The planets Uranus (left) and Neptune (right) have a few extra moons.

NASA, ESA, Mark Showalter (SETI Institute), Amy Simon (NASA-GSFC), Andrew I. Hsu, Michael H. Wong (UC Berkeley)

Astronomers have seen new moons around Uranus and Neptune for the first time in a decade. These are the faintest moons ever seen orbiting any planet, and they prove a long-held idea about satellites in the outer solar system.

Scott Sheppard At the Carnegie Institution for Science in Washington, DC, and colleagues found these moons using the Magellan telescope in Chile and confirmed them using several other large telescopes around the world. “We looked four times deeper than before,” Sheppard says. “These moons are at the edge of our ability—they’re just faint, faint points of light.”

Generally, when In search of the moon, you can only take a photo with a maximum exposure of 5 minutes before the photo is maxed out and the movement of the moon renders it useless. Sheppard and his team achieved this by taking many of these 5-minute images in a row, observing for hours, and then combining the dim parts of the images. This enabled them to find the faintest points of light shining from the faintest moons ever discovered – and the smallest moons ever found around their respective planets.

The new moon around Uranus has been tentatively named S/2023 U1, but will eventually be named after a character in a Shakespeare play. Other moons of the planet. It is only 8 kilometers across, and it completes one orbit once every 680 Earth days.

One of the new moons around Neptune is called S/2021 N1, and it’s awaiting an official name from Greek mythology. It is about 14 kilometers across and takes about 27 Earth years to orbit the planet, making it the farthest moon ever seen from its host planet. It is also the lightest moon ever seen.

Discovery image of new Uranian moon S/2023 U1, with scattered light from Uranus and trails from background stars

Scott S. Shepard/Carnegie Institution for Science

The bright, giant moon orbiting Neptune is called S/2002 N5 – as its name suggests, it was first spotted 20 years ago, but lost before astronomers could confirm its orbit. was “You can miss the moon really easily,” Shepard says. Everything needs precision.” If something goes wrong and a night of planned observations is lost, the moons move in their orbits and become extremely difficult to find again, as in S/2002. Happened with the N5.

Each of the three new moons orbits like two other satellites in their own planetary system, and these fellow travelers form small groups that orbit together. This means that each of these groups likely formed together when A big moon broke. In the chaos of the early solar system.

“It was not yet clear whether Uranus and Neptune had groups of outer moons like Jupiter and Saturn,” Shepard says. “We believe these are fragments of once large moons, and there are probably many more smaller ones to be found.” Unfortunately, they say, we are at the limits of what we can detect with current technology, so it may be another long wait before we see moons smaller than these around. Uranus and Neptune.