This Week's Sky at a Glance, January 9 – 18

FRIDAY, JANUARY 9

■ Jupiter is at opposition tonight, opposite the Sun as seen from Earth; exactly so 3 a.m. EST Saturday morning the 10th (8h UT Jan 10th). Jupiter rises at sunset and blazes in Gemini near Pollux and Castor all night.

■ Quite by coincidence, Jupiter's big moon Callisto will be crossing the planet's face right at opposition time late tonight. Moreover, Jupiter is a mere ¼° from the ecliptic. Consequently, Callisto will cover most of its own shadow! Will the shadow's slightly larger penumbra show around the relatively dark-surfaced moon, as a thin, perfect darker ring? The transit of Callisto and its shadow runs from 1:55 a.m. to 5:49 a.m. EST (10:55 p.m. to 2:49 a.m. PST). Read An extremely rare Callisto event. The Association of Lunar and Planetary Observers (ALPO) seeks images, drawings, and/or visual descriptions.

Also: Paolo Molaro at the Osservatorio Astronomico di Trieste, Italy, writes us,

At 08:40 UT, there will be a perfect alignment of the Sun, Earth, and Jupiter. For an observer located in the Jovian system, the Earth will transit across the [tiny] solar disk, with a total duration of approximately three hours.

Although Earth and Jupiter reach opposition every ~12 years (the Jovian orbital period), perfect Sun–Earth–Jupiter alignments of this kind are exceptionally rare. They occur in a series of five events spaced by 12 years, followed by a long hiatus. The 2026 transit will be the final event of the current series; the next such series will not begin until 2109.

This alignment offers a particularly favorable opportunity to observe the Galilean moons of Jupiter. Owing to the opposition surge, the satellites are expected to undergo a noticeable increase in brightness—possibly approaching one magnitude (though this estimate is approximate). Under optimal conditions, this enhancement could make the moons significantly easier to observe and, potentially, even visible to the naked eye. Observations using a coronagraph to suppress Jupiter’s glare should be especially rewarding.

The transit occurs on 10 January 2026, peaking at 08:40 UT, and will be observable from North  America, making it particularly relevant for your readership.

■ Algol should be at minimum light, magnitude 3.4 instead of its usual 2.1. for a couple hours centered on 9:02 p.m. EST.

SATURDAY, JANUARY 10

■ Here we are near the coldest very bottom of the year, but Vega, the Summer Star, is still hanging in. Look for it twinkling over the northwest horizon during and shortly after dusk. The farther north you are the higher it will be. If you're as far south as Florida, it's already gone.

■ Last-quarter Moon (exactly last quarter at 10:48 a.m. this morning EST). By the time the Moon rises around 1 a.m. tonight (on the morning of the 11th), look for its terminator to be slightly concave.

Above the Moon when it rises tonight, by three or four finger-widths at arm's length, will be springtime Spica making its cold, post-midnight January appearance. By tomorrow's dawn the Moon will be high in the south with Spica to its upper right, as shown above.

SUNDAY, JANUARY 11

■ How often have you looked at the Great Orion Nebula in your telescope? Think you've seen all here that your scope can show? Well then, do you know about T Orionis?

This very young variable star in the nebula is still gravitationally contracting and accreting clumpy matter on its way toward life on the Main Sequence. For now it appears as a hot subgiant. Normal hydrogen fusion has probably not yet caught fire in its core.

T Ori is having a wild babyhood, as new stars do. Its irregular variability, trackable by eye in amateur scopes across a matter of weeks, results from changes in its accretion rate of blobby material and shadowing by its circumstellar dust disk. It usually ranges between magnitude 10.2 and 11.0 but has been seen as bright as 9.6 and as faint as 12.5.

T Orionis lies just 10 arcminutes southeast of the Trapezium quartet at the heart of the nebula, as shown above. For lots more about this class of stars, and a finder chart for T with comparison-star magnitudes, see Bob King's Catch Birth Flickers of Budding Suns.

MONDAY, JANUARY 12

■ In early evening now, the enormous Andromeda-Pegasus complex runs from near the zenith down toward the western horizon.

Close to the zenith, spot Andromeda's high foot: 2nd-magnitude Gamma Andromedae (Almach), slightly orange. Andromeda is standing on her head.

About halfway down from the zenith to the west horizon is the Great Square of Pegasus, balancing on one corner. Andromeda's head is its top corner.

From the Square's bottom corner run the stars outlining Pegasus's neck and head, ending at his nose: 2nd-magnitude Enif, due west. It too is slightly orange.

That bright point off to the lower left of the Great Square is Saturn.

TUESDAY, JANUARY 13

■ Jupiter's moon Io slides behind Jupiter's western limb at 8:00 p.m. EST. It gradually emerges from eclipse out of Jupiter's shadow, barely off Jupiter's eastern limb, at 10:22 p.m. EST, with brighter Ganymede nearby.

■ Just before and during early dawn Wednesday morning, spot the waning crescent Moon low in the southeast as shown below. Orange Antares shines 3° to 4° to its left or lower left. Somewhat farther above the Moon is Delta Scorpii, the middle star of the line of three marking the head of Scorpius.

WEDNESDAY, JANUARY 14

■ Right after dark, face east and look very high. 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. Through heavy light pollution, many skywatchers are familiar with only two of them plus Capella.

THURSDAY, JANUARY 15

■ There's more to be found telescopically in and around the Pleiades than you probably know — including abundant double stars, most of them quite unlike each other. See the charts and pix in Ken Hewitt-White's "A Bang and a Whimper" in the January Sky & Telescope, page 55.

And late on these moonless evenings, if you have a big scope and a very dark sky, try finding and exploring the Thor's Helmet nebula, NGC 2359, using Howard Banich's "Going Deep" column, chart, and drawings in the same issue, page 58. An OIII filter helps. Thor's Helmet is 4° northeast of Gamma Canis Majoris in a crowded star field behind Canis Major's head. Don't get lost!

FRIDAY, JANUARY 16

■ 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 46° north: near Portland Oregon, Minneapolis, Montreal, Portland Maine, central France, Odesa, Kherson.

SATURDAY, JANUARY 17

■ If your sky is reasonably dark, trace out the winter Milky Way arching across the sky. In early evening it extends up from the west-northwest horizon along the vertical Northern Cross of Cygnus, farther up and over to the right past dim Cepheus and 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 Club, and on down toward the east-southeast horizon between Procyon and Sirius.

SUNDAY, JANUARY 18

■ 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.

■ New Moon (exact at 2:52 p.m. EST).

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This Week's Planet Roundup

Mercury, Venus, and Mars are still all out of sight behind the glare of the Sun.

Jupiter (magnitude –2.7, shining in the Pollux stick figure of the Gemini twins) is at opposition the night of January 9-10. All week it rises in the east-northeast around sunset, dominates the eastern sky early in the evening, then the high southeast. Castor and Pollux shine nearby. Jupiter is highest in the south and thus telescopically sharpest by 11 or midnight. It's a big 47 arcseconds wide across its equator this week and remains nearly as big all January. See "Jupiter Rules!" in the January Sky & Telescope, page 48, which includes a map of its dark belts and bright zones.

Saturn (magnitude +1.2, at the Aquarius-Pisces border) is the brightest dot high in the southwest at nightfall, lower left of the Great Square of Pegasus. It descends through the evening and sets in the west around 1o p.m.

In a telescope Saturn's rings are still very thin but, gradually, opening up. They're now tilted 1° to our line of sight. The rings' thin black shadow on Saturn's globe is slowly becoming a little wider too.

Uranus (magnitude 5.6, in Taurus 5° south of the Pleiades) waits high in the southeast these evenings. At high power in a telescope it's a tiny but non-stellar dot, 3.8 arcseconds wide. You'll need a detailed finder chart to identify it among similar-looking faint stars, such as the chart in the November Sky & Telescope, page 49.

Neptune is a telescopic "star" of magnitude 7.9, a dim speck just 2.3 arcseconds wide 4° above Saturn. For Neptune you'll need an even more detailed finder chart.

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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. UT is also known as UTC, GMT, or Z time.

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Want to become a better astronomer? Learn your way around the constellations. They're the key to locating everything fainter and deeper to hunt with binoculars or a telescope.

This is an outdoor nature hobby. For a more detailed constellation guide covering the whole evening sky, use the big monthly map in the center of each issue of Sky & Telescope, the essential magazine of astronomy.

For the attitude every amateur astronomer needs, read Jennifer Willis's Modest Expectations Give Rise to Delight.

Once you get a telescope, to put it to good use you'll want a much more detailed, large-scale sky atlas (set of charts). The basic standard is the Pocket Sky Atlas, in either the original or Jumbo Edition. Both show all 30,000 stars to magnitude 7.6, and 1,500 deep-sky targets — star clusters, nebulae, and galaxies — to search out among them.

Next up is the larger and deeper Sky Atlas 2000.0, plotting stars to magnitude 8.5; nearly three times as many, as well as many more deep-sky objects. It's currently out of print, but maybe you can find one used.

The next up, once you know your way around well, are the even larger Interstellarum Deep-Sky Atlas (with 201,000+ stars to magnitude 9.5 and 14,000 deep-sky objects selected to be detectable by eye in very large amateur telescopes), and Uranometria 2000.0 (332,000 stars to mag 9.75, and 10,300 deep-sky objects).

Read How to Use a Star Chart with a Telescope. It applies just as much to electronic charts on your phone or tablet — which many observers find handier and more versatile, if perhaps less well designed, than charts on paper.

You'll also want a good deep-sky guidebook. A beloved old classic is the three-volume Burnham's Celestial Handbook. It was my bedside reading for years. An impressive more modern one is the big Night Sky Observer's Guide set (2+ volumes) by Kepple and Sanner. The pinnacle for total astro-geeks is the new Annals of the Deep Sky series, currently at 11 volumes as it works its way forward through the constellations alphabetically. So far it's up to H.

Can computerized telescopes replace charts? Well, I used to say this:

"Not for beginners, I don't think, unless you prefer spending your time getting finicky technology to work rather than learning how to explore through the sky yourself. As Terence Dickinson and Alan Dyer say in their Backyard Astronomer's Guide, 'A full appreciation of the universe cannot come without developing the skills to find things in the sky and understanding how the sky works. This knowledge comes only by spending time under the stars with star maps in hand and a curious mind.' Without these, 'the sky never becomes a friendly place.' "

Well, things change. The technology has continued to improve and become more user-friendly — particularly with software that can now recognize any star field to determine exactly where the telescope is pointed — finally bypassing all aiming imperfections in the mount, tripod, gears, bearings and other mechanics, or in the user's skill in setting up.

The latest revolution is the rise of small, imaging-only "smartscopes." These take advantage of not only today's pointing technology, but also the vastly better capabilities of imaging chips and processing compared to the human retina and visual cortex. The most sophisticated image stacking and processing can also come built in. The result is decent deep-sky imaging from shockingly small, low-priced units. The image may be viewable on your phone or computer as it builds up in real time. Small smartscopes can enable direct contributions to citizen-science projects.

These are changing the hobby at the entry level. For more on this revolution see Richard Wright's "The Rise of the Smart Telescopes" in the November 2025 Sky & Telescope. And read the magazine's review of this especially small one.

If you get a larger, more conventional computerized scope that allows direct visual use, make sure that its drives can be disengaged so you can swing it around and point it readily by hand when you want to, rather than only slowly by the electric motors (which eat batteries).

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Audio sky tour. Out under the evening sky with your
earbuds in place, listen to Kelly Beatty's monthly
podcast tour of the naked-eye heavens above. It's free.

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"The dangers of not thinking clearly are much greater now than ever before. It's not that there's something new in our way of thinking, it's that credulous and confused thinking can be much more lethal in ways it was never before."
            — Carl Sagan, 1996

"Facts are stubborn things; and whatever may be our wishes, our inclinations, or the dictates of our passion, they cannot alter the state of facts and evidence."
            — John Adams, 1770

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