Questions tagged [planetary-formation]

Questions about the processes, theories and evidence for the formation of planetary bodies.

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8
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1answer
132 views

How likely are planets to form after neutron star collisions?

It is well known that planetary collisions can create moons orbiting the result of the merger if they happen in the correct way, and this is how the Earth's moon is believed to have been formed. See ...
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Could rocks from Earth have reached the Kuiper belt, or Neptune at least? If so, how?

This answer (currently edit 3) to How certain are we that we have not sent life to other planets/moons? begins: First of all, rocks from Earth are probably just about everywhere in the Solar System. ...
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Can the order of planets change in a young planetary system?

The Nice model and the Grand Tack model both show that the distance between a planet and its host star can change greatly over time. Is it possible in either of these models for the order of planets ...
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Are all the planets differentiated?

The Earth is differentiated, as it has a distinguishable core, mantle and crust with different compositions and densities. Are all the other planets differentiated as well?
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What's the critical mass of a rocky planet before its gravity traps enough gas in its atmosphere to start becoming a gassy planet

Looking at the latest theories, I've noticed that most rocky planets are below a certain mass range. I speculate that maybe the way gas giants and gas dwarfs form is a rocky planet during the ...
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What's the exact story of jupiter and our earth, not becoming a super-earth?

I've been watching the Cosmos documentaries by Neil DeGrass Tyson and the ones from Brian Cox, and in one episode (I don't remember from which series) there's something about the creation of the rocky ...
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Why is there so little nitrogen in the Martian and Venusian atmospheres?

Why don't our neighbors have much nitrogen? You would think that, without 'nitrogen-fixing' organisms and such, there might be more.....
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110 views

Are there other planetary systems where gas giants are on the inside to rocky planet orbits?

I understand that formation theories for gas giants suggest they should be born further away where there is more gas for them to monopolize vs the sun, and then to form Hot Jupiters they need to ...
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Was the solar system flat before the planets formed? Or does the Kozai-Lidov mechanism flatten orbits after the gas giants form?

An astronomer living on Jupiter measures the orbits of the inner planets against Jupiter's ecliptic. Their inclinations are; Mercury 5.7 deg. Venus 2.1 deg. Earth 1.3 deg. Mars 0.6 deg. It looks ...
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Composition of ice giants

After reading the paper "The Measured Compositions of Uranus and Neptune from their Formation on the CO Ice Line", I was left with doubts which I would like to clarify. Firstly, the paper proposes ...
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Is there any thing special with an axial tilt of roughly 25°?

Half of the planets in the solar system have an axial tilt of $25.5\pm 3^\circ$: earth (23.5°), mars (25.3°), saturn (26.7°) and neptune (28.3°). If random collisions in the early solar system caused ...
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Binary stars and gas giant formation

Say there's a young s-type binary star system with 2 Sun-like stars. From what I understand for a stable orbit to be possible, a planet's farthest orbital point from its host star has to be around 1/5 ...
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112 views

Is this a potential planetary setup for the Alpha Centauri System?

I originally posted this on the World Building SE, but I was suggested to post it here for a better answer. I am attempting to create a [semi]plausible star system in Alpha Centauri for a series. The ...
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77 views

Why does half of a planet's radius end up being the radius of the core?

This answer makes the assumption that the ratio between the radius of a planet and the radius of its core is roughly constant shortly after planetary formation. Why should this be the case? Do we know ...
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The compatibility of the Grand Tack hypothesis with the “core-warping impact” theory of Jupiter's diffuse core

In recent years, the Juno mission revealed that Jupiter's core was much more diffuse than astronomers had expected. One theory is that "within a few million years" of its formation, Jupiter ...
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Binary planet orbital distance

From reading various sources online, I see that some people talk about binary planets in very tight orbits (around 1 or 2 planet radii). I am wondering if it is possible for a binary planet (Double ...
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Is it only possible to look at solar systems with stars at least as old as ours to be able to find intelligent life?

Assuming the speed it takes to development intelligent life is the same in all solar systems, would we need to look at exoplanets with stars as old or older than ours to find intelligent life? A young ...
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896 views

Is the Moon not in hydrostatic equilibrium?

Given the recently-announced observations from VLT/SPHERE that 10 Hygiea may be sufficiently round to qualify as the second main-belt dwarf planet, I found myself perusing Wikipedia's Hydrostatic ...
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How can an accretion disk form around the central star of a planetary nebula?

I was reading the 2012 paper A tidally destructed massive planet as the progenitor of the two light planets around the sdB star KIC 05807616 about the possible origin of two exoplanets that orbit a ...
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466 views

Characteristics of the first planets in the Universe?

What would have the very first planets looked like, based on their most likely chemical compositions? For example: Were they mostly grey gas giants with atmospheres of hydrogen and helium, ...
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Why is a giant planet around a tiny star unusual when binary stars are normal?

Inspired by this BBC article and the corresponding journal article about the M dwarf star GJ 3512. The Jupiter-like world is unusually large compared with its host star, contradicting a widely held ...
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Exoplanets, Protoplanets, and planetesimals

So, most of the mass of the solar system (that isn't inside the sun) is inside Jupiter. And most of whats left after THAT is inside Saturn. So, all the rocky planets, moons, and asteroids in our solar ...
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Are there any openly available simulators describing how planets form from protoplanetary disk?

Out of pure interest, I wonder whether there are existing open-source simulators that can simulate the formation of stars and planets from a protostar and the surrounding protoplanetary disk?
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Are there any simulations of the Grand tack?

The BBC program with Brian Cox "The Planets" involved some description of the Grand Tack hypothesis to explain the current state of the solar system. This theory has Jupiter wandering through the ...
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141 views

How thick was Earth's primordial atmosphere?

Earth's first atmosphere was made of hydrogen and helium accumulated before fusion started in the Sun. As soon as this happened it was stripped away by the Sun. How many atm of hydrogen and helium had ...
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Did Io start out as an icemoon?

Looking at the big moons of the outer solar system a clear pattern can be seen. Thick icey surface layers covering rocky mantles and deep down metallic cores. The only outlier is Io as it has no icey, ...
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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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Does any asteroid we have ever seen have a hot core like earth.?

I was wondering if any of the asteroids we have ever seen has a hot core like Earth's. I'm thinking that Earth has a strong gravitational field and so formation would have involved a lot of ...
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Could a planet form without a molten state?

Based on what I know, the Earth accreted out of the solar nebula, had a period when it was entirely molten, and then slowly cooled. Could a planet form without ever passing through a molten phase?
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How can it be known that Venus does not have plate tectonics?

This answer provides some insight into Venus' surface geology: Water may be necessary as a lubricant for plate tectonics. Whether or not this is the case, Venus does not have plate tectonics. It ...
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Why do planets and satellites in the Solar system look so wildly different if they came from more or less the same matter?

First, the planets. We have Mercury, which is rocky, no atmosphere. But then we have Venus, which is completely different: thick atmosphere, very hot, geologically active. Then Earth - blue, full of ...
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Can a frost line exist around a protoplanet?

The Frost line is the border that marks where volatiles such as water, methane, ammonia, etc. (commonly referred to as 'ices') are able to condense into solid grains in the protoplanetary disk around ...
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Existence of planets larger than their host star?

The mass region of objects between ~ 0.5 Jupiter masses and 80 Jupiter masses (gas giants through to brown dwarfs and red dwarfs) is typified by an almost flat relationship with object diameter. There ...
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Is Naboo's core possible in real life?

In Star Wars, the planet Naboo has a plasma core, instead of a molten one. Can a planet really have a plasma core?
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Why isn't Ultima Thule spherical, while its two component parts are

The two component parts of the Ultima Thule contact binary are approximately spherical. Why have the same forces that made the two parts spherical when they were separate not made the whole thing ...
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3answers
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What process shaped Ultima Thule?

When I see this picture, I'm trying to understand how these two elements merged together and have two hypothesis : two balls of lava in fusion together two solid rocks fused at their contact point ...
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1answer
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What was earth's mass before the collision with theia?

Assume the "Big Splash" or "Giant Impact" (whichever name you prefer) theory is more or less correct. EDIT: With so many variations of this theory, with so many names and qualifiers on them, such as ...
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Gas Giant temperatures

Sudarsky's gas giant classification predicts the visual appearance of gas giant planets based on their temperatures. But what determines their temperatures in the first place? Is it just the ...
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Moons of migrated giant planets: Icy, Rocky, or none at all?

My understanding is that gas and ice giants form outside the "snow line" of their protoplanetary disk, then sometimes through gravitational interactions they are able to migrate into the inner star ...
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Estimates for “undetectable” planets in extra-solar systems

As far as I've been able to determine, it appears there are some significant limitations on our ability to detect exo-planets that are below certain sizes or beyond certain distances from their stars....
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What is the nature of “rock vapor” in this description of the formation of the Moon?

The NPR News item MacArthur Fellow And Planetary Scientist Sarah Stewart Discusses How The Moon Was Formed and audio podcast begins: Ari Shapiro, Host: Sarah Stewart likes to think about what happens ...
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Can a donut-shape planet or star be formed?

How stable is that configuration and under what conditions such object may form ? Is there any evidence suggesting that such objects might exist ?
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Are rogue planets ever born in isolation?

I'm using the term "rogue planet" here loosely to mean anything of planet-level mass that is not orbiting around a star. Popular discussions of these objects always describe them as forming around a ...
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How was Jupiter formed

Two days ago I went to a mathematics conference where there was a paper presented on Jupiter's formation via the disk-instability model. I know that there are two different theories for the formation ...
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Is there any planet out there which is half gaseous and half rocky ? is this possible?

I have heard many times that this planet is gaseous like jupiter this planet is like super earth like rocky planet etc. so is there any planet which is mix of gase and rock ?
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How did the lighter elements end up in the center of the solar system? Solar System Formation

The previous generation of stars famously are the origin of all the heavier elements (up until iron?) in the solar system. So a big portion of the solar system mass actually is made up of Carbon, ...
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Why are rocky and small planets nearer to the Sun whereas big, gas giants are farther?

Planets, including Mercury, Venus, Earth, and Mars are rocky planets and are small compared to gas giants. And all these planet are near to Sun. But mass is directly proportional to force. So why don'...
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Kuiper belt planet formation

There are a lot of objects of different sizes in the Kuiper belt. Are objects in the Kuiper belt stable? Is there any chance in the future that one of the larger objects would accumulate enough ...
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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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The most feasible hypothesis about Theia

The formation of the Moon had many hypothesis over the years, most of them involving a Mars-sized body called Theia, which presumably collided with the Earth. But even within the Theia hypothesis, is ...