Astronomers have discovered three moons orbiting the most distant planets in our solar system

(CNN) — Astronomers have discovered three moons around Uranus and Neptune, the farthest planets in our solar system.

The discoveries include a moon discovered in the orbit of Uranus (the first discovery of its kind in more than 20 years) and two moons discovered in the orbit of Neptune.

“The three newly discovered moons are the faintest moons ever detected around these two ice giant planets using ground-based telescopes,” astronomer Scott S. Shepard of the Carnegie Institution for Science said in a statement. “Special image processing was required to reveal such blurry objects.”

These revelations will be useful for future missions that may be planned to explore Uranus and Neptune more closely, a priority for astronomers since the icy planets were only seen in detail with Voyager 2 in the 1980s. I went.

The three moons were announced by the International Astronomical Union’s Minor Planet Center on February 23.

NASA’s Voyager 2 spacecraft captured these views of Uranus (left) and Neptune (right) during a flyby of the planets in the 1980s. NASA/JPL-Caltech/B. Johnson

Detecting Weak Moons

The newly discovered moon of Uranus is the 28th moon orbiting the ice giant and possibly its smallest, measuring 8 kilometers in diameter. The moon, called S/2023 U1, takes 680 Earth days to complete one orbit around the planet. In the future, in keeping with the tradition of Uranus’ moons having literary names, the small satellite will be named after a Shakespearean character.

Shepard observed the moons of Uranus in November and December using the Magellan telescopes at Las Campanas Observatory in Chile. He worked with Marina Brozovic and Bob Jacobson of NASA’s Jet Propulsion Laboratory in Pasadena, California, to determine the moon’s orbit.

Magellan’s telescopes also played an important role in helping Shepard discover the brighter of two new Neptunian moons, S/2002 N5. The Subaru Telescope, located on Hawaii’s dormant Mauna Kea volcano, helped Shepard and his colleagues, astronomer David Tholen of the University of Hawaii, astronomer Chad Trujillo of Northern Arizona University and planetary scientist Patrick Sophia Likawaka of Kindai University in Japan, focus their observations. Another extremely faint Neptunian moon, S/2021 N1.

Both moons, bringing the total number of Neptune’s known natural satellites to 18, were first discovered in September 2021, but confirmation of their orbits required follow-up observations with different telescopes over the past few years.

Shepard said, “Once S/2002 N5’s orbit around Neptune was determined using observations from 2021, 2022 and 2023, it detected an object that was found near Neptune in 2003 but “It was lost before it could be confirmed. While orbiting the planet,” .

The bright moon S/2002 N5 has a diameter of 23 kilometers and takes about nine years to complete one orbit around Neptune, while the fainter moon S/2021 N1 has a diameter of about 14 kilometers and a long orbit of about 27 years. Both would eventually receive new names that reference the Nereid sea goddesses of Greek mythology. Neptune was named after the Roman god of the sea, so the planet’s moons are named after nymphs and minor sea deities.

Finding three moons requires dozens of short, five-minute exposures over the course of three or four hours on separate nights.

This discovery image shows the new moon of Uranus S/2023 U1 captured using the Magellan telescope on November 4, 2023. Uranus (top left) is just outside the field of view. Scott Shepard/Carnegie Science

“Since the moons move relative to the background stars and galaxies every few minutes, long single exposures are not ideal for capturing deep images of moving objects,” Shepard explained. “By overlaying these multiple exposures, stars and galaxies appear with trails behind them, and moving objects similar to the host planet will be seen as point sources, bringing the Moon out from behind the background noise in the images. “

a chaotic solar system

By studying the far angular orbits of the moons, Shepard hypothesized that the satellites were drawn into orbit around Uranus and Neptune by the gravitational influence of the giant planets soon after their formation. The outer moons orbiting all the giant planets in our solar system (Jupiter, Saturn, Uranus and Neptune) have the same configuration.

“Even Uranus, which is tilted on its side, has a lunar population similar to that of the other giant planets orbiting our sun,” Shepard said. “And Neptune, which likely captured the distant Kuiper Belt object Triton, an ice-rich body even larger than Pluto, in an event that could disrupt its lunar system, has outer moons that are much larger than those of its neighbors. “Look alike.”

It is possible that some of the moons around the giant planets were once fragments of larger moons that were broken up by collisions with asteroids or comets.

Understanding how giant planets captured their moons helps astronomers reconstruct the chaotic early days of our solar system.