Early risers this month have been treated to an unusual celestial "pas de trois," as the three brightest superior planets — called "superior" because they move in orbits beyond the Earth from the sun — have been changing positions relative to each other in the dawn twilight. The three planets in question are (in order of brightness), Jupiter, Saturn and Mars.
Jupiter currently rises around 3:45 a.m. local daylight time, but is best seen, especially in telescopes, as dawn is starting to break about 2.5 hours later. At that hour the king-sized world shines fairly low in the southeast with the Teapot of Sagittarius to its right.
Meanwhile, having shifted from Sagittarius into Capricornus on the March 21, Saturn rises about 15 minutes after Jupiter, though in trying to view its famous rings through a telescope, its southern declination will keep it frustratingly low for northern observers. The best views will be after dawn begins, and the farther south you are the better.
Then comes Mars, which rises close to 4 a.m. and continues to get closer to Earth in its orbit, though the planet is brightening at a rather slow pace. But that increase in brightness will accelerate dramatically during spring and summer.
Earlier this month, Mars, Jupiter and Saturn were strung out diagonally in that order from upper right to lower left, low in the southeast sky, Jupiter equally spaced by 8 degrees from Mars and Saturn. In the days that followed, the arrangement of these three worlds noticeably changed. The main reason being that Mars moves rapidly eastward, while Jupiter and especially Saturn's motion are more sluggish.
On the first morning of spring, Mars and Jupiter were in conjunction with Mars passing just 0.7 degrees to the lower right of the much brighter Jupiter.
The best is yet to come!
But the best configuration of these three planets will come early on the morning of Thursday, March 26. They are equally spaced again but this time, much closer together. They will form an upside down isosceles triangle, with Mars serving as the point of the vertex angle, while the base angles are marked by Jupiter and Saturn. Jupiter and Mars and Mars and Saturn each separated by only 3.5 degrees, while Jupiter and Saturn are separated by 6.5 degrees. Going from right to left: Jupiter, Mars and Saturn.
Star of Bethlehem?
Traditionally during the Christmas season, some stargazers ponder the age-old question of the origin of the Star of Bethlehem. The star's appearance more than 20 centuries ago is surely the best-known celestial event in all of recorded history. The likelihood that the Wise Men could have confused one of the familiar planets with a new star seems remote. However, sometimes two or more of these restless wanderers come together in a striking conjunction.
A close conjunction of three or more planets is quite unusual. Over the last 500 years, Jupiter, Saturn and Mars have gathered together just eight times. On Feb. 25 in the year 6 B.C., one such gathering happened in the constellation Pisces. If you have visited a planetarium for the traditional Christmas show, you know the thrill of seeing these worlds approach each other as the projector races back through time to recreate this unusual event.
Could such a rare gathering of these three planets have been the Star of Bethlehem? At no point did the three planets come close enough to merge into a single blazing image like a star. However, their "celestial summit meeting" was undoubtedly watched with great interest by the Wise Men (who themselves were astrologers) and may have been interpreted as a portent. But opinions are divided on the validity of this explanation.
Interestingly, our upcoming gathering involving Jupiter, Saturn and Mars will very closely replicate the celebrated event of 6 B.C. So, if you want to see one of the possible explanations for the fabled "Star of the Magi" for yourself, check out the east-southeast sky about 90 minutes before sunrise on Thursday morning.
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Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for Natural History magazine, the Farmers' Almanac and other publications. Follow us on Twitter @Spacedotcom and on Facebook
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