Astronomers using the James Webb Space Telescope have found an unknown moon orbiting Uranus, bringing the planet’s total to 29 — and more likely remain undiscovered.

NASA’s James Webb Space Telescope has found a previously unknown moon orbiting Uranus. NASA announced the discovery on Tuesday, adding that the moon was first spotted on Feb. 2. Scientists estimate that the newly discovered moon is about six miles in diameter.

The discovery expands Uranus’s known family of satellites to 29, with the tiny moon measuring just 6 miles across.