November 3, 1997
The night sky on your birthday is never quite the same twice — the planets shift, the constellations drift, the Moon wears a different phase.
Irregular Moons Discovered Around Uranus
Birthday · November 3, 1997
A little universe, just for you
Your date.
Ready to give.
Free PNG · 1080 × 1350 · No account needed
Image rights and credit requirements apply when sharing or reusing imagery.
Date & occasion only
Change the year
APOD published November 3, 1997. Full image credits are on the original APOD entry below. A publication-date match, not a photo taken on your date. Independent of NASA.
Where did these two irregular moons of Uranus originate? Last week two previously undiscovered moons of the distant gas planet were confirmed, the first in irregular orbits. All fifteen previously known moons of Uranus are 'regular', circling near the planet's equator. Most of these were discovered by the passing Voyager 2 spacecraft in 1986. These newly discovered moons are thought to be odd-shaped and about 100 km across. They are considered irregular, though, because they orbit in odd directions and far from Uranus. If Uranus' irregular moons have the same origin as those orbiting Jupiter, Saturn, and Neptune, then they were probably caught from orbits around the Sun. Moons like this are discovered by their motion. One of these moons is shown above as the circled point of light moving from left to right. (To stop the movie from repeating, click "stop" on most browsers.)