Mars marches eastward among the dim stars of southeastern Pisces during August. It passes perihelion early in the month.
by Jeffrey L. Hunt
Mars is approaching opposition on October 13, 2020. At opposition Mars and the sun are in opposite directions in the sky. As the sun sets in the west, Mars rises in the east. Mars appears in the south around midnight (1 a.m. during daylight time). As morning twilight begins, Mars is low in the western sky, setting before sunrise.
In the sky, Mars appears as an overly-bright star. It is the brightest star in this region of the sky, making its identification easy.
During early August, Mars rises at around 11 p.m., appearing low in the east as midnight approaches. At this time, Jupiter and Saturn are in the south. This giant planet duo starts the evening low in the southeast as the sky darkens.
By early morning, about three hours before sunrise, Mars is part of a quartet of four bright planets that are stretched across the sky from the east to the southwest skyline. Bright Venus is in the east, Mars in the south-southeast, and Saturn and Jupiter in the southwest.
By midmonth, Mars rises about 30 minutes earlier and shines from higher in the eastern sky as midnight approaches. It continues to follow Jupiter and Saturn through the sky.
At this point that the planetary quartet begins to break up. Jupiter disappears below the southwest horizon as Venus climbs into the eastern sky.
By late in the month, when Mars rises around 9:30 p.m. and is well-up in the eastern sky by 11 p.m. By early morning, Jupiter and Saturn have left the sky, as Venus climbs into view.
Note that on the accompanying chart, the daily positions of Mars are farther apart than at the end of the month. The planet begins to retrograde next month. Before it reverses course and seems to move westward among the stars, it slows. (A chart in this article shows the retrograde pattern of Mars for this opposition.) The gaps between the daily positions decrease in distance. At the beginning of the month, Mars moves eastward about 0.4° each day. That’s a little less than the apparent size of the moon in the sky. By month’s end, the Red Planet appears to move about half that distance each day.
Because Mars’ orbit is not a perfect circle, Mars is not necessarily closest to the sun or closest to Earth at opposition. Mars is closest to the sun (perihelion) on August 2. Our planet is closest to the Red Planet on October 6, followed by opposition a week later.
Use a binocular to track Mars’ eastward motion in the starfield. Here are dates to note:
- August 1: Mars starts the month 1.2° to the upper right of 89 Piscium (89 Psc).
- August 2: Mars is closest to the sun (perihelion), 1.38 Astronomical Units from the sun. (An Astronomical Unit – AU – is equal to Earth’s average distance from the sun, about 93 million miles or 150 million kilometers). At this time the Earth – Mars gap is still 0.63 AU. Mars continues to brighten in our sky as we get closer to it.
- August 4: Mars passes 0.3° above 89 Psc.
- August 8: Before midnight, look eastward for Mars, 2.1° to the upper left of the gibbous moon that is 73% illuminated. They’ll still be together in the morning.
- August 14: The planet is 1.0° to the lower left of Mu Piscium (μ Psc).
- August 22: Mars passes 0.5° below Nu Piscium (ν Psc).
- August 31: Mars ends the month 2.7° to the lower right of Omicron Piscium (ο Psc).
For more about where to locate the planets in August, here is a semi-technical description of their locations for each day.