The Sky This Week from January 20 to 27

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By Admin

Tuesday, January 24

Setting slowly after dark tonight, the crescent Moon sits 5° below Neptune. You can use it as a jumping-off point to enjoy that distant blue-gray planet, which remains magnitude 7.8, through binoculars or a telescope.

But it’s also worth turning your gaze to the Moon itself, as our satellite repeats its strange libration from earlier this month. Libration is simply the apparent “nodding” motion our Moon goes through over time, as its slightly inclined orbit shows us more or less of certain regions as Luna circles the planet. Earlier this month, the Full Moon appeared distinctly odd thanks to a syncing up of the libration and illumination cycles.

Now, the same process essentially repeats, just two days earlier as those cycles begin to fall out of lockstep. Look over the illuminated northeastern portion of our satellite for the dark blotch of Mare Humboldtianum, with the oval-shaped crater Endymion to its southwest. Mare Crisium appears farther south and west than usual — compare it to the view of the Full Moon from earlier this month, as well as a “typical” lunar map. Now, Mare Smythii and Mare Marginis are readily visible on the limb as well.

Sunrise: 7:15 A.M.
Sunset: 5:10 P.M.
Moonrise: 9:27 A.M.
Moonset: 8:49 P.M.
Moon Phase: Waxing crescent (12%)

Wednesday, January 25

Steadily working its way along the ecliptic, the Moon passes 3° south of Neptune at 1 A.M. EST, then makes a closer pass of magnitude –2.2 Jupiter in Pisces, moving 1.8° south of the solar system’s largest planet at 9 P.M. EST. You can catch those two in the south starting at sundown; in the Midwest, Jupiter’s innermost Galilean moon, Io, is about a quarter of the way through a transit at sunset. An hour later (around 6:10 P.M. CST — that’s 7:10 P.M. EST), Io is now about three-quarters of the way across the disk and its shadow has joined in the journey, making its way inward from the eastern limb.

The pair cross the planet together as it sinks lower in the sky. Io slips off the western edge of the disk around 7:45 P.M. CST, with Jupiter still some 35° high in the Midwest. Io’s shadow is now halfway across, finally disappearing just over an hour later, shortly before 9 P.M. EST (when Earth’s Moon slides exactly due south of the gas giant).

Sunrise: 7:15 A.M.
Sunset: 5:11 P.M.
Moonrise: 9:53 A.M.
Moonset: 10:01 P.M.
Moon Phase: Waxing crescent (21%)

Thursday, January 26

Asteroid 6 Hebe reaches opposition at 4 A.M. EST. The magnitude 8.7 main-belt world lies in Cancer, rising in the east after sunset. Look with binoculars for two 6th-magnitude field stars some 6.8° south-southwest of the Beehive Cluster (M44). Hebe lies midway between those stars, slightly west of a line connecting them.

Since you’re in the area, don’t ignore M44, a stunning open cluster visible even without any optical aid. The Beehive Cluster has been known since antiquity, thanks to its naked-eye magnitude of 3.7; it spans some 95′ and contains roughly 350 stars, many of which are visible with binoculars or a telescope.

But M44 isn’t the only open cluster in Cancer by far. Just over 6° east of Hebe’s position (and about 8° southeast of M44) is M67, a fainter, more compact cluster that glows at magnitude 6.1 and spans 30′, similar to the apparent size of the Full Moon. Although it is also an open cluster of young stars, it’s one of the oldest in this category — astronomers estimate M67 is some 3.2 billion years old. Compare that with M44, which is an estimated 703 million years old! Because M67 is roughly the same age as our solar system, it’s a great place for researchers to study Sun-like stars.

Sunrise: 7:14 A.M.
Sunset: 5:12 P.M.
Moonrise: 10:17 A.M.
Moonset: 11:11 P.M.
Moon Phase: Waxing crescent (31%)

Friday, January 27

Mercury is growing more prominent in the morning sky, now magnitude 0 and rising nearly an hour and a half before the Sun. An hour before sunrise, Mercury sits about 5° high in the southeast, to the upper left (east-northeast) of the triangular top of Sagittarius’ Teapot asterism, which is just peeking above the horizon. Through a telescope, the tiny planet spans 7″ and appears just over half (57 percent) lit.

Mercury is accompanied by several bright stars still visible against the growing twilight: the prominent red giant Antares in Scorpius stands to its upper right, with Altair in Aquila to its upper left. Some 34° above Altair blazes Vega in Lyra, matching Mercury in brightness at magnitude 0. Look to Vega’s left to locate Deneb in Cygnus the Swan. These three stars — Altair, Vega, and Deneb — form the famous Summer Triangle, which rises the morning during the winter but in the evening during the summer. Meanwhile, look to Vega’s far upper right to locate Arcturus, the bright alpha star in Boötes. Through binoculars or a telescope, this aging luminary appears distinctly golden.

Sunrise: 7:13 A.M.
Sunset: 5:13 P.M.
Moonrise: 10:42 A.M.
Moon Phase: Waxing crescent (41%)

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