2I/Borisov - The Interstellar Comet

Hello!

Let's start with a math lesson (yay).

If you did high school mathematics, you probably have learnt of "conic sections" and its four types: circle, ellipse, parabola and hyperbola and how each of them are derived from a cone (Go here in case you want to check).

Every conic section has a property known as eccentricity, which basically tells us how "non-circular" a conic section is. A circle has an eccentricity of 0, an ellipse is between 0 and 1, a parabola is 1, a hyperbola has greater than 1 and a straight line has an eccentricity of infinity. 

Now, you might ask "How is this related to an interstellar comet?". Don't worry, we'll get to it soon.

If you have ever heard of the dwarf planet Sedna or have checked the orbits of comets, you can see how elongated some of the orbits are. Like how Sedna's orbit has an eccentricity of roughly 0.84 and Halley's Comet's orbit has an eccentricity of 0.97, which is very close to a "parabolic orbit". The eccentricity of Sedna and other similar objects in the Kuiper Belt might be caused by a "Planet 9", but that's a topic for another day (or year, considering my schedule).

Basic mathematical laws and Kepler's third law are used to find the eccentricity of an object's orbit. This also allows us to find out if any object in the solar system's vicinity is actually orbiting the Sun (has an eccentricity below 1) or is an interstellar visitor (has an eccentricity above 1).

2I/Borisov, when first observed was thought to be a normal comet, like the rest in our solar system. However, when astronomers tried to track its trajectory, they found odd results. They found out that the eccentricity of 2I/Borisov's orbit is 3.357, which tells us that the orbit is hyperbolic and confirms that the comet is interstellar in origin. 

To date, only two interstellar objects have been detected, the other one being 1I/'Oumuamua (blog for that coming soon, I hope...) and it allowed us to find out lots about the nature of objects outside our solar system. 2I/Borisov is the only interstellar comet that we know of.

Oh, it broke up into pieces sometime after it reached its perihelion.

Join us next time where we talk about complex number integration and use it in finding the distance between the Earth and the Sun (not really)!

Thanks for reading!

Image source: https://solarsystem.nasa.gov/asteroids-comets-and-meteors/comets/2I-Borisov/in-depth/