2021, April 11: Wandering Stars, Jupiter, Saturn

April 11, 2021: Jupiter and Saturn are wandering through Capricornus.  They can be found low in the southeast before sunrise.

2021, April 11: Morning planets bright Jupiter and Saturn are low in the southeast before sunrise. Saturn is approaching Theta Capricorni (θ Cap), while Jupiter has passed Deneb Algiedi (δ Cap).
2021, April 11: Morning planets bright Jupiter and Saturn are low in the southeast before sunrise. Saturn is approaching Theta Capricorni (θ Cap), while Jupiter has passed Deneb Algiedi (δ Cap).

by Jeffrey L. Hunt

Chicago, Illinois:  Sunrise, 6:16 a.m. CDT; Sunset, 7:28 p.m. CDT.  Check local sources for sunrise and sunset times for your location.

One hour before sunrise, Saturn is over 15° above the southeast horizon.  Jupiter is slowly moving away from the Ringed Wonder, toward the east compared to the stars.

Jupiter is 13.0° to the lower left of Saturn.  The Jovian Giant is the brightest “star” in this part of the sky.  Saturn is dimmer.

Use a binocular to note the planets’ places compared to the starry background.  Saturn is 2.0° to the upper right of Theta Capricorni (θ Cap on the chart).  Jupiter is 2.1° to the upper left of Deneb Algiedi (δ Cap).

To the earliest sky watchers, the planets were not the worlds we see through a telescope or from images made by a robot spacecraft.  To our ancestors, the word “planet” originates with the Greek name planete asters, meaning wandering stars.

The constellations are known as the “fixed stars.”  The individual stars seem to be in the same place relative to each other night after night and year after year.  There were five special stars – Mercury, Venus, Mars, Jupiter, and Saturn – that moved mainly eastward compared to the constellations.  When the sun and moon are included, the days of the week ultimately received their names for the seven special celestial objects.

Each day the fixed stars of the constellations, along with the seven “planets,” rise in the east and set in the west, but the planets move slightly each day compared to the constellations.

We saw this during 2020 when Jupiter slowly overtook and passed Saturn.

Each month the moon moves eastward as its phase changes, appearing near bright stars and the planets.

Use a binocular to watch Jupiter and Saturn move relative to the stars of Capricornus.  In the evening sky, Mars is moving eastward compare to the stars.

When Venus becomes visible in darker skies during late spring and summer, watch it move past bright stars.  It catches and passes Mars before Mars ducks into bright twilight and into the sun’s glare.

Make observations each clear morning to note the location of the morning planets compared to the starry background.

Detailed Note: One hour before sunrise, Saturn is over 15° above the southeast horizon.  Brighter Jupiter is 13.0° to the lower left of the Ringed Wonder.  Use a binocular to observe the dimmer background stars with the planets.  Saturn is 2.0° to the upper right of θ Cap, while Jupiter is 2.1° to the upper left of Deneb Algiedi.  One hour after sunset, Mars is nearly halfway up in the west.  It is below a line from Elnath to ζ Tau.  The planet is 3.9° to the lower left of Elnath and 4.1° to the lower right of ζ Tau.  The moon reaches its New moon phase at 9:31 p.m. CDT.

Read more about the planets during April 2021.

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