Three secret moons have been discovered lurking out of sight in our outer solar system.
These moons were found orbiting the furthest planets in our solar system: one around Uranus, and the other two Neptune.
This discovery increases the final count of these planets' moons to 28 and 16, respectively, the International Astronomical Union's Minor Planet Center announced on Friday.
"The three newly discovered moons are the faintest ever found around these two ice giant planets using ground-based telescopes," Scott S. Sheppard, an astronomer at the Carnegie Institution for Science, said in a statement. "It took special image processing to reveal such faint objects."
The new Uranus moon has been named S/2023 U1 for now, but will be renamed after a character in one of Shakespeare's plays, just like all of Uranus' other moons. It is about 5 miles across, and orbits its planet once every 680 days.
Uranus is the seventh planet from the Sun, and its moons vary widely in size, composition, and surface features. These moons are divided into two main groups based on their characteristics: the inner moons and the outer moons. Its major moons include Miranda, Ariel, Umbriel, Titania, and Oberon. Uranus's other moons are more irregular in shape and orbit, and include Caliban, Sycorax, Juliet, Cordelia, Ophelia, Puck, and Mab.
Neptune, the eighth planet from the sun, also has a varied collection of moons, the largest of which is Triton, the seventh-largest moon in the solar system. Its other moons include Proteus, Larissa, Galatea, and Despina. Many of Neptune's moons are thought to be objects from the Kuiper Belt at the edge of our solar system that got caught in Neptune's gravity.
The two new Neptunian moons have been named S/2002 N5 and S/2021 N1, but will also be renamed after Nereid sea goddesses from Greek myth. S/2002 N5 is about 15 miles across, while S/2021 N1 is about 9 miles in diameter.
All three of the new moons have distant, skewed, and oval-shaped orbits around their planets, suggesting that they too may have been asteroids or chunks of debris caught in their planets' orbits during the early solar system. The new moons were also found to have similar orbits to other smaller moons of their planets, indicating they might be fragments of the same proto-moon that split apart long ago, as a result of collisions with ancient comets or asteroids.
"Even Uranus, which is tipped on its side, has a similar moon population to the other giant planets orbiting our Sun," Sheppard explained. "And Neptune, which likely captured the distant Kuiper Belt object Triton—an ice-rich body larger than Pluto—an event that could have disrupted its moon system, has outer moons that appear similar to its neighbors."
The new Uranus moon was spied by Sheppard using the Magellan telescopes at Carnegie Science's Las Campanas Observatory in Chile on November 4, 2023, while the Neptunian moons were spotted for the first time in September 2021 using the Magellan telescope and the Subaru telescope. Follow-up observations and data from previous observations were used to confirm the presence of these moons
"Once S/2002 N5's orbit around Neptune was determined using the 2021, 2022, and 2023 observations, it was traced back to an object that was spotted near Neptune in 2003 but lost before it could be confirmed as orbiting the planet," Sheppard said.
Spotting these moons required several long-exposure images taken over several hours, across a series of nights.
"Because the moons move in just a few minutes relative to the background stars and galaxies, single long exposures are not ideal for capturing deep images of moving objects," Sheppard said. "By layering these multiple exposures together, stars and galaxies appear with trails behind them, and objects in motion similar to the host planet will be seen as point sources, bringing the moons out from behind the background noise in the images."
Sheppard and his fellow astronomers hope that these moons can help explain the days of the early solar system, and how the planets and their moons became the way they are today.
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Jess Thomson is a Newsweek Science Reporter based in London UK. Her focus is reporting on science, technology and healthcare. ... Read more
