Month's planets
Dusk to dawn belongs to the ice giants this month
Uranus marks a turning point in our exploration of the Solar System, discovered by William Herschel in 1781 from the city of Bath. Uranus is tipped on its side by 98 degrees – it appears to roll around the Sun, and currently its north pole is facing us at an angle of 50 degrees. Scientists are not sure why Uranus is on its side, but suspect a giant impact long ago may have knocked it over.
Uranus is an ice giant, which is a mysterious kind of gaseous world that also contains lots of ices – water, methane, nitrogen and so on – and our lack of knowledge about this kind of world is not helped by the fact that only one spacecraft has ever visited Uranus to explore it – NASA’s Voyager 2 mission back in 1986.
Throughout autumn Uranus can be found slowly wandering through the southern part of the constellation of Aries, the Ram. It comes to opposition on the night of 31 October and reaches a healthy 54 degrees above the horizon in the sky, which is the highest it has been seen from the UK in over five decades. Uranus shines at magnitude +5.7, which means that technically it can be seen without binoculars or a telescope, but you would need a very dark sky and to know exactly where to look, so almost everyone will need a telescope to see it.
Uranus will appear as a fuzzy, turquoise disc when seen through a 100mm-aperture telescope. It is unlikely that you will be able to see any details on its globe – it takes a very large aperture, in excess of 300mm, or the talents of the best astrophotographers – to tease out any vague details, and indeed Uranus notoriously appeared bland when Voyager 2 visited it. The same goes for its five main moons, which shine at around 14th magnitude, but the accomplishment comes from just seeing the planet that lies 2.84 billion kilometres (1.76 billion miles) away from us.
Look for Uranus from about 23:00 BST onwards this month, when it has climbed up to about 15 degrees in the sky and the sky has become sufficiently dark. Uranus should then be visible, climbing higher and higher in the sky until dawn breaks the following morning.