Retrograde ends of Mars, western planets in line

January 12, 2023: Mars resumes its eastward march in Taurus this evening. With Mars in the east, Venus, Saturn and Jupiter are aligned in the western sky.

Photo caption – February 26, 2022: Venus, Mars and the Moon before sunrise in the southeast.

by Jeffrey L. Hunt

Chicago, IL: Sunrise, 7:17 a.m. CST; Sunset, 4:41 p.m. CST. Check local sources for sunrise and sunset times for your location. The times are calculated from the MICA computer program of the US Naval Observatory.

The sunrise time moves earlier every few days. At the end of the month, the sun rises at 7:04 a.m. CST in Chicago.

Transit time of Jupiter’s Great Red Spot, when it is at the center of the planet in the southern hemisphere: 4:27 UT, 14:23 UT; January 13, 0:19. Convert the time to your time zone. In the US, subtract five hours for EST, six hours for CST, etc. Use a telescope to see the place. The hours are from Sky & Telescope magazine.

The window to see the red spot shrinks. Jupiter begins the evening in the south-southwest and sets nearly six hours after sunset. When the planet’s altitude – height above the horizon – is less than about 30°, the image of the planet is blurred by the Earth’s atmosphere. Light from the planet travels through a thicker atmospheric layer when lower in the sky. We see this large distortion in the reddening of the distorted sun near the horizon. The window for a clear view of Jupiter is about four hours. With the planet rotating approximately every two hours, occurrences of viewing the long-lasting storm during this appearance are decreasing. Later in the spring, Jupiter disappears into the bright evening twilight, reappearing in the eastern sky before sunrise later in the year. Observation of the red dot starts again at this time.

Map legend – From the north of the solar system, the relative orbits of Earth and Mars are shown. The line of sight from Earth to Mars shows how the Red Planet looks in relation to distant stars.

Mars retrograde ends for this opposition season. Retrograde motion is an illusion when the Earth passes in front of an outer planet. In the orbit annotated above, the line of sight from Earth to Mars moves eastward or counterclockwise across the map as Earth approaches the planet. The planet appears to be moving eastward against the star field. On October 30, 2022, the line of sight began to move clockwise across the map. Although Mars keeps moving east in its orbit, it appears to be moving west as this line of sight moves west. Tonight, that line of sight begins to move eastward again, and Mars resumes its eastward march through the stars.

Chart legend – This chart shows the apparent movement of Mars relative to Taurus. The retrograde motion ends tonight.

On the annotated sky map, the apparent motion of the red planet is shown against the starry background. Unlike a land map, east is on the left on the map and west is on the right. Earlier in the year, Mars appeared to be moving east as Earth began to catch Mars. On October 30, when the line of sight moves west, the planet appears to stop moving east and appear to move west or retrograde. Tonight, the planet stops retrograding and resumes its eastward march.

Here is today’s planetary forecast:

morning sky

Chart legend – January 12, 2023: The moon is below the brightest stars in Leo, near the border of Virgo.

An hour before sunrise, the waning gibbous moon, 75% illuminated, is halfway up southwest, 9.2° lower left of Denebola, meaning “lion’s tail.” .

It is on the third morning that the moon appears in front of the stars of Leo. The constellation is a west-facing lion that we see in silhouette. To the west is an upside-down question mark or sickle with Regulus glowing below. To the east is a small triangle. The eastern shining star is the tail.

The lunar orb is near the boundary of the constellation Leo-Virgo. The star Zavijava – which means “the corner of the barking dog” – is 5.6° to the left of the moon and is part of Virgo. Tomorrow morning, the moon is in front of Virgo, between Zavijava and Porrima.

Mercury rushes through the morning sky, rising at least eight minutes earlier each morning. This morning, it rises 56 minutes before the sun. It will be visible, but a challenge to see, in about three mornings, becoming easier to see for the rest of the month.

evening sky

Chart legend – 12 January 2023: Venus, Saturn and Jupiter are in the western sky after sunset.

Three of the four bright planets line up in the southwestern sky after sunset. Forty-five minutes after sunset, bright Venus is less than 10° up in the west-southwest. It appears further north along the horizon each evening.

The Evening Star sets later each night and heads toward Saturn on January 22n/a conjunction. Tonight, Venus is at 11.3° lower right of the Ringed Wonder.

Saturn moves slowly east in eastern Capricorn. At the slow pace of Saturn, it moves only a tenth of Venus’ change from night to night.

Venus’s encounter with Jupiter is the second luminous conjunction of 2023. Venus catches and overtakes the Jovian giant on March 1st.

Map Legend – 12 January 2023: Mars is visible to the east, upper left of Aldebaran.

Farther east, Mars ends its retrograde ahead of Taurus, 8.5° upper left of Aldebaran. At this time, find the red planet halfway up in the eastern sky.

Chart legend – January 12, 2023: One hour after sunset, Taurus is seen behind Mars.

As the sky darkens further, the stars of Taurus are visible behind Mars. Aldebaran and the Hyades star cluster form the bull’s head. Binoculars may be needed to see the “V” pattern. The horns are pointed by Elnath and Zeta Tauri. Resembling a small ladle, the Pleiades star cluster straddles the bull’s back. This is an impressive stellar beam of mostly blue stars through a binocular.

Chart legend – 12 January 2023: Through binoculars, Saturn is ahead of the stars in eastern Capricorn.

Farther west through the binoculars, Saturn is 1.3° from Deneb Algedi to the right. Note that the Ringed Wonder passes Sun 45 Capricorni (45 Cap on the chart). The separation is only 0.2°.

Jupiter (Photo NASA)

At 6:19 p.m. CST, the Great Red Spot is visible through a telescope. The planet is about 45° southwest, a favorable location for a good view from the central United States. At this time, Jupiter’s large satellite, Europa, is visible against the cloud tops. As Jupiter rotates and the satellite rotates, Europa moves past the planet at 6:35 p.m. Around this time, the satellite’s shadow is cast on the cloud tops. This continues until almost 9 p.m. CST.

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