Planetary Definition and 306 Threads

Hi, From a retired thread I (roughly) quote the following: "To plot the path that a point on the Earth takes through space, you would need to calculate these movements: The Earth relative to the Sun. The Sun relative to the Galaxy centre. The Galaxy relative to the Local Group. The...

All of you may have heard this. Without the Moon, Earth's axis would fly wildly out of control due to the other planets' gravity. Now, that makes sense, the Moon giving a stabilizing effect. But what confuses me is why Venus and Mercury both have near 0 degrees of tilt. They don't have a moon to...

Hello everyone. I am trying to calculate the focal points of the ellipse traced by a planet in orbit around a star, given the following known parameters: M_{sun} Mass of the sun r_{planet} Position vector of the planet from the sun m_{planet} Mass of the planet v_{planet} Velocity of the planet...

Homework Statement Determine the escape velocity of a planetary body that has a radius 5 times greater than its Schwarzschild radius. Homework Equations Schwarzschild radius=(2GM)/c^2 escape velocity=√(2GM/r) The Attempt at a Solution v=√((2GMc^2)/(10GM))=√(c^2/5) Is this...

My main interest in physics is b/c of astronomy. I'm doing physics undergrad as a stepping stone to grad school astronomy/astrophysics. However upon introspection I notice that my main interest in space lies in the solar system and exoplanets and the potential for life. Is astronomy then the...

Hello Everyone. If a planetary gear set has 4 (or more) planets, it is more robust, and is able to handle higher torque loads than a planetary gear set with only 3 (or less) planets. Is there an equation that proves this theory?

I've been searching all over the place, and I cannot find any data showing the error bars of orbital periods of planets. Once source estimates the uncertainty of Jupiter to be "1 arcsec per 250 years" but I cannot find anything to back this up. Does anybody have any hints as to where I should...

Gyroscopic effect on planetary motion! Hi PFians This is my first ever post in astrophysics since I've got very interested in it from last 2 days... I was wondering when Earth rotates about it's axis and at the same time changes it's direction due to revolution about sun...won't it have...

I'm reviewing my old calculus textbook and I stumbled upon a proof of Kepler's First Law of Planetary Motion which uses vector valued functions along with all of the operations to demonstrate the material. I understand the math and how to to DO it but what I am struggling with is why. It goes...

This suddenly entered my mind while studying magnetic fields. I know of course that it is the gravitational force that holds the planets in orbit, but do their magnetic fields also have an effect, even by an infinitesimal amount? Do the magnetic fields of the planets have a small influence on...

I read this article in Nature (http://www.nature.com/nature/journal/vaop/ncurrent/full/nature10768.html) as it describes two circumbinary planets. If it is assumed that most stars have a planet orbiting it and most Binary Star systems are elliptical, then wouldn't the majority of Binary Stars...

Why is it that for instance the Earth and the moon orbit their common center of mass? I mean surely the moon feels a gravitational force as though the mass of the Earth were concentrated at its center? If yes, what is that then makes it orbit around their center of mass rather than this point. I...

I find this (quite new web page I think) very interesting: http://phl.upr.edu/projects/habitable-exoplanets-catalog/results How can they determine that there are more potential habitable exomoons than actual confirmed and unconfirmed habitable exoplanets? Through how it looks like in this...

before i ask my question i want to review two points: 1. place a body like a moon or a planet near a black hole, as the body approaches the extreme gravity affects the body deferentially. 2. review the tidal forces on Jupiter's moon Io leading to volcanic/tectonic consequences. now take...

Homework Statement Kepler's third law of planetary motion relates P, the period of a planet's orbit, to R, the planet's mean distance from the sun, through the equation log P = \frac{1}{2} (log K + 3log R), where K is a constant. Rewrite the formula as a single logarithm. Homework...

Hi, I know that centripetal force for planetary motion is the same as the force of gravity between that satellite and planet. For example (I know these numbers may be completely unrealistic but just for the sake of easy calculation...) if the mass of the Earth is 1x10^30 kg and the mass of...

Homework Statement Hi I am doing this gear problem, I have attached the question and how I've started this off I am having problems working it all out as the question said I should try and have the casing rotating at a speed of 15-25 rpm. I have, these gear sizes which were obtained from a...

The understanding of the origins of our planet (as well as the other planets in the Universe) has always remained a question to astronomers. Inherently, the application of Newton’s known concepts of gravity has granted us the ability to make educated assumptions concerning planetary formation...

Hi, I have a question/doubt/general-lack-of-understanding here: I have a simulated solar system here, with simplified orbital mechanics. The main simplification is that at anyone time, only one celestial body exerts gravitational forces on the spaceship. So, my problem is: What would be the...

Newtonian physics correctly predicts that a planetary orbit will be an ellipse and general relativity correctly predicts that this ellipse will rotate, as was demonstrated with mercury. The only thing that I can think of is that because the orbit is an ellipse then the planet will be...

Is the speed of different bodies in the same planetary orbit equal to each other? I think it should be the same because the acceleration is always the same in such a case. But it was not so when i compared the speed of moon per m/s with that of the international space station.

Hi, I am having a problem analysing the kinematics of an epicyclic gear system. The system contains 2 planetary gears, one on top of the other. The centers of the planetary gears and the sun gear are all in line. The system also contains a ring gear on the top most planetary gear. Both planetary...

Visibility of a "solar shade" from a planetary surface Hello everyone, I'm a fiction writer in the process of publishing my first science-fiction novel, and have a question which I'm having trouble answering, relating to the visibility of a "solar shade" placed between a star and one of its...

Hi there I am currently trying to implement Newtons law of gravitation into a planetary model. I have 2 objects with mass of 500 and 20. The distance between them is 150. From what I gather from wikipedia I could use the following formula: GravityField = G * ((500*20)/(150^2)) Where G...

http://news.nationalgeographic.com/news/2011/07/110726-soccer-ball-nebula-space-science-stars/ Apparently the formation of planetary nebulae is a hot topic in astrophysics. See also - http://www.gemini.edu/node/11656

I am learning about General Relativity. The planetary orbits can be calculated with more precision especially Mercury. I am stuck on how to get from the Schwarzschild Metric: a four variable Differential Equation to a radius(r,theta,phi,t) and velocity(r,theta,phi,t) of a single planet...

Hello I want to ask that is it possible to have the number of teeth of sun gear and pinion will be same? As In my case the ratio is 4:1...outer ring is fixed and sun gear is the input. I want to use three planets. and if I take 14,16,17 for the sun gear then the condition of (Z1 +Z3)/number...

I know what each word mean independently, I'm just confused as to what sort of motion is trying to be described as a whole.

Hello, I have to design a series planetary gear speed reducer. I have to ask first that what is SERIES planetary gear? Can anyone give some detail about this. I have to design a gearbox with three stages with a motor power of 45 KW. Input speed of Motor is 2800 rpm, Max outer dia of...

1. The pro blem statement, all variables and given/known data the question: 9.0 × 10^3 kg satellite orbits the Earth at the distance of 2.56 × 10^7 m from Earth’s surface. What is its period? They give me a multiple choice, but let's figure this out without it. okay so my variables known...

Homework Statement A satellite is to be launched from Earth to venus. It is to make two complete circuits of the earth, then travel to venus, and complete one orbit of venus in 12 hours. Find the velocities of the satellite around venus, around the earth, and the radius of the orbit around...

Q: Why is it that objects in orbit around other objects, tend to do that in elliptical patterns, and not circular patterns? I can picture objects of great mass, planets and stars warping the fabric of space time, and how moons and whatnot get caught spinning in the orbit. But can't wrap my head...

Homework Statement A meteor is moving at a speed of 20000mi/hr reltiave to the centre of the Earth when it is 350 mi from the surface of the earth. At that time, the meteor has a radial velocity component of 4000 mi/hr toward the center of the earth. How close does it come to the Earth's...

Homework Statement You are one of the first astronomers in a civilization on Planet B in another solar system. With your unaided eye, you follow planet A in the same solar system and note that it never gets further away than 16 degrees from the star (around which both planets orbit). What...

Hello, Imagine two stars orbiting in circles around their center of mass. Is this movement generally called a translation, a rotation, or both? The concept of "revolution" is bothering me; is this always nothing but a rotation? Is a revolution a certain part of a rotation? A specific case...

Hi guys, I've had a question nagging at me for a while - When I was at school, my chemistry teacher taught us that the outer electrons of atoms were bound to the attraction of the nucleus, and the more layers of electrons that were added, the weaker the attraction due to electron "shielding"...

I really love planetary sciences, especially the science concerning the moons of the gas giants (although lots of this research is constrained by the availability of space probes). But are planetary scientists rare in astrophysics departments? In my university, almost all of them are in the...

Homework Statement An explorer plans a mission to place a satellite into a circular orbit around Jupiter, the radius of the planned orbit would be R. a)The explorer wants the satellite to be sychronized w/ Jupiter's rotation. Determine the required orbital radius in meters. b) What must...

Homework Statement Planet X rotates in the same manner as the earth, around an axis through its north and south poles, and is perfectly spherical. An astronaut who weighs 950.0 N on the Earth weighs 917.0 N at the north pole of Planet X and only 860.0 N at its equator. The distance from the...

How dense could Earth's atmosphere potentially be, as opposed to how dense it is now? Assume that Earth's mass and position in the solar system do not change. Al

Hello all, My name's Greg. I'm an airline pilot (my day job) and a fiction writer (my hobby). Right now I'm working on a story that borders on science fiction (a first for me). I've got a question: What is the upper limit on planet size (mass) that would effectively rule out putting...

http://www.eso.org/public/news/eso1035/" A discovery that enthusiasted scientists from all the world. It seems this discovery leads to a better understand of planets and mater.

better DIY planetary telescope: 8" or 6" Hey all, I'm starting to design my first home built telescope. I already own a 10" dob which works great but I've decided I would like something more transportable that is easier to take camping or wherever else. So right now I'm leaning towards a 6 or...

Attached is a Excel program given a Date it will susposedly give the Keplarian data for each of the Planets. It does not work. The Data is given from Nasa JPL: http://ssd.jpl.nasa.gov/txt/p_elem_t2.txt Julian Date and J2000 are calculated. J2000 or just J is plugged into the JPL data...

Has anyone ever come across any research or articles concerning the effects of the initial blast and fallout of an nuclear weapon and its effects on surrounding magnetism? Theories are welcome too, but research is preferred.

Hi I'm a bit confused, I hope you can help. The question is - In the course of their orbits, the distance between the Earth and Venus changes. The radii of the orbits of the two planets are 1.5 x 10e8 km and 1.1 x 10e8 km. If a radio pulse is transmitted from Earth towards Venus, calculate...

why does mercury move with such velocity while pluto is much slower?

This coursework question I am faced with is very specific and quite difficult to explain so I have attached the question. The writing on the side is not that important so don't try and make sense of it. The question asks to find the angular velocity of 2 planetary gears (which are connected...

Hi everyone, I'm really confused with a particular question: Homework Statement A space shuttle orbits the Earth at 6720 km from its centre. The gravitational field strength is 8.9N/kg. Calculate the shuttle's orbital period in minutes... Homework Equations g=4pi^2...