The Sky This Week from May 19 to 26: Deep-sky delights

A thin crescent Moon paves the way for faint targets and Mercury returns to the sky from May 19 to 26.
By | Published: May 19, 2023

Friday, May 19
The Moon reaches its New phase at 11:53 A.M. EDT, leaving a perfectly dark sky overhead for us to seek out fainter targets like the Lagoon Nebula. Also cataloged as M8, the Lagoon is located in northwestern Sagittarius. It sits some 5.5° west of magnitude 2.8 Kaus Borealis (Lambda [λ] Sagittarii). You’ll find it rising in the southeast about an hour before local midnight, though if you’re not opposed to staying up rather late, feel free to give it time to gain some height in the sky.

M8 is a bright emission nebula associated with a young cluster of forming stars, similar to the more famous Orion Nebula (M42). Its is just brighter than magnitude 5, rendering it visible to the naked eye as a hazy patch of light under particularly good conditions. The Lagoon spans some 45′ by 30′, or slightly larger than the Full Moon, and several details become discernible with a telescope. You may notice varying shades to its gray coloring, as well as a dark dust lane running through the nebula’s middle. The young star cluster NGC 6523 lies just to the east of this dust lane, while the 6th-magnitude star 9 Sagittarii lies to its west.

Sunrise: 5:42 A.M.
Sunset: 8:12 P.M.
Moonrise: 5:29 A.M.
Moonset: 8:39 P.M.
Moon Phase: New
*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, May 20
The large, bright moon Titan sits due north of Saturn this morning. An hour before sunrise, the ringed planet stands some 25° high in the southeast, floating amid the stars of Aquarius and shining at a respectable magnitude 0.8. Zoom in with a telescope to enjoy the planet’s stunning ring system, which stretches just over twice the span of its 17″-wide disk. The outermost ring is the A ring, divided from the B ring (interior to it) by the Cassini Division. You may spot this dark gap if your seeing conditions are good. The innermost ring is the C ring, sometimes called the Crepe ring for its gauzy appearance.

Titan, shining at magnitude 8.7, lies north and just a little east of Saturn this morning. Several other moons also cluster nearby: 10th-magnitude Dione sits due east, while Rhea (closer) and Tethys are west of the rings, also 10th magnitude. If you’ve got particularly good conditions, try also spotting 12th-magnitude Enceladus, which lies just off the rings’ eastern edge.

Pulling back for a broader view, Saturn sits some 20° to the upper left (north-northwest) of 1st-magnitude Fomalhaut in Piscis Austrinus. This young star sports a huge protoplanetary disk of dust, ice, and gas; for years, astronomers followed what they believed was a forming planet as it orbited inside this disk. However, in recent years, the planet “disappeared” and astronomers concluded it had never been a planet at all, but instead the icy remains of a collision of debris within the disk.

Sunrise: 5:41 A.M.
Sunset: 8:13 P.M.
Moonrise: 6:05 A.M.
Moonset: 9:46 P.M.
Moon Phase: Waxing crescent (1%)

Path of Comet 237P/LINEAR
Comet 237P/LINEAR Try to spot Comet 237P/LINEAR in the second half of the month — though note that unless it experiences an outburst, you’ll need a large scope to do the job. Fortunately, there are plenty of other targets nearby. Credit: Astronomy: Roen Kelly

Sunday, May 21
Comet 237P/LINEAR is an excellent early-morning object for those with large scopes and plenty of patience. Now around 13th magnitude, LINEAR is in far southern Aquila about 10° south of 3rd-magnitude Theta (θ) Aquilae and 6° northwest of 4th-magnitude Algedi in Capricornus. About two hours before sunrise, the comet has reached an altitude of more than 35° in the southern sky.

If you have that big scope (think 12 inches or so), you can net not only the comet’s faint, fuzzy coma, but plenty else in the area, too. LINEAR is surrounded by several deep-sky objects, including spiral galaxy NGC 6814 about 3° to the comet’s west. This is a beautiful grand design spiral is oriented face-on toward us, showing off sweeping arms and a bright center.

Also near comet LINEAR this month are dwarf galaxy NGC 6822 (also known as Barnard’s Galaxy) about 5° to the comet’s southwest, as well as planetary nebula NGC 6818 nearly 5° to the comet’s southwest (slightly more west than NGC 6822). In particular, the magnitude 9.4 planetary will look a bit like the planet Uranus, with a similar gray-blue glow. Often called the Little Gem, this object sits some 6,000 light-years away and spans about half a light year in space.

Sunrise: 5:40 A.M.
Sunset: 8:14 P.M.
Moonrise: 6:47 A.M.
Moonset: 10:46 P.M.
Moon Phase: Waxing crescent (5%)

The constellation Corvus
The constellation Corvus the Crow can lead you to globular cluster M68. Credit: Astronomy: Roen Kelly

Monday, May 22
Hovering due south about an hour after sunset is the constellation Corvus the Crow. This small star pattern is made up of five bright suns, the brightest of which — at magnitude 2.6 — is cataloged as Gamma (γ) Corvi. Slightly fainter is magnitude 2.7 Beta (β) Corvi some 7.3° to its southeast; Alpha (α) Corvi, which lies about 7.5° south of Gamma, is a magnitude 4 star.

Let’s go back to Beta, then drop 3.5° south-southeast from this star. That will land you right on M68, a magnitude 7.3 globular cluster just over the border in Hydra. This compact grouping of stars spans 12′ and can be difficult to catch in binoculars, so try switching to a telescope if you’ve got the option.

M68 is a bit odd for a globular because of where it’s located — the celestial hemisphere opposite the galactic center. Nearby — as in, projected on the sky, not physically nearby — is the variable star FI Hydrae, less than 10′ northeast of the cluster’s center. Because FI Hya can brighten or fade considerably over the course of its nearly-year-long period, the region around M68 can appear significantly different, depending on whether this star is bright (around magnitude 9 or 10) or faint (magnitude 13 to 14).

Sunrise: 5:39 A.M.
Sunset: 8:15 P.M.
Moonrise: 7:37 A.M.
Moonset: 11:40 P.M.
Moon Phase: Waxing crescent (10%)

Tuesday, May 23
The Moon passes 2° north of Venus at 8 A.M. EDT. You can catch the pair long into the evening tonight — at sunset, they are some 5.5° apart and still 40° above the western horizon. Venus won’t set until nearly midnight for most of the U.S. and won’t sink below the horizon at all for very northerly locations (i.e., much of Alaska).

Venus now forms the point of an upside-down triangle with the bright stars Castor (upper right) and Pollux (upper left) creating the base. Blazing at magnitude –4, the planet far outshines the 1st-magnitude stars. Through a telescope, Venus shows off a worthy 21″-wide gibbous face that’s 56 percent lit. If you slide that telescope up to Castor, you can enjoy the fact that this star splits easily into two suns just a few arcseconds apart. The brighter of these is magnitude 1.9, while the fainter component is magnitude 3.0.

The Moon, to Venus’ upper left, lies nestled between Pollux and magnitude 3.6 Kappa (κ) Geminorum. Our satellite is now nearly 4.5 days past New, a sliver of its eastern limb lit by the Sun as is slowly rises over the lunar surface. With your telescope, zoom in on the large, circular splotch visible near the northeastern limb — that’s Mare Crisium, the Sea of Crises. Compare its relatively smooth, dark floor to the more rugged, lighter terrain beyond its clear border. The darker Mare is younger, with only a few small impact craters marring it.

Sunrise: 5:39 A.M.
Sunset: 8:15 P.M.
Moonrise: 8:33 A.M.
Moon Phase: Waxing crescent (16%)

May 24, 2023, 90 minutes after sunset, looking west
The Moon and Mars congregate near the Beehive Cluster (M44) in late May. As our satellite moves away, Mars inches closer to the young group of stars. Credit: Astronomy: Roen Kelly

Wednesday, May 24
Continuing along the ecliptic, the Moon passes 4° north of Mars at 2 P.M. EDT. This evening, look west above Venus in Gemini to find the Red Planet directly below the now-27-percent-lit Moon, both in Cancer the Crab. The pair is still some 40° high an hour after sunset and will linger late into the night. Mars won’t set until after local midnight for many U.S. states.

The magnitude 1.5 planet now appears just 5″ across through a telescope. Its surface will look reddish-orange as its rusty soil reflects sunlight back toward us. Mars lies just 5° west-northwest of the Beehive Cluster (M44), a 4th-magnitude open cluster of stars normally visible to the naked eye. However, with the waxing Moon nearby, their light may be difficult to make out without binoculars or a small scope. You’ll want to stick with a small aperture, though — the Beehive stretches more than a degree across, so zooming in with higher magnification will cut many of the cluster’s stars out of your field of view. Also called Praesepe, or the Manger, M44 is some 730 million years old and lies a little less than 600 light-years from Earth.

Even as the Moon pulls away along the ecliptic in the coming days, Mars will continue moving toward the Beehive, mingling with its stars for the first few days of June.

Sunrise: 5:38 A.M.
Sunset: 8:16 P.M.
Moonrise: 9:34 A.M.
Moonset: 12:23 A.M.
Moon Phase: Waxing crescent (24%)

Thursday, May 25
Following its inferior conjunction on the first of the month, Mercury has moved into the morning sky and is now ripe for intrepid early risers to catch. About 30 minutes before sunrise this morning, you’ll find Mercury some 4° high, sitting to the lower left (east) of Jupiter. Much farther to Jupiter’s upper right is Saturn, bringing the number of naked-eye planets in the morning sky up to three. (Uranus and Neptune are also above the horizon, but the former is still very close to the Sun and the latter requires binoculars to spot.)

Your best chances of seeing Mercury come if you have a clear eastern horizon with no tall buildings or trees — or if you can get to an observing spot a little higher in altitude than the surroundings. Even a hill might help. The solar system’s smallest planet is now magnitude 0.8; it will continue to brighten slightly as it heads for its greatest elongation west in just a few days, when it will reach magnitude 0.5. Through a telescope, Mercury appears 9″ across and is a slim 32-percent-lit crescent.

The Moon reaches apogee, the farthest point from Earth in its orbit, at 9:39 P.M. EDT. At that time, it will sit 251,350 miles (404,509 kilometers) away. Our satellite now sits just over the border from Cancer in Leo, hanging between Mars to its west and the bright star Regulus to its east this evening.

Sunrise: 5:37 A.M.
Sunset: 8:17 P.M.
Moonrise: 10:35 A.M.
Moonset: 1:00 A.M.
Moon Phase: Waxing crescent (32%)

Jupiter and moons, May 26, 2023, 520 A.M. CDT
Shortly before sunrise in the Midwest on May 26, Io and its shadow are crossing the face of Jupiter. Io’s shadow will slip off the disk moments before Ganymede disappears in an occultation. Europa is behind Jupiter and not visible at this time; Callisto lies far east of the planet. Credit: Astronomy: Roen Kelly

Friday, May 26
Let’s return to the early-morning sky to enjoy the intricate dance of Jupiter’s largest moons.

What you’ll see depends on your time zone: East Coast observers will be able to watch the small, dark shadow of Io slide onto Jupiter from the east just before 4:20 A.M. EDT, roughly an hour before sunrise. Io itself sits a few arcseconds from the eastern limb. You can follow the westward progress of the moon and its shadow as the minutes tick by, but make sure to put away any optics shortly before the Sun is set to rise from your location, which may differ from the time given below. The only other moon visible at this time, Callisto, sits 7′ to the planet’s east.

In the Midwest, Jupiter rises with Io and its shadow both visible on the planet’s large disk. They continue toward the western limb as Europa and Ganymede, invisible inside Jupiter’s long, dark shadow, make their way toward the eastern edge of the planet. Europa never crosses out of the shadow before it slips behind Jupiter, but Ganymede will pop briefly into view shortly after 4:30 A.M. CDT, closing in on the limb. Io’s shadow slips off the disk around 5:24 A.M. CDT — just minutes before Ganymede disappears again behind the planet’s northwestern limb (around 5:27 A.M. CDT). This is just minutes before sunrise in many parts of this region, so again, take care to stop using your telescope or binoculars before the Sun is due to peek above the horizon.

In the Mountain time zone, observers can watch Io leave the disk around 5:10 A.M. MDT. And on the West Coast, skywatchers will see Europa pop into view from behind Jupiter’s northeastern limb around 4:45 AM PDT. Ganymede won’t reappear until after sunrise.

Sunrise: 5:37 A.M.
Sunset: 8:18 P.M.
Moonrise: 11:38 A.M.
Moonset: 1:30 A.M.
Moon Phase: Waxing crescent (41%)

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