July 12, 2021: Venus – Mars conjunction evening. Evening Star Venus passes 0.5° to the upper right of the Red Planet. The crescent moon is nearby. This is the first of three conjunctions of Venus and Mars – a triple conjunction.
by Jeffrey L. Hunt
Step outside about 45 minutes after sunset. Brilliant Evening Star Venus is over 8° above the west-northwest horizon. This evening Venus passes 0.5° to the upper right of Mars. The crescent moon, only 9% illuminated is 6.7° to the upper left of Venus.
From our home planet, Venus appears in the same direction as Mars, although they are millions of miles apart in space.
These groupings show an interesting perspective. Likely Venus and Mars are the most attractive planets to us because of their proximity to our home planet. Jupiter and Saturn offer intrigue for their beautiful views through a telescope.
Less than a year ago, Mars was spectacularly bright in the night sky. Compared to its current location in the solar system compared to Earth, the Red Planet is near its dimmest. Its brightness varies greatly from its changing distance from our planet.
A fundamental notion of how light and brightness work is that an object’s brightness varies by its distance. The concept is that when the distance increases, the brightness decreases by the square of the distance. This principle is called the “inverse square law.” The force of gravity diminishes in the same fashion.
In October 2021, Mars was less than 40 million miles from Earth. The planet, approaching its largest distance from Earth, is almost 6 times farther away than it was during early October. At this distance change, the planet is about 1/36th of its brightness than when it was nearest our world.
Venus is the brightest “starlike” object in the sky. Only the sun and moon are brighter. No other planet, reflecting sunlight, or distant sun shines with the apparent intensity of Venus. If the stars were closer, they would shine brighter than the planet. A star is a distant sun that produces its own light, while the planets, moons, and other solar system stuff appears to our eyes by reflected sunlight or the effects of it.
When Mars and Venus appear together in our sky, Mars is at nearly its dimmest visual intensity. The appearance together is exciting, but the Red Planet is much dimmer than Earth’s Twin planet.
A conjunction occurs when when two planets share the same celestial latitude, the system used in these articles. The coordinate system uses the ecliptic for its latitude and longitude locations.
The July 12 conjunction is the first of three in a triple conjunction of the two planets. Mars passes behind the sun during early October and then Venus follows early during 2022.
Then in the morning sky as Venus concludes its retrograde motion, Mars – moving eastward – passes Venus. The gap is 6.2°. Venus picks up speed and passes Mars on March 6 as both planets move eastward along the ecliptic. This gap is 4.4°.
Venus is at its greatest celestial latitude during January. As the planets race eastward, its latitude decreases quickly. While not in conjunction, Venus is 3.9° from Mars on March 16, the closest passage during this time span.
Venus continues rapidly move away from Mars. Both soon overtake Saturn.
After the conjunction on July 12, watch Venus move away from Mars and approach the star Regulus.
Articles and Summaries
- Venus as an Evening Star
- Venus Evening Star (Summary)
- Mars during 2021 (Summary)
- Planets during June 2021
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