2021, July 29: Mars – Regulus Conjunction

Astronomy, Sky Watching
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July 29, 2021:  In a challenging-to-see conjunction, Mars passes 0.6° to the upper right of the star Regulus.

Chart Caption – 2021, July 29: Through a binocular, Mars passes 0.6° to the upper right of Regulus.

by Jeffrey L. Hunt

Chicago, Illinois:  Sunrise, 5:42 a.m. CDT; Sunset, 8:12 p.m. CDT.  Check local sources for sunrise and sunset times for your location.

On this evening of the Jupiter – Mars opposition, Mars passes Regulus.

Mars and Regulus are very low in the west-northwest after sunset.  Here’s how to find them with a binocular.  Brilliant Venus is the guide to the planets.  Step outside about 45 minutes after sunset.  On a hilltop, elevated structure, or spot with a clear natural horizon, find brilliant Venus, sparkling in the colorful hues of evening twilight.  Venus is to the upper left of the Mars – Regulus conjunction.

Place Venus to the upper left portion of the field of view. Move the binocular to the lower right about one field diameter. Regulus and Mars appear in the view.  The conjunction is near the horizon.  This a challenging observation to make.

Mars passes Regulus again on July 10, 2023.  Coincidentally, Venus is nearby, 4.8° to the lower right of Mars.  During this appearance of Venus, it does not pass Mars.  Earth’s Twin moves to 3.5° of Mars on June 30 and then moves away.  Low in the western sky on July 16, 2023, Venus moves to within 3.5° of Regulus, but the planet does not pass the star.  A very close conjunction of Mercury and Regulus occurs on July 28, 2023.

Detailed Daily Note: One hour before sunrise, the moon (19.4d, 71%), in front of the stars of Cetus, is over halfway up in the south-southeast.  Use a binocular to see Deneb Kaitos, over 18°to the lower right of the lunar orb.  Farther west, bright Jupiter, retrograding in Aquarius and over 28° up in the southwest, is 1.3° above ι Aqr.  Saturn, 19.4° to the lower right of Jupiter and nearly 14° up in the southwest, is retrograding in Capricornus, 3.6° to the lower right of θ Cap.  As the sky darkens after sundown, look for brilliant Venus low in the west.  Use a binocular or spotting scope to locate the star Regulus nearly 10° to the lower right of Venus.  Mars is 0.6° to the upper right of the star.  As Earth rotates, this trio is lower in the sky and a challenge to see the Mars – Regulus conjunction near the horizon.  By 45 minutes after sunset, Regulus is only about 3° up in the sky.  At this time, Saturn is nearly 6° up in the east-southeast.  About 80 minutes after sunset, Venus is only 2° above the western horizon, yet bright enough to be seen without optical aid.  Jupiter, in the east-southeast, is about 3° above the horizon.  It can be seen at this altitude.  Saturn is to Jupiter’s upper right.  Three bright planets after sunset.  Tonight, Jupiter and Mars are at opposition, separated by 180° of ecliptic longitude, the fourth planet – planet opposition this month. Mars sets about the time Jupiter rise. While the Red Planet is becoming more difficult to see after sunset, four bright planets are soon to be visible simultaneously.  Add Mercury on August 18 and five planets are visible after mid-August. Three hours after sunset, Jupiter and Saturn are over 20° up in the southeastern sky.

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