Planet Definition and 812 Threads

How we can prove (using geomtry and not differential equation) that the orbit of planet have to be a conic section.

Just looking for a place to start, not all the work. Homework Statement 3 The asteroid belt between Mars and Jupiter consists of many fragments (which some space scientists think came from a planet that once orbited the Sun but was destroyed). (a) If the radius of the asteroid belt (where...

In the first part of Brian Cox's documentary series 'Wonders of the Universe', he explains how the entropy of the universe always increases, and that we are therefore headed for a state of total 'disorder' where all is left of the universe is photons and dying black holes. But wasn't this...

Homework Statement An object of mass 104 kg moves in a smooth straight tunnel of length 1540 km dug through a chord of a planet of mass 3.2 × 1024kg and radius 1 × 109 m. Determine the effective force constant of the harmonic motion. Answer in units of N/mHomework Equations Force of gravity=...

A certain talk show keeps bringing up this planet x supposedly in our solar system. An astronomer I heard on that same show said it couldn't be because we would know it was there because of the influence it would have on the orbits of the other planets and there is none. I'd like to...

Homework Statement Jupiter's moon Io is has an orbital radius of 421,000 km, around the planet Jupiter (MJ = 1.9 x 1027 kg). Io's radius is 1821 km and its mass is 8.93 x 1022 kg. Calculate the tensional force inside Io, as a result of Jupiter's gravitation.Homework Equations Fg= GMm / r2The...

Homework Statement A science-fiction tale describes an artificial "planet" in the form of a band completely encircling a sun, as shown in the figure . The inhabitants live on the inside surface (where it is always noon). Imagine that this sun is exactly like our own, that the distance to the...

Hi. I'm planning to use an all-ocean planet as a setting in a science fiction story, and I was wondering, what would the effect of an absence of continents be on the planet's weather? The planet is something like 98% water-covered, its only land is a number of islands, mostly small, the...

Say there are two atomic clocks floating through space, both completely stationary with respect to each other. They are exactly synchronized, and not under the influence of any significant gravitating bodies. One is significantly farther ahead in the direction of motion than the other, but they...

Does someone know where to find information about what time different planets have their perihelion? For example Earth is 3 January.

There is a problem: "The distance of Barnard’s star is 1.83 pc and mass 0.135 M. It has been suggested that it oscillates with an amplitude of 0.026"

in 25 year periods. Assuming this oscillation is caused by a planet, find the mass and radius of the orbit of this planet." My question is...

http://www.nationalpost.com/m/blog.html?b=news.nationalpost.com/2011/02/15/new-giant-planet-may-repeat-may-be-discovered-in-our-solar-system&s=Opinion http://www.independent.co.uk/news/science/up-telescope-search-begins-for-giant-new-planet-2213119.html Any comments on the planet...

Kepler recently found the first confirmed small, rocky planet: http://www.universetoday.com/82362/kepler-discovers-it%E2%80%99s-smallest-and-first-rocky-planet/ The arxiv preprint was released a few days ago: http://arxiv.org/abs/1102.0605 The planet is remarkably small - only about 1.5x the...

Could it be possible for a jovian planet to have an oxygen atmosphere breathable by humans? Let's say that the humans live in blimp-like stations, and the jovian planet is small like Neptune to reduce the high gravity.

How can I give a fictional planet a realistic mass and surface gravity based on radius? Mercury and Mars are near equal in surface gravity strength, so it does seem that I have some room for variation. From Wikipedia: Earth Average radius 6,371.0 km Surface gravity 9.8 m/s2 Mass...

A star that has been ejected from a galaxy probably wouldn't be any different from stars within galaxies. It could be possible for a planet to orbit this star. What would the night sky appear like? Would the galaxies be too dim to see, and the night sky fully black? Lets say that the star is...

On Planet X, a 70 kg object can be lifted by a force of 400 N Suppose your car was taken to Planet X. If the car has a mass of 1500 kg, what would its weight be? W=mg a=W/m a=400/70 a=5.7m/s/s W=1500*5.7 W=8550N on the site http://library.thinkquest.org/10796/ they say that the answer is...

Homework Statement Need to figure out if a planet can have a hydrogen atmosphere Homework Equations ves=(2GM/R).5 Vrms=(3kt/m).5 The Attempt at a Solution Ok so I would first find the escape velocity of the planet, than find the velocity of the molecule. I am given the mas of...

Homework Statement I have been able to complete section a and b but c doesn't match the answer a)The acceleration of free fall at the surface of a planet is g and the radius of the planet is R. Deduce that the period of a satellite in a very low orbit is given by T=2pi sqrt(R/g). b)Given...

Say floating around in space there was a galaxy sized planet of nothing but water. Assuming this was enough mass to have gravity kick in, if we placed an object that is not buoyant in the planet's water, at what point would it stop sinking? Would it stop at the centre? Would it go through the...

So after reading the planet of lies thread I thought it would be interesting to figure out the optimal way to play the number game described. It is played as follows: There are five players and ten rounds. During each round every player picks a number between 1 and 5, This choice is secret...

Hello. I have a question concerning the stability of a hypothetical binary planet system. I'm sorry if this properly belongs in general astronomy instead of astrophysics, but it does concern orbital mechanics. The hypothetical system is an Earthlike planet orbiting a relatively bright K class...

I found this puzzle in some other forums. I found it to be very difficult. Maybe somebody would like to that a crack at it :smile: Anyway, here it is: The human race spread out to the stars, eventually terraforming and colonizing thousands of planets. On one planet, P3, they decided to...

Homework Statement Planet X has a mass of 6.42x10^20 kg and a radius of 2400km. A satellite with a mass of 1500kg is in orbit around Planet X at an altitude of 300km. a) what is the Force of Gravity? b) What is the acceleration of the satellite while in orbit? c) Find the speed of the...

well, not quite... imagine an earth-like planet totally enclosed in a shell of some material which conducts heat and has near black-body properties both inside and out. The shell is at a distance of some 100s of kilometres from the planet's surface. The shell is light enough so that it has no...

Could we "blow up" a planet with our current technology? Could we "blow up" a planet with our current technology?

Homework Statement A uniform rod of mass M and length L lies along the x-axis with its center at the origin. Determine the gravitational field at the point x=d where d>L/2. Homework Equations The Attempt at a Solution I know I will have to take the integral of dg in order to find...

Homework Statement A uniform, spherical planet of mass M and radius R moves SLOWLY with an essentially uniform speed v through a cloud of interstellar dust particles, whose density is ρ. The dust particles are attracted towards the planet, and some of them would eventually fall onto its...

Homework Statement An astronaut lands on a new planet of radius R=3000km, and wants to measure its density. In order to do that, he drops a stone of unknown mass from the top of the space shuttle, which has a height of 92.5m and measures the time it takes it to reach the ground. t= 5s. What...

What do you think about the decision?

I am kind of new to astronomy and I have a few questions.. I need to be able to determine an equation expressing the elliptical orbit of Oberon around Uranus. I have four nights of data showing Oberon in different positions relative to Uranus. I am able to calculate the RA and Dec for both...

Is there any new on the new goldilocks planet and if there is water on it? also what website is good for following this data

Homework Statement A satellite is in a circular orbit very close to the surface of a spherical planet. The period of the orbit is T = 2.52 hours. What is density (mass/volume) of the planet? Assume that the planet has a uniform density. Hint: "very close to the surface" means that Rorbit =...

Homework Statement If the eccentricity of a planet's orbit about the sun is 0.4, find (a) the ratio of the lengths of the major to minor axes of the planet's orbit, and (b) the ratio of the speeds of the planet when it is at the ends of the major axis of its elliptical orbit. Homework...

Homework Statement a projectile of mass m is launched vertically from the surface of Planet Islander at a speed that is one-third the escape speed from the surface. If the projectile reaches a maximum height that is a distance h from the surface of the planet, what is the radius of planet...

The current planet count stands at 490 but can scientists gurantee 100% that they are planets. For instance, isn't it possible to identify a star passing in front of another star (binary) when looking at the light curve?

"Earth Masses" I've been stuck on a problem for a few days now, and I know that it is a lot easier than I am making it out to be. My goal is to find how many Earth masses lie within a planet who has the same size as Earth, and the same density as the moon. I honestly do not know how to go...

I read somewhere that the size and gravity of a planet is one factor in its ability to support life. What would be the consequences for life if a planet's gravity were too strong? I can imagine that moving around would be difficult, but would there also be consequences for bacteria...

My question was piqued by this article: http://news.discovery.com/space/earth-like-planet-life.html The article claims that the planet discovered is tidally locked, but does not explain how this was determined. Presumably the planet is much too far away to be resolved by any telescope, and...

Homework Statement We will compute the orbit of Eris, the infamous \tenth planet" that caused Pluto to be demoted to \dwarf planet" status. Eris (also called 2003 UB313 in the textbook) has a semimajor axis a = 68:048 AU and eccentricity e = 0:4336 based on the best current observations...

Hi! I need help with the method to approach a question, if I wish to calculate how long it will take for a radio message to reach a certain planet (just the general concept), what will be the key pieces of information I require? I know I need: the distance from Earth to said planet the...

Hello. Me and a friend of mine were trying to get our heads around a few of the paradoxes that are found within Einstein's theory of relativity and he came up with something we could not work out ( though I am sure someone here will be able to :) Imagine you were in a spaceship...

If I am in free-fall towards Earth or in this case let's use a planet with no atmosphere to get rid of air drag. So I am in free-fall and then I throw a ball up above me. From my point of view the ball would appear to keep going away from me until i hit the ground. Is this correct?

Homework Statement A projectile is launched over level ground on an unnamed planet. The equation of the projectile's vertical position is y(t)=-6t2+48t-90. a. Determine the acceleration due to gravity on this planet b. Determine (ymax, tymax), the coordinates of the maximum height of the...

I've been working on this for five hours and I am on the verge of despair! Can anybody help with this question? All I need is an equation! There are two extrasolar planets (X and Y) that are orbiting two stars with the same mass as our Sun (1.9891 × 10^30 kg), i.e. the planets are in two...

Homework Statement Two spacecraft are flying towards a planet at 0.9c and 0.3c relative to the planet, respectively. If they fire their laser beams simultaneously from a range of 109 m, which will strike the planet first and what will be the delay before the other beam strikes? Homework...

Dear all, A very simple (almost embarrassingly so) question here, but I just want to double-double check what is going on. Kepler's Third Law states for a planet of mass Mp orbitting star of mass M* at a semi-major axis $a$ with a period P, that: [P/(2pi)]^2 = a^3/G (Mp+M*) Now what I want...

Homework Statement Spherical planet has only one inhabitant that can move freely on the surface of the planet with speed u. A spaceship approaches the planet with velocity v. Show that if v/u > 10, the spaceship can always see the inhabitant regardless of his movement. Homework Equations...

Hello. Up until this point I have been solving this numerically, by propagating the state vectors and checking for a collision, however that is inefficient, so I would like an analytic solution. Given lengths r, and d, as well as angle t, is there a way to find length s?

Dear all, I am currently in a MSc program, in a different subject matter, and for some time I have had a ningeling thought, my question is... As an example, say planet Earth weighed 100 tons, at its current state, what would the weight of been 100 years ago? Some of my associates are of...