Space isn’t really so empty as we might think. There are planets, moons, asteroids, comets, and rings. And dust. Beyond our local neighborhood, there’s also gas, lots of it. And, of course, we get the errant comet or asteroid from another solar system, like the newly found 2I/Borisov.
Earlier this year, an amateur astronomer named Gennadiy Borisov was out observing. On August 30, he found something that looked like a comet. He reported his find in a notification to the IAU. Other observers went to work looking at it, too. Using their observations, the IAU Minor Planet Center came up with a preliminary orbit. It turns out this thing isn’t just any comet. It’s coming from outside the solar system. Its official designation means it’s the second interstellar object and it was discovered by Borisov.
2I/Borisov is Hyperbolic!
This alien comet is in a hyperbolic orbit. That means its origin is from outside the solar system and it will (unless captured gravitationally by the Sun (unlikely), end up sailing right through our planetary system and back out to interstellar space. A hyperbolic orbit is not a “closed” orbit. That is, it isn’t an ellipse (like a squashed egg) It’s ...