2020, July 13: Jupiter at Opposition Leads Planet Parade


Jupiter at opposition and Saturn, July 13, 2020.
Jupiter, at opposition, leads the July planet parade. See Jupiter, Saturn, Mars, and Venus before sunrise.

Jupiter, at opposition, leads the July planet parade.  Saturn is at opposition July 20, 2020.

by Jeffrey L. Hunt

Bright Jupiter is at opposition.  Earth is between the sun and this giant planet.

At opposition the planet is very bright in the sky because it is closest to Earth.

Jupiter rises at sunset.  It appears in the south around 1 a.m., midnight when daylight time is not in effect.  The planet sets in the southwest at sunrise.

Saturn is 6.7° to the lower left of Jupiter.  Earth passes between the sun and Saturn on July 20.

This planetary pair is retrograding in eastern Sagittarius.  This apparent motion is an illusion as our faster moving Earth overtakes, passes between the sun and planet, and moves away from the planet.

This motion was the cosmological problem of early astronomers.  The philosophical part of the issue was whether the sun was at the center of the universe or the Earth held the central position.

With a stationary Earth at the center, several circles were employed to make the planetary models fit what was occurring in the sky.  With a central sun and a fast-moving earth, the retrograde motion was an optical illusion.

Earth’s revolution around the sun was not measured until the 19th Century.  Retrograde motion is an illusion.

Both planets retrograde until September, but as they continue to move westward compared to the starry background, the gap continues to grow.

When they reverse direction, Jupiter inches toward Saturn.  Jupiter slowly overtakes and passes the Ringed Wonder.  This Great Conjunction occurs on December 21, 2020.

This is the closest conjunction of Jupiter and Saturn since 1623, although there is little evidence that this conjunction was observed.

Mars follows the Jupiter – Saturn pair across the horizon after midnight.  It clears the landscape by 1 a.m. and appears low in the eastern sky.  The moon rises about an hour after Mars (on July 14).

As Earth rotates, Jupiter, Saturn, Mars, and the moon appear farther west.

By the beginning of morning twilight, Jupiter and Saturn are in the south-southwest and Mars is in the southeast.  The moon is to the lower left of Mars.

Venus then rises into the east-northeast sky.  It is near Aldebaran in Taurus.

As the sky brightens, the four bright planets and the moon stretch across the sky from the east-northeast horizon to the southwest skyline.

Mercury joins the planet parade beginning July 19, when the “Classic 9” planets are in the sky simultaneously with the moon, about 45 minutes before sunrise. 

For observers with large-aperture telescopes, Uranus, Neptune, and Classic Planet Pluto are visible as well.

In a few mornings (July 17) the moon appears with Venus and Aldebaran.  With the Pleiades in view, this will be a picturesque scene!

The four bright planets, Venus, Mars, Jupiter, and Saturn, are visible in the morning sky until about mid-August, although at an earlier hour as August progresses.

Here’s more about the planets during July.

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