Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2021 December 19

Planetary Alignment over Italy

Image Credit & Copyright: Antonio Finazzi

Explanation: It is not a coincidence that planets line up. That’s because all of the planets orbit the Sun in (nearly) a single sheet called the plane of the ecliptic. When viewed from inside that plane — as Earth dwellers are likely to do — the planets all appear confined to a single band. It is a coincidence, though, when three of the brightest planets all appear in nearly the same direction. Such a coincidence was captured earlier this month. Featured above (right to left), VenusSaturn, and Jupiter were all imaged together in a line just after sunset, from the San Fermo HillsBergamoItaly. Joining the alignment are Earth’s Moon, and the position of the more distant Uranus. Bands of clouds streak across the sky toward the setting Sun. As Comet Leonard fades, this planetary alignment — absent the Moon — should persist for the rest of the month.


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