Our solar system may be small in relation to the universe, but amazingly it’s still yielding new discoveries.
Scientists have discovered three new moons – two orbiting Neptune and one orbiting Uranus.
Uranus’ new moon – the first to be discovered around the planet in more than 20 years – is likely its smallest, at just five miles across.
Meanwhile, the two new moons of Neptune include the faintest moon ever discovered by ground-based telescopes.
They bring Neptune’s total known moons to 16, while Uranus now has 28, although this is still modest compared to the solar system’s two biggest planets.
The Uranian moon S/2023 U1. Uranus is just off the field of view in the upper left, as seen by the increased scattered light
Pictured, 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 figure is rising regularly.
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.
‘It took special image processing to reveal such faint objects.’
The new moon of Uranus is provisionally named S/2023 U1, but it will eventually be named after a character from a Shakespeare play, in keeping with the naming conventions for Uranian moons.
It was first spotted in November last year by Dr Sheppard using the Magellan telescopes at Carnegie Science’s Las Campanas Observatory in Chile.
At only around 5 miles (8km) in diameter, it is likely the smallest of Uranus’ moons that exists and takes 680 days to orbit the planet.
Sheppard also used the Magellan Telescope to find the brighter of the two newfound Neptunian moons, provisionally called S/2002 N5.
It is about 14 miles across (23km) and takes almost nine years to orbit the ice giant.
Pictured are the known outer moons of the giant planets. The new Uranian (pink) and Neptunian (blue) discoveries are shown as solid symbols
S/2023 U1 was first spotted on November 4, 2023, by Sheppard using the Magellan telescopes at Carnegie Science’s Las Campanas Observatory in Chile (pictured)
Meanwhile, the dimmer Neptunian moon, S/2021 N1, is about 8.5 miles (14km) across with an orbit of almost 27 years and was found using the Subaru telescope in Hawaii.
Both will receive permanent names based on the 50 Nereid sea goddesses in Greek mythology.
All three moons have distant and ‘eccentric’ orbits, meaning their orbit of their planet 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 probably formed when a large body about the size of Mars collided with Earth, ejecting a lot of material from our planet into orbit.
According to NASA, there are likely thousands more moons awaiting discovery in our solar system.
Even with the most powerful ground-based telescopes, many are small enough to be too faint to see.
Even satellites that are sent over a billion miles to the outer planets may miss 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 paler shade of greenish blue 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 mainly made up of a hot dense fluid of icy materials – water, methane, and ammonia – above a small rocky core.
Scientists recently revealed new images of what both planets really look like, claiming previous photos of them misrepresented their true colours.
Neptune is known for being a rich blue and Uranus green, but the two ice giants are actually far closer in colour than typically 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.
