2021, June 21: Jupiter Retrogrades

June 21, 2021:  Jupiter begins retrograde, moving westward compared to the distant stars, today. The Jovian Giant, among the stars of Aquarius, is in the southern sky before sunrise.

2021, June 21: Jupiter begins to retrograde in front of the stars of Aquarius.
Chart Caption – 2021, June 21: Jupiter begins to retrograde in front of the stars of Aquarius.

by Jeffrey L. Hunt

Following Saturn’s lead, Jupiter begins to retrograde this morning.  Retrograde motion is an illusion from our planet catching and passing the outer planets.

In the combined motion of Earth and the planets revolving around the sun, the other worlds normally move eastward along the plane of the solar system, the ecliptic.  They appear to move in front of the distant constellations that have familiar names, like Taurus and Aquarius, as well as others, such as Cetus and Ophiuchus.

Saturn, over 19° to the lower right of Jupiter, began retrograding in front of the stars of Capricornus on May 22.  The planet is slowly moving westward.  With a binocular find it to the lower right of the star Theta Capricorni (θ Cap on the chart).

Earth passes between Saturn and the sun on August 2, an event known as opposition.  The planet continues to retrograde until October 10 when it resumes its eastward trek compared to the sidereal background.

Jupiter begins its retrograde in Aquarius, near the stars Iota Aquarii (ι Aqr), Theta Aquarii (θ Aqr) – also known as Ancha, “the hip” – and Sigma Aquarii (σ Aqr).

Use a binocular to find the starfield behind the Jovian Giant.

For several days, Jupiter does not appear to move much westward as it begins to pick up speed.

This planet is at opposition on August 19 and ends its retrograde October 17.

Both planets are rising early during the evening, before midnight in Chicago.  Saturn rises in the east-southeast nearly 2.5 hours after sunset, about the end of evening twilight.  Jupiter follows about an hour later.  By one hour before sunrise, both are in the southern sky.

Jupiter is the brightest “star” in the morning sky.  Saturn is only dimmer than the Jovian Giant and the stars Arcturus and Vega.  By month’s end, Mercury begins to move into the morning sky and becomes the morning’s second brightest “star” during July.

Carefully note the positions of Jupiter and Saturn compared to the starry background during the next few months as they retrograde.

Articles and Summaries

2021, May 13: The crescent moon is 3.2° to the upper left of Mercury.

2021, August 9: Evening Moon, Mars

August 9, 2021: After the New moon yesterday morning, the crescent moon appears in the evening sky during bright twilight near Mars.

2021, May 13: Brilliant Venus, Mercury, and the crescent moon in the evening sky.

2021, August 3: Four Evening Planets: Venus, Mars, Saturn, Jupiter

August 3, 2021:  Four planets appear in the evening sky.  Brilliant Evening Star Venus and dim Mars are in the west after sunset.  A little later during the evening, Saturn and Jupiter are easily visible in the southeast.

Saturn (NASA)

2021, August 2: Saturn at Opposition

August 2, 2021: Saturn is at opposition with the sun.  Earth is between the sun and the planet.

2020, July 17: The crescent moon appears near Venus before sunrise. The night portion of the moon is gently illuminated by earthshine.

2021: August 1 – 6: Morning Moon, Bright Stars

August 1 – 6, 2021:  The morning moon wanes toward its New moon phase in the eastern sky.  It passes the bright stars that are prominent in the evening sky during the winter season in the northern hemisphere.  The stars have been making their first appearances in the morning sky during summer.  At this hour, Procyon and bright Sirius are the last stellar duo to appear.

2021, July 8: The flowers celebrate summer.

2021, August 6: Summer’s Midpoint

August 6, 2021:  In the northern hemisphere, summer’s midpoint occurs today at 6:27 p.m. CDT.



Categories: Astronomy, Sky Watching

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