Two of the brightest objects in the night sky head towards a close encounter on Monday night. The sky show begins after local nightfall on the 21st when the waxing gibbous moon snuggles up to brilliant white Jupiter in the southeast. This closeness is of course just an illusion – they are in reality separate by hundreds of millions of kilometers.
Lunar conjunctions with planets are not that unusual, however they are rarely this close, says Raminder Singh Samra, a resident astronomer at the H.R. MacMillan Space Centre in Vancouver, Canada.
“Each month the Moon will pass by every planet in the night sky but they are usually a few degrees or few moons discs apart,” said Samra. ” This time we get to witness them passing within half a degree of each other – that’s less than the width of a finger held at arm’s length apart.”
If you miss this alignment, the next time Jupiter and the Moon will pass close to each other will be on March 17 but won’t appear to North Americans quite as close as this one. On August 2016 when the pair will appear even closer in North American skies.
Here are some of Samra’s observing tips…
Who can see event?
The cosmic encounter will be best seen throughout both of the American continents. The exact time the Moon appears closest to Jupiter will depend on location – 7 p.m. in the Pacific time zone, 8:30 p.m. Mountain, 10 p.m. Central, and 11:30 p.m. Eastern time. Some parts of South America will be in for a special treat as they will witness the Moon completely block out Jupiter in the sky.. for local observing times click onto the International Occultation Timing Association website (http://www.lunar-occultations.com/iota/planets/0122jupiter.htm).
What is happening?
Both the Moon and all the planets appear to follow the ecliptic line in the sky – the plane of the solar system through which all orbits are seen edge on from our line of sight here on Earth. The close proximity of the Moon to Jupiter in the sky however is just an optical illusion as they are actually very far apart. While the moon is on average 400,000 km from Earth, Jupiter sits 1700 times further away at about 680 million km.
What is most unusual about this event?
This extra close encounter affords a unique opportunity for keen observers to try and spot Jupiter during daytime- before local sunset. First step is to locate the Moon about halfway up the late afternoon southeast sky and then take binoculars to scan the sky just to its lower left. Special observing challenge will be to see how far before local sunset skywatchers can spot Jupiter in daylight.
How is it best seen?
The conjunction will be a very impressive sight for any observer regardless of location as long as there is a clear line of sight towards the southeast horizon. Even from large, light polluted cities, it promises to be easy to observe with nothing more than naked eyes. Train any sized optical aid on these worlds however, much more details can be glimpsed.
“For those who have a small telescope or a pair of binoculars the view will be greatly enhanced, as even with moderate power both the Moon and Jupiter will be visible at the same time,” adds Samra.
Update 20/1/2013 10 am EST : The story was originally published with errors on the actual distance separating the Moon and Jupiter and there is some confusion regarding this being the tightest conjunction until 2026. This claim appears to be the expectation for North Americans and is based on geocentric calculations (from the center of the Earth) which shows that on Oct.6, 2026 the two will be separated by only 0.17 degrees – as the conjunction would theoretically appear from the center of the Earth. But since we don’t skywatch from there, what an observer at the surface of our planet actually sees (ie. separation of the Moon from the planet in the sky) depends on their geographical location.
Andrew Fazekas, aka The Night Sky Guy, is a science writer, broadcaster, and lecturer who loves to share his passion for the wonders of the universe through all media. He is a regular contributor to National Geographic News and is the national cosmic correspondent for Canada’s Weather Network TV channel, space columnist for CBC Radio network, and a consultant for the Canadian Space Agency. As a member of the Royal Astronomical Society of Canada, Andrew has been observing the heavens from Montreal for over a quarter century and has never met a clear night sky he didn’t like.