2021, October 24: Saturn Inches Toward Jupiter

October 24, 2021:  Saturn is at its closest to Jupiter as the Jovian Giant picks up eastward speed.  The morning moon and Mercury are visible before sunrise.  Brilliant Evening Star Venus, Saturn, and Jupiter are in the sky after sunset.

2021, October 24: Before sunrise, the bright moon is nearly 7° to the upper right of Aldebaran.
Chart Caption – 2021, October 24: Before sunrise, the bright moon is nearly 7° to the upper right of Aldebaran.

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by Jeffrey L. Hunt

Chicago, Illinois:  Sunrise, 7:14 a.m. CDT; Sunset, 5:55 p.m. CDT.  Check local sources for sunrise and sunset times for your location.

Jupiter and Saturn are slowly moving eastward compared to the stars of Capricornus.  Saturn ended its retrograde direction on October 10.  Jupiter followed over a week later.  As Saturn is now noticeably moving eastward compared to the stars, Jupiter is beginning to pickup speed.  This evening Saturn moves to within 15.36° of ecliptic longitude of the Jovian Giant. By the end of the year, Jupiter opens the gap to Saturn to 18.64° of ecliptic longitude.

The ecliptic is the plane of the solar system.  It is the reference line for one astronomical coordinate system.  Objects are measured in longitude from the vernal equinox point and latitude above and below the ecliptic.

Morning Sky

An hour before sunrise, this morning the bright moon, nearly 90% illuminated is over halfway up in the sky in the west-southwest.   It is nearly 7° to the upper right of the star Aldebaran.  The horns of the Bull – Zeta Tauri and Elnath – are above the moon.  Block the moon’s glare to see the stars.

2021, October 24: Forty-five minutes before sunrise, bright Mercury is low in the eastern sky.
Chart Caption – 2021, October 24: Forty-five minutes before sunrise, bright Mercury is low in the eastern sky.

Farther eastward, Mercury, is low in the eastern sky, about 9° above the horizon.  It is bright, but find a clear spot to see the speedy planet.  Take along a binocular to spot the star Porrima, 2.7° above the planet.  Notice the star Arcturus is at about the same altitude – height above the horizon – as Mercury and in the east-northeast, about 30° to the left of the planet.

Evening Sky

2021, October 24: After sunset, Venus is in the southwest, 3.4° to the lower right of Theta Ophiuchi.
Chart Caption – 2021, October 24: After sunset, Venus is in the southwest, 3.4° to the lower right of Theta Ophiuchi.

Evening Star Venus is low in the southwest at forty-five minutes after sunset.  It is stepping through Ophiuchus.  This evening, the planet is 3.4° to the lower right of Theta Ophiuchi (θ Oph on the chart).

2021, October 24: Two hours after sunset, Jupiter and Saturn are in the south. Saturn is at its closest this evening as both planets have resumed their eastward motion.
Chart Caption – 2021, October 24: Two hours after sunset, Jupiter and Saturn are in the south. Saturn is at its closest this evening as both planets have resumed their eastward motion.

At this hour, Jupiter and Saturn are in the southeastern sky.  By two hours after sunset, the planets are in the south.  As noted previously, they are at their closest this evening as Jupiter picks up its eastward speed.  During the next few weeks, watch Saturn pass Upsilon Capricorni (υ Cap on the chart).  Jupiter moves eastward (to the left) compared to Deneb Algedi.

Detailed Daily Note: One hour before sunrise, the moon (18.0d, 87%), over 50° above the west-southwest horizon, is 6.8° to the upper right of Aldebaran. Fifteen minutes later, Mercury, nearly 9° up in the east-southeast, is 2.7° below Porrima. The moon is at apogee at 10:28 a.m. CDT, 252,037.5 miles away. Forty-five minutes after sunset, brilliant Venus is 11.0° up in the southwest, 3.4° to the lower right of θ Oph.  Farther eastward, Jupiter (m = −2.5) is nearly 29° up in the east-southeast, 15.3° to the left of Saturn. This evening the planets are closest as Saturn moves eastward and Jupiter is picking up its eastward speed.  The gap is 15.36° of ecliptic longitude.  By two hours after sunset. Jupiter is almost 33° up in the south, east of the meridian.  In the starfield, the Jovian Giant is 3.7° to the lower right of μ Cap, 2.0° to the upper right of Deneb Algedi, and 1.4° above Nashira.  Saturn is over 28° above the southern horizon, west of the meridian.  Through a binocular, the Ringed Wonder is 1.3° to the lower right of υ Cap.  As the calendar day ends, the moon (18.7d, 82%) – over 34° above the eastern horizon – is to the right of a line from Elnath (β Tau, m =1.6) to Zeta Tauri (ζ Tau, m = 3.0). The lunar orb is 4.0° to the lower right of Elnath.

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