Planet Definition and 812 Threads

Question: Just as in the title. How large can a planet be and still have the Earth's mass? Obviously, this depends on its composition, just as long as it's solid and life can exist on it.

Maybe not the correct sub-forum for the question, but is the total amount of water on the planet constant ? I know the basics of meteorology and the whole sky, sea and land cycle but we put so much water into the land, how does that water get recycled ? If it is constant then why is it...

Giant Alien Planet Discovered in Most Distant Orbit Ever Seen \http://www.space.com/23858-most-distant-alien-planet-discovery-hd106906b.html

Dear members, My name is Gilberto F. A. and I would like to ask your help regarding a topic in Gravitation. I have formal education in engineering and recently, as part of an attempt to refresh my knowledge of physics I started to study again on my spare time whenever I can. A few days ago...

Homework Statement A newly discovered planet has a mean radius of 1230 km. A vehicle on the planet's surface is moving in the same direction as the planet's rotation, and its speedometer reads 130 km/h. If the angular velocity of the vehicle about the planet's center is 6.18 times as large...

first, what I know about black hole is; It has so much mass that collapse into itself create gravity field so strong that even light can't escape. and normally, black hole born only in giant star explosion. but what 'IF' normal rocky planet happen to collect mass (by asteroid, gas or...

So my teacher said that an object farther from the center experiences greater centripetal acceleration. How is that possible? let's say we have a sun + planet system. F = GmM/r^2 so when the planet's r is greater, wouldn't the force become lower compared to the planet being closer to the sun?

Homework Statement This question has two parts; the first part I understand but the second part I do not. Part 1: What is the rotational energy of a planet about its spin axis? Model the planet as a uniform sphere of radius 6420 km, and mass 5.59x10^24 kg. Assume it has a rotational period...

Homework Statement Venus and Earth may be regarded as behaving as black bodies. The mean temperature at the surface of Venus is about 600K and at the surface of Earth is about 300K. Which of the following is the best estimate for the ratio...

Homework Statement Consider a simple model for the interior of the Earth: there is a spherical iron core with constant mass density ρ0 and radius a; outside the core is "rock" with constant density ρ1. Use these values for the densities: ρ0= 8.70×103 kg/m3 and ρ1= 4.10×103 kg/m3. The radius of...

Hi, I would like to calculate the pressure inside a liquid planet in rotation. How can I do ? Pressure depend of depth under gravity but it depend of rotational speed too. Is it gravity pressure less centripetal pressure ? Is it \frac{1}{2}ρω^2r^2 - ρgh ?

Hello! I had this doubt when I was 14-15 years old, and I waited for many years (I'm 49 now) to ask about it, as I always thought this to be a silly question. In case someone can help with this, that's a thought experiment. It starts with this: if you have a sphere of gas, and then apply...

Lets say there is an exoplanet 50 light years away. The radius of this planet is 2x Earths with 8x Earths mass and a density of 5.52 g cm/3. What is the composition of this planet?

Homework Statement (a) Consider a planet orbiting a star of mass M?, on a circular orbit with circular velocity vp. What is the planet's orbital radius, in terms of vp and M? (b) Now suppose that the star (carrying the planet along with it) enters a nearly radial orbit around a black hole of...

Neptune has a masss 17.2 times larger than that of Earth and a radius 3.88 times larger. A person weighing 176 lb on the Earth would weigh how much on Neptune? Earth's mass is 6x10^24; Earth's radius is 6.4x10^6. Neptune's mass is 1.032x10^26; Neptune's radius is 24832000. 176 lbs is 80 kgs...

I feel curious about Earth having one supercontinent in a global ocean; it seems a little lobsided. Could it be that, once upon a time, Earth was much smaller, and then water was added? If a small planet was somehow globally deluged (No, not Noah's Ark - millions of years earlier) would...

I understand how conservation of momentum leads to planet formation and planet rotation. However, after studying this model, I have ran into a point of confusion that I cannot find the answer to: Why don't the planets collapse into the sun just as dust particles collapsed inward via...

Can a moon orbit close to its host planet and have no tidal heating? Say there is a moon with 0.5 Earth masses and 0.8 Earth radii orbiting a Jupiter mass planet every 18 hours with an eccentricity of 0.00001. There are no moons within 3 million miles of the exomoon in question. Could this moon...

Does anyone know of a (relatively) cheap astronomy book which has Ceres officially labelled as a planet? I realize it may not be extremely cheap seeing that it would have to be from the 1800s, but perhaps there's one that was commonly enough in print to not be so hard to find? It's both...

http://www.cnn.com/2013/07/11/world/space-blue-planet/index.html?hpt=hp_t1

Homework Statement A planet of mass ##M## moves around the Sun along an ellipse so that its minimum distance from the Sun is equal to ##r## and the maximum distance is ##R##. Making use of Kepler's laws, find its period of revolution. (Ans: ##\pi \sqrt{(r+R)^3/(2GM)}##) Homework...

Imagine that we have a system that consists of a massive black hole, and the asteroid revolving around it on a stable orbit. What method can determine the distance to these asteroids observer who is still close to the event horizon? The first thing that came to mind is to determine the signal...

We know that the orbit of a planet and its star is a conic section. For a closed orbit, it will be an ellipse described by x^2/a+y^2/b =1, or its equivalent equation in r and θ What would be the equation of the path under GR? and how will it approximate to a conic section when r(s)/r tends to...

[SIZE="3"] [SIZE="2"]I'm a writer, damn it, not a physicist! My imagination takes me to a world where a moon can be a habitable planet that orbits the largest planet possible that could be completely engulfed by liquid water.

"Planet X" Gravitation Question Homework Statement Planet X is a planet that has two spherical moons in circular orbits. The table summarizes the hypothetical data about the moons. Both moons have low axial spin rates. (G=6.67*10-11 Nm2/kg2). Moon A: Mass=4.0*1020 kg. Radius - Data not...

1. Description of Problem A binary planet system comprises two identical planets of mass M and radius R with their centers a distance 10 R apart. The minimum energy that the engines of a spacecraft need to supply to get a rocket of mass m from the surface of one planet to the surface of the...

Lets say there is an exoplanet with 0.5 Earth masses and is 0.8 Earth radii. This planet has an atmospheric pressure of 0.10 bar/10% as thick as Earths atmosphere with an average surface temperature of 285 K. Can this planet have a body of liquid water the size of an ocean with the low...

Would it be possible to have a satellite orbiting Earth slowly enough that it always stays between Earth and the sun? Not necessarily directly between so that its shadow is always on Earth, but such that, with an orbit that would take it "behind" Earth, it would orbit at a speed such that when...

Not to mention that I am one of those who thinks that sitting on a metal chair and table is no big of a deal as long as we can preserve the natural beauty of this planet and also I don't like egoistic people who think only about themselves now this being said this video is both a great idea , a...

Homework Statement Two remote planets consist of identical material, but one has a radius twice as large as the other. IF the shortest possible period for a low altitude satellite orbiting the smaller planet is 40 minutes, what is the shortest possible period for a similar low altitude...

Thanks in advance - this problem has been bothering me for a while! I'm working with an unpowered spaceship orbiting a large mass M. The orbit is circular and it is following the geodesic freely. It has an orbit radies of r = R. My question is this. The metric of the space-time curvature...

Planet PSR J1719- 14386 is a planet completely made of diamond. I've wondered what the estimated worth of the planet's material, perhaps you guys know?

A satellite is in a circular orbit very close to the surface of a spherical planet. The period of the orbit is 1.94 hours. What is density of the planet? Assume that the planet has a uniform density. density = kg/m^3 T = 2∏/ω = 2∏r/v GMm/r^2 = (mv^2)/r v^2 = GM/r v = rω So I know I...

i was just thinking , a planet comes close to a very massive star but doesn't collide .how can i calculate the its angular deflection.? i can calculate the velocity afterwards the deflection(given the initial and final perpendicular distances of its course from center of the star) using...

Homework Statement a planet of mass m orbits a star. The Velocity at point A = 10^4 m/s the Radius at point A = 10^7, Vb = (10^4)/3, Rb = 3*10^7 Numerically calculate the angular momentum! Homework Equations The main question is how would you calculate the mass? The Attempt at a Solution L =...

Can we see if a planet is inhabited 1 million lightyears away (presently)? No, correct? We we actually be seeing the planent inhabited 1 million years ago, right?

Starting from rest, an object is sliding down a frictionless inclined plane on the planet Org. Using the animation, determine the acceleration due to gravity ('g') on the planet. Use the protractor shown on the screen to measure the angle of inclination...

Let's say that a planet of approximately Earth's size - containing, as Earth does, core heat - were tossed out of orbit. Could it maintain any sort of atmosphere, or would all the component gases liquify and freeze, or be gradually lost to space? If it could retain any atmosphere, what gaseous...

Hello, I was wondering what the effect of gravity in a planet sized ring would be. If any of you have played the Halo game series, the ring structure is what I have in mind. -Would you be able to walk on the inside of the ring, and what forces will or will not permit you to? -Would you be...

You know, donut shaped. ISTM that the rivers would run towards the center, rather than towards lower altitudes. Depending upon the proportions of the planet, anything on the surface of the "hole" in the middle of Planet Toroid could experience negative gravity and float towards the center...

Homework Statement See attachment Homework Equations W = mg The Attempt at a Solution I did this : W(on Mars) = 93*8.8 (since the measuring machine was calibrated on venus) Mass = 93*8.8/3.8 My answer is 215Kg. Can someone confirm its validity ?

Most Earth-Like Alien Planet Possibly Found (Space.com via Yahoo) http://news.yahoo.com/most-earth-alien-planet-possibly-found-213629737.html The planet is reported to be 1.5 Earth masses. The host star is a G-type star, just slightly cooler than our own sun, and it apparently orbits the...

Hey everyone. I am a lurker here, and I have posted once, I think; however, I literally stumbled upon a very interesting question posed here: https://www.physicsforums.com/showthread.php?t=174274/ Anyway, I decided to see if I could expand upon and get a more "exact" solution for this...

Homework Statement Dear all, This is my first post and I need some help. The exercise I am trying to solve is this one: A star has a radius of 6 × 10^8 m and a period of rotation of 30 days. Eventually it becomes a neutron star with a radius of 10^4 m and a period of 0.1 s. If the...

Hi guys, (Have you ever asked yourself what would happen if you drill a hole into the Earth's surface that reaches to the other end of the planet and then jump in?) It's a question that many pupils have asked me already. I bet you've thought about it at least once in your life... I asked...

Homework Statement A meteor is approaching a planet of mass M and radius R with speed while it is far away. If there were no gravity, it would miss the center of the planet by a distance b. Gravity makes the meteor barely graze the planets surface as it passes. Find in terms of other given...

Hi All, I wanted to see if it were conceivable to create a spreadsheet you could calculate the position of planets within our solar system given a lat and long position and using the current time? I've tried searching for something similar, or formulas to calculate these, but haven't had...

This is what I tried doing, but I ended up getting an answer that isn't listed above 1. frequency = speed/wavelength 2. On Earth 480 Hz = (343 m/s)/wavelength wavelength = 343 / 480 wavelength = 0.714 is the wavelength for the Coke bottle 3. On Earth 2 Since they already gave me...

Homework Statement find acceleration due to gravity near the surface of a planet with a satellite by finding the mass of the planet and substituting it into the formula for the law of universal gravitation Homework Equations fc=mac fg=GMm/R^2 fg=fc fg=mg The Attempt at a...

Here is a simple problem in classical gravitation. Consider a spherical planet of radius R, and let the radial coordinate r originate from the plant's center. If the density of the planet is ρ from 0 ≤ r < R/2 and ρ/3 from R/2 < r < R, then my work tells me that the maximum force due to...