In celestial mechanics, the Roche limit, also called Roche radius, is the distance from a celestial body within which a second celestial body, held together only by its own force of gravity, will disintegrate because the first body's tidal forces exceed the second body's gravitational self-attraction. Inside the Roche limit, orbiting material disperses and forms rings, whereas outside the limit, material tends to coalesce. The Roche radius depends on the radius of the first body and on the ratio of the bodies' densities.

The term is named after Édouard Roche, the French astronomer who first calculated this theoretical limit in 1848.

Explanation

The Roche limit typically applies to a satellite's disintegrating due to tidal forces induced by its primary, the body around which it orbits. Parts of the satellite that are closer to the primary are attracted more strongly by gravity from the primary than parts that are farther away; this disparity effectively pulls the near and far parts of the satellite apart from each other, and if the disparity (combined with any centrifugal effects due to the object's spin) is larger than the force of gravity holding the satellite together, it can pull the satellite apart. Some real satellites, both natural and artificial, can orbit within their Roche limits because they are held together by forces other than gravitation. Objects resting on the surface of such a satellite would be lifted away by tidal forces. A weaker satellite, such as a comet, could be broken up when it passes within its Roche limit.

Since, within the Roche limit, tidal forces overwhelm the gravitational forces that might otherwise hold the satellite together, no satellite can gravitationally coalesce out of smaller particles within that limit. Indeed, almost all known planetary rings are located within their Roche limit. (Notable exceptions are Saturn's E-Ring and Phoebe ring. These two rings could possibly be remnants from the planet's proto-planetary accretion disc that failed to coalesce into moonlets, or conversely have formed when a moon passed within its Roche limit and broke apart.)

The Roche limit is not the only factor that causes comets to break apart. Splitting by thermal stress, internal gas pressure and rotational splitting are other ways for a comet to split under stress.

Megathreads and spaces to hang out:

reminders:

  • 💚 You nerds can join specific comms to see posts about all sorts of topics
  • 💙 Hexbear’s algorithm prioritizes struggle sessions over upbears
  • 💜 Sorting by new you nerd
  • 🌈 If you ever want to make your own megathread, you can go here nerd

Links To Resources (Aid and Theory):

Aid:

Theory:

Remember nerds, no current struggle session discussion here to the general megathread, i will ban you from the comm and remove your comment, have a good day/night :meow-coffee:

  • SorosFootSoldier [he/him, they/them]
    ·
    2 years ago

    Drunk driving is a time honored american tradition and pass time, the responsibility of not getting killed is on the sober drivers and pedestrians in the vicinity of a hero drunkard exercising his freedom to booze and cruise. The criminalization of drunk driving is just another example of the left's authoritarian communism discriminating against men.

    • SorosFootSoldier [he/him, they/them]
      ·
      2 years ago

      Hero Drunk Driver Saves Lives In Foiling Spree-Shooter Plot:

      On Saturday a young man, radicalized by "incel" message boards planned to carry out a spree massacre at the south creek mall with his ar-15. Luckily his plot was dashed when a good guy with a car came along. "It was a normal Saturday night for me" said Bob Austin Taggart, 65, of Newberry Township, "I just left the bar at 10 pm, drunk as usual, ready to go home and sleep it off" when he ran up on the sidewalk outside the mall, running over Jayden Newbert, 21, of Cross City, who was entering the mall with an ar-15 style rifle to carry out an attack. Police and EMTs were quick to the scene to treat the wounded Newbert, Police found "involuntary celibate" hate speech material and a manifesto on his phone. "Happy to help" says Taggart who's set to meet with the mayor on Monday and the chief of police to receive a reward for his citizenship.

    • hahafuck [they/them]
      ·
      2 years ago

      As much as the Alabama concept of 'and one for the road' being as literal as it is there shocked me, I must say in pure blood-alcohol terms french countryside people still take the prize here