Our solar system may be small relative to the universe, but it is surprisingly still generating new discoveries.
Scientists have discovered three new moons: two orbiting Neptune and one orbiting Uranus.
Uranus’s new moon, the first discovered around the planet in more than 20 years, is probably the smallest, just five miles in diameter.
Meanwhile, Neptune’s two new moons include the faintest moon ever discovered by ground-based telescopes.
They bring the total number of known moons of Neptune to 16, while Uranus now has 28, although this figure is still modest compared to the two largest planets in the solar system.
The moon of Uranus S/2023 U1. Uranus is just outside the field of view at the top left, as seen by the increased scattered light.
In the photo, Uranus (left) and Neptune (right). Uranus and Neptune, the seventh and eighth planets, are the only two ice giants in the outer solar system.
Jupiter has 95 moons and Saturn has a whopping 146, and the number increases periodically.
Dr. Scott S. Sheppard, an astronomer at the Carnegie Institution for Science, led the discovery of the three new moons.
More than 30 million miles away, they orbit the two most distant planets in our solar system.
“The three newly discovered moons are the faintest ever found around these two ice giant planets using ground-based telescopes,” he said.
“Special image processing was necessary to reveal such faint objects.”
The new moon of Uranus is tentatively called S/2023 U1, but will eventually be named after a character from a Shakespeare play, in accordance with naming conventions for Uranus moons.
It was first discovered in November last year by Dr Sheppard using the Magellan telescopes at Carnegie Science’s Las Campanas Observatory in Chile.
At only about 5 miles (8 km) in diameter, it is probably the smallest of Uranus’s moons in existence and takes 680 days to orbit the planet.
Sheppard also used the Magellan Telescope to find the brighter of the two newly discovered Neptunian moons, provisionally named S/2002 N5.
It is about 14 miles wide (23 km) and takes almost nine years to orbit the ice giant.
Shown in the photo are the well-known outer moons of the giant planets. The new discoveries of Uranus (pink) and Neptunian (blue) are shown as solid symbols.
S/2023 U1 was first detected on November 4, 2023 by Sheppard using the Magellan telescopes at Carnegie Science’s Las Campanas Observatory in Chile (pictured)
Meanwhile, the faintest Neptunian moon, S/2021 N1, is about 8.5 miles (14 km) in diameter and has an orbit of nearly 27 years and was found using the Subaru Telescope in Hawaii.
Both will receive permanent names based on the 50 Nereid sea goddesses from Greek mythology.
All three moons have distant, “eccentric” orbits, meaning their planet’s orbit is not perfectly circular.
They were captured by the gravity of these planets during or shortly after Uranus and Neptune formed from the ring of dust and debris that surrounded our sun in its infancy.
Earth’s only moon likely formed when a large body the size of Mars collided with Earth, ejecting a large amount of our planet’s material into orbit.
According to NASA, there are likely thousands more moons waiting to be discovered in our solar system.
Even with the most powerful ground-based telescopes, many are small enough to be too weak to see.
Even satellites sent more than a billion miles to the outer planets may not reach the moons depending on where they are in their orbit.
It was in 1989 that NASA’s Voyager 2 spacecraft provided the first close-up images of Neptune, although Neptune is actually a paler blue-green hue than this image suggests.
Uranus and Neptune, the seventh and eighth planets in our solar system, are the only two ice giants in the outer solar system.
They are formed mainly by a dense, hot fluid of frozen materials (water, methane and ammonia) over a small rocky core.
Scientists recently revealed new images of what both planets really look like, claiming that previous photographs of them misrepresented their true colors.
Neptune is known for being deep blue and Uranus green, but the two ice giants are actually much closer in color than is usually thought.
Neptune is actually a pale bluish-green or “cyan,” similar to Uranus and much lighter than the famous deep blue in images from the Voyager 2 spacecraft.