Planetary Definition and 290 Threads

Hi pf, please could someone explain why the orbital velocity increases as you get closer to the sun. I treated the situation like circular motion and did a load of calculations. I calculated the orbital velocity of all 8 planets and then the force between each of the eight planets and the sun. I...

Hey Guys! I've been doing a few equations in regards to planetary escape velocity and gravitational force. The below links have the escape velocity of listed planet on the left side of the board, the gravitational force between the Sun and given planet on the right side. In the middle of the...

Our sun rotates in counter clockwise direction and hence frame dragging will be also in that direction. Suppose if we put a satellite in sun's orbit (almost circular) to revolve in opposite direction to the sun's spin, what would happen to the orbit of the satellite? Would it fall into the sun?

Homework Statement The Attempt at a Solution Honestly I'm completely lost, this is an assignment for my calc 3 class. I tried to do (a) but I think I'm completely off track so any helps appreciated. r x a=0 |r x a|=0=|r||a|sin(theta) r cannot be 0 since it's in the denominator Assuming...

Good afternoon folks. I am getting ready to start a Planetary Physics course next week and have been doing some of the old homework that is posted on the course site. I am struggling to figure this one out and would love some help. It's been about 5 years since first year calculus, so I am a...

Hey there folks, As a forward: I'm trying to build a "high fantasy" universe in which to write stories, but within its historical timeline of events there are some cosmological happenings that I'd prefer to not just wave a wand at, so to speak. I'd like there to be at least SOME solid...

Homework Statement Assume that a planet can have an atmosphere if the escape speed of the planet is 6 times larger than the thermal speed of the molecules in the atmosphere (also known as the root-mean-square molecular velocity). Suppose a hypothetical object having the same mass and radius...

I was reading Planetary Motion (page 117) in Barry Spain's *Tensor calculus*, and stupidly enough, I didn't understand this. The equations are: $$\frac{d^2\psi}{d\sigma^2} + \frac{2}{r}\frac{dr}{d\sigma}\frac{d\psi}{d\sigma} = 0,$$ $$\frac{d^2t}{d\sigma^2} +...

I'm struggling to get my head around tidal acceleration. I get what is IS, I know how to calculate it, but what I'm not sure is how to apply it in a way that's meaningful to me. So. If we took a stationary Earth (i.e. non rotating, tide-locked) and have the moon magically appear in orbit and...

Homework Statement A 20 kg satellite has a circular orbit with a period 2.4 h and radius 8.0×106m around a planet of unknown mass. If the magnitude of the gravitational acceleration on the surface of the planet is 8.0 m/s2, what is the radius of the planet? Homework Equations F =...

http://imageshack.com/a/img33/5853/ge7y.gif In the above diagram,the part 3 the planetary wheel(its not the gear at the input or output side but in the middle of the differential). I call it the planetary wheel because I consider a bevel gear differential just an approximation of a planteary...

My Son is in 5th Grade and currently his class is studying the solar system. he wanted to know why only Gas giants had rings and the smaller planets did not. His Teacher apparently side stepped the question so he asked me. I assumed it is due to the Gravity but I didn't have enough information...

[b]1. "Calculate the radius of a planet with mean density of 3.0x10^3 m2kg-3, from which a golf ball can be thrown to infinity as a velocity of 40 ms-1" Homework Equations I've been looking at the equation of: Vesc=sqroot of 2*G*M/r and rearranging to r=2*G*M/Vesc. However, the...

Schwarzschild solution for Planetary Motion: ##g_{ij}= \left( \begin{array}{cccc} \frac{1}{(1-(\frac{2*m}{r}))} & 0 & 0 & 0 \\ 0 & r^2 & 0 & 0 \\ 0 & 0 & r^2*(sin\theta)^2 & 0 \\ 0 & 0 & 0 & c^2*(1-\frac{2*m}{r}) \end{array} \right) ## where ##m=\frac{G*(Mass of Sun)}{c^2}##...

So... Theoretically, planets (that are not gas giants, or water planets) could be composed of silicon, iron, or carbon. Are there any other elements that could make up most of a planet?

This is from last week (I was on vacation and then I worked like a dog to make up for the vacation): Nature news article on the subject: http://www.nature.com/news/nasa-funding-shuffle-alarms-planetary-scientists-1.14304 Eric Berger on the subject...

Is a solar system possible where there was constant planetary alignment (syzygy) Let's make it the simplest scenario : just two planets orbiting a sun [the planets are different ]

Homework Statement A planet with a mass of 8.99·1021 kg is in a circular orbit around a star with a mass of 1.33·1030 kg. The planet has an orbital radius of 1.21·1010 m. a) What is the linear orbital velocity of the planet? b) What is the period of the planets orbit? c) What is the...

What are the main differences between Astrophysics* and Planetary Science? What are their roles? And, which of the two is responsible for the first cloud map of a planet outside of our solar system? http://www.space.com/23043-alien-planet-cloud-map-image-kepler-7b.html *I mean just the...

Homework Statement a planet with radius of 12km spins at 520revs/s find: a) avg speed of a point on the planets equator over 2.5 of a revolution b)find avg acceleration on stars circumfrance over 3/4 of a rev c)find distance covered by point on the equator in 1 second d) find displaement...

Hi everyone. I would like to apologise in advance for my inherent lack of information in regards to what I am about to ask. I do not have a great understanding of the physics of the universe and such, but I suppose that is partially the reason for forums - to expand knowledge! Anyway, I...

Possible "criteria" or parameters for planetary collision? Suppose a computer model were created to simulate two proto-type planets on a collision course (for example, the Earth-Moon collision in the Hartman theory of the Moon formation). We know that the Moon is spiraling outwards (tidal...

I am currently majoring in astrophysics as an undergrad, but my eventual goal is to have a masters or PhD in planetary science. I'm at the point of the course ladder where I've finished up the vanilla physics and math prereqs in order to start on my major specific courses. Long story short...

I am looking for strange and interesting planetary circumstances for basing a board game around. This can involve any configuration of planetary bodies and their environments, but must be at least a theoretically possibility in general terms. Perhaps it would be best to illustrate with some...

Earth to Venus Hohmann transfer alignment time. Earth is at periapsis and Venus is at 190 degrees at ##t = 0##. For a Hohmann transfer, Venus must be lagging Earth by ##36.0298## degrees. I am trying to find the time it takes for the planets to align from their current positions. Is...

What would happen if two large planetary masses (such as our earth) collided by their poles (ie, north hits north)? Would the repellent magnetic force be negligible compared to the masses and gravity, or would the collision be altered or averted? Also, while I am thinking about it, what size...

Since gravity gets stronger the closer you get to the center, would a slightly egg shaped planet just continue to squeeze until it flattens out? The closer in areas would feel an ever stronger force of gravity and the poles of the "egg" will feel a progressively weaker force of gravity.

Homework Statement At a ertain point between Earth and the moon the total gravitation force exted on an object by both planets is 0. The Earth - moon distance is 3.84 x 10^5 and the moon has 1.2% of the mass of earth. Where is this point located. Homework Equations Fg=GmM/R^2 The...

Hello, The inverse square law of Newton's gravitational force, is it somehow related to each other? I mean to say P^2 is directly prop.a^3. Is it from the third law that the derivation of inverse sq.law of G=M.m/R2 is derived? Thanks.

Homework Statement Compute the mass of volatile material (specifically just H and He) not accreted by the Earth. Assume the mass accreted by the Earth is 7e23 kg. How does the mass of the missing volatiles compare with the actual mass of the Earth? Use the following table: Principal...

Homework Statement Two spheres of mass m and radius r, are released from rest in empty space. The centers of the spheres are separated by a distance R. They end up colliding due to gravitation attraction. Find the magnitude of the impulse just before they collide.Homework Equations Eg= -Gmm/r...

Hi I read up on astronomy for fun and I find the cosmos very fascinating my question is what determines the speed of a planet? whys does Earth spin at its current speed where's Venus spins almost 224 Earth days. I believe I read that the reason why the Earth spins in the first place is...

Homework Statement A certain binary star system consists of two stars of masses m and 3m respectively separated by a distance of 1.5 * 10^12 m measured between their centres. These stars revolve in sync with each other around their common centre of mass. If the smaller star has a mass of 1.0 *...

so, I'm a mechanical engineering student, fairly new at it though. I have a really strong real world grasp of mechanical principles, and really enjoy doing things like auto repair (consequently, my schedule is often interrupted by folks that know this fact, and want cheap auto repair) so with...

Homework Equations e=(product of number of driving teeth)/(product of number of driven teeth) e=(n_{out}-n_{arm})/(n_{in}-n_{arm}) The Attempt at a Solution e=(N_{p1}/N_{s1})*(N_{s2}/N_{p2}) e=1.25926 e should be 0.7941 however From there out it seems pretty trivial. I just need...

Guys, I've just come across this question regarding planetary gear train. I was asked to find the rpm of a gear within the train. but the solution given doesn't include the carrier speed within the calculations. I was asked to find the rpms to gear 4. The carrier is between 4 and 6. What...

Hey guys so I'm kind of stuck on the second part of this question, here it is. It’s possible to make a rough estimate of how often planetary systems form by making some basic assumptions. For example, if you assume that the stars we see have been born at random times over the last 10 billion...

Hey guys so I'm kind of stuck on the second part of this question, here it is. It’s possible to make a rough estimate of how often planetary systems form by making some basic assumptions. For example, if you assume that the stars we see have been born at random times over the last 10 billion...

Wheeee! More confusing thread titles! Here, let me elaborate: What I intend to do here is figure out a way to roughly model the results of planetary (or larger) bodies impacting, or a planetary (or larger) sized body being impacted by a smaller body that is moving with enough relative...

I am studying about various payloads that can be used on a planetary rover; I want to know their size , weight , what does it do ; and what is the science that it uses ; Where will I get this info... ?

Hi I'm curious of how much of an effect our atmosphere has to do with the global temperature. I mean, just the LOCATION of where you are on the planet makes an immense difference. On venus, with a much more dense atmosphere (and a lot closer to the sun) it's superhot instead, is it mainly...

Hello all: I have a quick question concerning a variation of a planetary gear train I am working on. If I want a sun gear and then two planetary gears in between the sun and ring gear (like is shown in the attached picture), how do I find the number of teeth for the ring gear? Would the...

I'm world-building for a SF-story and need some help figuring out what the ocean tides would look like. My planet orbits a close binary star system; it does not have any satellites itself. The mass of the binary is 5/3 Mo [solar masses]. The orbit is closer than that of Earth and is highly...

lets say i have an electric dc motor and i connected its shaft to a planetary gear system. this planetary gear systems last stage's ring (outer rim) spins a drum. this drum feels an outer torque T as a consequence of loads. my question is motor will feel torque T, becuase i read that the...

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...

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...