The Sky This Week: Catch Comet Leonard at its best (2024)

Friday, December 10
The Moon passes 0.5° north of asteroid 2 Pallas in Aquarius at 8 A.M. EST; meanwhile, asteroid 44 Nysa reaches opposition in Taurus the Bull at 9 A.M. EST. Although these objects are below the horizon and the sky is light, if you wait until this evening, you can spot these asteroids in the nighttime sky.

Pallas is the third-largest asteroid in the main belt. By two hours after sunset, the Moon has pulled away slightly and sits 6.2° east-northeast of the 10th-magnitude asteroid. For a closer signpost, start at 3rd-magnitude Skat (Delta [δ] Aquarii). Pallas sits 3.7° north-northeast of this star tonight.

Nysa is about a magnitude brighter than Pallas. You’ll want to give it until about 7:30 P.M. local time to get high enough for good viewing in Taurus, located above Orion in the sky as the pair rises in the east. You’ll find Nysa about 7.2° west-southwest of 3rd-magnitude Alheka, floating near two open clusters: NGC 1807 and NGC 1817.

The Moon passes 4° south of Neptune at 8 P.M. EST, still in Aquarius. Slightly brighter than our two asteroid targets tonight, Neptune shines at magnitude 7.8 as a “flat” blue-green disk spanning 2″ through a telescope.

Finally, First Quarter Moon occurs tonight at 8:36 P.M. EST.

Sunrise: 7:11 A.M.
Sunset: 4:34 P.M.
Moonrise: 12:32 P.M.
Moonset: 11:49 P.M.
Moon Phase: Waxing crescent (47%)
*Times for sunrise, sunset, moonrise, and moonset are given in local time from 40° N 90° W. The Moon’s illumination is given at 12 P.M. local time from the same location.

Saturday, December 11
Mars has reappeared in the morning sky. Early risers will be rewarded with a view of the Red Planet this morning, just 6° high in the southeast an hour before sunrise. You’ll find it in Libra, shining at magnitude 1.6 near the constellation’s eastern boundary. The nearest bright star, magnitude 2.6 Arcab in Scorpius, lies 5° east of the planet. Mars will cross into Scorpius late on the morning of the 15th, then move into Ophiuchus by the 25th.

The small planet currently sits nearly 2.4 astronomical units (AU, where 1 AU is the average Earth-Sun distance) from Earth and spans a mere 4″ on the sky. Although it will appear as a small, relatively featureless disk, you should still be able to make out its orangey-red color, with or without optical aid.

Sunrise: 7:12 A.M.
Sunset: 4:35 P.M.
Moonrise: 12:56 P.M.
Moonset: —
Moon Phase: Waxing gibbous (57%)

Sunday, December 12
This week is Comet C/2021 A1 (Leonard)’s time to shine! Today marks its closest approach to Earth, and also the day when observers should switch from looking for the comet in the predawn sky to searching it out in the evening sky, instead.

If you’re trying to catch one last glimpse of Leonard in the morning, you’ll find it in Ophiuchus, floating within 5° of both M10 and M12. An hour before sunrise, Leonard is just 5° high and will continue rising in the brightening dawn. Leonard is around 6th magnitude — just bright enough to count as a naked-eye object, but only in a dark sky. You’re better off observing it through binoculars or a telescope, but take care to call off the search several minutes before sunrise to avoid any danger of damaging your eyes.

This evening, Leonard sits 12° above the western horizon at sunset. Half an hour later, it’s just 7° high but the sky is darker and our icy target will be easier to find. A full hour after sunset, Leonard is a mere 1° high, about 5.5° northwest of magnitude 4.6 Mu (μ) Ophiuchi.

The best comet viewing for the rest of the month will be in the evening sky, as Leonard pulls away from Earth but approaches the Sun and slowly fades to around magnitude 8. Keep watching this stunning comet throughout the week; we’ll check back in on Friday, when it will appear close to Venus in the sky.

If you aren’t able to catch the comet for yourself, consider clicking over to astronomy livestreamer David Brewer’s YouTube channel, where he’s been streaming the comet daily (weather permitting) from Denver, Colorado.

Sunrise: 7:13 A.M.
Sunset: 4:35 P.M.
Moonrise: 1:19 P.M.
Moonset: 12:52 A.M.
Moon Phase: Waxing gibbous (67%)

Monday, December 13
Gemini the Twins is our target for tonight, climbing higher in the east as the hours tick by toward midnight. Although the Twins’ heads, bright Castor and Pollux, are easy to spot some 43° northeast of Orion’s Belt, tonight we’re zooming in on Gemini’s northern foot, depicted by Mu and Eta (η) Geminorum. Nearby are two beautiful open clusters: M35 & NGC 2158.

Let’s start with brighter M35, which glows at magnitude 5.3 less than 2.5° north-northwest of Eta. Spanning about 28′, this cluster contains several hundred stars and is visible under good conditions as a smudge with the naked eye.

NGC 2158 sits some 15′ southwest of M35. It’s smaller and fainter, glowing around magnitude 8.6 and spanning just 5′. You’ll need binoculars or a telescope to see it, well within the same field of view as M35. But it’s only smaller in relative terms — this cluster is more compact and contains more stars than M35. It’s also about five times more distant, which accounts for its smaller apparent dimensions on our sky.

Sunrise: 7:14 A.M.
Sunset: 4:35 P.M.
Moonrise: 1:42 P.M.
Moonset: 1:53 A.M.
Moon Phase: Waxing gibbous (76%)

Tuesday, December 14
Let’s head back to Gemini again today, as the annual Geminid meteor shower peaks this morning with a waxing Moon in Pisces. That means bright moonlight will wash out the sky until about 3 A.M. local time (when the Moon sets), so that’s when you’ll want to step outside to scan for shooting stars until dawn.

Around 4 A.M. local time, the radiant is some 65° high in the west. It’s located just northwest of the bright star Castor. The best strategy to catch shower meteors is actually a to look a bit away from the radiant. That’s because meteors originate at the radiant, so their trails will streak away from this point. The Geminids are expected to produce up to 150 meteors per hour at their peak, so you should expect to see several shooting stars the longer you stay outside, with numbers diminishing as dawn approaches and lightens the sky. If possible, pick an observing site well away from any light pollution, bundle up (for those in colder climates), and avoid using a telescope, as its small field of view will limit or eliminate any streaks you might see. Instead, scan the sky with your eyes or binoculars to catch the most meteors.

Sunrise: 7:14 A.M.
Sunset: 4:35 P.M.
Moonrise: 2:05 P.M.
Moonset: 2:54 A.M.
Moon Phase: Waxing gibbous (83%)

Wednesday, December 15
The Moon passes 1.5° south of Uranus at 1 A.M. EST. At that time, the pair is relatively high in the west, located in the southern portion of Aries the Ram. Our Moon is a waxing gibbous some 87 percent lit, while the distant ice giant Uranus shines at magnitude 5.7. That makes it easy to capture with binoculars or a telescope, although the bright moonlight may increase the challenge a bit.

Once you’ve found the planet, you may notice that its small, 4″-wide disk is colored grayish-blue. The planet’s cloud tops typically show no detail, so it should appear uniform in color. Uranus is well known for its odd — and extreme — tilt, which is nearly 98° and essentially places the planet on its side. This means its ring system (unfortunately invisible in your scope) is also tilted, circling the planet face-on from our point of view.

Sunrise: 7:15 A.M.
Sunset: 4:36 P.M.
Moonrise: 4:30 P.M.
Moonset: 3:54 A.M.
Moon Phase: Waxing gibbous (90%)

Thursday December 16
Venus has become an unmistakable beacon in the evening sky, seated in northeastern Sagittarius and setting some two hours after the Sun. Nearby, just one constellation over in Capricornus, is Saturn, glowing a much more muted magnitude 0.6 to Venus’ spectacular magnitude –4.9. The two began the month 18° apart and have been creeping closer over the past two weeks. Tonight, they reach their closest approach, separated by 14°. Once you’ve found Venus, simply scan east on the sky, along the ecliptic, to find dimmer Saturn. Beyond it, now having passed into Aquarius, is Jupiter, now magnitude –2.2.

Take some time to enjoy these planets through a telescope. Venus is the smallest of the three but also the closest to Earth. It presents a disk that is just 15 percent illuminated but spans 50″ on the sky. Its phase will continue to diminish but its size grow for the rest of the month. Saturn, the farthest of the three and middling in physical size, appears 16″ wide, flanked by its fantastic rings, which stretch 35″ end to end. Now is the time to view this planet with a telescope, as it will continue sinking toward the horizon in the coming weeks. Finally, the largest planet in the solar system, Jupiter, appears 37″ across and is flanked by all four of its Galilean moons this evening. Europa lies alone to the planet’s east, while, stretching from closest to farthest, are Io, Ganymede, and Callisto to the west.

Sunrise: 7:16 A.M.
Sunset: 4:36 P.M.
Moonrise: 2:58 P.M.
Moonset: 4:55 A.M.
Moon Phase: Waxing gibbous (95%)

Friday, December 17
Let’s check back in tonight with both Comet C/2021 A1 (Leonard) and the planet Venus, which tonight float just 5° apart in the evening sky. Leonard now appears directly below the planet, sandwiched between it and the horizon. Depending on how much the comet has brightened, there’s a chance it may be just visible to the naked eye in the darkening sky. Begin looking southwest just after sunset, when Venus — still blazing at an unmissable magnitude –4.9 — is nearly 20° high. As the sky grows darker, look below the planet for Leonard’s faint, fuzzy outline.

If you can’t see it without optical aid, don’t worry. Binoculars will definitely net it, and then you can zoom in on the comet with a telescope once you’ve found it to see its coma and perhaps even a stubby tail. Because it is at the edge of naked-eye brightness, Leonard will show up best in photographs — and photographers will definitely want to record this stunning scene, with two bright solar system bodies in close proximity on the sky.

The Moon reaches apogee, the farthest point from Earth in its orbit, at 9:15 P.M. EST. At that time, it will sit 252,475 miles (406,319 km) from our planet.

Sunrise: 7:16 A.M.
Sunset: 4:36 P.M.
Moonrise: 3:32 P.M.
Moonset: 5:56 A.M.
Moon Phase: Waxing gibbous (98%)