October 30, 2022: Red Planet Mars begins to retrograde tonight. The planet’s eastward direction halts and it begins to move westward or retrograde compared to Taurus.
by Jeffrey L. Hunt
Even with the bright appearance of Jupiter for most of the night, the spectacle of the autumn season this year is the opposition of Mars that occurs on December 7th.
Mars appears with many bright stars during this season. The planet rises in the east-northeast 2.5 hours after sunset. During the night it appears higher in the sky and by morning twilight it is high in the west-southwest above the Bull’s horns – Elnath and Zeta Tauri. Sky watchers in urban and suburban may need a binocular to see Taurus. The planet is easily visible. Only Sirius is brighter.
Mars has been steadily moving eastward in front of Taurus for nearly three months. Its motion has been easy to see. Recently, though, its eastward march has slowed and for several mornings it seems to be in nearly the same place compared to Zeta Tauri – the southern horn.
A planet’s motion against the sidereal background is a combination of Earth’s and the planet’s orbital motions around the sun. We see them appear against the background of distant stars, normally appearing to move eastward.
As our planet catches and moves inside the slower-moving outer worlds, they appear to stop and move westward, an illusion. The planets do not suddenly halt their direction and backup. There would be serious gravitational consequences if the planets stopped in their orbital motions. They would fall into the sun.
On this annotated chart, the orbits of Earth and Mars are displayed. Lines of sight are drawn from Earth through Mars toward the starfield for specific dates when the Red Planet appears near certain stars. Beginning August 16, the first date on the chart, the lines appear to turn eastward or counterclockwise on the chart. When Mars nears the Bull’s horns, the lines are nearly parallel, indicating that the eastward march slows. On October 30, the arrows start to pivot clockwise or westward until January 2023, when they turn eastward again.
One interesting aspect is that Mars passes several stars three times – triple conjunctions. Each triple is identified with a color. Notice that when Mars passes each star, the line of sight points to the same direction. Stated another way, the lines for each triple conjunction are parallel, indicating they are pointing toward the same direction in space or toward the particular star.
This second annotated chart shows Mars’ path through Taurus. When it nears the horns, the daily change slows and then the planet seems to reverse its direction.
Earth passes between the horns and is nearest the Red Planet on November 30. Mars’ orbit is not a perfect circle and after this date Mars is getting farther away.
This is not the closest opposition, when Earth is between the planet and the sun, but Mars is high in the sky. The current position is near the sun’s position during late spring. When the opposition appears closest to Earth – a so-called perihelic opposition, Mars is low in the sky, near the region where Saturn is this evening. It is no higher than one-third of the way up in the sky.
Through a telescope, Mars shows a red-ochre globe. Depending on the clarity of the sky, large features might be visible.
Watch the planet begin to retrograde. By early December, Mars is low in the east-northeast during early evening hours.
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