2021, July 4: Venus Aims at Mars


July 4, 2021: The Venus – Mars conjunction is eight days away.  This evening Venus moves to within 5° of the Red Planet.

Chart Caption – 2021, July 4: After sunset, brilliant Venus is 4.9° to the lower right of dimmer Mars.

Chicago, Illinois:  Sunrise, 5:21 a.m. CDT; Sunset, 8:29 p.m. CDT.  Check local sources for sunrise and sunset times for your location.

by Jeffrey L. Hunt

Step outside this evening shortly after sunset.  Brilliant Venus shines from low in the west-northwestern sky.  Find a clear horizon.  A view from a hillside or elevated structure is helpful. Take along a binocular for an optical assist to find Mars.

About 45 minutes after sunset, brilliant Venus is over 8° above the west-northwest horizon and 4.9° to the lower right of Mars.  The gap between them closes each evening as Venus overtakes Mars.

Venus moves eastward compared to the stars about twice as fast as Mars.

The star Regulus is over 20° to the upper left of Venus.

On July 12, Venus passes Mars for the first conjunction of a triple conjunction that extends into next year.

Unlike its brightness earlier in the year, Mars is near its dimmest.  The distance between Earth and Mars has increased nearly sixfold from when Mars was at its brightest.  This distance increase has reduced Mars brightness by a factor of 36.

When Venus and Mars are near each other, Mars is always quite dim, an unexpected view of two bright planets near each other.

A conjunction occurs when two planets are at the same celestial longitude.  Two coordinate systems are used to note the planets’ positions and other celestial objects.  One uses an extension of Earth’s coordinate system into the sky – an equatorial system.  The second uses the plane of the solar system – the ecliptic – as the foundation of the coordinate system.  They are inclined about 23.5° compared to each other and their origin is at the vernal equinox point, the (0,0) location in the sky.

In these articles, typically, the ecliptic coordinate system is used to determine conjunction dates.

Detailed Note: One hour before sunrise, the moon (23.9d, 27%), nearly 27° up in the east, is over 20° to the right of the Pleiades.  The lunar crescent is between Menkar (α Cet, m =2.5) and Hamal (α Ari, m = 2.0), 10.0° above the former star and 13.5° below the latter star.  Farther southward, Jupiter is nearly 37° up in the south, slightly west of the meridian.  It is retrograding in Aquarius, 3.0° to the upper left of ι Aqr, 4.0° below θ Aqr, and 3.8° to the lower right of σ Aqr.  Saturn, 19.7° to the lower right of Jupiter, is 1.9° to the lower right of θ Cap.  Mercury (m = 0.4) rises 77 minutes before sunrise, about the time of Nautical Twilight. Forty-five minutes before sunrise, the speedy planet is nearly 5° up in the east-northeast and 11.4° to the lower left of Aldebaran.  The planet is at its morning greatest elongation (21.5°) at 2:45 p.m. CDT. One hour after sunset, Venus is nearly 6° up in the west-northwest, above a line from γ Cnc to δ Cnc.  The Venus – Mars gap is 4.9°.  Mars is to the upper left of brilliant Venus.  Their conjunction is on July 12. 

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