2021, October 20: Mercury, Morning Planet

October 20, 2021: Mercury is brightening in the morning sky.  Brilliant Venus, Jupiter, and Saturn are in the evening sky.  The bright moon starts the evening low in the eastern sky.

2021, October 20: Forty-five minutes before sunrise, Porrima is 1.4° to the upper left of Mercury.
Chart Caption – 2021, October 20: Forty-five minutes before sunrise, Porrima is 1.4° to the upper left of Mercury.

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by Jeffrey L. Hunt

Chicago, Illinois:  Sunrise, 7:09 a.m. CDT; Sunset, 6:01 p.m. CDT.  Check local sources for sunrise and sunset times for your location.

DAILY NOTES FOR OCTOBER 2021

VENUS AS AN EVENING STAR 2021

Morning Sky

Mercury is appearing in the eastern sky before sunrise. It is becoming easily visible about 7° up in the eastern sky at 45 minutes before sunrise.  Use a binocular to locate the star Porrima, 1.4° to the upper left of the speedy planet.

One of the best times to see Mercury is during fall mornings.  The plane of the solar system is highly inclined compared to the eastern horizon.  The planet is always near the sun and when it is seemingly hurled into the morning sky, its stands at its highest above the eastern horizon.

Its best evening appearance occurs during spring evenings.

At this hour the bright moon is low in the western sky.

The moon is at its Full moon phase at 9:51 a.m. CDT after it sets in North America.

Evening Sky

2021, October 20: After sundown, Venus is 4.6° to the upper left of Antares and 3.9° to the upper left of Tau Scorpii.
Chart Caption – 2021, October 20: After sundown, Venus is 4.6° to the upper left of Antares and 3.9° to the upper left of Tau Scorpii.

After sunset three bright planets – Venus, Saturn, and Jupiter – are visible from southwest to southeast. 

Brilliant Venus is nearly 11° up in the southwest at 45 minutes after sunset.  It is near the Scorpius-Ophiuchus border, 4.6° to the upper left of Antares – “the rival of Mars” – 3.9° to the upper left of Tau Scorpii (τ Sco on the chart).

Venus is setting later each evening, now over two hours after sundown.

2021, October 20: Bright Jupiter and Saturn are in the southeastern sky after sunset.
Chart Caption – 2021, October 20: Bright Jupiter and Saturn are in the southeastern sky after sunset.

Farther eastward, bright Jupiter is less than one-third of the way up in the south-southeast.  The planet appears to be moving gently eastward compared to the background stars of eastern Capricornus.  It is 2.1° to the upper right of Deneb Algedi. 

After Venus sets, Jupiter is the brightest “star” in the sky.  Arcturus, Vega, and Saturn are next in brightness.  Saturn is over 15° to the right of the Jovian Giant, in western Capricornus.

Saturn sets in the southwest 6.5 hours after sunset. Jupiter follows about 80 minutes later.  Earlier during the evening, they are low in the southern sky.

After sunset, the moon is very low in the eastern sky.

Detailed Daily Note: One hour before sunrise, the moon (14.0d, 100%) is nearly 9° up in the west. Forty-five minutes before sunrise, Mercury (m = −0.1) is nearly 7° up in the east, 1.4° to the lower right of Porrima (γ Vir, m = 3.4).  Use a binocular to spot the star near Mercury. The moon is at its Full (Hunter’s) moon phase at 9:51 a.m. CDT.  Forty-five minutes after sunset, brilliant Venus is nearly 11° above the southwest horizon, 4.6° to the upper left of Antares and 3.9° to the upper left of τ Sco.  Farther eastward, bright Jupiter is nearly 28° up in the south-southeast. Saturn is 15.3° to the upper right of the Jovian Giant.  The bright moon (14.5d, 100%) is a few degrees above the eastern horizon.  Two hours after sunset, the lunar orb is over 17° up in the eastern sky.  Jupiter and Saturn are in the south.  The Jovian Giant is nearly 33° up in the sky, east of the meridian.  Saturn is west of the meridian, nearly 29° above the horizon.  Use a binocular to see the dimmer background stars.  Jupiter is 3.8° to the lower right of of μ Cap, 2.1° to the upper right of Deneb Algedi, and 1.4° above Nashira.  Saturn is 1.4° to the lower right of dim υ Cap.

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