Planet Definition and 820 Threads

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...

Alright, so here's the situation: I'm a writer, and I want to write in a setting on a planet that isn't the Earth. To be more exact, I want it to be larger than the Earth. But I want to have credible writing, rather than claim that magic has made everything stable and feeling like the Earth. As...

I've got a pretty simple question, and it may sound dumb, but I'm going to ask it anyway: First, I'll preface by saying that from what I understand (and please verify or correct me), planetary orbit in a star system decays over time a la net force. I also have come to understand that the...

Hi. Upon doing some research I’ve stumbled on this site. As someone very ignorant about the mechanics of the universe, I wonder if I could ask a very random question here. I am a writer, currently working on the premise of a novel which must adhere to the following brief: the story must be set...

Last year while thinking about it, I thought it will make more sense if we were pushed on our planet rather than being attracted to it. Mathematically, there is no change made to the current equation by reversing the force vector's direction! While I am read "Reinventing Gravity" from John W...

1. A newly found planet with a density of 4950 kg/m3 has no atmosphere and is orbited by a low altitude satellite with an orbital speed of 3.55 km/s. What is the mass of the planet? 2. density*velocity=mass G= 6.67E-11 3. After a process of equations, I ended up with mass=...

Are all the planets moving away from the Sun? If so, how much?

Homework Statement The escape velocity of Mars is 5 x 10 ^3 m/s . If the temperature of Mars is 300K , determine whether or not oxygen can exist on the planet . (Molecular mass of oxygen is 32 g/mol) Homework Equations The Attempt at a Solution Using p=1/3 rho <c^2> p= 1/3...

For a Grade 9 textbook: "Many more objects exist in the solar system besides the eight major planets. These are smaller and include moons, comets, protoplanets, such as Pluto, and tiny grains of dust and ice." Is this acceptably-worded or is it misleading? My take is that the term...

Is there a term for the vertical elongation of a planet? This would be the angular distance above the horizon that a planet appears at the instant the sun sets, or in mathematical terms it would be: x=elongation theta=angle between the ecliptic and the horizon "vertical elongation" = x *...

Lately I've read some articles about the possibility of a Jupiter-sized planet hidden in the Oort cloud. This assertion is based on analysis of cometary deflections and observations of Sedna. What is the likelihood of this? We all know that there must be lots of planet-sized stuff out...

I adored the Discovery's Planet Earth series and Disney's Earth. Is anyone looking forward to Disney Oceans!? I can't wait, I will be at the midnight show! (jk). I think these shows and movies do a great service in getting kids and people interested in nature and science...

Not sure if this has already been posted on the board, but here is another fascinating bit of information collected by the Cassini spacecraft as it floated near Saturn. Check the link below for pictures & the video...

I observe light originating from a planet which has a much stronger gravitation field than our own earth. The wavelength of the light is recognized as having been emitted from hydrogen-1 atoms, but is red-shifted due to the higher gravitation of that planet. I have a container of some kind...

Hello! I was wondering if there are anyone here who could help me with a little physics and logic pertaining to the behavior of planets. I've been working on a science fiction story set in a fictional planetary system containing an earth-sized planet and a mars-sized planet. It's important to...

Homework Statement An astronaut on a strange planet finds that she can jump a maximum horizontal distance of 15 m if her initial speed is 3 m/s. What is the free fall acceleration on the planet? Homework Equations R=Vi^2sin2α/g The Attempt at a Solution 15=9sin2α/g g=9sin2α/15

Hi all, I'd like to write a story whose setting is a planet that is, on the one hand, hospitable to earth-like flora and fauna, while on the other hand being as different as possible from Earth in as many respects as possible. In other words, which parameters can I fiddle with without greatly...

why planethunters and astrobiologists are concentrating on finding life on Earth like planet with an orbit around host star rather than on jupiterlike planets moon i was browsing through the essentials of complex life to evolve on a planet. i am sure you all pretty much know that. plate...

Homework Statement Hint: Disregard any dissipative effects of the atmosphere of the planet. A projectile is launched from the surface of a planet (mass M, radius R) with a launch speed equal to 61 percent of the escape speed for that planet. The projectile will rise to a maximum height...

Homework Statement Calculate the ratio between the kinetic energy of rotation of a planet (mass=4.30E+24 kg, radius=7.60E+6 m) to the kinetic energy of its center of mass orbiting around its sun at a distance of 1.20E+12 m. Like the Earth, it has a day lasting 24 hours and a year lasting...

Homework Statement As an astronaut, you observe a small planet to be spherical. After landing on the planet, you set off, walking always straight ahead, and find yourself returning to your spacecraft from the opposite side after completing a lap of 25.9 km. You hold a hammer and a falcon...

Homework Statement Determine the dip in magnitudes and flux in the optical light curve caused by the planet in front of the star if the planet orbits at 0.1,1 and 5 AU: The star is a solar type star and the mass of both the planet and star are known as are their radii: The observer is 10pc...

Homework Statement A science fiction tale describes an artificail "planet" in the form of a band completely encircling a sun, the inhabitants living on the inside surface (where it is always noon). Imagine the sun is like our own, that the distance to the band is the same as the Earth-Sun...

Homework Statement The trajectory of a rock thrown from a height with an initial speed of 16.9 m/s is shown in the figure below. Evaluate the magnitude of the gravitational field at the surface of the planet. The planet has no atmosphere. The graph is as follow...

Homework Statement A hypothetical planet has a radius 2.5 times that of Earth, but has the same mass. What is the acceleration due to gravity near its surface? R(earth)= 6.38 x 10^4 m M(earth)= 5.98 x 10^24 kg G= 6.67 x 10^-11 Homework Equations g=GM/r^2 The Attempt at a...

Homework Statement A spacecraft of mass m0 is descending with velocity v0 to land on an alien plant where the value of g is 1/6 of g on the earth. In order to land safely (meaning the final velocity upon landing is zero), fuel has to be burnt at a constant rate dm/dt=-k, where k is a...

Homework Statement An astronaut on the planet Zircon tosses a rock horizontally with a speed of 6.95 m/s . The rock falls through a vertical distance of 1.10 meters and lands a horizontal distance of 8.85 meters from the astronaut. Homework Equations The Attempt at a Solution ΔX...

Homework Statement An explorer wants to find the mass and radius of a planet he has landed on. He uses a pendulum he has with him and observes it takes a period of T1 to complete. He then climbs 2km up and observes period t2. Find planetary Radius r and Mass m Homework Equations g =...

Carl Sagan and his wife, Ann Druyan, fell in love and decided to marry while creating the "Golden Record" contained on the Voyager satellites launched in 1977. The "Golden Record" contains images, sounds, greetings, and music from the Planet Earth (in fact, Sagan and Druyan decided to get...

Homework Statement A planet orbits around the Sun with an orbital period of 14.5 years. It is observed it has a moon. At opposition, the moon has an almost circular orbit, and a radius of 7 arcminutes as seen from the telescope. Its orbital period around the planet is 3 days. What is the mass...

Homework Statement Astronauts visiting Planet X have a 2.5 m-long string whose mass is 5.0 g. They tie the string to a support, stretch it horizontally over a pulley 1.8 m away, and hang a 1.3 kg mass on the free end. Then the astronauts begin to excite standing waves on the string. Their...

Homework Statement Hi! This is from Physics for Scientists and Engineers, Vol. 6 by Tipler and Mosca. 44. Kepler's third law relates the period of a planet to its orbital radius r, the constant G in Newton's law of gravitation, and the mass of the Sun Ms . What combination of these factors...

Planet Orbits, finding radius HELPP! Homework Statement The planet Mars has a mass of 6.418*1023kg and completes an orbit around the sun in 687 days. The sun has a mass of 1.99 * 1030kg. what is the average radius of the orbit of mars? Homework Equations Force Gravity = G*(m1m2)/r2...

If you halve the radius of a planet.. what happens to the volume/mass/density ?? Okay so g on Earth is about 9.8 I know that Mass = Density X Volume... so if you double the radius you quarter the "g" ? What if you double the density and halve the radius.. can you please show me clearly...

A distant planet is inhabited only by knights and knaves. Knights always tell the truth, and knaves always lie. Eight inhabitants of the planet: Marge, Mel, Betty, Bob, Bill, Carl, Zeke and Alice are busy at a conversation, when a visitor from a neighboring planet stops by and asks each of...

Hi, I'm actually a Design Engineer but I find the topic of Relativity extremely interesting and I was wondering if somebody could give me some guidance on this. If Planets and Stars (due to their mass) 'warp' Space-Time then this means that our Sun distorts the fabric of space just like a...

Hello all: I'm interested in minor planet.Could you tell me how to calculate the orbit of a minor planet accurately? Is there any software to calculate it? And how to get the latest information of the minor planets?Any websites of famous international institutes who observe and...

How can the kinetic energy of a rotaing planet be calculate? I know the KE equation, - but how can I calculated the mass momentum (average speed) of the mass of a rotating body.

I understand that planets orbit follows a curve in spacetime created by the sun. Most of the planets follow the curve with seemingly a consistent radius. However Pluto follows an ellipse around the sun an appears to be inconsistent with the curve in spacetime created by the sun. Apologies if...

Would you be in apparent weightlessness?

Hello, sorry for my English:D Homework Statement I am trying to find motion equations for a mass moving around a big mass (ex. planet around sun), assumption is that the mass in middle is static (so this can be reduced to moving of mass around central force in middle of cartesian system), and...

Homework Statement A neutron star has a radius of 10,000 km, and takes a planet 30 days to complete one revolution around the star. When the star collapses, the new radius is 3 km. Find the new period of revolution of the newly formed neutron star. Homework Equations T=2(pi)/omega omega...

Homework Statement A distant star has a single planet circling it in a circular orbit of radius 3.33 × 1011 m. The period of the planet’s motion about the star is 836 days. What is the mass of the star? The value of the universal gravitational constant is 6.67259 × 10−11 N · m2/kg2...

Homework Statement While on planet X, an object is thrown vertically upward with an initial velocity of 5m/s. If this object returns to the point of release in 3s, what is the acceleration of a free falling object on this planet? Homework Equations a=vf-vi/t The Attempt at a...

Is it common for rocky planets to form closer to a star and gas planets further? Why or why not is this?

How do find the mass of the Sun using the following data: Planet r ... T Mercury 57.9... 0.241 Venus 108... 0.615 Earth 150... 1 Mars 228... 1.88 Jupiter 778 ... 11.9 Saturn 1,430... 29.5 Uranus 2,870... 84 Neptune 4,500... 165 Pluto...

On planet X, an object weights 18.6N. Planet B, the magnitude of the free-fall acceleration is 1.42g (g=9.8m/s2) is the gravitational acceleration on earth) the object weights 29.8N acceleration of gravity is 9.8 m/s2. a) what is the mass (kg) of the object on planet X? b) what is the...