CINCINNATI — It was an astronomical event that humans haven't been able to observe in the night sky since the 13th century, and Cincinnati Observatory astronomer Dean Regas wasn't going to miss it.
Monday evening, Regas pointed the observatory's 175-year-old telescope at a small field of space and captured video of the "Great Conjunction" of Jupiter and Saturn. It was the closest approach between the solar system's two largest planets since 1623, but it was roughly four centuries prior that the spectacle was last visible at night.
While the two planets were at their closest Monday night, it's not too late to catch the rare celestial show: Weather permitting, the planets would still be visible in close conjunction again Tuesday night, Regas said.
"Face southwest between 6:00-6:45 p.m., where you will see two bright dots," Regas said. "To the naked eye, Jupiter will be the brighter one with dimmer Saturn to the side. Through a backyard telescope, you should be able to see both planets at the same time."
While the two planets converge at a relatively close range once every couple of decades, the distance being this close and this visible from the earth is exceedingly rare, according to NASA officials.
“You can imagine the solar system to be a racetrack, with each of the planets as a runner in their own lane and the Earth toward the center of the stadium,” said Henry Throop, an astronomer in the Planetary Science Division at NASA Headquarters in Washington. “From our vantage point, we’ll be able to see Jupiter on the inside lane, approaching Saturn all month and finally overtaking it on December 21.”
It was coincidental that Jupiter and Saturn aligned at their closest on the evening of the winter solstice, the longest night of the year.
Its proximity to the Christmas holiday was also coincidental but caused some to dub the event the "Christmas star," even though the event only involves planets.
Scripps National Desk reporter Justin Boggs contributed to this story.