Sky at a Glance: January 5–14 This Week

FRIDAY, JANUARY 5

Sirius rises at the end of twilight, during this almost-coldest time of year. Almost near the rising location of Sirius, see the three stars in Orion’s Belt.
Once in orbit, Sirius twinkles slowly and profoundly through the dense layers of low atmosphere. As it ascends, however, its twinkling becomes quicker and shallower. As it ascends to shine through thinner air, its vibrant bursts of color likewise moderate and merge into sparkling whiteness. See the shot of Sirius’s jumbled rainbow flashing when reflected on water in Steve O’Meara’s “Scintillating Sirius” in the January issue of Sky & Telescope, on page 45.

In southern Aries, Jupiter is bright. How easy is it to see the little star pattern of Aries? At magnitudes of 2.0 and 2.6, Hamal and Sheratan are its two brightest stars. Mesarthim, magnitude 3.9, is located at the end of this small purple line, just below Sheratan. Triangulum, the larger, dimmer star, has three stars with magnitudes of 3.0, 3.4, and 4.0.

The blue 10° scale is roughly the size of your hand at arm’s length and may be used to help you find your way in a light-polluted sky. Nearly vertically piled approximately that distance apart are Jupiter, Hamal (Alpha Arietis), and Alpha Trianguli.

January 6, Saturday

■ There are four pairs of occurrences taking place this evening among Jupiter’s moons. They also come with a double shadow transit!

  • Io vanishes into occultation behind Jupiter’s west (preceding) edge at 5:47 p.m. EST. Ganymede appears from in front of the same edge just nine minutes later. Only those in the Eastern and Atlantic time zones will be able to see these two occurrences, and depending on where you are, the sky may still be brilliant with twilight.
  • Europa leaves Jupiter’s west limb at 8:27 p.m. EST. After nine minutes, the little dark shadow of Europa trails behind and appears on the opposite limb of Jupiter.
  • Io emerges from eclipse by Jupiter’s shadow at 10:13 p.m. EST, a little way off the planet’s east border. After seven minutes, the shadow of Ganymede moves across to the other side of Jupiter, starting a 35-minute sequence during which two shadows move simultaneously.
  • Europa’s shadow departs the western limb around 10:55 p.m. EST. Ganymede’s bigger shadow follows suit at 11:58 p.m. EST, a little over an hour later.
    Furthermore, at around 11:05 p.m. EST, the Great Red Spot—which is neither very large nor especially red these days—should cross Jupiter’s central meridian.

■ For a few hours around 9:01 p.m. EST, Algol should be at its lowest brightness, magnitude 3.4 rather than its typical 2.1. A comparison-star diagram.

Sunday, January 7

Procyon and Sirius are in jeopardy. After supper, Sirius, the Dog Star, twinkles low in the east-southeast. To Sirius’s left, in the east, shines Procyon, the Little Dog Star, which is roughly two fist’s length away. If you live anywhere around latitude 30°, such in Tijuana, New Orleans, or Jacksonville, the two dog stars will soon rise to exactly the same height over your horizon. Procyon is higher if you’re north of that latitude. Sirius will be the higher one if you are south of that point.

■ This week’s moonless evenings are ideal for viewing telescopic objects in Eridanus, west of Orion. These include the easiest white dwarf in the sky, several intriguing doubles, and a beautiful, circular planetary nebula. Use the chart and column “Suburban Stargazer” by Ken Hewitt-White from the January issue of Sky & Telescope, starting on page 55.

■ The waning crescent Moon will occult first-magnitude Antares low in the southeast on Monday morning, the 8th, either at dawn for the western United States and Canada or during darkness for them. For the majority of the remaining parts of North America, Central America, and the Caribbean, the occultation will occur during the day. Even with a telescope, the event might be difficult to observe in a bright sky depending on the air quality and atmospheric seeing, which is often bad throughout the day but good around sunrise.

Schedule and map for this event. For many cities, the first two tables are rather lengthy. The first indicates when Antares vanished, and the second shows when it reappeared behind the dark limb of the Moon. Make sure you’re using the correct table by scrolling and keeping an eye out for the new heading as you go below. Each entry’s nation abbreviation appears in the first two letters (“CA” stands for Canada, not California). January 8th, UT (GMT) is five hours ahead of Eastern Standard Time, six ahead of CST, seven ahead of MST, and eight ahead of PST.

Use the first table, for example, to see that Antares vanishes for Denver around 6:43 a.m. MST, when the Sun is 7° below the horizon (brilliant twilight) and the Moon is 15° above the horizon facing east-southeast (azimuth 114°).

The declining crescent Moon is in conjunction with Antares, Venus, and Mercury during the morning hours of January 7–9. For the West Coast, the Moon occults Antares on the eighth during morning darkness. The occultation occurs in broad daylight or twilight farther east.

MONDAY, JANUARY 8

Try drawing the outline of the Milky Way’s winter arch across the sky if your sky is even somewhat black. It rises in the early evening from the west-northwest horizon along the vertical Northern Cross of Cygnus. It then stretches upward and to the right, passing through Cassiopeia in the north and past dim Cepheus. It then stretches to the right and lower right, passing through Perseus and Auriga, descending between the feet of Orion’s Club and Gemini, and finally extending toward the east-southeast horizon between Procyon and Sirius.

January 9, a Tuesday

■ The massive Andromeda-Pegasus complex now stretches from near the zenith down into the western horizon around dinnertime. Near the zenith, locate Gamma Andromedae (Almach), a faintly orange star of second magnitude, near Andromeda’s high foot. She is standing atop Andromeda’s head. The Great Square of Pegasus, which balances on one corner, is located about midway from the zenith to the west horizon. The stars trace the contour of Pegasus’s head and neck, finishing at his nose, starting from the bottom corner: Enif of second magnitude, somewhat orange and pointing directly west.

Wednesday, January 10 

Despite the fact that it is the coldest time of year, Vega, the Summer Star, is persevering. Look for it right before and right after dusk, flashing above the northwest horizon. It will be higher the more north you are. Say goodbye to it already if you’re as far south as Florida.

January 11, Thursday

■ As the hours and weeks pass, Orion’s upward march toward the southeast continues, and his form is starting to spin clockwise, as all constellations on the southern portion of the sky do. As a result, his three-star Belt is beginning to go off course.

■ New Moon (today, precisely at 6:57 a.m. EST).

January 12, Friday

The faint Little Dipper (Ursa Minor) hangs straight down from Polaris after dinnertime at this coldest time of year, as if—according to Leslie Peltier—from a nail on the chilly north wall of the sky.

Meanwhile, the Big Dipper is slowly approaching from the north-northeast. Its bowl is pointing upward toward the top right, yet its handle is quite low.

JANUARY 13, SATURDAY

■ At late sunset, as seen above, the waxing crescent Moon forms a long triangle with Saturn and Fomalhaut.

Sunday, January 14th

Reversing their position along the axis between the planet and star, the Moon, Saturn, and Fomalhaut now create a triangle like the one they formed yesterday.

■ These January evenings, the Gemini twins lie on their sides, to the left of Orion. One of their head stars, Castor, is further away from Orion than the other, Pollux. (The top one is Castor.) Just to the left of Orion’s (very faint) Club are the feet of the stick figure Castor.

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