Jupiter and Saturn will align in the night sky today (Dec. 21) in an event astronomers call the “great conjunction,” and you can watch it online with webcasts from The Virtual Telescope Project, Slooh and more.
Tonight’s great conjunction — also nicknamed the “Christmas Star” — marks the closest apparent encounter of Jupiter and Saturn in nearly 400 years. The two planets will be closest to each other in the sky tonight, which is also winter solstice, and may be viewed as one point of light, appearing only a tenth of a degree apart. They will remain in close alignment for a few days and will be easily visible to the naked eye when looking toward the southwest just after sunset.
You can watch the winter solstice great conjunction webcasts live here throughout the day.
A conjunction occurs when planets appear incredibly close to one another in the sky because they line up with Earth in their respective orbits. While Jupiter and Saturn align about once every 20 years, this year’s conjunction marks the first time since 1623 that the two gas giants have passed this close to one another in our sky — and nearly 800 years since skywatchers were able to witness the event at night. The planetary alignment has also been called a “Christmas star,” since it falls on the first day of winter in the Northern Hemisphere and only a few days before Christmas.