By Jove It’s Thors Day

Jupiter & moon Europa from Hubble Space Telescope, 25 Aug 2020 (photo from Wikimedia Commons)

13 October 2022

Today is Thursday, Thor’s Day, or Jove’s Day. We’ll celebrate with some quick facts about Jupiter.

The Romans named the fifth day of the week dies Jovis (“Jove‘s Day”) after the planet Jupiter. In Germanic mythology, Jupiter is equated to Thor, whence the English name Thursday for the Roman dies Jovis.

— From Wikipedia: Jupiter

Jupiter was big in the news last month when on 27 September 2022 the planet was at its closest, brightest and best in 70 years. On that date the Earth flew between Jupiter and the Sun, putting Jupiter in opposition and in bright sunlight as it rose at sunset.

Three days later it rose after sunset so the sky was dark showing off Jupiter’s four largest moons, the ones first seen by Galileo in 1610.

Jupiter & Galilean moons, 30 September 2022 (photo by George E. Koronaios via Wikimedia Commons)

Modern day space probes and telescopes can see the Galilean moons in full color. The image caption on the photo below explains: From left to right in order of increasing distance from Jupiter, Io is closest, followed by EuropaGanymede, and Callisto.

Jupiter’s Galilean moons as seen from NASA’s Galilean spacecraft (image from Wikimedia Commons)

Timelapse photography allows us to see the Galilean moons orbiting Jupiter as NASA’s Juno spacecraft approaches. These are only four of the 80 known satellites of Jupiter, most of which are less than 10km (6.2 miles) in diameter. 80 moons!

Jupiter and the motion of the four Galilean moons taken by JunoCam aboard the Juno spacecraft, June 2016 (animation from Wikimedia Commons)

Moons Io and Europa have sparked a lot of interest.

Jupiter doesn’t have rings like Saturn, but it ought to. Why not?

Because it’s bigger, Jupiter ought to have larger, more spectacular rings than Saturn has. But new UC Riverside research (21 July 2022) shows Jupiter’s massive moons prevent that vision from lighting up the night sky.

Science Daily: Why Jupiter doesn’t have rings like Saturn

And finally, Thursday is a good day to feel jovial. According to Wikipedia, the older adjectival form jovial, employed by astrologers in the Middle Ages, has come to mean “happy” or “merry”, moods ascribed to Jupiter’s astrological influence.

Happy Thursday!

(images from Wikimedia Commons; click on the captions to see the originals)

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