Neptune's pair of new moons brings the planet's total count up ... is the faintest moon ever discovered by ground telescopes with a size of only 9 miles (14 km) and a vast orbit of nearly 27 ...

However, it is the fainter Neptune moon, provisionally named S/2021 N1, that presents a unique challenge. With a size of approximately 14 kilometers and an orbit spanning almost 27 years ...

The larger moons of Pluto and Earth likely formed through a collisional process with Charon and our moon, respectively, rather than by gravitationally capturing them. Due to Pluto and Charon's rocky, ...

From January to March, the night sky will host a spectacular parade of planets featuring Venus, Mars, Jupiter, Saturn, Uranus ...

Alignments of five or more planets are rare—there will be two more featuring five or more planets this year, but after that ...