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Astronomers have discovered three previously unknown moons around Uranus and Neptune, the most distant planets in our solar system.
The find includes a moon orbiting Uranus (the first discovery of its kind in more than 20 years) and two moons detected orbiting Neptune.
“The three newly discovered moons are the faintest moons ever found around these two ice giant planets using ground-based telescopes,” he said. Scott S. Sheppardastronomer from the Carnegie Institution for Science said in a statement. “Revealing such faint objects required special image processing.”
These discoveries will be useful for future missions that may be planned to explore Uranus and Neptune more closely; This is a priority for astronomers since ice planets were only observed in detail with Voyager 2 in the 1980s.
The three moons were announced by the International Astronomical Union’s Minor Planet Center on February 23.
Finding faint moons
The newly discovered moon of Uranus is the 28th moon observed orbiting the ice giant and is also likely the smallest, measuring 5 miles (8 kilometers) in diameter. The Moon, named S/2023 U1, takes 680 Earth days to complete one rotation around the planet. In the future, the small moon will be named after a character from Shakespeare, in keeping with the tradition of Uranus’ moons bearing literary names.
Sheppard detected the moon Uranus while making observations using Magellan telescopes at the Las Campanas Observatory in Chile in November and December. He worked with Marina Brozovic and Bob Jacobson of NASA’s Jet Propulsion Laboratory in Pasadena, California, to determine the moon’s orbit.
Magellan telescopes also played a key role in Sheppard’s discovery of the brighter of two new moons of Neptune, S/2002 N5. The Subaru telescope, located on Hawaii’s dormant volcano Mauna Kea, was built by Sheppard and colleagues by astronomer David Tholen of the University of Hawaii, astronomer Chad Trujillo of Northern Arizona University, and planetary scientist Patryk Sofia Lykawka of Kindai University in Japan. It helped him focus on. the other extremely faint Neptune moon S/2021 N1.
Both moons, which bring the total of Neptune’s known natural moons to 18, were first detected in September 2021, but their orbits required follow-up observations with different telescopes over the past few years to confirm.
“Once S/2002 N5’s orbit around Neptune was determined using observations from 2021, 2022 and 2023, it was tracked to an object that was detected near Neptune in 2003 but disappeared before it could be confirmed to be in orbit around the planet,” Sheppard said. .
The bright moon S/2002 N5 is 14 miles (23 kilometers) in diameter and takes about nine years to complete an orbit of Neptune; faint S/2021 N1 is about 8.7 miles (14 kilometers) in diameter and has an elongated orbit about 200 meters long. 27 years. Both will eventually be given new names referencing the Nereid sea goddesses of Greek mythology. Neptune is named after the Roman god of the sea, so the planet’s moons are named after lesser sea gods and nymphs.
Finding all three moons required dozens of short, five-minute exposures over three or four hours on different nights.
“Since the moons move relative to background stars and galaxies in only a matter of minutes, a single long exposure is not ideal for capturing deep images of moving objects,” Sheppard said. “By combining these multiple exposures, stars and galaxies are revealed with trails behind them, and moving objects similar to the home planet will be seen as point sources, revealing moons from behind background noise in the images.”
A chaotic solar system
By studying the distant, angular orbits of the moons, Sheppard hypothesized that the moons were pulled into orbit around Uranus and Neptune by the gravitational influence of the giant planets shortly after they formed. The outer moons orbiting all the giant planets in our solar system (Jupiter, Saturn, Uranus, and Neptune) share similar configurations.
“Even Uranus, which is tilted on its side, has a similar moon population as other giant planets orbiting our Sun,” Sheppard said. “And Neptune, which has likely captured the distant Kuiper Belt object Triton (an ice-rich body larger than Pluto), an event that could disrupt the lunar system, has outer moons that appear similar to their neighbors.”
It is possible that some moons around giant planets are fragments of once larger moons that were blown apart by collisions with asteroids or comets.
Understanding how giant planets capture their moons is helping astronomers piece together the chaotic early days of our solar system.
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