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31 Dec 2018

January Astronomy: The First Month of the New Year Brings Planetary Pairings and a Total Lunar Eclipse

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The opening month of 2019 features outstanding sights for the unaided eye, as well as the eye aided with binoculars and telescopes.

Who would fail to wonder at the sight of brilliant Venus near a predawn crescent moon? Separated in time by about a month, we have close pairings on Jan. 1 and 31, providing two easy chances to locate Venus in the daytime with the unaided eye and binoculars. Telescopic views reveal Venus’ changing phase, from 48 to 62 percent this month, and its shrinking apparent size as the planet moves from the near side toward the far side of its nearly circular orbit around the sun.

Venus in January shines at magnitude -4.6 to -4.3, faded some since its peak in early December, but still at its best for 2019. Rising in a dark sky three hours or more before sun-up, it remains impressive!

Another astronomical highlight is a total lunar eclipse, on Sunday, Jan. 20, during convenient evening hours. The partial phase of the eclipse gets under way at 7:34 p.m. as the moon begins to encounter the umbra, or dark central core of Earth’s shadow. After several minutes, the curvature of the shadow’s edge will become obvious. At 8:41 p.m., the eclipse becomes total, and remains so for 62 minutes, until 9:43 p.m. A complete timetable of the eclipse appears on the January 2019 Sky Calendar (click link or see below; right click on the image and view in a new window), which also provides illustrations of that month’s outstanding planetary and lunar gatherings described in the following paragraphs. See also our separate article on the eclipse.

With the deepest total eclipse happening at 9:12 p.m. PST, should you encourage young children to observe this lunar eclipse? Well, if you miss this opportunity, the next chance to catch one during convenient evening hours won’t come until May 2022.

Planets at dawn: On New Year’s morning, Jan. 1, around 6 a.m. in the Coachella Valley, face southeast to enjoy a predawn lineup of the crescent moon with three planets to its lower left, in order: Venus, Jupiter and Mercury. Venus then is within 4 degrees to the lower left of the crescent moon, with Jupiter 18 degrees to the lower left of Venus; and Mercury 13 degrees to the lower left of Jupiter. When the moon reaches its highest point in the south, around 8:22 a.m. that day, Venus is an easy find within 3 degrees to the moon’s lower left—even though it’s daytime. Watch the waning crescent moon slide downward past three planets before sun-up Jan. 1-4.

On Thursday, Jan. 3, Jupiter appears 4 degrees to the upper right of the moon, while Mercury appears 12 degrees to the moon’s lower left. On Jan. 4, Jupiter appears 16 degrees to the lower left of Venus, while the thin old moon appears the same distance to the lower left of Jupiter, with Mercury, in turn, 2.5 degrees to the lower right of the moon. Mercury is getting lower each morning. Its departure after a few more days leaves two bright planets remaining. Masquerading as the two brightest “stars” in the entire predawn sky, the Venus-Jupiter pair becomes ever more striking as it closes to 10 degrees apart on Jan. 11, 5 degrees on Jan. 17, and a shortest distance of 2.4 degrees on Jan. 22. On the latter date, use binoculars to try to see Saturn just emerging from the morning twilight glow, 28 degrees to the lower left of the bright pair. Rising longer ahead of the sun and higher each morning, Saturn within a few days will become easy to see with unaided eye, and we’ll again see three naked-eye planets. From late January through mid-February, their arrangement from the upper right to the lower left will be Jupiter-Venus-Saturn. The waning crescent moon slides past this lineup, producing close pairings with planets on Jan. 30-Feb. 2.

The pairing of Venus and the crescent moon on Thursday morning, Jan. 31, will be unusually close and very striking, before dawn and for long after sunrise. From the Coachella Valley, the angular distance between Venus and the center of the moon’s disk will be just 1.5 degrees and closing at 5 a.m. By 6 a.m., the distance closes to 1.2 degrees. Sunrise occurs in Palm Springs at 6:43 a.m., with Venus just more than a degree from the moon’s center, or three-fourths of a degree from the moon’s edge. The closest approach of the moon and Venus occurs in daytime hours, between 9:45 and 10 a.m., with Venus about 0.4 degrees—less than the moon’s half-degree width—from the moon’s northern cusp (the upper point of the crescent). From 8:30 through 11:15 a.m., Venus will appear no more than a moon’s width from the moon’s edge. A telescope at low power will fit Venus and the moon in the same field, with Venus showing at gibbous phase, 62 percent illuminated.

At dusk: Mars is high in the south-southwest to southwest at dusk, halfway or more from horizon to overhead. Although fading slowly from magnitude 0.5 to 0.9, Mars shouldn’t be confused with any star while the red planet passes through the background of Pisces, which includes no stars brighter than magnitude 3.6.

In early January at dusk, the Summer Triangle of Vega, Altair and Deneb is still easy to see, with Vega and Deneb above in the northwest, and Altair in the west. Fomalhaut, mouth of the Southern Fish, is in the south-southwest, and the earliest stars of winter—Capella in the northeast to east-northeast, and Aldebaran in the east—are prominent. Although Aldebaran marks the eye of Taurus, its Arabic name means “The Follower,” of the Pleiades star cluster 14 degrees above it.

By early January, Orion’s Betelgeuse and Rigel, with his vertical three-star belt between them, have appeared above the eastern horizon. Two more of winter’s bright stars soon follow: Watch for their risings in twilight, by mid-January—first, Procyon in the east, and finally Sirius, the brightest nighttime star, in the east-southeast, below and in line with Orion’s belt. Sirius completes the nearly equilateral Winter Triangle with Procyon and Betelgeuse. When Sirius first appears low in the east-southeast, Altair is still visible, very low just north of west (if no mountains block your view), and both the Summer and Winter Triangles can be seen simultaneously.

The waxing moon returns to the early evening twilight scene as a thin crescent low in the southwest to west-southwest on Jan. 6; passes Mars on Jan. 12; skips past Aldebaran Jan. 16-17; and appears full to the lower right of the “Twin” stars Pollux and Castor on Sunday, Jan. 20, the same evening as the total lunar eclipse.

The website of the Astronomical Society of the Desert (www.astrorx.org) has a listing of our evening star parties at two locations. Sawmill Trailhead, our high-altitude site (elevation 4,000 feet), will have a star party starting at dusk on Saturday, Jan. 5. Our primary, more-accessible star-party site is the Visitor Center of the Santa Rosa and San Jacinto Mountains National Monument, on Highway 74, within 4 miles south of Highway 111 in Palm Desert. Our next monthly star party there is scheduled for Saturday, Jan. 12, from 5 to 8 p.m. Star parties can be cancelled in poor observing weather.

Also, check the Impromptu Star Parties link. I’ll be offering sky watches in Palm Springs at the pedestrian bridge over Tahquitz Creek at North Riverside Drive and Camino Real, including some in predawn to follow Venus’ conjunctions with the moon and other planets. Members of the Astronomical Society of the Desert may be offering a lunar eclipse watch at one or more locations on Sunday, Jan. 20.

On Friday, Jan. 18, I’ll present a preview of 2019’s sky events, including Sunday’s total lunar eclipse, and the year’s beautiful planetary gatherings. The talk begins at 7 p.m. at the Portola Community Center, 45480 Portola Ave., in Palm Desert.

Abrams Planetarium publishes a monthly Sky Calendar with an evening sky map. Subscriptions are $12 per year at www.abramsplanetarium.org/skycalendar for three printed issues mailed quarterly. The January 2019 issue of the calendar features the total lunar eclipse happening after nightfall on Jan. 20, and the four bright planets in the morning sky.

Wishing you clear skies!

Robert C. Victor was a staff astronomer at Abrams Planetarium at Michigan State University. He is now retired and enjoys providing sky watching opportunities for a variety of groups in the Coachella Valley. Robert D. Miller did graduate work in planetarium science and later astronomy and computer science at Michigan State University and remains active in research and public outreach in astronomy.

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