Sky This Week is brought to you in part by Celestron.
Friday, May 23
The Moon passes 4° north of Venus at 8 P.M. EDT, although neither is visible at that time.
Instead, let’s look tonight for the small constellation Sagitta the Arrow, which lies north of Aquila the Eagle. Although Sagitta is small, covering just 80 square degrees (it is ranked 86th out of the 88 constellations in size) it hosts a few worthy deep-sky objects. The brightest is M71, a globular cluster that shines at magnitude 8.2 and spans roughly 7’.
You’ll find M71 1.4° west of magnitude 3.5 Gamma (γ) Sagittae. This globular is considered relatively “loose” — in fact, astronomers debated for some time whether it was an open or globular cluster. We now know it is the latter, residing some 13,000 light-years away and containing stars that are roughly 10 billion years old.
M71 is a gorgeous sight through binoculars or any small scope, making it an ideal target for amateur observers looking to bag some easy sights. If you’re a more experienced observer with a larger aperture, look at M71 under high magnification to see if you can spot the dark notch on its western side, almost as if it’s missing a chunk of stars.
Sunrise: 5:38 A.M.
Sunset: 8:16 P.M.
Moonrise: 3:12 A.M.
Moonset: 4:23 P.M.
Moon Phase: Waning crescent (17%)
*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 24
Let’s check in with the Moon and Venus this morning, as the delicate waning crescent stands directly to the left of the bright planet before dawn. An hour before sunrise, the pair is some 10° high in the east, easily visible together in Pisces the Fish.
The Moon is now just 11 percent illuminated, well on its way to New in just two days. Through binoculars or a telescope, only a sliver of its western limb is illuminated, while the rest is in shadow. However, you might notice that even the shadowed regions of the lunar surface are visible, thanks to sunlight reflecting off Earth — a phenomenon called earthshine.
Telescopic observers, move next to Venus, sitting to the Moon’s right. It’s the brightest point of light in the morning sky, shining at magnitude –4.5. The disk spans an impressive 26” and is now a 45-percent-lit crescent. Venus is approaching dichotomy, the time when it appears exactly half-lit by the Sun. It will reach this phase June 1, so watch its crescent grow ever-so-slightly over the next few days.
Sunrise: 5:38 A.M.
Sunset: 8:17 P.M.
Moonrise: 3:39 A.M.
Moonset: 5:42 P.M.
Moon Phase: Waning crescent (9%)
Sunday, May 25
Mars has now crossed the border from Cancer into Leo, standing in the far western regions of the Lion’s domain. The Red Planet is visible after sunset this evening, slowly sinking in the west and setting around 1 A.M. local daylight time.
This offers plenty of time to inspect the ruddy world, which now glows at magnitude 1.2. It is fading slightly, losing about 0.1 magnitude every few weeks, and will continue to do so until October, when it slowly begins brightening again. Through a telescope, the martian disk is just 6” wide, offering little in the way of detail.
Just to the upper left of Mars in the sky as it sets is an asterism called the Sickle of Leo. So named for its similarity in shape to the farm implement, the Sickle also looks like a backwards question mark. It is anchored at the base of its handle by Regulus, the Lion’s alpha star, which glows at magnitude 1.4 — just a tad fainter than Mars. From Regulus, move 4.8° due north to magnitude 3.5 Eta (η) Leonis, the next star in the Sickle, then 4.3° northeast to reach magnitude 2.0 Gamma Leo. Jump another 3.7° north of this star to reach magnitude 3.4 Zeta (ζ) Leo, then travel 6° northwest to magnitude 3.9 Mu (μ) Leo. Finally, take a short 2.7° hop southwest to Epsilon (ε) Leo, shining at magnitude 3.0, to end your journey at the tip of the Sickle’s blade.
The Moon reaches perigee — the closest point to Earth in its orbit — at 9:34 P.M. EDT this evening, when it will stand 223,086 miles (359,022 kilometers) away.
Sunrise: 5:37 A.M.
Sunset: 8:18 P.M.
Moonrise: 4:09 A.M.
Moonset: 7:03 P.M.
Moon Phase: Waning crescent (3%)
Monday, May 26
With New Moon occurring late tonight at 11:02 P.M. EDT, today is an excellent opportunity for yet more deep-sky observing. This morning, we’re dipping into the Lagoon Nebula (M8) in Sagittarius. This stunning nebula is best seen around 3 A.M. local daylight time, when it stands 25° high in the south.
The Lagoon lies within the diffuse, cloudy glow of the plane of the Milky Way. It sits to the upper right of the Teapot asterism in the Archer, about 5.6° west-northwest of magnitude 2.8 Lambda (λ) Sagittarii, the top of the Teapot’s triangular lid. Glowing at magnitude 4.6 and stretching some 90’ at its widest, the Lagoon is an emission nebula as well as a star-forming region that surrounds the young open star cluster NGC 6523. There’s also a notable dark lane of dust running through the nebula, visible with 10×50 binoculars. However, you’ll want to pull out a telescope to enjoy all the intricate detail the Lagoon has to offer. The brightest inner regions form a distinct hourglass shape, sometimes known separately as the Hourglass Nebula.
This lovely object is a favorite not only for observers but for astrophotographers as well, and you don’t need a lot of skill and experience to capture it. Even a medium-sized scope will net you gorgeous images with only about 20 minutes of exposure time.
Sunrise: 5:36 A.M.
Sunset: 8:18 P.M.
Moonrise: 4:46 A.M.
Moonset: 8:24 P.M.
Moon Phase: New
Tuesday, May 27
If you’ve got binoculars or a small scope at your disposal, take them out tonight to observe the lovely — and bright — edge-on lenticular galaxy NGC 3115, sometimes called the Spindle Galaxy. Located in Sextans, you’ll find this galaxy still 25° high in the southwest 90 minutes after sunset, in a region to the lower left of Mars in the evening sky.
To locate the Spindle, first find the magnitude 5.1 star Gamma Sextantis. Move your gaze 3.2° east of this star and you’ll spot the Spindle, glowing at magnitude 8.9. It’s roughly four times as long as it is wide, stretching just over 8’ at its longest. Appearing much like its namesake, this galaxy has a bright, round bulge bordered by thinner protrusions on either side — these are not spiral arms, however, because NGC 3115 is not a spiral galaxy.
Lenticular galaxies are neither spirals nor ellipticals, but a sort of in-between object with a bulge and disk, but no arms. Astronomers aren’t sure whether they are an evolutionary step as spirals age, or if they might be the results of long-ago mergers.
Sunrise: 5:36 A.M.
Sunset: 8:19 P.M.
Moonrise: 5:33 A.M.
Moonset: 9:41 P.M.
Moon Phase: Waxing crescent (1%)
Wednesday, May 28
The Moon passes 5° north of Jupiter at 9 A.M. EDT. Just six percent illuminated by this evening, you can try to spot the young crescent Moon hanging above the gas giant in the western sky after sunset.
An hour after the Sun disappears, Jupiter (shining at magnitude –1.9) is just 4° high in the west. Some 8.5° above it is the crescent Moon, near the border of Gemini and Auriga. You should be able to spot the brightest stars in these constellations quite well — Castor and Pollux mark the heads of Gemini to the Moon’s upper left, while Capella anchors the outline of Auriga to the Moon’s upper right. High above the Moon, the Big Dipper appears to stand on the end of its bowl in the early evening, its handle sticking straight up into the sky.
Jupiter’s Galilean moons are also visible this evening, but spotting them may be challenging with the planet so low. If you want to try, note that your location — which will affect the time you’re viewing the planet — will affect their positions.
About an hour after sunset on the East Coast, Ganymede lies farthest from Jupiter to the east, with Europa closer to the planet. Callisto sits just off the gas giant’s northeastern limb, while Io may be hidden in the planet’s shadow — it will reappear just after 9:30 P.M. EDT just east of the planet, roughly in line with its equator and south of Callisto.
An hour after sunset in the Midwest, Io is now farther from the planet than Callisto (still near the northeastern limb), while Europa lies just to Io’s east, with Ganymede still farthest from the planet. An hour after sunset in the Mountain time zone, Callisto has moved into Jupiter’s shadow and is invisible, while Io has moved northeast of Europa and the latter is now closer to the planet. (They stand directly in line with each other with Io north of Europa around 9:10 P.M. MDT, potentially visible to those in the eastern half of this time zone.)
Finally, by an hour after sunset on the West Coast, Callisto is again visible, forming the northern apex of a triangle with Europa to its southwest and Io to its southeast. Ganymede still lies far east of the other three moons, and all are still east of the planet.
Sunrise: 5:35 A.M.
Sunset: 8:20 P.M.
Moonrise: 6:31 A.M.
Moonset: 10:46 P.M.
Moon Phase: Waxing crescent (4%)
Thursday, May 29
Binocular observers, this one’s for you: Upgren 1, a small grouping of stars discovered in 1963 within the constellation Canes Venatici. High in the west around 10:30 P.M. local daylight time, the Hunting Dogs lie beneath the curve of the Big Dipper’s long handle.
Upgren 1 contains about 10 stars in an area roughly 14’ wide. It sits 5° southwest of 3rd-magnitude Alpha (α) Canum Venaticorum, also called Cor Caroli, and appears like a tiny triangle in binoculars. The discoverer, Arthur Upgren, thought he was looking at an ancient cluster of stars. Today, however, we know this grouping is just a chance superposition on the sky, or an asterism, rather than an associated family of suns.
Mercury is in superior conjunction at midnight EDT and it is invisible for the time being. The small planet will reappear in the evening sky by the end of June’s first week.
Sunrise: 5:35 A.M.
Sunset: 8:21 P.M.
Moonrise: 7:39 A.M.
Moonset: 11:39 P.M.
Moon Phase: Waxing crescent (9%)
Friday, May 30
Let’s close out the week with a peek at the early-morning duo of Saturn and Neptune, rising together in Pisces around 2:30 A.M. local daylight time. By 4 A.M. local daylight time they are some 15° high, with blazing Venus visible to their lower left. Saturn stands out well to the naked eye at magnitude 1.1, but Neptune (magnitude 7.8) will require binoculars or a telescope to see.
The two planets are now 1.7° apart and will fit well within the field of view of binoculars, a finder scope, or a wide-field telescope. Through a telescope, Saturn’s disk spans 17” and its rings stretch 38”. They are tilted some 3° to our line of sight, showing off their southern face. The planet’s largest moon, Titan, should be visible some 1.5’ east of the ringed planet this morning.
Neptune’s disk is tiny, appearing just 2” across. The distant planet is northeast of Saturn and may appear like a “flat,” bluish-gray star.
The two planets will continue closing in on each other in the coming weeks, passing within 1° of each other late next month in a conjunction.
Sunrise: 5:34 A.M.
Sunset: 8:21 P.M.
Moonrise: 8:52 A.M.
Moonset: —
Moon Phase: Waxing crescent (17%)
