by Sign up for CNN’s Wonder Theory science newsletter. Explore the universe with news on exciting discoveries, scientific advances and more.
Astronomers have discovered three previously unknown moons around Uranus and Neptune, the most distant planets in our solar system.
The discovery includes one moon seen orbiting Uranus — the first such discovery in more than 20 years — and two detected orbiting Neptune.
“The three newly discovered moons are the smallest ever discovered around these two ice giant planets using ground-based telescopes,” said Scott S. Sheppard, an astronomer at the Carnegie Institute of Science, in a statement. “It took special image processing to reveal such faint objects.”
The publications will be helpful for missions that could be planned to explore Uranus and Neptune in more detail in the future, a priority for astronomers since the icy planets were only observed in detail by Voyager 2 in the 1980s.
The International Astronomical Union’s Minor Planet Center announced the three moons on February 23.
Finding thin moons
The new Uranian moon is the 28th to be observed orbiting the ice mass and is probably the smallest, 5 miles (8 kilometers) across. The moon, known as S/2023 U1, takes 680 Earth days to complete one orbit around the planet. In future, the small satellite will be named after a Shakespearean character, in keeping with the tradition of Uranus’ moons having literal names.
Sheppard saw the Uranian moon in November and December while observing using the Magellan telescope at the 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.
The Magellan telescope also played a key role in helping Sheppard discover the brighter of the two new Neptunian moons, S/2002 N5. The Subaru telescope, located on Hawaii’s dormant volcano, Mauna Kea, helped Sheppard and his collaborators, astronomer David Tholen at the University of Hawaii, astronomer Chad Trujillo at Northern Arizona University, and planetary scientist Patryk Sofia Lykawka at Kindai University in Japan, focus on Neptune’s other very faint moon, S/2021 N1.
The two moons, which bring the total of known natural satellites of Neptune to 18, were seen for the first time in September 2021, but follow-up observations with different telescopes were needed over the last few years to confirm their orbits.
“Once the orbit of S/2002 N5 around Neptune was determined using the 2021, 2022, and 2023 observations, it was traced back to an object seen near Neptune in 2003 but lost before it could be confirmed it orbits the planet,” Sheppard said.
The bright moon S/2002 N5 is 14 miles (23 kilometers) in diameter and takes nearly nine years to complete an orbit around Neptune, while the narrow S/2021 N1 is about 8.7 miles (14 kilometers) across and has a long orbit around it. 27 years. Both will eventually get new names that refer to the Nereid sea goddesses from Greek mythology. Neptune was named as the Roman god of the sea, so the planet’s moons are named after lesser sea gods and nymphs.
To get the three moons, many short exposures of five minutes were required over a period of three or four hours on different nights.
“Because the moons move in minutes relative to the stars and galaxies in the background, long single exposures are not ideal for capturing deep images of moving objects,” said Sheppard. “By layering these multiple exposures together, stars and galaxies are seen with trails behind them, and moving objects like 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 distant, angular orbits of the moons, Sheppard hypothesized that the satellites were drawn into orbits around Uranus and Neptune by the gravitational influence of the giant planets shortly after their formation. The outer moons orbiting the giant planets throughout our solar system – Jupiter, Saturn, Uranus and Neptune – have similar configurations.
“Even Uranus, which is stuck on its side, has a population of moons similar to the other giant planets orbiting our Sun,” Sheppard said. “And Neptune probably captured the distant Kuiper Belt object Triton – an ice-rich body larger than Pluto – an event that could affect its moon system, there are external moons that are similar to its neighbors.”
It is possible that some of the moons around the giant planets were fragments of moons that were once larger than that and were broken apart by collisions with asteroids or comets.
Astronomers help astronomers understand our solar system’s chaotic early days and how the giant planets formed their moons.
For more CNN news and newsletters create an account at CNN.com
