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EI2GYB > ASTRO 21.01.23 13:44l 124 Lines 10536 Bytes #999 (0) @ WW
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Subj: This Week's Sky at a Glance, January 20 - 29
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This Week's Sky at a Glance, January 20 - 29
By: Alan MacRobert January 20, 2023
Binocular Comet ZTF! Comet C/2022 E3 (ZTF), known to its friends as ZTF E3, has been brightening ever since the automated Zwicky Transient Facility discovered it at 17th magnitude last March. Now it's finally having its best time in the sun, while crossing the northern sky. As of January 19th it's about magnitude 6.0, on its way to maybe 5.5 when brightest around the end of January and the beginning of February.
The comet should be 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 the stars in your sky outdoors. The comet may even become dimly visible to the naked eye in a really dark, moonless sky - again, if you know the right spot to examine.
See Bob King's article Circumpolar Comet ZTF (C/2022 E3) is Here! It has the finder chart you need as well as a table of the best observing times by date and the moonlight situation. On the chart, the dates on the comet's track are for oh Universal Time, which falls on the evening of the previous date in North America.
As of Saturday night January 21-22 the comet is at the Boötes-Draco border, some 25ø up in the northeast by about 1 a.m. and highest in a dark sky before the first light of dawn (which means go out at least 2 hours before sunrise to leave some observing time after you get set up). The Moon is out of the picture.
The comet is traveling north, and by January 26th it's nicely up from 9 p.m. until dawn as it reaches the Little Dipper. It will pass Kochab on the North American night of the 27th and Polaris on the 29th and 30th, but by then moonlight will pose growing interference in the evening, with the Moon setting later and later in the night.
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, the middle star of Canis Major's bright rear triangle.
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 Algol tonight should be at minimum brightness, magnitude 3.4 instead of its usual 2.1, for a couple hours centered on 12:27 a.m. EST; 9:27 p.m. PST.
Ý New Moon (exact at 3:53 p.m. EST.)
SUNDAY, JANUARY 22
Ý Venus and Saturn reach conjunction «ø apart, as shown below. Use binoculars in bright twilight. And look too for the thin crescent Moon rather far below them.
Both planets will fit together in a telescope's low- to medium-power eyepiece. You will be struck by how radically different the surface brightnesses of Venus and Saturn really are! Saturn is 13.5 times farther from the Sun than Venus is, so its clouds are lit by sunlight that's 13.52 or 180 times fainter than the sunlight striking Venus.
MONDAY, JANUARY 23
Ý Now Saturn glimmers 1.3ø to Venus's lower right in the fading twilight, while the crescent Moon looks on from the upper left.
TUESDAY, JANUARY 24
Ý The big Northern Cross in Cygnus, topped by Deneb, is roughly upright in the west-northwest after dark. By 6 or 7 p.m. it's standing on the horizon. How upright it stands there depends on your latitude.
Ý Algol should be at minimum brightness for a couple hours centered on 9:16 p.m. EST.
WEDNESDAY, JANUARY 25
Ý Right after dark, face east and look very high, almost overhead. The bright star there is Capella, the Goat Star. To the right of it, by a couple of finger-widths at arm's length, is a small, narrow triangle of 3rd and 4th magnitude stars known as "The Kids." Though they're not exactly eye-grabbing, they form a never-forgotten asterism with Capella.
THURSDAY, JANUARY 26
Ý After dark the Great Square of Pegasus sinks in the west left of Jupiter. It's tipped onto one corner. Meanwhile the Big Dipper is creeping up in the north-northeast, tipped up on its handle.
FRIDAY, JANUARY 27
Ý Orion is now high in the southeast right after dark, and he stands highest due south around 9 p.m. Orion is the brightest of the 88 constellations, but his main pattern is surprisingly small compared to some of his dimmer neighbors. The biggest of these is Eridanus the River to his west, enormous but hard to trace. Dimmer Fornax the Furnace, to Eridanus's lower right, is almost as big as Orion! Even the main pattern of Lepus, the Hare cowering under the Hunter's feet, isn't much smaller than he is.
Do you know the constellation down below Lepus? It's a tough one: Columba the Dove, faint, sprawly, and to my eye not a bit dove-like. See the constellation chart in the center of the February Sky & Telescope. Its brightest star, Alpha Columbae or Phact, is magnitude 2.6. To find it, draw a line from Rigel through Beta Leporis (the front of the bunny's neck) and extend it an equal distance straight on.
SATURDAY, JANUARY 28
Ý First-quarter Moon (exactly so at 10:19 a.m. EST). The Moon is partway between Mars to its left and Jupiter farther to its lower right. During twilight Venus and Saturn complete the lineup low in the west-southwest; a line from the Moon through Jupiter points to them - because, of course, they all lie nearly on the great circle of the ecliptic. Uranus and Neptune are also part of the evening lineup, out of naked-eye sight.
SUNDAY, JANUARY 29
Ý The waxing gibbous Moon shines on the edge of Taurus somewhat west of the Pleiades, Mars, and Aldebaran, as shown below.
Tomorrow night January 30th, the Moon's dark limb will occult Mars for the southern US from north Florida through central California, and south into northwestern South America. Skywatchers elsewhere in the Americas will observe a near miss. Map and timetables.
This Week's Planet Roundup
Mercury is having a nice dawn apparition. Starting about 50 minutes before your local sunrise, look for it low in the southeast. It's the brightest thing there, shining at about magnitude 0.0 all week.
Don't confuse it with Antares about three fists to its right or upper right. Or Altair a little farther to Mercury's left or upper left.
Venus, very bright at magnitude -3.9, shines low in the west-southwest in evening twilight. It sets just after twilight's end. Dimmer Saturn passes it this week. They go through conjunction on January 22nd about «ø apart, as shown at the top of this page. Thereafter Saturn descends rapidly away to Venus's lower right.
Mars, in Taurus, shines very high toward the south in early to mid-evening. Mars continues to fade, from magnitude -0.6 to - 0.4 this week, as it shrinks from 12 to 11 arcseconds wide. Aldebaran, mag +0.8, is 8ø below it.
Jupiter, magnitude -2.2 in Pisces, shines high in the southwest in twilight, then sinks toward the west. It sets around 10 p.m. Telescopically, Jupiter has shrunk to 37 or 36 arcseconds wide.
Look for the Great Square of Pegasus to Jupiter's right. Extend the line of the Square's upper left side down to the planet. Jupiter crosses this line on Monday January 23rd. To help judge this, hold a straightedge up to the sky or stretch a string tightly between your hands.
Saturn, magnitude +0.8 in Capricornus, passes brilliant Venus this week in the twilit southwest. On Friday January 20th, Saturn is still 2ø above Venus as shown at the top of this page. They go through conjunction on the 22nd, about «ø apart. Thereafter Saturn descends rapidly away to Venus's lower right.
Uranus, magnitude 5.7 in southern Aries, is high in the south in early evening. It displays a tiny, very slightly blue-greenish gray disk 3.6 arcseconds wide. It a telescope at high power it's obviously non-stellar. See the Uranus finder charts in the November Sky & Telescope, page 49.
Neptune, magnitude 7.9 at the Aquarius-Pisces border, is getting lower about 10ø to the lower right of Jupiter. So try for it immediately after dark. Neptune is just 2.2 arcseconds wide, again non-stellar in a telescope but requiring more effort than Uranus. See the Neptune finder charts in last September's Sky & Telescope, page 49.
All descriptions that relate to your horizon - including the words up, down, right, and left - are written for the world's mid-northern latitudes. Descriptions and graphics that also depend on longitude (mainly Moon positions) are for North America.
Eastern Standard Time (EST) is Universal Time minus 5 hours. Universal Time is also called UT, UTC, GMT or Z time.
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