Uranus and its Moons

Like the other giant planets of the Solar System, also Uranus has a large court of satellites (27 are known today), of which the five imaged here (Miranda, Ariel, Umbriel, Titania and Oberon) are the brightest. These moons are however still very tiny: their combined mass is less than half that of Triton, the largest moon of Neptune alone! Titania, Uranus largest satellite, has a size of less than half of our Moon. These small sizes combined with the distance from us and the low surface albedo, make the Moons of Uranus very faint to be observed, with a brightness variation between 13.9 of Titania to only 16.5 of Miranda, the Moon barely visible in the "glare" of Uranus. Despite requiring 84 Earth years to complete a full rotation around the Sun, at high telescopic power the proper motion of Uranus is still well noticeable comparing the background stars. In this animation, covering about an hour of time, the telescope was tracking Uranus so it was the star to the left (a star of Mag. 13.6 named by its GAIA catalogue number) showing this proper motion over the imaging period. C14 + Siebert 1.5x (@ f/16) - ZWO ASI290MM - iOptron CEM120 - Singapore

Uranus on November 24, 2020

Uranus is the 7th planet from the Sun and, being near the limit of naked eye visibility, was the first planet discovered with the use of a telescope, by William Herschel in 1781. Uranus is also the third-largest planet in our Solar System, after Jupiter and Saturn, but due to the enormous distance from us it appears very small. At around 2.9 billion kilometers (1.8 billion miles) away, the apparent size of Uranus (3.7" at the time of this image) is equivalent to what a US dime or an Euro 2 cents coin looks at 1 km / 0.6 miles of distance! Light takes about 2.5 hours to travel from Uranus to us and it took 4.5 years to Voyager 2 to get there, the the only human spacecraft ever visiting the planet, in 1986. Uranus makes one trip around the Sun every 84 Earth years and it looks like rolling around the Sun on its side, as the planet is tipped over with an axial tilt of 98 degrees. It also has one of the shortest day among the planets in the Solar System: one rotation on Uranus takes just about 17 hours to complete. Unfortunately Uranus doesn't show many details in visible light but it shows some brightness differences of its atmosphere when observed in Infrared light, as visible in the image panel where a >642nm IR pass filter was used as luminance of the final color image. C14 + Siebert 1.5x (@ f/16) - Drizzle 1.5x - ZWO ASI290MM - iOptron CEM120 - Singapore