Magazine
Latest Issue

Lab report

A new astronomical discovery means that we will either have to lose Pluto as a planet, or admit that our solar system has far more planets than the textbooks say

By Philip Ball   March 2006

Downsizing Pluto When Pluto was discovered in 1930, it was entirely reasonable to call it a planet. It seemed, after all, to correspond to the so-called “Planet X” that was wrongly thought to be perturbing the orbits of Uranus and Neptune. Pluto’s own orbit was odd—more elliptical than that of other planets, and set at a rakish tilt to the plane of the solar system—and the planet was very far away and rather small, barely two thirds the diameter of our moon. Nevertheless, it became accepted as the ninth planet, even if its discovery four years before Holst’s death came…

Register today to continue reading

You’ve hit your limit of three articles in the last 30 days. To get seven more, simply enter your email address below.

You’ll also receive our free e-book Prospect’s Top Thinkers 2020 and our newsletter with the best new writing on politics, economics, literature and the arts.

Prospect may process your personal information for our legitimate business purposes, to provide you with newsletters, subscription offers and other relevant information.

Click here to learn more about these purposes and how we use your data. You will be able to opt-out of further contact on the next page and in all our communications.

We want to hear what you think about this article. Submit a letter to letters@prospect-magazine.co.uk

More From Prospect