2023, January 3: The Summer Triangle Morning, Evening Planets, Moon

January 3, 2023: The Summer Triangle is visible before sunrise and after sunset.  Four planets are strung across the sky after sundown.  The gibbous moon is near Mars.

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by Jeffrey L. Hunt

Chicago, Illinois:  Sunrise, 7:18 a.m. CST; Sunset, 4:32 p.m. CST.  Check local sources for sunrise and sunset times for your location.  Times are calculated from the U.S. Naval Observatory’s MICA computer program.

Sunrise is at its latest time.  This continues through the 10^th.  The length of daylight slowly increases during January to ten hours by the end of the month.

Jupiter’s Great Red Spot’s transit times, when it is in the center of the planet in the southern hemisphere: 1:59 UT, 11:55 UT, 21:50 UT. Convert the time to your time zone. In the US, subtract five hours for EST, six hours for CST, and so on.  Use a telescope to see the spot.  Times are from Sky & Telescope magazine.

Here is today’s planet forecast:

Morning Sky

Without a bright planet or the moon, the morning sky continues as a study of bright stars.  Altair, the brightest star in Aquila, is making its first morning appearance, also known as the heliacal rising. At forty-five minutes before sunrise, it is low in the eastern sky.  Each morning it is slightly higher and a week from today it is noticeably higher in the sky.

Sky watchers connect Altair with Vega, less than halfway up in the east-northeast at this hour, and Deneb, less than 20° above the northeast skyline, to make a very large shape, the Summer Triangle. Each star is formally part of other constellations.  Vega belongs to Lyra, Deneb, Cygnus, and Altair with Aquila.  The pattern makes its first appearance in the evening sky after sunset on about the first day of summer each year at the mid-northern latitudes.

The triangle appears in both morning and evening skies.  Rising before sunrise, it moves westward during the day under the camouflage of daylight. It appears in the western sky after sunset.  Deneb is over halfway up in the west-northwest.  Vega is about halfway from the horizon to Deneb, while Altair, slightly lower than Vega, is above the west horizon.

Unlike more southerly stars like Sirius, Betelgeuse, and Antares, these northern stars can appear in both the morning and evening skies during the same calendar day. The southern stars disappear into bright twilight after sunset to reappear in the morning sky before sunrise.

Evening Sky

Four bright planets are strung across the sky from the east to southwest after sunset.  About forty-five minutes after sundown, the bright moon, 92% illuminated, is over one-third of the way up in the east.  Look carefully for bright Mars 2.5° to the upper right of the lunar orb, while Aldebaran is 7.5° to the lower right of the moon.

Earlier today the moon covered or occulted Mars as seen from the South Atlantic, southern Africa, and the Indian Ocean.  This is the first of five lunar occultation events with Mars during the calendar year.

Last month, the moon occulted Mars on the planet’s opposition night.  While occultations of planets is not rare, an occultation of Mars on its opposition night, when Earth is between the sun and the planet, is rare.  The next lunar occultation of Mars within 24 hours of its opposition (during a 48-hour window) is February 26, 2059.

The year’s second lunar occultation occurs on the evening of January 30th.  It is visible from the American Southwest, Mexico, Central America, northwest South America, and Pacific Ocean.

Mars is retrograding in front of Taurus, 8.4° to the upper left of Aldebaran.  This continues until the 12^th.  After resuming its eastward march, Mars passes the star again on the 30^th.

Venus, Saturn and Jupiter are farther westward.  After sunset, Venus, slowly climbing into the western evening sky, is over 5° above the southwest horizon. 

Saturn is 21.6° to the upper left of the Evening Star.  The gap between them is closing quickly. It closes at about 1° each evening, that’s about twice the full moon’s size in the sky.

Bright Jupiter is over halfway up in the south, nearly 40° to the upper left of Saturn.  Venus overtakes the Jovian Giant on March 1^st.  Beginning February 20^th, Venus closes to within 10° of Jupiter.

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