Three bright planets – Jupiter, Mars, and Saturn – shine from the southern skies during the overnight hours.
by Jeffrey L. Hunt
Jupiter and Saturn rise into the southeastern sky as the sky darkens each evening. Mars rises before midnight, and it is higher in the sky after midnight.
By 3 a.m. Jupiter and Saturn are in the southwest and Mars is high in the southeast.
Bright Jupiter and Saturn are near each other, 7.3° apart. In the photo above, Jupiter and Saturn are in eastern Sagittarius. The stars of the distant constellation form the backdrop for the moving planets.
Normally, the planets move eastward compared to the starry background. About each year, our faster moving planet approaches Jupiter and Saturn. These planets appear to stop moving eastward and begin to move westward compared to the stars. This is known as retrograde motion. Earth then passes between Jupiter and the sun, then Saturn and the sun. This is known as opposition. As Earth moves away the planets continue to appear to move backwards, then they start their forward motion again.
For now, Jupiter and Saturn are retrograding, and Jupiter is getting farther from Saturn. By the end of August, Jupiter is about 1° farther away from Saturn than it is this morning. One degree is about the apparent size of two full moons.
Jupiter’s retrograde ends September 12. Even as Jupiter resumes its eastward motion, Saturn continues to retrograde. Saturn’s retrograde ends September 28. Jupiter then closes in on Saturn for a Great Conjunction, December 21, 2020.
Use a binocular to watch the planets move against the stars. This morning Jupiter is 0.9° to the left of the star 50 Sagittarii (50 Sgr on the photo above) and 4.8° to the upper left of Pi Sagittarii (π Sgr). Observe that Jupiter passes 50 Sgr and moves closer to π Sgr during the next month.
Meanwhile, Saturn’s retrograde puts it 3.5° to the upper left of 56 Sagittarii (56 Sgr) and 4.6° to the lower right of Sigma Capricorni (σ Cap). The Ringed Wonder appears to move closer to 56 Sgr and farther from σ Cap during the next month.
Farther east, Mars is marching eastward, over halfway up in the southeast at this hour. The Red Planet is in front of the stars of Cetus. In three mornings, it moves back into Pisces.
About every two years, Earth approaches and passes between the sun and Mars. This year opposition occurs on October 13, 2020. Mars begins to retrograde on September 9, 2020. The planet is moving eastward, but its eastward progress slows in about three weeks.
Mars is well passed 20 Ceti (20 Cet on the photo) and heading toward a starfield in Pisces that includes Zeta Piscium (ζ Psc on the photo), 89 Piscium (89 Psc), Mu Piscium (μ Psc), Nu Piscium (ν Psc), and Omicron Piscium (ο Psc). Including Epsilon Piscium (ε Psc) and Delta Piscium (δ Psc), Mars’ motion during the next month is within the dim starfield displayed on the photo.
This morning Mars is 5.6° to the lower right of ε Psc, and 3.6° to the upper left of 20 Cet. Each clear morning, observe Mars’ place among the stars with binocular.
Here’s more about the planets during July.