Mars appears at opposition on December 7, 2022. Throughout the summer, autumn and early winter, Mars dances with the stars of Taurus.
by Jeffrey L. Hunt
The study of Mars brings out fanciful visions of canals, flowing water, lakes, and life – Martians. The changing view of Mars with unaided eyes, telescopes, and robot spacecraft provided sharper views of a nearby world. Visions of life on Mars have inspired books, movies, and television shows about life elsewhere.
Mars revolves around the sun, just outside Earth’s orbit. Even though it’s close to Earth, the Red Planet revolves around the sun in 1.88 years. Moving at about half Earth’s speed around the sun, our home world catches and moves between Mars and the sun every two years, fifty days on average.
When Earth is between Mars and the sun (or any other planet farther away), this is known as opposition. Mars rises in the eastern sky as the sun sets, seems to travel across the sky during the night as Earth rotates, and sets in the west as the sun rises in the east.
The best observations of Mars occur when the planet is near opposition, and at this time, spacecraft are launched toward the Red Planet as Earth approaches it. Less rocket fuel is needed for course corrections and the shortest travel time occurs during these windows of opportunity.
To complicate matters, Mars’ orbit is elongated. It is nearly 10% out of round, making some of the opposition distances closer than others. Each successive opposition is farther eastward along the orbits and with the constellations that make the starry backdrop for the planets. In 2018, Mars was near its closest point to the sun (perihelion), the distance was the closest opposition distance since 2003. Another perihelic opposition occurs in 2035, although at this year’s opposition, Mars is over 40% farther away than it was just four years ago.
The closest point between the two planets is not on the opposition night but on dates that are typically before one day to over a week before or after opposition. This occurs from Mars’ elliptical pathway and whether the planet is approaching perihelion or aphelion (farthest point from the sun). After the closest approach, Mars is still moving away from Earth as the alignment date approaches.
Important observations were made through telescopes at the time of perihelic oppositions. In 1877, Asaph Hall first observed a pair of small Martian moons. A closer opposition did not occur until 47 years later.
During the 1894 opposition, two years after the perihelic opposition, Percival Lowell, began his observations where he thought he saw Martian canals and other watery features.
In November 1964 and 101 days before opposition, NASA launched the first Mars-bound craft, Mariner 4, to photograph, record, and radio to Earth, the first close-up views of Mars. The spacecraft passed Mars on July 16, 1965 – 240 days after launch. The spacecraft did not land, but began a journey around the sun, passing the Red Planet on the way. Other spacecraft have landed, photographed the scenery, sniffed the air, tasted the soil, and roamed the planet, while others investigated Mars from above. For up-to-date photos and stories about the crafts’ explorations, monitor NASA’s Mars web site.
To the eye, Mars is not red, but more like the gem Topaz. Even when Mars is closest., the planet resembles a bright star. It never looks as large as the moon, as some recurring Internet memes suggest.
The outer planets’ regular routes through the solar system are eastward along the plane of the solar system, compared to the starry background. Suddenly, they seem to slow down and reverse directions, heading westward compared to the stars. They brighten and then a short time later they reverse their directions, heading east again and dimming.
The apparent westward movement is known as retrograde motion. The change in direction and brightness change puzzled our ancestors, and they constructed various mental and mathematical models to explain and predict the planets positions compared to the starry background. The chart above shows the position of Mars from August 16. 2022, through March 30, 2023, with Taurus the Bull. Mars retrogrades from October 30, 2022, through January 12, 2023.
Today’s model explains retrograde motion as when the faster moving Earth passes a slower moving outer planet. The planet’s location in the sky is from Earth’s place on the orbit and Mars spot. So, it’s a line-of-sight view, like looking past the nearby trees to see the ocean. As Earth passes the outer planet, the line of sight seems to back up or move westward. After Earth passes by, the line of sight shifts eastward again.
The orbit chart above shows the relative orbits of Earth and Mars during the same as the planet – star plots chart. Earth overtakes Mars and the line of sight shows Mars near various stars.
Today, computer programs predict the locations of the planets with high accuracy from the effects of Newton’s Laws and Einstein’s Theory of General Relativity. This shows the integrity of science and its ability to make precise predictions. The US Naval Observatory’s computer program MICAwas used to generate the dates for the charts. Microsoft Excel was used to make the plots.
Taurus is a rich starfield of bright and dim stars, many of them can be seen from suburban backyards. The Bull’s head is made by the Hyades star cluster and Aldebaran, a star with nearly the same color as Mars. The horns are tipped by Beta Tauri and Zeta Tauri. The famous Pleiades star cluster, or Seven Sisters, rides on the animal’s back.
Early in the school year, Taurus is in the northeast before sunrise. Watching the planet’s changing place takes some patience and persistence because it requires an early morning alarm until mid-October. Near opposition, Mars becomes visible after sunset in the east-northeastern sky. As the new year begins, Mars and Taurus are higher in the eastern sky and by the first day of spring it is high in the south-southwest after sundown.
One interesting observational point about this Martian opposition is that the planet passes several stars three times – twice during its eastward track and once during retrograde. These triple conjunctions are worth noting and the dates are listed on the charts. In particular, the triple conjunctions occur with Aldebaran, Beta Tauri, and Zeta Tauri. They occur with other stars as well. Follow Mars as it passes your favorite stars in Taurus.
|Star Name||Conjunction #1||Conjunction #2||Conjunction #3|
|Aldebaran||September 7, 2022||December 26||January 30|
|Beta Tauri||October 10||November 18||March 9, 2023|
|Zeta Tauri||October 22||November 7||March 14|
Monthly summaries follow to help guide any observing projects
Mars is on its way toward its opposition as it moves eastward in western Taurus near the Pleiades star cluster. Mars is rising over five hours before sunrise and is easily visible in the east-southeast as morning twilight begins. After appearing with the moon and the Pleiades on the 19th, the Red Planet passes the star cluster the next morning, making its way toward the brighter stars in the famous checkmark pattern named the Hyades star cluster.
It passes between Aldebaran and the Pleiades at month’s end. During morning twilight, four planets, Venus, Mars, Jupiter and Saturn, are scattered along the ecliptic, from the east-northeast to the west-southwest.
Continuing its eastward march in Taurus, Mars continues to pass the Hyades star cluster and Aldebaran on the 7th. As Mars moves eastward through the constellation’s rich starfield, the moon passes on the 17th. By month’s end, Mars is rising about 3.5 hours after sunset (before midnight in many locations) and appearing high in the south-southeast as morning twilight begins.
Mars eastward march slows and the planet’s eastward motion ends at month’s end. It begins a series of triple conjunctions with the Bull’s horn stars, Zeta Tauri (ζ Tau) and Beta Tauri (β Tau). The Red Planet passes between the horns on the 17th. By month’s end, Mars rises 2.5 hours after sunset. During the month, it is in the west-southwest and southwest as morning twilight begins.
Mars begins to retrograde slowly, moving westward only 1.9° of ecliptic longitude during the first half of the month. In reversing direction, the planet passes each of the horns again for the second conjunctions. During November’s second half month, Mars retrogrades 4.9° of ecliptic longitude, placing it 11.6° northwest of Aldebaran. Earth and Mars are closest on November 30, 0.544 Astronomical Unit apart.
Mars retrogrades during the month, passing its opposition on the 7th that is accompanied by a Full moon occultation of the planet that is visible from Europe, North Africa, Greenland, large regions in North America, Japan and eastern Russia. During the month, the planet moves 9.8° of ecliptic longitude westward. From December 20 through January 12, Mars’ celestial latitude is higher than from January 13 through February 8. The distance to Mars changes nearly 15% after its closest approach and the apparent size diminishes by the same amount. The planet’s brightness decreases 0.7 magnitude after the closest point.
The planet is in the east-northeast after sunset. Mars’ retrograde ends as it begins to pass stars in the Hyades star cluster and Aldebaran. It slows, reverses its apparent direction on January 12, and begins to accelerate eastward again, ending the month with its third conjunction with Aldebaran. Its brightness decreases nearly a full magnitude while its distance increases 33%. The moon passes Mars twice during the month.
Appearing higher in the sky during February, Mars advances eastward nearly 13°, moving toward the horns of Taurus. It dims 0.6 magnitude. The moon passes by on the 27th.
Now high in the southwest as night falls, the Red Planet marches eastward 13.5° during the month and now seems to follow the annual westward parade of the constellations. It fades in brightness, ending the month slightly dimmer than Aldebaran. Mars passes between the horns of Taurus for the third time before it crosses into Gemini and passes the star cluster Messier 35. The moon is nearby on the 28th and 29th.
While this opposition is not the best, it occurs high in the sky among the myriad of bright stars in Taurus.
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