spaceSpace and Physics

Astronomers Have Tracked The Rate Of Starman's Spin


Stephen Luntz

Stephen has a science degree with a major in physics, an arts degree with majors in English Literature and History and Philosophy of Science and a Graduate Diploma in Science Communication.

Freelance Writer

starman and Earth

Even at a distance of more than a million kilometers astronomers have been able to measure the light curve from the car SpaceX launched to work out its spin. SpaceX via Wikimedia Commons

There were mixed feelings from astronomers about SpaceX's launch of a Tesla Roadster beyond the Earth's gravity well. However, one team decided it was a chance to do some science, and have responded by tracking the car, and measuring its spin rate.

Many astronomers and space engineers thought the Falcon Heavy's launch was a missed opportunity to put something beyond the atmosphere that could take measurements that might prove useful. Deprived of that data, some scientists decided to collect their own. Although the work was mostly for fun, it has been noted that measuring something whose shape we already know can calibrate the methods we apply to unknown objects.


Time on large telescopes is precious, but a team at the University of North Carolina at Chapel Hill managed to squeeze out enough on the 4.1-meter (13.5 feet) SOAR telescope in Chile to collect the spacecar's lightcurve.

The changing brightness of the space Tesla reveals the rate at which it is spinning. Eric Dennihy/University of North Carolina

It may never make a published paper, but Dr JJ Hermes alerted the world to their success.


In the spirit of science, others have reviewed the conclusions and questioned them.


This has led to some good-natured discussion. On the one hand, many agree that since the vehicle is still attached to the second stage launch rocket there should be two peaks per rotation, resulting from the reflectiveness of the rocket's sides. On the other hand, prior to the last burn, the live feed SpaceX provided showed the Earth coming into view every 4.75 minutes, making the original estimate more likely.


NASA has registered the roadster, and accompanying driver, as an official space object, designated Starman, 2018-017A.

A spinning object creates what is sometimes called “artificial gravity”, where the acceleration applies a force to anything inside that replicates a gravitational field. It's likely that future missions to Mars will use artificial gravity to prevent the loss of muscle and bone that accompanies long periods of weightlessness. Otherwise, the astronauts would probably be less than ready to do their job on arrival at the Red Planet and would be completely destroyed by a return to Earth gravity.

Unfortunately for the Bowie-playing, Adams and Asimov-reading “astronaut” in the Tesla's driver's seat, a rotation rate of once every 4.7 minutes, let alone 9.5 minutes, on such a small object is far too slow to create the sort of forces needed to keep in shape.

Meanwhile, a preprint of a paper looking at the Roadster's future orbit is available to read on ArXiv under the delightful title “The Random Walk Of Cars And Their Collision Probabilities With Planets”. It concludes Starman's eventual fate is probably to crash into Earth or Venus, but not for tens of millions of years.

spaceSpace and Physics
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