2021, May 24: Planets in a Plane

May 24, 2021: Morning planets Jupiter and Saturn are in the southeast before sunrise.  In the evening sky, brilliant Evening Star Venus, Mercury, and Mars line up along the solar system’s plane.  The bright moon is in the southeast near Zubenelgenubi, “the southern claw.”

2021, May 24: Jupiter and Saturn are bright morning planets. Jupiter is moving eastward in Aquarius, while Saturn retrogrades in Capricornus.
Chart Caption – 2021, May 24: Jupiter and Saturn are bright morning planets. Jupiter is moving eastward in Aquarius, while Saturn retrogrades in Capricornus.

by Jeffrey L. Hunt

Chicago, Illinois:  Sunrise, 5:23 a.m. CDT; Sunset, 8:13 p.m. CDT.  Check local sources for sunrise and sunset times for your location.

Morning Sky

Bright morning planets are in the southeast before sunrise.  Saturn begins the morning planet parade when it rises over 4 hours, 30 minutes before sunrise.  Jupiter follows about 45 minutes later.

By one hour before sunrise, bright Jupiter is over 25° up in the southeast.  The planet is moving eastward compared to the stars in Aquarius.  Use a binocular to see the starfield behind the planet.  The Jovian Giant is 2.3° to the upper left of Iota Aquarii (ι Aqr on the chart), 4.3° below Ancha, “the hip” (θ Aqr), and 4.6° to the upper right of Sigma Aquarii (σ Aqr).

On the chart above, notice the pattern of Aquarius.  This constellation is difficult to recognize.  One of the parts that is easy to see, if bright street lights do not block the view, is the “water jar.”  The four stars that resemble a propeller at the top left corner mark that part of the constellation.  The flood of water flows from the water jar downward.  As noted above, the star Ancha is the water bearer’s knee.  Skat (δ Aqr) is the character’s lower leg, “that is from the ankle to the knee,” according to a 1944 article about star names.

Saturn is dimmer than Jupiter, Arcturus, and Vega, but it is brighter than the other stars in the sky this morning.  The Ringed Wonder, 17.5° to the upper right of Jupiter, is retrograding in Capricornus, 0.6° to the right of Theta Capricorni (θ Cap).

The star Fomalhaut, “the mouth of the southern fish, is the brightest star in Picis Austrinus.  It is below Jupiter, near the horizon.

Evening Sky

2021, May 24: Brilliant Venus, Mercury, and Mars line up along the plane of the solar system in the western sky after sunset.
Chart Caption – 2021, May 24: Brilliant Venus, Mercury, and Mars line up along the plane of the solar system in the western sky after sunset.

After sunset, the trio of evening planets is lined up along the plane of the solar system in the west-northwest, while the bright moon is in the southeastern sky.

About 45 minutes after sunset, brilliant Venus is over 5° above the horizon.  Mercury is 4.2° to the upper left of Venus and the same distance to the lower left of the star Elnath. The trio fits in the same binocular field.

Speedy Mercury was at its greatest separation from the sun eight days ago.  It is on its way back into bright sunlight.  It is dimmer each evening.  Mercury passes 0.4° from Venus on May 28.

Mars, about one-third of the way up in the west, is nearly 30° to the upper left of Venus. The Red Planet is marching eastward in Gemini. This evening it is 6.7° to the lower left of Pollux.

The planets revolve around the sun in nearly the same plane.  The maximum deviation from the plane is by Mercury.  Its orbit is inclined 7° to the solar system. 

Since we are on a planet in that plane, we perceive the other planets along a line in the sky.  Connect the three planets by drawing a line in the sky with your hand.  Then extend the line eastward below Regulus and above Spica to the bright moon. The arc your hand traced the ecliptic from Taurus to Libra.  The constellations behind the imaginary line are known as the “circle of animals” or zodiac.  The moon and planets can appear in 15 of them.

2021, May 24: After sunset, the moon is in the southeastern sky, near Zubenelgenubi.
Chart Caption – 2021, May 24: After sunset, the moon is in the southeastern sky, near Zubenelgenubi.

The bright moon is 1.4° to the upper left of Zubenelgenubi, “the southern claw.”

Articles and Summaries

Venus sets 77 minutes after sunset, while Mercury follows over 20 minutes later.  Mars sets nearly 3.5 hours after sundown.  Saturn rises nearly 70 minutes after Mars sets.

Detailed Note: One hour before sunrise, bright Jupiter is over 25° above the southeast horizon.  Saturn is 17.5° to the upper right of the Jovian Giant.  Use a binocular to spot the starfield behind Jupiter. The planet is 2.3° to the upper left of ι Aqr, 4.3° to the lower right of θ Aqr, and 4.6° to the upper right of σ Aqr.  Saturn is 0.6° to the right of θ Cap.  Three bright planets, along the ecliptic, are in a diagonal line above the horizon in the western sky after sunset.  As early as 30 minutes after sunset, Venus is nearly 8° up in the west-northwest sky.  Use a binocular to see Mercury (m = 1.4), 4.2° to the upper left of Venus.  At this time, the bright moon (13.3d, 97%) is over 20° up in the southeast.  By 45 minutes after sunset, as the stars appear, Venus is over 5° above the horizon, while Mercury is nearly 9° up in the west-northwest, to the upper left of Venus. Mars is less than one-third of the way up in the west in Gemini.  The moon is 1.4° to the upper left of Zubenelgenubi (α Lib, m = 2.8).  An hour after sunset, Venus is less than 3° up and Mercury is over 6° in altitude.  Mars is 25.0° up in the west, over 25° to the upper left of Mercury.  In the starfield, Mars is 1.6° to the upper right of δ Gem and 6.7° to the lower left of Pollux.

 Read more about the planets during May 2021.



Categories: Astronomy, Sky Watching

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