A bright light will hang next to the moon over Ireland tonight as the largest planet in the solar system, Jupiter, passes by.

Astronomy Ireland have received calls in the past reporting this phenomenon as a UFO. “We’re spoiling the unidentified part now,” jokes David Moore, founder of the society.

“It will look like an extremely bright star — it’s 20 times brighter than the brightest star in the sky,” he says.

“Anybody out walking the dog who glances up at the moon is going to see Jupiter right next to it. It wasn’t there last night and it won’t be there tomorrow.”

The moon is less than half a million kilometres from the earth, while Jupiter is almost 2,000 times that.

Mr Moore says size is the reason Jupiter will be so blinding. “Although it’s five times further from the sun than we are, it’s so big, it reflects more light. You’d need 1,300 balls of Earth squished together to fit inside Jupiter.”

Spheres

While this event happens technically every month, the two spheres are rarely this close. “This is a probably a once a year or so event,” he says. “Eighteen-year cycles exist behind all these close approaches, and we’re at a part where the close approaches can be very close.”

The spectacle of glowing orbs will be visible for a window of three hours all over the island, from sunset at 9pm until Jupiter sets just after midnight.

“You’ll see it north and south, with the naked eye,” says Mr Moore. “There’s no need for telescopes or binoculars.”

“The only potential problem is the Irish weather — three out of four nights in Ireland are cloudy,” he adds. “But you can even see a glow through the clouds.”

Ireland is home to many astronomy-enthusiasts, with Astronomy Ireland being the most popular astronomy society in the world relative to population size.

The society is inviting the public to send photos of this rare sight to be published in the Astronomy Ireland magazine.