On February 6, SpaceX wrote a new chapter in the ongoing book on commercial spaceflight with the successful launch of its Falcon Heavy rocket. Along for the ride was Musk’s red Tesla Roadster, which is now on an elliptical orbit around the Sun. But what about the risk to Earth? Could the car, which is estimated to last up to a few tens of millions of years, ever pose the threat of raining down from the sky as a fireball in the future?
The answer, as it turns out, is probably not. A paper posted on Cornell University Library’s arXiv preprint server February 13 (and to be submitted to the Monthly Notices of the Royal Astronomical Society) with the jaunty title The random walk of cars and their collision probabilities with planets concludes that there is just a six percent chance that the Tesla will collide with Earth in the next one million years. The chance does rise to 11 percent in the next three million years; but even if you’re a pessimist, “it will either burn up or maybe one component will reach the surface,” said first author Hanno Rein in a press release. “There is no risk to health and safety whatsoever.”
The authors calculated the probabilities by fast-forwarding the Tesla’s orbit — along with the orbits of the planets — over time and observing whether collisions occurred over the course of many simulations. In addition to the probability of colliding with Earth, they also found only a 2.5 percent chance the Tesla will collide with Venus in the next one million years. Though they predict several close calls with Mars, they don’t believe it is likely to collide with the Red Planet. After three million years, they only observed one collision with the Sun.
The Tesla, which is estimated to rotate about once every five minutes based on reflected light measured with the 4.1-meter SOAR telescope in Chile, is on an orbit that will cross the orbits of not only Earth, but also Venus and Mars, several times over the course of its dynamically stable lifetime. According to Rein, this orbit is not unlike that of many near-Earth Asteroids regularly observed. In fact, the Tesla has been officially labeled by NASA as a Near-Earth Object and listed in the Jet Propulsion Laboratory’s Horizon’s database as object -143205 SpaceX Roadster (spacecraft) (Tesla). It is one of about 150 manmade objects in the database, which allows you to chart any object’s position on the sky. According to the database, the Tesla is currently following an orbit with a perihelion of 0.99 astronomical units (AU, where 1 AU is the Earth-Sun distance) and an aphelion of 1.67 AU (Mars’ average distance from the Sun is about 1.5 AU).
Early this morning we measured the brightness changes of a car tumbling in space! Credit to Erik Dennihy (@UNC), we can report that Tesla Roadster (Starman, 2018-017A) is rotating with a period of 4.7589 +/- 0.0060 minutes. pic.twitter.com/LA4YzdvjK9
— JJ Hermes (@jotajotahermes) February 11, 2018