In a once-in-a-lifetime event, Jupiter dances with Saturn木星と土星が大接近

The evening sky over the Northern Hemisphere treated stargazers to a once-in-a-lifetime illusion on Dec. 21 as the solar system’s two biggest planets appeared to meet in a celestial alignment that astronomers call the “Great Conjunction.”

The rare spectacle resulted from a near convergence of the orbits of Jupiter and Saturn that happened to coincide with the Dec. 21 winter solstice, the shortest day of the year. For those able to observe the alignment in clear skies, the two frozen-gas spheres appeared closer and more vibrant than at any time in 800 years.

Jupiter – the brighter and larger of the pair – has been gradually nearing Saturn in the sky for weeks as the two planets proceed around the sun, each in its own lane of an enormous celestial racetrack, said Henry Throop, an astronomer at National Aeronautics and Space Administration headquarters in Washington.

At the point of convergence, Jupiter and Saturn appeared to be just one-tenth of a degree apart, roughly equivalent to the thickness of a dime held at arm’s length. In reality, of course, the planets remained hundreds of millions of kilometers apart, according to NASA.

A conjunction of the two planets takes place about once every 20 years. But the last time they came as close together in the sky as on Dec. 21 was in 1623 and it was during daylight, making it invisible from most places on Earth. (Reuters)