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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How many planets are there in this solar system?
So, in school (that's a long time ago) they have been teaching us there are 9 planets in our solar system.
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
Pluto
But every now and then I keep ...
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Why hasn't the "9th Planet" been detected already?
In the comments to this question, there was considerable doubt placed as to the subject of if the so called "9th planet" really exists. That wasn't really the intent of the previous question, so I ask ...
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9th planet location?
I've seen a number of news reports indicating there is likely a 9th planet in our Solar System, something with an orbital period of between 10k-20k years, that is 10 times Earth's mass. I haven't seen ...
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Why do (most of) the planets rotate counterclockwise, i.e. the same way the Sun does?
Referring to the mechanisms explaining the solar system formation and to the initial rotation of the gaseous cloud that collapsed, I understand easily why the planets orbit the Sun the same way this ...
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Can small gas planets exist?
Most of the known gas planets (Jupiter, Saturn, etc.) are huge. They are even called "gas giants".
is it possible to exist a gas planet around the size of Earth? If yes, why; if no, why?
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Considering our methods of exploration, how likely is it that there are unfound planets (not dwarf planets) in our solar system?
I think it's probably unlikely that there are more planets between Mercury and Mars, but out from Jupiter, there's lots of empty space between the planets. Could there be some small planet hidden out ...
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Why do the planets in our solar system orbit in the same plane?
(Yes I'm excluding Pluto from this the same way it was excluded for not being a planet)
Observing the planets orbit of the Sun they all seem relatively planar and roughly all orbit along the same ...
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Did I see another planet?
A couple days ago, I zoomed in with my 30x optical zoom camera, and after some exposure adjustments, a bright star in the night sky turned into this:
Are those other planets or other stars? Or is ...
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Is it odd that our Sun has so many planets?
The internet is abuzz with the new evidence of the possible ninth planet in our Solar System. With those nine objects, the asteroid belt, the Kuiper belt, and everything else in our Solar System - the ...
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Which planet, viewed from which other planet would appear the largest?
Inspired by this question, I'm curious: Which planet in our solar system, when viewed from which other planet, would appear the largest/brightest? You probably can't really see much of Uranus from ...
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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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Why do the planets orbit in the same direction?
Theoretically, planets would have an approximately equal chance of going one way in their orbit or another but in reality, this is not the case (at least in our solar system). Why is this?
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Does a planet's mass or gravity affect the height of it's mountains?
According to this Wikipedia page, the top five highest mountains on Mars (and the highest on Venus) are all taller than Mount Everest (and Mauna Kea as measured from the ocean floor).
Does a planet's ...
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What makes protoplanetary disks start rotating? (Initial energy needed to rotate)
Planets form from a protoplanetary disk that has been rotating around its star. The initial energy that makes them rotate really matters to me.
Why did the protoplanetary disk start rotating around ...
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Is there a upper limit to the number of planets orbiting a star?
Our sun has 8 planets orbiting as well as a number of dwarf planets. Are there any calculations that hint as to whether this number is close to some theoretical maximum value or are we simply an ...
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Why doesn't the IAU definition of "Planet" disqualify Mercury and Venus as planets?
Here's the IAU definition of a planet (source):
A celestial body that (a) is in orbit around the Sun, (b) has
sufficient mass for its self-gravity to overcome rigid body forces so
that it assumes a ...
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Does this smartphone photo show Mars just below the Sun?
I live in Essex, England (51.7678° N, 0.0878° E). On 25 July 2019 (hottest day ever in the UK, btw), 06:43 BST, I took this smartphone photo of the Sun. Is that white dot just below and left of the ...
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How bright would the sun appear from the hypothetical Planet Nine proposed by Caltech?
Theoretical Planet Nine, proposed by Caltech's Mike Brown and Konstantin Batygin, is said to have a 15-20 thousand year orbit. Approximately how bright would the sun appear from Planet Nine aphelion ...
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Why are orbits elliptical instead of circular?
Why do planets rotate around a star in a specific elliptical orbit with the star at one of it's foci? Why isn't the orbit a circle?
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Hypothetical trans-Neptunian planets orbiting the Sun
The planet HD 106906 b was found at 650 AU from its home star, a star not so different from the Sun. Fomalhaut b is also a young planet that is orbiting very far away from its star.
These two planets ...
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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 ...
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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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Why are most discovered exoplanets heavier than Earth?
Looking at all discovered exoplanets (4393 exoplanets), I found than only 17 of them (less than one percent!) have masses less or equal to Earth's mass. Why so?
Is it because it is very difficult to ...
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Doesn't gravity attract objects in space until they collide?
If the formula to calculate the force of gravity between two objects is:
$$F = GM_1M_2/r^2,$$
why do planets stay in orbit? Or is there another formula at work?
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What are Kepler's laws (as he wrote them)?
There are of course many, many sources that quote Kepler's laws of planetary motion. This is preventing me from finding out what I really want to know: which is - what are Kepler's laws as he wrote ...
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How do you call it when two celestial bodies come as close to each other as they will in their current orbits?
On Earth, we say Mars is in opposition when it is 180º from the Sun, which also marks the times when Mars and Earth come closest to each other.
Is there a specific name for such proximity events? For ...
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How many undiscovered planets might be in our solar system?
Some people talk about the possibility of a planet 9. Could there be a planet 10 or 11? How many undiscovered planets could there be in our solar system?
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What physical features determine if a planet is a major, minor or dwarf planet?
Like many, when I was growing up, we always were taught, hence always learned that there were 9 planets. However, recently, decisions were made and all of a sudden there were 8 major planets and a ...
user8
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How do/did we figure out that planets move in orbits?
I've learned that planets move in orbits around the Sun, but I really don't know how I would come to this conclusion myself. I've only seen planets in the sky a couple times (knowingly), and I am ...
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Could the 9th planet be virtual?
Astronomers recently claim that there is evidence for a 9th planet. As far as I understood it, this is mainly based on coinciding orbital parameters of a few Kuiper belt objects.
Could the 9th planet ...
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Moon orbits crossing each other
Some planets, such as Mars, have 2 or more moons. Giants, like Jupiter of Saturn have a lot of moons!
How likely the orbit of one crosses another one's orbit? Is it possible for two moons to collide? ...
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How long should it take for us to observationally determine if Caltech's Planet Nine is really there?
Caltech just released a report that says there is possibly a large (10 earth mass) planet in a remote orbit (10 - 20 thousand year) that explains a lot of observations of Kuiper Belt objects. How long ...
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How did scientists determine an estimate of the number of planets greater than Sedna's size to exist in the Inner Oort Cloud?
In the article, New Dwarf Planet Found at Solar System's Edge, Hints at Possible Faraway 'Planet X' (Wall, 2014) where they report on research and observations performed by astronomers that discovered ...
user2449
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Do celestial objects need to be big to have liquid water on their surfaces?
I mean no asteroid, planetoid that I am aware of has water on its surface. It is way more common to see ice in it. So I figured that the size of the celestial body has something to do with the cycle ...
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If planets are ellipsoids why don't we have 3 diameters?
We know that each ellipsoid has 3 diameters named $2a$, $2b$, and $2c$.
The Earth and all planets, in general, are ellipsoids (Saturn is the best example because it's the most oblate planet in the ...
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Kepler space telescope undetected planets
The Kepler space telescope detects planets based on the dip in brightness caused by planets moving past the star.
Wouldn’t that mean that there are an unknown amount of planets that have an orbit ...
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What reason is there to doubt the existence of the hypothesised planet Tyche in the far distant solar system?
Please note, I do not necessarily believe in its existence, just after a scientific (hence, non-Wikipedia) reasoning to doubt the planet's existence, other than the "we would have seen it" argument. ...
user8
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Can the paper narrowing Solar System's barycentre to within 100m help find Planet Nine?
I've just read this recent news article, Astronomers Have Located The Centre of The Solar System to Within 100 Metres, reporting on a paper[1] that claims narrowing the Solar System barycentre to ...
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Orbital velocity of a planet - why is my calculation off by about 10%?
I am not sure if I am doing something wrong, or misunderstanding Reider and Kenworthy (2016).
I'm just trying to reproduce the orbital velocities listed in Table 1. The second paragraph of Section II ...
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When will all eight planets in our solar system align?
Ignoring expansion of the universe, entropy, decaying orbits, and interference from any bodies colliding with or otherwise interfering with their orbits, will the eight planets known planets in our ...
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Any possibility for life on moons of planets in our Solar System
We all focused on our moon, to find water or life, or any thing related to life. But my question is, is there any chance for life in moons of other planets in our solar system, others have too many ...
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Open problems in astronomy that an amateur (with a PhD in some other field) would have a chance of solving?
What are some open problems in astronomy that an amateur would have a chance of solving? Suppose the amateur has a PhD in some other field, owns a basic telescope, a set of filters, diffraction ...
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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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Do planetary rings have geometric bounds?
Are there any bounds on where a planetary ring can form and maintain orbit relative to the planet?
Do they have to be in a circular equatorial orbit?
Is there a min or max altitude, say with respect ...
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Do the orbits of planets change sometimes?
Do planets sometimes wobble and get off their paths? What if an asteroid were to hit it?
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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 ...
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How would I measure that I'm at a pole?
How would a person measure that he is at a planetary pole? My first inclination is to use a sextant to ensure that the Sun remains at a constant inclination. However, due to the orbit around the Sun ...
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What wavelength to best detect the "9th planet"?
We know that the reflected sunlight will make detecting the 9th planet very difficult in the visible light. Is there another band that will be more likely to detect it? What is the surface temperature ...
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Is there a name for a planet and its moons/satellites?
I'm wondering if there's a name that encapsulates the concept of a planet and the objects that orbit in its gravity. There's a solar system that encapsulates a star and its multiple planets and other ...
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