure the level is ...
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### Could a planet be toss from a galaxy just like it's theorized rogue stars are?

According to this, https://en.wikipedia.org/wiki/Intergalactic_star Rogue stars are theorized to be the intergalactic space because of this, The way these stars arise is still a mystery, but the ...
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### Longest and Shortest day of the year in all planets

Can we trace the longest and shortest day of the year in other planets of Solar system similar to earth planet i.e. Mars, Saturn, Venus, Jupiter, Mercury, Neptune, Uranus?
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### Converting Invariable plane to J2000 ecliptic

I've been following the answer given by Mike G here: How to calculate the orientation of planets at current epoch to get planets to have the correct orientation in my program, but all the angles are ...
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### Astronomical events and Celebrations

In the past people celebrated important astronomical events and some of those events are still celebrated in some cultures and traditions. For example: March/September equinox, New Moon, Winter/...
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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 ...