Amateur astronomers are preparing for a heavenly treat from Friday as the five planets visible to the naked eye line up in order of their distance from the sun across the pre-dawn sky.
For those who can face the early start, and have an unobstructed view of the horizon to the east and south-east, Mercury, Venus, Mars, Jupiter and Saturn, could all be visible before the faintest, Mercury, vanishes in the glare of sunrise.
It is not uncommon to see two or three planets close together, but the five that can be spotted with the naked eye have not appeared in order, as viewed from the northern hemisphere, since December 2004.
“This is really cool,” said Prof Beth Biller, personal chair of exoplanet characterisation at Edinburgh University’s institute for astronomy. “We now know of many other stars hosting multiple planets. This is a rare opportunity to see the same thing closer to home, with all five ‘naked eye’ planets in our solar system visible at once.”
The planets of the solar system orbit the sun in a remarkably narrow plane, meaning that when viewed from Earth, they appear to lie close to an imaginary line in the sky called the ecliptic. The five planets will rise above the horizon in the early hours of Friday, though it may be hard to see them all until later in the month.
Dr Greg Brown, the public astronomy officer at Royal Museums Greenwich, said Venus and Jupiter would be the easiest to see, with Venus above the horizon from about 4am UK time and Mars and Jupiter visible from about 2.45am.
Saturn rises above the horizon at about 1.30am, but like Mars will become difficult to see at twilight. Mercury will be the toughest to spot as it only rises at about 4.30am, when it will be hard to see in the pre-dawn light, and will stay close to the horizon.
“Your only chance to see all five planets at the same time is during a very narrow window after Mercury has risen but before the sun has,” Brown said.
“A pair of binoculars or a telescope may well be enough to overcome the twilight in the case of the fainter planets, but do be very careful when trying to observe particularly Mercury in this way. Ensure that the sun is below the horizon to avoid accidentally looking directly at it, which would be very dangerous for your eyes.”
Mercury will be easier to spot later in June as it rises in the sky and brightens. On 24 June, the five planets will be joined by a crescent moon between Venus and Mars, making for an “extraordinary scene”, according to Dr Samantha Rolfe, the principal technical officer at the University of Hertfordshire’s observatory. Because Mercury will be so faint as dawn is breaking, Rolfe recommends using an app such as Stellarium to find its position in the sky.
“You do not need binoculars or a telescope if you don’t have them – just enjoy the sight from wherever you can, even if you can’t see all five from your location,” Rolfe said. “This is a rare spectacle that can help us feel connected to nature and the world around us, and enjoying the night sky in general is a great wellbeing exercise.
“Knowing that so many people are looking up at the same sky, as our ancestors did, and our descendants will, is something to behold. Check the weather forecast for clear or even partially clear skies, and set an alarm – it will be worth getting up for.”
