BlackSky Blog

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by | Jan 26, 2021

A heavenly view of the christmas star

Jupiter and Its Moons

In the heavens, it’s all about perspective.

A rare astronomical event occurred just after sunset on Dec. 21, 2020, when our solar system’s two largest planets – Jupiter and Saturn – appeared (to the naked eye) to cross paths, creating what appeared to be one bright star and the most luminous object in the night sky.

Called a conjunction, it’s what occurs when two astronomical objects pass each other due to their movement. Seen just above the evening horizon in the Western sky, it has been popularly dubbed “The Christmas Star” for the planets’ extraordinary celestial dance performed on the winter solstice and very near Christmas Day.

Saturn and Jupiter Conjunction

For science, the facts are simple. It was the closest great conjunction (a term reserved only for Jupiter and Saturn only) since July 16, 1623, and the first easily visible one since March 4, 1226, the most recent such conjunction. Prior to that, this last great planet passing visible from Earth occurred in 7 B.C.

That 7 B.C. sighting lends to the calling of this astronomical event the Christmas Star for its proximity to the birth of Jesus and its tie to the biblical Star of Bethlehem. That event purportedly guided the Bible’s three Magi, or wise men, to the baby Jesus – a heavenly portend and shining hope for humanity.

From Earth, the Christmas Star won’t occur again until 2080. This conjunction, putting them visibly a mere 0.1 degrees from each other, occurs every 19.85 Earth years. Jupiter orbits our sun every 11.86 years and Saturn 29.4 and, despite being 465 million miles (730 million km) apart, it’s only natural that from our perspective they occasionally “pass” each other. Johannes Kepler, a 17th century scientist who studied planetary motion, made note of the passing and offered one of the earliest conjectures about it being the actual Star of Bethlehem.

Jupiter was 550 million miles (890 million km) from Earth during the great conjunction; Saturn, nearly twice as far away. However you view the significance of this great Jupiter/Saturn conjunction, BlackSky offers several significant and visually arresting images captured by its satellite constellation orbiting at about 400km above the Earth. Our science also portends a bright future for what can be gleaned from leading edge geospatial intelligence.

Conjunction Time Lapse

Conjunction Vertical