2021, April 21: Morning Planets, Jupiter, Saturn, Capricornus

April 21, 2021: Jupiter and Saturn are the bright morning planets in the southeast before sunrise.  The stars are in front of the backdrop of Capricornus.  The constellation looks like an oversized boomerang or stealth fighter.

by Jeffrey L. Hunt

Chicago, Illinois:  Sunrise, 6:01 a.m. CDT; Sunset, 7:39 p.m. CDT.  Check local sources for sunrise and sunset times for your location.

Bright Jupiter and Saturn shine from the southeastern sky before sunrise.  Saturn is over 18° above the horizon.  It continues its eastward trek in Capricornus, 1.4° to the upper right of Theta Capricorni (θ Cap in the chart).  Use a binocular to see the stars with this giant planet duo.

Bright Jupiter is over 14° to the lower left of Saturn.  It is the brightest “star” in the region.  In the starfield, it is 3.6° to the upper left of Deneb Algiedi (δ Cap), 0.7° to the lower left of Mu Capricorni (μ Cap), and 2.5° to the upper right of ι Aqr.

Capricornus represents a celestial mutant, part fish and part goat.  It is sometimes referred to as the “Sea goat.”

The constellations is part of a set of three constellations associated with water, Capricornus, Aquarius, and Pisces, that form a backdrop for the apparent motions of the sun, moon, and planets.

The pattern is made of dimmer stars, that make a distinct shape that could be an oversized boomerang or stealth airplane.

The four brightest stars and the meanings of their name:

• Algiedi – “the kid”
• Dabih – “the lucky star of the sacrifice or slaughterer”
• Nashira – “the lucky star of the verdant fields at the end of summer”
• Deneb Algiedi – “the kid’s tail.”

The meanings of the star names are from 1944 article by George Davis, Jr.

Detailed Note: One hour before sunrise, Saturn is over 18° above the southeast horizon and 1.4° to the upper right of θ Cap.  Jupiter – 14.2° to the lower left of Saturn – is nearly 14° up in the east-southeast.  In the starfield, Jupiter is 3.6° to the upper left of Deneb Algiedi, 0.7° to the lower left of μ Cap, and 2.5° to the upper right of ι Aqr.  Use a binocular to note the changing position of Jupiter compared to the sidereal background.  Twenty minutes after sunset, Venus is over 2° above the west-northwest horizon.  In a darker sky forty minutes later, the moon (10.0d, 68%) is over two-thirds of the way up in the sky above the southern horizon.  It is 7.5° to the right of Algieba (“the forehead,” γ Leo, m = 2.0) and 7.6° to the upper right of Regulus.  In the west about 40° up in the sky, Mars is 3.1° to the lower right of the star cluster M35 and 5.1° to the lower right of Propus (“the projecting foot,” η Gem, m = 3.3). This trio of celestial treasures and other nearby background stars easily fit into the view of wide-field binocular.

Read more about the planets during April 2021.