Questions tagged [planetary-formation]

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

Filter by
Sorted by
Tagged with
20
votes
2answers
2k views

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.....
20
votes
1answer
4k views

How did Mars come to have a 24 hour 39 minute day?

Mercury rotates three times for every two revolutions around the Sun, apparently due to a gravitational resonance with the Sun.Venus takes about 225 days to rotate, and rotates in the opposite ...
15
votes
2answers
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, ...
13
votes
4answers
2k views

How did the Earth come to be in orbit around the sun?

I'm not sure if this post should be in the physics subject forum, but this seems to fit here too. I have been reading a book about chemistry and how the universe came to be with the theory of stars ...
13
votes
2answers
1k views

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, ...
13
votes
2answers
303 views

Can protoplanetary disks form main-sequence stars?

As has been pointed out by @Envite in the context of a more general discussion (see Generalised planets?), there seems to be a moderate possibility for protoplanetary discs forming main-sequence stars ...
12
votes
1answer
390 views

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 ...
11
votes
2answers
341 views

What's the distinction between “planetary formation mechanisms” and “gravitational collapse”?

As I was curious about the exact identical comment to my title here: https://astronomy.stackexchange.com/a/16135/10102 And as it seems no one asked it yet, I'm simply interested in the difference of ...
11
votes
1answer
594 views

Why haven't asteroid belts turned into new large bodies?

If gravitation (attraction of mass) is the cause of the formation of all celestial bodies then how come the numerous small bodies found in asteroid belts spread over an orbit instead of clustering ...
10
votes
3answers
304 views

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 ...
10
votes
3answers
574 views

Why don't we have in-between planets?

The planets in our system are most often grouped into two categories: Terrestrial: Mercury Venus Earth Mars Gas Giants: Jupiter Saturn Uranus Neptune Why is it that we don't see "in-between" ...
10
votes
1answer
201 views

What could be the possible origin of boron found in the Martian soil if not from ancient groundwater?

In a recent observation reported in the ScienceAlert article 'Boron has been detected on Mars for the first time" reporting that The Curiosity rover has found boron on the surface of Mars, ...
10
votes
0answers
69 views

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 ...
9
votes
4answers
633 views

Why do planets tend to rotate in the same direction although they have formed from tumbling asteroids?

The axial tilts of asteroids seem to vary randomly (let me know if this premise is wrong), while the planets have a strong tendency to rotate in the same way. If planets were formed by colliding ...
9
votes
2answers
3k views

Why Only Saturn Has Visible Rings

It may be surprising to know that all four giants in our solar system have rings orbiting around them. Yet only Saturn has a system of rings visible to the naked eye. Why is that? What's so ...
9
votes
1answer
196 views

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 ...
9
votes
1answer
273 views

What's special about Saturn that it has distinctive rings?

This may overlap with other questions, but I'm asking what is unique about Saturn in location, properties, etc that is has far more pronounced rings? It's between Jupiter and Uranus and Neptune in ...
8
votes
2answers
191 views

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 ...
8
votes
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 ...
8
votes
1answer
207 views

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....
8
votes
1answer
245 views

Orbital resonances and position of planets

I am interested in quick generation of planetary systems for programs similar to Space Engine or Pioneer Space Simulator. As far as I understand, formation of planets is a complex process and the ...
8
votes
1answer
313 views

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 ...
7
votes
2answers
2k views

Maximum and minimum gas giant & ice giant densities

I'm working on a star system generator for a game; I'd like its results to be plausible but they needn't be super-realistic. I've got the orbital distances and masses of each body in the system, and ...
7
votes
1answer
235 views

How close can planets form to one another?

With the NASA announcement today regarding the discovery of a system containing seven earth-sized planets (3 within the habitable zone), I wondered about the seemingly crowded conditions. What ...
7
votes
1answer
191 views

Is there any way a planet could form independent of a star?

I just recently heard that there are currently no theoretical models that support planet formation without a star, but I can't remember where. So, I thought I would request all of your expertises. ...
6
votes
1answer
229 views

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 ...
6
votes
1answer
131 views

Do planets migrate suddenly or gradually?

Current models of the configurations of the planets conclude that Neptune once migrated outwards. AFAIK this refurbishment came about by Jupiter and Saturn gradually getting into and leaving a ...
6
votes
2answers
298 views

Do most planetary systems have fewer planets than the solar system?

It is my impression that most planetary systems have, at most, three to four planets. Is that real? Or is it just that we lack the ability to detect most planets?
6
votes
1answer
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 ...
6
votes
1answer
127 views

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 ...
6
votes
1answer
407 views

What is the origin of the dust near the sun?

In this question I asked about the Solar Probe Plus mission. Reading a 2008 report I saw that there is an elevated exposure to high velocity dust near the sun. I understand the high velocity, anything ...
6
votes
1answer
127 views

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. ...
6
votes
1answer
311 views

How can you determine the initial volume of a planet's atmosphere?

Since the surface pressure of a planet is determined by the mass of the column of gasses above it one would surmise that to determine the pressure you must know the volume and mass of the atmosphere. ...
6
votes
1answer
362 views

Lack of planets in the Oort Cloud

With the current news about the possibility of a planet in the Oort cloud, I was thinking, why is the matter in the Oort cloud distributed so? It makes sense that inside the planet region there is not ...
6
votes
1answer
315 views

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 ...
5
votes
1answer
123 views

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 ...
5
votes
2answers
688 views

How large (that is, radius) could a planet be?

I know that normal planets don't get any larger than Jupiter (or 2 Jupiter radii if hot), as adding more gas just increases density, not radius, until you reach the point of being a brown dwarf star. ...
5
votes
2answers
214 views

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 ...
5
votes
4answers
330 views

Generalised planets?

There is somewhat of an abstract way of generalising the notion of planets. Standard definition of planets is, obviously: "planets are the objects formed from the residual material surrounding a ...
5
votes
1answer
139 views

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 ...
5
votes
1answer
406 views

Why do rocky planets form?

When a star system forms from a cloud of gas and dust, why doesn't the dust migrate towards the centre of gravity with the gas to form a star? Why does dust in the accretion disk aggregate to form ...
5
votes
1answer
67 views

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 ...
5
votes
3answers
1k views

Why, in the Solar System, all the mass seems to be concentrated at the centre?

Is this a consequence of planet formation in accretion disks ?
5
votes
1answer
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 ...
5
votes
3answers
123 views

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 ...
5
votes
1answer
210 views

What stabilizes rings or accretion disks?

We think, more or less, that our Moon was formed from an accretion disk caused by a Mars-sized impactor. Cool. Tidal forces can break apart a moon, causing rings. Ashes to ashes, dust to dust: the ...
5
votes
1answer
334 views

Formation of “hot Jupiters” before star ignition

I'm watching a BBC special on the formation of solar systems, and they're covering the topic of "hot Jupiters" that exist near their host stars. The prevailing theory, according to this 2015 special, ...
4
votes
1answer
148 views

Is there any theoretical or empirical research about planetary systems with a black hole in their center?

I assume such a system would be hard to detect due to a lack of radiation, at least if the vicinity of the black hole does not contain a lot of mass which falls into it over time, thus creating (a lot ...
4
votes
1answer
133 views

Star System Formation questions

I'm making a game in which I'd like to randomly generate star systems. Which is cool. The trouble I'm having is working out exactly what limits I need to place on the generation. So far, the ...
4
votes
1answer
67 views

How do proto-planetary nebulae gain momentum?

currently I am curious about proto-planetary nebulae. At first I was curious about how planets spin but I read in a couple of articles that they got their spin from when they were in a proto-planetary ...