Posted: Jun 06, 2011 9:09 am
Hello,
Yesterday we saw Melancholia - a beautiful film about the end of the world. To put it concisely, an extrasolar planet falls from the interstellar void into the solar system, makes a close fly by about the sun, and apparently, passes close to the Earth (close enough to "take some of our atmosphere"), and first recedes, then the two planets make a head-on collision. It has not interacted with any other astronomical body. According to the film, the Melancholia has a diameter about four times that of Earth. One allegedly informed astronomically inteersted person makes the observation that the planet is receding at a speed of 100000 km/hr, so about 28 km/sec.
To me, this sounds wrong. If it falls from beyond the solar system, shouldn't it have the solar system escape velocity when it passes Earth?
Also, I am curious about the mechanics of the fly-by of a massive object. If, as would appear likely, Melancholia is a gas planet, it still would have the volume about 64 times that of Earth; with a density of 1 (like Uranus), the mass would be more than 10 times that of Earth. What would the mechanics look like in this situation? I speculated to what extent a close fly-by would cause a slingshot rather than a collision (not as spectacular in terms of FX, but quite deadly to life on Earth I would assume).
Yesterday we saw Melancholia - a beautiful film about the end of the world. To put it concisely, an extrasolar planet falls from the interstellar void into the solar system, makes a close fly by about the sun, and apparently, passes close to the Earth (close enough to "take some of our atmosphere"), and first recedes, then the two planets make a head-on collision. It has not interacted with any other astronomical body. According to the film, the Melancholia has a diameter about four times that of Earth. One allegedly informed astronomically inteersted person makes the observation that the planet is receding at a speed of 100000 km/hr, so about 28 km/sec.
To me, this sounds wrong. If it falls from beyond the solar system, shouldn't it have the solar system escape velocity when it passes Earth?
Also, I am curious about the mechanics of the fly-by of a massive object. If, as would appear likely, Melancholia is a gas planet, it still would have the volume about 64 times that of Earth; with a density of 1 (like Uranus), the mass would be more than 10 times that of Earth. What would the mechanics look like in this situation? I speculated to what extent a close fly-by would cause a slingshot rather than a collision (not as spectacular in terms of FX, but quite deadly to life on Earth I would assume).