Planet Definition and 821 Threads

Hey, this is a research question for a novel. All advice, comments are much appreciated. Can a planet have two suns? If so, what are the implications on the length of day and night, casting of shadows, temperatures, etc. Does the planet revolve around just one sun or both at the same time...

Consider a moon that is 1.15 x 10^6 km from the planet it is orbiting... Homework Statement Consider a moon that is 1.15 x 10^6 km from the planet it is orbiting. This moon makes one complete orbit every 27 days. What is the orbital period of a satellite orbiting the planet at a distance of...

If the mass of the planet is 1.38 x 10^25 kg and its radius is 4.30 x 10^7 m... Homework Statement {attachment} (all the formulas in the attachment too) I don't know how to start this question Please help -[

Homework Statement A satellite of mass M = 683 kg is in circular orbit at height ho = 6.15x106 m above the surface of the Earth. Find: w, the weight of an astronaut of mass m = 75.5 kg inside the satellite. Homework Equations I believe it's something like: F = Gm_1*m_2/r²...

Homework Statement Planet X has a radius double of Planet Y. Planet X also has a mass that is double planet Y. How do the surface gravitational fields of X and Y compare? Homework Equations g=GM/R The Attempt at a Solution So because were looking for the ratio of gx to gy, we can use...

http://en.wikipedia.org/wiki/HD_40307_g technical paper http://arxiv.org/abs/1211.1617 Habitable-zone super-Earth candidate in a six-planet system around the K2.5V star HD 40307 Mikko Tuomi, Guillem Anglada-Escude, Enrico Gerlach, Hugh R. R. Jones, Ansgar Reiners, Eugenio J. Rivera, Steven S...

The escape velocity on Planet X is the speed the rocket needs in order to never fall back down again in a universe in which X is the only object. In order for the rocket to not fall back down, its velocity to never become negative, how far away does the rocket have to be when the velocity is 0...

From here: http://blogs.discovermagazine.com/badastronomy/2012/10/16/alpha-centauri-has-a-planet/

Using the equation P2 = (4 * pi2 * a3)/(G(M+m)) to find the orbital period of Earth where: P = orbital period a = semi-major axis = 1.50e11 m G = 6.67e-11 m3 kg-1 s-2 M = mass of sun (in this case) = 1.989e30 kg m = mass of Earth = 5.972e24 kg I have been trying to find the orbital...

what is the gravity of a planet 2 times the radius and 3 times the mass of earth

Homework Statement Is it possible to calculate the mass of the Milky Way knowing only the speed of a planet in a circular orbit? I fail to see how, but if yes, then how? Thanks in advance Homework Equations The Attempt at a Solution

A person stands on a cliff overlooking the sea. He is 100m above the sea level and he observes the horizon to be 5mrad below the local horizontal. How do you calculate the radius from this information without using a calculator? Trigonometry I am guessing, but I need a better hint.

Dear Physics Forums community, This question has been bothering me for a few days, and I must apologize for the ambiguity of it. I'll try to explain it a little bit. I am not asking when the Sun will expand or the Earth cool down via radiative processes. So what I asked myself was: if you...

If I wanted to figure out the gravitational time dilation at different points in a the field around earth, could I just use v=gt. and find the speed that I would be moving if I went into free-fall from point x to point y. To figure out the time difference between x and y? and the t in v=gt...

Homework Statement Imagine you are observing a spacecraft moving in a circular orbit of radius 128,000 km around a distant planet. You happen to be located in the plane of the spacecraft 's orbit. You find that the spacecraft 's radio signal varies periodically in wavelength between...

If I am orbiting a charged planet that is like being in free-fall around the planet. So would I see a B field in my frame? Is me orbiting the planet the same as me floating in space and have the planet rotate.

Homework Statement We have a homogenous toroidal planet. Its cross-section is half of a square, so that the hypotenuse is parallel to the z-axis. Find the orbits of constant (especially lowest) energy around that planet. Homework Equations 1) Homogenous planet: \rho=const. 2) Potential...

Hi, this is my first post - i need some help with my astrophysics. I'm writing a sci-fi story where an Earth like planet has 2 moons. One of them is habitable and has conditions like Earth - like an atmosphere and so on (almost like a twin planet). The other moon would be smaller and more...

Hi. (Not sure whether this should go in the "science fiction" or "real science" section, since while it's about something often featured in science fiction, I'm asking about real science.) We've all (well, perhaps not literally _all_, but you get the point) seen those movies where they blow up...

Consider a planet with a period of orbit to be 0.241 years and an average radius of 0.39 astronomical units. Calculate the period of a planet with an average radius of 1.4 astronomical units. If someone can answer and explain this question to me, I would be very thankful. I know it has...

Homework Statement Knowing you can jump about 1m high on Earth's surface, how high can you jump on the unknown planet. Munknown= 4.19*10^21kg Radius Unknown= 1*10^6m Homework Equations Not sure if can be used in this question K1+U1 = K2 + U2 1/2MV2 + mgh = 1/2MV2 + mgh U=-GM/r and U = mgh...

Hello! I'm new here, and already did a search. Sorry if the answer is elsewhere, I just couldn't find it! I'm writing a sci-fi novel and have been brushing up on general and special relativity. I'm running into a small problem with the twin paradox, and how to describe it from another planets...

With respect to time in empty space, how massive does a planet have to be to affect the time to the point where the planet's time runs half the speed of empty space time?

I've got a nifty java program done which calculates the orbit of a body around a gravity source. The math and physics are all done for a body around a single gravity source and how to figure whether it's an ellipse, parabola, hyperbola or straight line. But now I've got a new problem. If...

Problem: One of the asteroids, Ida, looks like an elongated potato. Surprisingly it has a tiny (compared to Ida) spherical moon! This moon called Dactyl has a mass of 4.20x1016kg, and a radius of 1.57x104 meters, according to Wikipedia. Solve: - Find the acceleration of gravity on the...

How big does a planet have to be in order for it to have a molten core or a magnetic field? Assuming no other large objects were close enough to affect the planet with their own pull or magnetic field. I would imagine the composition/density of the planet would play a factor as well, but do we...

This problem is*using*real*data*of*the*first*extrasolar*planet*discovered*around *a normal*star*to*calculate*the mass of the planet. I am really stumped on this equation.I put it as an attachment because I had a hard time entering it by keyboard. So far I figured out from graphs and conversions...

Hi there! I'm developing a game that involves simulating a star system. I'm using the Unity engine and its physics engine. I've got gravity working perfect. I've also developed an algorithm that works out how much force you would need to apply to a body to start it orbiting around another...

Hi all, I know that if you drill a hole from one side of the planet to the other, through the planet's center, that a particle dropped in this tunnel will oscillate back and forth forever, like a mass on a spring, with the restoring force given by gravity. What if the tunnel forms a chord...

Hi All, Very new to this forum, and hoping for some assistance. I am in the planning stages for a science fiction sequence of books. I am not planning on writing true 'hard' sci-fi as unfortunately I do not have the knowledge base required, however I would like the world building in my...

I had an idea of a planet that was spinning fast enough that at its equator, the outward force from the centripetal force would almost equate the planet's own gravity. However, this would change as you got closer and closer to the poles. I was just wondering what this planet might look like...

Homework Statement One of the moons of Jupiter, discovered by Galileo, has an orbital period of 1.44x106s and a mean orbital radius from the centre of Jupiter of about 1.90x109m. From this information, determine the mass of planet Jupiter. Homework Equations I have made a list of...

Homework Statement An astronaut weighs 833N on the surface of the Earth. Determine the weight of the astronaut on Planet Z if the planet's mass is 50.0 times the mass of the Earth and has a radius of 10.0 times the radius of the Earth. Homework Equations Kepler's 3rd law...

I searched for "definition" and "planet" but found no thread which matched this purpose; if one already exists then it is significantly old, but I will apologize anyways. It used to be that our solar system had Nine planets. Then some trans-Neptunian object (Eris) forced some astrological...

Homework Statement A wall clock on Planet X has two hands that are aligned at midnight and turn in the same direction at uniform rates, one at 4.27×10−2 rad/ s and the other at 1.62×10−2 rad/s . At how many seconds after midnight are these hands first aligned and next aligned? Homework...

I worked through a simple twin paradox problem, and I think I have the correct solution. However, I wanted to confirm that my numbers are correct. There is nothing fancy about the solution, but it resolves the "paradox" completely for me. Every other resolution I have looked at either leaves...

I often hear that for planet to have life on it it must have proportionaly large moon to keep it's axial tilt small like Earth is between 21.5° to 24.5° and not like Mars that varies from 15° to 35° which makes destructive effect on possible life that could flourish. But doesn't Venus have...

Hello. I am programming a 2d solar system simulation for a game. All went fine until I got to this part. Tried learning it in the past 3 days but could not understand most of it. Hoped to find help hhere. I have the location of both planets, their mass, their initial velocity and that's it. How...

Homework Statement Determine the density of fictional planet in SI units from the information Homework Equations Planets mass 1.28x10^22 Kg divided by radius 1.12x10^3Km = 1.14x10^25 Kg/m3 The Attempt at a Solution My answer seems all wrong, the SI unit should be in Kg/m cubed. Is...

Realm of the Mad God actually takes place on a spherical planet where Oryx's minions thrive. This planet has a mass of 2.73 x 10^24 kg and a gravitational acceleration of 11.2 m/s^2 at its surface. Roughly 840,000 minions live per square kilometer. Together, the players of the realm kill 1500...

I am writing a science fiction book that includes the idea of a planet orbiting within the habitable zone of Alpha Centauri A and I'm hoping this is a good place to get some questions answered. It's science fiction, so I'm perfectly fine with stretching the limits of possibility, here, just...

I am writing a novel set on a ringed planet. The plot calls for the rings to be about a thousand years young, more a torus of gas and dust and speeding moonlets. Would a person standing on the night side of this planet be able to see stars? Or would the rings scatter enough light from the sun...

Homework Statement Zero, a hypothetical planet, has a mass of 3.0 x 10^23 kg, a radius of 3.0 x 10^6 m, and no atmosphere. A 17 kg space probe is to be launched vertically from its surface. If the probe is launched with an initial kinetic energy of 5.0 x 10^7 J, what will be its kinetic...

I'm trying to cook up an interesting desert planet. Dune made me wonder if a tool-using species could turn a planet with plenty of water into a desert planet. Say, one nation starts hoarding water via the "catchments" we saw on Arakis (with some plausible mechanism to prevent evaporation)...

Specifically, could Venus have otherwise formed as one, while leaving the rest of the structure of the solar system pretty much intact? Failing that, could one have formed anywhere in the solar system?

OK I'm fairly new to these topics but eager to learn but as I'm sure most of you know the closest know habitable planet is gliese 581g. They say at 11 miles a sec it will take 79 years but I'm wondering does that take into account the universes expansion and would it be 79 Earth years and if so...

What are the top bio signatures we should be looking in exo planet spectra? What sort of telescope would be needed to obtain good spectra of potential Earth twins? Would it require Darwin or TFP or could something cheaper obtain such spectra?

Homework Statement A particle, unknown mass, has velocity v0 and impact parameter b. It goes towards a planet, mass M, from very far away. Find from scratch (? I'm not sure why it says from scratch), the distance of closest approach. Homework Equations I believe this equation is...

Given a planet of the same (relative) density as Earth, and a G-force on said planet of 1.916G, what is the procedure to determine the radius and surface area for such a planet, given it having only 57% water coverage? I will admit that I am working on this for a book series I started in...

Homework Statement It’s your lucky day! You have been chosen by NASA to be the astronaut for its first intergalactic expedition. In your excitement for the mission, however, you forgot to read the road map and you have no idea where your spacecraft landed. Your intimate knowledge...