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EI2GYB > ASTRO 16.01.23 10:40l 107 Lines 8998 Bytes #999 (0) @ WW
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Subj: This Week's Sky at a Glance, January 13 - 21
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This Week's Sky at a Glance, January 13 - 21
By: Alan MacRobert January 13, 2023
Binocular Comet ZTF! Comet C/2022 E3 (ZTF), known to its friends as ZTF E3, has been gradually brightening ever since the automated Zwicky Transient Facility discovered it at 17th magnitude last March. Now it's finally having its weeks in the sun (so to speak), crossing the northern sky. It's currently about magnitude 6.5 or 7.0, on its way to perhaps mag 5.5 around the end of January and the beginning of February.
The comet should become in reach of binoculars even through a somewhat light-polluted sky - if you have a chart that pinpoints the location to examine each night, and you know the constellations well enough to match the chart to your sky outdoors. The comet may even be visible to the naked eye in a really dark, moonless sky - again, if you know the right spot to examine.
Use the charts in the January Sky & Telescope, pages 48 and 49. Or, for now, you can try the coarser charts here (the comet is currently crossing the second frame; its path begins at the top left of the frame with an unlabeled dot for 0h UT Jan. 11). On both sets of charts, the dates for the marks on the comet's track are at oh Universal Time, which falls on the evening of the previous date in North America.
As of the morning of January 16th the comet is in northern Boötes, highest in the hours before dawn. The moonlight is rapidly waning away. By the night of the 18th the comet is fairly well up in the northeast as early as midnight or 1 a.m. The comet is traveling north, and by January 26th it's nicely up for the entire night as it cruises by the Little Dipper. It will pass Kochab on the North American night of the 27th and Polaris on the 29th and 30th.
FRIDAY, JANUARY 13
Ý Orion leans bravely upward in the east-southeast after dark this week, and by 7 p.m. he's nice and high in the southeast with Sirius shining below him. Orion stands upright and highest by 10 p.m.
Ý How well do you know Orion's Sword telescopically, beyond the familiar M42 and M43 nebulae and M42's Trapezium? Many double stars and groupings await. Use Ken Hewett-White's "Sword Scene" article, chart, and list in the January Sky & Telescope, page 54.
Ý Below Orion's feet, you may know Lepus the Hare. But how about the scattering of Columba the Dove below Lepus? See Fred Schaaf's "Evenings with the Stars" column in the January Sky & Telescope, page 45. By late evening when the Orion-Lepus-Columba stack is highest in the south, the constellation chart to use is the one in the center of the February issue.
SATURDAY, JANUARY 14
Ý Last-quarter Moon tonight (exactly so at 9:10 p.m. EST). The Moon rises around midnight or 1 a.m., with Spica about half a fist to its upper right. Brighter Arcturus is two fists to the Moon's upper left. Even in cold January, spring stars emerge from hiding if you go out late enough!
Ý Have you ever seen edge-on Mare Orientale peeking around the Moon's celestial eastern limb? And the Rook and Cordillera Mountains, Lacus Veris, and Lacus Autumni in its near-limb foreground? It takes a favorable lunar libration to tilt this region into telescopic view, and we get one of these for a few days around tonight. Or rather, tomorrow morning. The waning Moon, with its celestial-east limb sunlit, will be up in the hours before dawn. Best view will be not long before the start of your local dawn. Plan to take your scope out two hours before sunrise. The Moon will be shining nicely high in the southeast.
Use your Moon map and Tom Dobbins' "Observing on the Edge" article, with guide photo, in the January Sky & Telescope, page 52. Add a sea and a couple of lakes to your lunar life list!
SUNDAY, JANUARY 15
Ý The Gemini twins lie on their sides these January evenings, well up in the east left of Orion. Their head stars, Castor and Pollux, are farthest from Orion, one over the other. (Castor is the top one, slightly the fainter of the two.) The Castor figure's feet are just left of Orion's very dim Club. The bright star below Gemini's legs is Procyon in Canis Minor.
MONDAY, JANUARY 16
Ý More action at Jupiter: At 8:30 p.m. EST, Jupiter's largest moon Ganymede slowly disappears behind Jupiter's western limb, just as Io is approaching Jupiter's opposite limb. Io crosses the limb onto Jupiter's face 31 minutes later, at 9:01 p.m. EST. Then at 10:16 EST Io's following shadow crosses onto Jupiter's eastern edge. In the Eastern time zone Jupiter is already setting by then, but westerners still have a decent view, seeing permitting.
This cosmic playfulness around Jupiter has been carrying on steadily, day by day and hour by hour, since the solar system formed 4.6 billion years ago. Only in the last ten-millionth of that time has any living creature had a telescope to witness it. Consider yourself lucky.
TUESDAY, JANUARY 17
Ý The big Northern Cross in Cygnus, topped by Deneb, is roughly upright in the west-northwest after dinnertime. By 7 p.m. it's standing on the horizon. How upright it stands there depends on your latitude.
Ý Early in the dawn of Wednesday the 18th, look southeast for the waning crescent Moon with Antares 2ø or 3ø to its right, as shown below. Bring binoculars in case the sky is getting too bright.
And see if you can spot Mercury yet, nearly three fists to the Moon's lower left.
WEDNESDAY, JANUARY 18
Ý If your sky is even moderately dark, try tracing out the winter Milky Way now arching very high. In early evening it extends up from the west-northwest horizon along the Northern Cross of Cygnus, up and over to the right past dim Cepheus and then through Cassiopeia high in the north, then to the right and lower right through Perseus and Auriga, down between the feet of Gemini and Orion's dim club, and on down toward the east-southeast horizon between Procyon and Sirius.
THURSDAY, JANUARY 19
Ý As we enter the coldest depths of winter (on average), the bowl of the Little Dipper hangs straight down from Polaris around 7 or 8 p.m. - as if (per Leslie Peltier) from a nail on the cold north wall of the sky.
The brightest star of the Little Dipper's dim bowl is Kochab, the bowl's lip. It's the equal of Polaris. Kochab itself passes precisely below Polaris about 30 minutes before the center of the bowl.
The Big Dipper, meanwhile, is creeping up low in the north-northeast. Its handle is low and its bowl is to the upper right.
FRIDAY, JANUARY 20
Ý Sirius twinkles brightly after dinnertime below Orion in the southeast. Around 8 or 9 p.m., depending on your location, Sirius shines precisely below fiery Betelgeuse in Orion's shoulder. How accurately can you time this event for your location, perhaps judging against the vertical edge of a building? Of the two, Sirius leads early in the evening. Betelgeuse leads later.
Continue the line from Betelgeuse through Sirius on down, and it runs right along Canis Major's back by another 10ø to the dog's rear end: Delta Canis Majoris, or Wezen.
SATURDAY, JANUARY 21
Ý Zero-magnitude Capella high overhead, and equally bright Rigel in Orion's foot, have almost the same right ascension. This means they cross your sky's meridian at almost exactly the same time: around 9 or 10 p.m. now, depending on how far east or west you live in your time zone. So, whenever Capella passes its very highest, Rigel always marks true south over your landscape, and vice versa.
Capella goes exactly through your zenith if you're at latitude 46ø north: Portland, Oregon; Montreal; Portland, Maine; central France; Odesa.
Ý New Moon (exact at 3:53 p.m. EST.)
SUNDAY, JANUARY 22
Ý Venus and Saturn reach their conjunction «ø apart, as shown below. Use binoculars in bright twilight. And look too for the thin crescent Moon rather far below them.
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