Questions tagged [formation]

Questions about the dynamical processes leading to the assembling of a celestial object.

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Besides Luna, are there any models of how moons become spherical and round?

Question Given the theorized exceptional formation of Luna, (Giant-impact Hyphothesis, Wikipedia), are there any similar animated models of how the other, much smaller, moons in our solar system ...
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Explanation for Planck 2018 temperature fluctuations strongest peaks

As it can be seen from Plank 2018 Cosmic Microwave Background temperature fluctuations data- There are 3 sharp peaks at multipole expansions $\ell \approx 250, 550, 800 $. Also as multipole expansion ...
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If Theia did collide with Earth, would it have produced rings? If so, would we expect to still see at least some remnants today?

Before I get into the actual question, I'll just specify two things: Few billion years ago, a planet as big as Mars named Theia, is hypothesized to have crashed into the Earth, leading to the ...
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How do bars form in barred spiral galaxies?

I am aware this duplicate question exists, but its only answer is unfortunately a rather unsatisfying quote which I could not even find within the provided link. Also, that question is from 2017 so ...
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About the formation of ultra diffuse galaxies (UDGs), what are "failed L∗ galaxies"?

Recent studies show that ultra diffuse galaxies or UDGs were formed by tidally disturbed dwarf galaxies and failed L∗ galaxies. So I've been searching for the failed L∗ galaxies but can't find what it ...
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Why is Mercury's Density So Low?

I know the title sounds odd. You might be thinking "Doesn't Mercury have the highest uncompressed density of any terrestrial planet? Much higher than a planet its size normally should have?&...
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Relation between absolute magnitude of UV and star formation rate

I surfed the internet and searched a lot of sites, so far I got this but unable to find the formula which relates only Muv and the Ψ as I don't know the value of parameters Auv and μ(z). If there ...
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How has the average distance between asteroids in the asteroid belt changed over time?

Just about every webpage related to asteroids states that, on average, asteroids are about 600,000 miles apart from one another. Have planetary scientists hazarded a guess at how close they might ...
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What is the "hypothesized lower mass gap" between 2.5 and 5 solar masses?

Searching here for "mass gap" yields nothing yet. Penn State's Black hole or neutron star? LIGO-Virgo scientists find mystery object in 'mass gap' begins: When the most massive stars die, ...
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How do disk-shaped galaxies then form at the sites of spherical galactic halos? Do the halo stars start orbiting or just sit in place?

Phys.org's Astronomers detect large amounts of oxygen in ancient star's atmosphere mentions "Stars like J0815+4729 are referred to as halo stars," explained UC San Diego astrophysicist Adam ...
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Are all satellites thought to be the result of collisions with the planets?

The leading hypothesis for how the Moon was formed was that another object collided with the Earth, throwing off a large lump of matter which formed into the moon. Is this thought to be the case with ...
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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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Who discovered the relation between CMB fluctuations and large-scale structure formation?

I haven't been able to find a reference to the first who showed that the small density fluctuations in the cosmic microwave background led to the formation of large scale structure as we know it.
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Are all impact craters circular?

I'm aware for over 100 years the reason has been known how impact craters are almost always circular, but my question really is has there been any recent insights in the area? What other topologies ...
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How is the bar formed in a Barred-Spiral galaxy?

How does the bar in a barred spiral galaxy form? What prevents it from being spirals all the way down like water spiralling down a plughole?
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Group of satellite like objects moving through the sky in a formation [closed]

This evening while siting in the garden I saw an unusual group of light objects in the sky. On their own each of the 5 objects would look like a satellite and I would not give it a second thought. ...
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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 ...
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What factors influence the Widmanstätten pattern in iron meteorites?

The cores of iron meteorites exhibit beautiful Widmanstätten patterns, as shown below in the Alvord meteorite (photo by Jim H): I understand these patterns form when the molten nickel-iron core of ...
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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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What are the implications if the Sun was formed in a warm nebula?

Molecular oxygen O2 has been found on comet 67P/C-G in a ratio of 3.8% to water, which is much higher than expected. An explanation proposed is that the Solar System formed from a molecular cloud ...
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How did the moon's orbit become eccentric?

The Moon's orbit is more eccentric, 0.0549, than most planets. I can understand that planets get eccentric by disturbing each other like under the late heavy bombardment. And likewise for multiple ...
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Is there some upper limit in the moon size distribution?

The planets range hugely in sizes, Jupiter is more than 300 times as massive as Earth. But the sizes of the large moons seem to be uncorrelated with the sizes of the planets they orbit. Why doesn't ...
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Accidental or deliberate? [duplicate]

We know that the visual size of the Sun and Moon from the Earth in our lifetime (!) is nearly equivalent. Now my question: Is this event is random? Or have a scientific reason? For example, maybe ...
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Is there a mechanism that makes small moons more rounded than comets?

67P/Churyumov–Gerasimenko has a highly irregular dumbbell shape. But the sample of comet shapes observed is very small, so I wonder if irregular shape is the norm for comets and for small moons. Many ...
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How are boulders formed on asteroids?

For example: Are they soft landed meteorites? Or do they form from melted material during a violent impact? Or are they the result of some kind of erosion process?
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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 ...
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Why do comets come from our local Oort cloud instead of from interstellar sources?

Comets form where stars form. And they are then ejected by the orbital changes of giant planets. But why are they ejected to form specifically a local Oort cloud instead of going interstellar and ...
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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 ?
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Evidence behind Giant Impact hypthesis

The giant impact hypothesis is a theory to explain how the moon was formed. What evidence is there that supports the theory and led us to find the current theory?
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Milky Way Formation

Is the Milky Way a collection of merged galaxies, or has it only been one galaxy that was created from the interstellar media?
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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 ...
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Why do some celestial bodies have atmospheres, and not others?

Question is rather self-explanatory. An answer touching upon how/why atmospheres are formed in the first place would be ideal as well. An example of such astral bodies would be The Earth and it's moon....
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Do origin theories imagine each planet to first orbit the Sun very irregularly before stabilizing?

What I was wondering is that, for example, toss a few balls into zero gravity space randomly, what would be the steady state motion? Would not all the balls go on weird directions and undergo ...
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In the end what is the ultimate matter/element in the universe, due to fusion process in stars?

We know that, in stars, hydrogen is used by the stars and due to the fusion in two hydrogen elements we get helium -> Carbon -> Oxygen ->Other elements -> Iron -> then Super/Hypernova. If everywhere ...
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The reason behind Big Bang

It always amuse us to research about things around us and we always start our research with a question that - what must be the reason for happening of that phenomenon? As we know that the formation ...
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If galaxies are moving away from each other then why are the Milky Way and Andromeda galaxy coming towards each other?

The Andromeda Galaxy is approaching the Milky Way at about 684000 mi/hours, making it one of the few blueshifted galaxies. The Andromeda Galaxy and the Milky Way are thus expected to collide in about ...
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Will Saturn's rings become a moon?

Planets form from disks of matter orbiting around a star; some moons form from disks of matter orbiting planets. If this were going to happen around Saturn, approximately how much time would it take?
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Mechanisms of binary/multiple star formation

What are mechanisms of binary/multiple star formation in different mass ranges (low, intermediate and high stellar masses)?
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Where is all the antimatter?

The universe supposedly started off with equal parts matter and antimatter and they are said to annihilate each other. Also, nature is famous for it's balance between everything. So all we see is ...
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The life course for a massive star from birth to death using the HR Diagram

Could you explain to me the life course for a massive star (30-40 solar masses) from birth to death using the HR Diagram (by showing key events in its life)?
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What are the current accepted theories of the formation of the Uranian moon Miranda?

Miranda, a moon of Uranus is unique in that it has a very fractured surface Source: University of Oregon The surface is said to be jagged and fractured, with comparatively large disjointed cliffs ...
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2 answers
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What is radiation pressure and how does it prevent a star from forming?

This is a follow up to: Is there a theoretical maximum size limit for a star? The answer there talks about the radiation pressure preventing a star from forming. What reaction is causing this ...
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8 votes
1 answer
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What does observational evidence say about the number of protoplanets believed to exist in the early solar system?

Currently, the solar system has 8 major planets, a handful of dwarf planets and a plethora of asteroids, comets and natural debris, and of course, a rather locally dominant star (the Sun). There are ...
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47 votes
7 answers
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What is in the center of the universe?

If the universe has formed & originated by a Big Bang Explosion, then there must be empty space left in the center of the explosion site, as all the matter is travelling at tremendous speeds away ...
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What theories are there in explaining the formation of the Pluto-Charon system?

After reading the question and answer to Effect of Charon on Pluto, a further question is this: how is the Pluto-Charon relationship explained? Specifically, what theories are there in how did the ...
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1 answer
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How long does it take to produce a star? Why does it take that long?

I wonder, why stars take a really long time to become stars? Is it because it needs to gain mass? Or heat up? Something like that? And could it be sped up at all?
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