Seventh Planet

This week is a very good time for amateur astronomers to easily spot the planet Uranus, weather permitting. It is very close now in the sky to Venus, just after sunset and can easily found with just a pair of binoculars. Uranus is the seventh planet from the Sun. It has the third largest and the fourth heaviest in the Solar System. In classical mythology it is named after the father of Saturn and the grandfather of Jupiter. Uranus is actually just visible to the naked eye, given good seeing conditions, but it was never recognized as a planet by ancient observers because it is not very bright and it has a very slow orbit. It was in fact spotted a number of times by some famous astronomers, including English astronomer John Flamsteed almost a hundred years earlier but was always thought of as a star.

Its formal discovery was credited to Sir William Herschel in 1781 from the garden of his house in Bath. This discovery expanded the known boundaries of the Solar System for the first time in history. Uranus was also the first planet to be discovered with a telescope. A gas giant, it takes 84 years to go around the Sun at an average distance of some 3 billion kilometres. Bizarrely it is tilted by almost 90 degrees onto its side, the result of some ancient event, probably a collision early on in the formation of the solar system. It has a faint ring system, first spotted possibly by Herschel himself and confirmed during the fly-by of the probe Voyager 2. Uranus has 27 known moons in total, 5 of these are the large 'main' moons, but the Uranian satellite system is the least massive of all the gas giants.

 If you get clear skies in the next few days, now is a great time to spot Uranus. Given dark skies, good seeing and good eyesight it is just possible to spot it with the naked eye, but you need to know where to look. The best way to do it is with a pair of binoculars. Consult a start chart or an astronomical website. Look close to Venus just after sunset and see if you can spot the pale blue/green dot that doesn't quite look like a star. In fact, binoculars tend show some colour better than a small telescope. If you do spot her, remember you are probably in the less than one percent of humanity who has ever seen the seventh planet with their own eyes.