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.
763
questions
5
votes
1
answer
108
views
Assuming a hypothetical system without gas but only solid rocks, how big of a planet can form through the coalescing of these rocks?
I have heard that gas giants are primarily huge solid bodies like regular rocky planets that exponentially gained more and more gas in their atmosphere through their increase in mass which they use ...
- 503
12
votes
1
answer
227
views
How to measure mass of planets' core from orbit
I am told in an astrophysics lecture the following.
The mass of Saturn's core was measured by Cassini when it completed its final flyby between the rings and the planet itself. It was also found that ...
- 481
3
votes
1
answer
245
views
Why don't we detect planets around OB stars and no terrestrial planets around A or early F stars?
Looking at an exoplanet database, I noticed that there are very few planets detected around main-sequence OBA stars, and most of them are gas giants/brown dwarfs. Why can't we detect low-mass planets ...
- 6,613
2
votes
0
answers
57
views
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 ...
7
votes
4
answers
2k
views
Could an orphan/rogue planet have a moon?
Is there some reason why an orphan or rogue planet wouldn't have a moon? Let's say it started out in a normal system and then just got flung out by an unstable orbit.
Joe Smith
-4
votes
2
answers
86
views
What makes a star? [closed]
What are the properties of a star? How do astronomers classify the properties of stars?
1
vote
1
answer
208
views
Why does Wikipedia state that the Solar System has one unconfirmed planet?
I was looking at exoplanets on Wikipedia, and found this surprising information:
The table states that the Sun has 8 planets (obviously) and one unconfirmed planet. Why is this here? I think it's ...
5
votes
0
answers
91
views
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 ...
3
votes
1
answer
386
views
Synodic Day and Sidereal Day
If given the sidereal day, is it possible to derive the synodic day of Earth? If a derivation is possible, could anyone illustrate it or point me in the right direction?
Wikipedia's Synodic day begins:...
6
votes
1
answer
133
views
Fate of a planet orbiting a Lagrange point behind a star?
Let's say there is a planet orbiting at L5 behind a star, which is in turn orbiting a more massive star, like so:
What is the ultimate fate of this planet? I'm predicting that it will spiral into the ...
5
votes
1
answer
814
views
Can a habitable planet be smaller than 0.58 Earth radii?
According to the below image, the lowest escape velocity a planet can have in order to still be able to retain water on its surface and have a temperature above freezing is 6.5 km/s minimum.
With ...
- 403
4
votes
1
answer
250
views
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, ...
- 555
2
votes
0
answers
133
views
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 ...
- 6,613
2
votes
1
answer
171
views
What will a future cold and "dead" Jupiter look like? [duplicate]
I heard Jupiter is dying like getting smaller. For example, from Guillot et al. 2004 3: The Interior of Jupiter (also here):
(Jupiter)... is still contracting at the rate of ~3 cm per year while its ...
4
votes
1
answer
39
views
How do pressure, temperature, and gravity affect a smaller body than Earth with the same bulk composition?
Earth has a density of about ${\rm 5.513 ~g/cm^3}$ with one Earth radius and one $g$. Venus, a very similar planet to Earth and likely with about the same bulk composition, has a density of about ${\...
- 403
0
votes
1
answer
72
views
If a Jupiter-sized sphere of a translucent liquid were to suddenly appear, what would the inner core consist of? Would the planet refract light?
Assuming Jupiter is suddenly replaced, or if a giant sphere of fruit juice or other translucent mixtures/liquids were to appear bearing a similar radius to that of Jupiter, hypothetically , what would ...
- 503
1
vote
1
answer
163
views
Recently, the most distant object in the solar system was discovered. How was this accomplished?
It was recently announced that the most distant object in our solar system was discovered. This object averages 132 AU from the sun. The object, initially named Farfarout, was estimated to be 400 km ...
- 4,476
6
votes
0
answers
145
views
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&...
- 161
1
vote
0
answers
86
views
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 ...
- 555
8
votes
1
answer
330
views
Feasibility of Grand Tack Hypothesis
Something I've been wondering lately is how much the grand tack hypothesis stands up to present scrutiny. While the grand tack proposes that Jupiter and Saturn were caught in a 3:2 mean-motion ...
- 265
3
votes
0
answers
82
views
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 ...
8
votes
1
answer
560
views
If the fifth gas giant in the early Solar System was completely ejected, where would it be now?
I've read about the possible 5th gas giant in the Solar System, and about its ejection about ~100 million years after the formation of the Solar System. However, I have not seen anything about its ...
- 6,613
0
votes
1
answer
258
views
Could a star become a planet?
Could a star become a planet? I am asking this because the gas giants are ¨Failed Stars¨ and they are classified as planets in our solar system.
user37892
2
votes
1
answer
235
views
Would dropping a white dwarf or a "still-hot" stellar core into a large planet or brown dwarf create a star?
In the Wikipedia article about stellar engineering, I found this quote:
In The Saga of the Seven Suns, by Kevin J. Anderson, humans are able to convert gas giant planets into stars through the use of ...
- 6,613
-5
votes
1
answer
448
views
Why was Pluto declassified as a planet? [closed]
I have been wondering this and the teachers at my high school never really gave me an answer. Please help, why was Pluto kicked out of the solar system?
4
votes
2
answers
4k
views
Calculating the Angular Momentum of a planet
I want to calculate the Angular Momentum of any planet at any point on the orbit around the Sun.
Example: I want to calculate the Angular Momentum of Pluto today, on Jan 27, 2021 00:00:00 Hrs
Where ...
- 555
1
vote
0
answers
24
views
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 ...
- 218
3
votes
2
answers
2k
views
Planets just look like dots! Beginner telescope, hoping for some advice
I'm very new to astronomy and got myself a cheap, used 700mm 70mm diameter refractor scope and am able to see (what I think are) good images of the moon. However when I try to view planets I see ...
- 31
2
votes
0
answers
73
views
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. ...
- 5,526
4
votes
5
answers
319
views
If an orbit is shifting due to orbital precession, is it still a Keplerian orbit?
I was thinking about orbits a few days ago, and realized that orbits shift/precess naturally. Given that a two-body problem with a star and a planet, if the planet has an eccentric orbit that ...
- 6,613
3
votes
1
answer
82
views
How do we differentiate between a star or planet and noise introduced due to equipment?
I understand that differentiating between celestial bodies and noise due to equipment is a fundamental problem in astronomy. I also understand that we solve this problem by looking at something called ...
- 31
6
votes
3
answers
372
views
Kepler's Law, focal points - Heliocentric or Barycentric?
It is known that all the mass in the Solar system moves around the Barycenter.
For the two focal points in Kepler's law; is the first focal point $F_1$ a Heliocenter? Or is it actually a Barycenter?
...
- 555
13
votes
4
answers
4k
views
Is it at all possible for the sun to revolve around as many barycenters as we have planets in our solar system?
Though it is understandable that the sun and the earth may be revolving around a barycenter, but, if so, not only the sun and Jupiter should also be revolving around some barycenter, the same should ...
- 745
3
votes
2
answers
119
views
When (yyyy-mm-dd) does the north pole of uranus most nearly point towards the sun?
When (yyyy-mm-dd) does the north pole of uranus most nearly point towards the sun?
The information I've found suggests this happened in 1944 or 1945, but would like to find a more precise date or ...
- 31
5
votes
2
answers
966
views
Where is the Solar system's barycenter located?
Where is the Solar system's barycenter located?
The solar system as a whole, Where is the center of the mass for the combined mass of the Sun, inner planets, and gas giants, is it inside the Sun? Is ...
- 555
6
votes
2
answers
891
views
Can moons exist inside a planet's roche limit?
Saturn's rings are inside its own Roche Limit - the limit beyond which bodies start disintegrating due to the tidal forces of the parent body. But as every rock in the ring can be regarded as a ...
- 63
11
votes
1
answer
559
views
Is there convection in Mars' mantle?
Mars is differentiated, with a core, a mantle and a crust. There are no (longer any) plate tectonics on Mars. Does this mean there is no convection in the mantle? Could there be convection in the ...
- 17.4k
4
votes
2
answers
4k
views
Does the earth spiral around the sun's movement/motion path?
I have watched the following video (How Earth Moves by Vsauce) regarding how earth moves:
I have some questions:
Does the earth spiral around the sun's path as it is ...
3
votes
2
answers
393
views
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.
...
- 415
0
votes
2
answers
817
views
How much solid matter is in the observable Universe?
I want to know the volumetric ratio of empty space to planets, stars, and all other solid matter combined. Not considering any dark matter, dark energy, or black holes.
For example, you can say X ...
- 119
20
votes
1
answer
3k
views
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 ...
- 203
6
votes
1
answer
725
views
If Jupiter and Saturn were considered stars, which of their moons would qualify as planets by 'clearing the neighbourhood'?
Jupiter has four and Saturn seven spherical satellites. Jupiter's moon Ganymede and Saturn's Titan are larger than Mercury and they're the most massive moons at 0.0248 M♁ (Ganymede) and 0.0225 M♁ (...
- 387
2
votes
1
answer
197
views
Where did the nickel in the Earth's core come from?
Why is there nickel in the core of the earth? Does it come from collisions of two neutron stars? And how did we know the core of our planet is made of nickel-iron alloy? Thank you.
- 1,296
6
votes
2
answers
854
views
Has any moon achieved "retrograde equatorial orbit"?
There are many moons which have low (almost negligible) inclination and can be considered to rotate at the planet's equatorial plane. For instance, Galilean moons have almost negligible inclination (&...
- 4,392
3
votes
1
answer
2k
views
Minimum distance between planets
In our solar system, MOIDs (minimum orbital intersection distance) of different planets reach a minimum of ~30 million miles (Mercury and Venus). However, other star systems have more compact planets. ...
- 6,613
4
votes
2
answers
444
views
Probability of planets in binary star systems?
There is much fiction on binary stars with planets, for whatever reason, and this keeps supporting the popular impression that those systems are frequent. Indeed, the methods for identifying ...
- 5,526
3
votes
0
answers
54
views
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 ...
- 5,526
2
votes
1
answer
350
views
What would be the year length of a habitable planet of 40 Eridani A?
The planet Vulcan, in Star Trek, is one of the most famous fictional planets.
The length of a Vulcan year comes up in my answer at:
How old was Spock in Star Trek while he was serving on the ...
- 7,439
8
votes
1
answer
402
views
How long do thunderstorms on Venus last?
A while ago, I learned about field of exometeorology (the study of other planets ' atmospheres) which fascinates me. In particular, I read about thunderstorms on Venus, e.g. about the results from ESA'...
- 5,526
3
votes
1
answer
191
views
Is there any "scale" for measuring salinity of extraterrestrial water?
Continuation of Is the water underneath Europa's ice cap potable?
The referenced question discussed if water from Europa's ice caps is potable or not and from the answers, it was gathered that ...
- 4,392