2024, December 30: Spotlight Jupiter

December 30, 2024:  Bright Jupiter is in the eastern sky after sunset.  Sky watchers with telescopes can see its satellites move.

Jupiter, Mars, Moon gather, August 27, 2024
Image Caption, 2024, August 27: Jupiter, Mars, Moon gather before sunrise

by Jeffrey L. Hunt

Spotlight Jupiter

Jupiter
Chart Caption – 2024, December 30: Jupiter is in front of Taurus in the eastern sky after sundown.

Bright Jupiter is in the eastern sky as darkness falls.  As the second brightest starlike body in the sky tonight, it is noticeably dimmer than Venus, shining from the southwestern sky.

2024, October 9 – 2025, February 4: Earth and Jupiter from above the solar system, showing Jupiter’s retrograde.
Chart Caption – 2024, October 9 – 2025, February 4: Earth and Jupiter from above the solar system, showing Jupiter’s retrograde.

Jupiter retrogrades in front of Taurus, 5.8° to Aldebaran’s upper left, the Bull’s brightest star.  Retrograde is an illusion as our planet passes between an outer planet and the sun.  The line of sight from Earth through the planet and extended toward the background stars that normally moves eastward, shifts westward as we pass.

Jupiter’s retrograde began October 9th.  Earth was between Jupiter and the sun, known as opposition on December 7th.  Retrograde ends February 4th.

Moons’ Shadows on Jupiter

Jupiter's volcanically active moon Io casts its shadow on the planet in this dramatic image from NASA's Juno spacecraft. As with solar eclipses on the Earth, within the dark circle racing across Jupiter's cloud tops one would witness a full solar eclipse as Io passes in front of the Sun. (NASA Photo)
Photo Caption – Jupiter’s volcanically active moon Io casts its shadow on the planet in this dramatic image from NASA’s Juno spacecraft. As with solar eclipses on the Earth, within the dark circle racing across Jupiter’s cloud tops one would witness a full solar eclipse as Io passes in front of the Sun. (NASA Photo)

In the Americas after sunset, sky watchers with larger aperture telescopes that can clearly reach magnifications over 150x see Europa moving in front of the planet and casting its shadow on Jupiter’s cloud tops.

With Jupiter low in the western sky before sunrise in the Americas this morning, Io and Ganymede are in front of Jupiter. Beginning about 3:45 a.m. Central Time, Io’s shadow is visible on Jupiter’s cloud tops and Ganymede’s appears about an hour later, but the planet is very low in the western sky from mid-America.  For sky watchers in other time zones, Io’s shadow appears at 09:45 UTC and Ganymede’s, 10:45 UTC.  Convert this time to local time zones.

Whether you have a large telescope to see the moons in front of Jupiter, its retrograde is easy to watch compared to Aldebaran.

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