Scientists were wrong in estimating the length of a day on Uranus, the Hubble telescope showed

Analysis of Hubble telescope observation data for Uranus, the seventh planet in the Solar System, has made it possible to determine the length of a day on this planet with high accuracy. This information will help plan space missions to Uranus and organize observations of it. However, the most valuable was the development of a method for remotely determining the length of a day on planets, including distant exoplanets, which expands the possibilities for studying other worlds.

Uranus up close. Image source: NASA

The length of a day on Uranus was first determined by the NASA Voyager 2 space probe during its flyby of the planet in January 1986. This was done based on an analysis of Uranus’ magnetic field and, as it later turned out, with a large margin of error. Nevertheless, the length of a day was then established as 17 hours, 14 minutes, and 24 seconds. Since this value was in doubt, scientists decided to re-analyze the planet’s magnetic field – this time based on observations of the polar lights on Uranus by the Hubble telescope.

Archived Hubble observations of Uranus’ auroras

The researchers used data from the Hubble archive for the period from 2011 to 2022. They analyzed the movements of the polar lights over the planet. The analysis and calculations showed that the previous estimate of the length of the day was inaccurate: the error was 28 seconds. The most accurate value for the length of the day on Uranus to date is 17 hours 14 minutes and 52 seconds. Applying a similar technique to exoplanets will allow us to find out the length of the day on worlds located tens and hundreds of light years from Earth. This will provide more information about planets that humanity may never reach.