The Moon visits Saturn and Neptune

Sky This Week is brought to you in part by Celestron.

Friday, July 11
The Moon passes just 0.02° north of the dim, distant dwarf planet Pluto at 7 P.M. EDT. However, the bright light from our satellite will make Pluto — already a challenging object requiring the largest amateur instruments — even more difficult to spot. Chances will be better later in the month, however, so stay tuned for a shot at viewing this faraway world.

High in the north late tonight is Draco the Dragon, arcing gracefully above the Little Dipper. Just to the left (west) of the Dragon’s head is the lovely double star Struve 30, which consists of 16 and 17 Draconis. You’ll find the pair just over 8° due west of magnitude 2.8 Rastaban (Beta [β] Dra).

This is a great pair for beginners, as you can split them through binoculars or any small scope, no advanced equipment required. 16 and 17 Dra shine at magnitude 5.5 and 5.1, respectively. They are separated by roughly 90”. If you do have a telescope, you’ll want to use it — it will show a third star in the system, shining at magnitude 6.4 just 3” east of 17 Dra. 

From this triplet, there’s another nearby: 3° northwest lies DQ Dra, a line-of-sight triple star consisting of 7th-, 8th-, and 9th-magnitude suns. These, too, are visible in binoculars or any size scope.

Sunrise: 5:41 A.M.
Sunset: 8:30 P.M.
Moonrise: 9:34 P.M.
Moonset: 6:07 A.M.
Moon Phase: Waning gibbous (99%)
*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, July 12
Already high in the east an hour after sunset is the constellation Lyra the Lyre, easy to locate thanks to its brightest star, magnitude 0 Vega. Tonight, we’re looking southeast of this star at M56, an 8th-magnitude globular cluster in near the border of Lyra and Cygnus. In fact, one of the easiest ways to locate M56 is to slide 3.8° northwest of Beta (β) Cygni, the famous colorful double star Albireo. As this region is rising tonight after dark, M56 appears directly above Albireo. 

M56 shines at magnitude 8.3 and spans about 8’ on the sky. Although it doesn’t have a particularly dense or bright core, it is still easy to spot and enjoy, even with beginner’s equipment. You should be able to see the inner 3’ visually, standing out amid the scattered stars of the background, which lies near the plane of the Milky Way. More advanced observers with larger scopes (8 inches or more) can pick up many more fainter stars farther from the core, as well as increase the number of suns visible in the center of the cluster. 

Sunrise: 5:42 A.M.
Sunset: 8:29 P.M.
Moonrise: 10:05 P.M.
Moonset: 7:17 A.M.
Moon Phase: Waning gibbous (96%)

Sunday, July 13
Venus passes 3° north of Aldebaran in Taurus at midnight EDT; the pair is visible in the early-morning sky, well positioned in the east for two hours before sunrise. 

Venus is notably brighter — magnitude –4.1, far outshining magnitude 0.9 Aldebaran, the brightest star in the Taurus and cataloged as Alpha (α) Tauri. Together, the two give the Bull a pair of eyes this morning, rather than its characteristic one. 

Above them as they rise are the lovely Pleiades, a young open cluster visible to the naked eye. Using low power such as binoculars or a finder scope, you’ll uncover many more stars than the half-dozen or so readily observable without optical aid. Taurus continues to rise as the sky lightens with twilight, until blazing Venus is the last point of light visible in the dawn sky. 

The so-called Demon Star Algol reaches its minimum this morning, visible from the western half of the U.S. Located in Perseus to the upper left of Taurus, Algol dims to its faintest magnitude — 3.4 — at 4:45 MDT. It will stay this faint only for a few hours, after which it will rush back up to full strength, shining at magnitude 2.1. Observers to the east: If you’re able to catch the constellation before dawn begins to wash out the sky, note the magnitude of Algol compared to its neighbors this morning, and then come back tomorrow morning to see the difference. 

The rapid dip and return to brightness is due to Algol’s companion star, which orbits on a path that takes it between Earth and Algol once every 2.867 days, briefly blocking the star’s light from view and causing it to plunge in brightness before recovering as the companion moves out of the way once more. 

Sunrise: 5:43 A.M.
Sunset: 8:29 P.M.
Moonrise: 10:32 P.M.
Moonset: 8:28 A.M.
Moon Phase: Waning gibbous (91%)

Monday, July 14
Saturn stands stationary amid the stars of Pisces at 4 A.M. EDT. It is followed two hours later by asteroid 3 Juno, which reaches its stationary point in Libra at 6 A.M. EDT. 

Only Saturn is visible in the morning sky, while Juno is up after sunset. Starting in the morning, look for magnitude 0.9 Saturn 40° high in the southeast two hours before sunrise. It hangs to the lower left of the Circlet in Pisces. Just 1° to Saturn’s north is magnitude 7.7 Neptune, visible together with the ringed planet in binoculars or a telescope. Neptune will appear as a faint, “flat” star with a bluish or grayish tinge. Saturn’s motion has been keeping it relatively the same distance from Neptune for the first half of the month; now, the ringed planet will begin moving retrograde, pulling slowly away from Neptune as it slides southwest relative to the background stars. However, Saturn and Neptune will still remain within about 1° of each other through the rest of the month.

Through a telescope, you’ll also spot Saturn’s stunning ring system and likely easily find its mid-8th-magnitude moon, Titan, some 3’ east of the planet. Take note, as that moon will close in on Saturn by the end of the week and its shadow will transit the gas giant’s cloud tops.

Evening observers can look for 11th-magnitude Juno in far northern Libra, near the border of the Balance and Serpens Caput. Wait until full dark — by 10:30 P.M. local daylight time, Juno is still 40° high in the southwest, about 7.1° north of magnitude 2.6 Zubenesch (Beta Librae). Note that Juno is just 16’ southwest of a brighter, 7th-magnitude field star, and 5’ southwest of a second field star that is roughly the same magnitude as the main-belt world. 

Today marks the end of Juno’s retrograde (westward) motion, and it will now start slowly sliding southeast of its current position. It will cross the boundary into Serpens by the 23rd.

Sunrise: 5:44 A.M.
Sunset: 8:28 P.M.
Moonrise: 10:56 P.M.
Moonset: 9:38 A.M.
Moon Phase: Waning gibbous (84%)

Tuesday, July 15
The center of the Milky Way is on display during summer evenings, arcing slowly through the southern sky. The galactic center is located near the magnitude 4.5 star 3 Sagittarii, which sits just 4.7° northwest (to the upper right, late this evening if you’re facing south) of Gamma (γ) Sgr, the star at the tip of the Teapot asterism’s spout.

The galactic center is rife with stars, gas, and so very many deep-sky objects! There’s a lot to explore here, so take your time, scanning the area slowly with binoculars or a telescope. To get you started, within 0.5° of Gamma are two relatively bright globulars: NGC 6528 and NGC 6522. Both can be viewed together in binoculars or a telescope. NGC 6528 is closer to the star and fainter, shining at mid-9th magnitude. NGC 6522 is about a magnitude brighter and slightly farther from Gamma’s position. Located just east of NGC 6528 is a dark nebula of cold dust, which blocks out some of the copious starlight behind it, forming a V-shaped region with fewer background stars noticeable to the visual observer, as well as in astrophotos of the region.

Sunrise: 5:44 A.M.
Sunset: 8:27 P.M.
Moonrise: 11:19 P.M.
Moonset: 10:48 A.M.
Moon Phase: Waning gibbous (75%)

Wednesday, July 16
The now-waning Moon is passing through Pisces in the early-morning sky. Our satellite slides 3° north of Neptune at 6 A.M. EDT, then passes 4° north of Saturn at 7 A.M. EDT.

It’s a lovely view for early risers, who can catch the scene in the few hours before dawn. Two hours before sunrise, the trio is some 40° high in the southeast. The Moon lies just to the upper left of magnitude 0.9 Saturn, with Neptune between the two. The most distant planet in the solar system is too faint to see with the naked eye, but binoculars or any telescope will pick up its magnitude 7.7 glow, just 1° north of Saturn. Both are visible in the same field of view as the planets appear to “line up” on the sky from Earth, despite the fact that they are nearly 1.9 billion miles (3.1 billion kilometers) apart. 

The Moon’s light may make viewing Neptune more challenging, but shift our satellite out of your field of view and look closely amid the stars for a “flatter” star that looks disklike, with a grayish-blue hue. That’s the planet, which spans about 2” on the sky. 

Over at Saturn, a telescope will show that the bright moon Titan has closed in a bit since earlier in the week. It now stands just over 2’ east of the planet and will continue nearing the ringed world — its shadow will transit early Friday morning, so prepare to return then. 

Sunrise: 5:45 A.M.
Sunset: 8:27 P.M.
Moonrise: 11:43 P.M.
Moonset:11:59 A.M.
Moon Phase: Waning gibbous (65%)

Thursday, July 17
Mercury stands stationary at 3 A.M. EDT amid the stars of Cancer. The solar system’s smallest planet will now start sliding westward, or retrograde, appearing to “fall” back toward the Sun as it moves through its tight, 88-day orbit. 

You can catch Mercury in the evening sky, but only if you’re quick — it’s just 4° high in the west 20 minutes after sunset and sinking fast. It’s now 17 percent lit and shining at magnitude 1.4, spanning 11”. You’ll need binoculars or a telescope to find it, though take care not to pull out any optics until at least several minutes after the Sun has set from your location (which may differ from the time given below). The planet will not only set earlier in the coming days, but it will also quickly fade as its phase continues to wane. It will return to the sky in early August, shining in the morning before dawn.

Evening observers can continue to enjoy Mars, however, now hovering higher in the western sky near the back paws of Leo the Lion. The Red Planet is currently magnitude 1.5 but remains in the sky after dark, making it easier to spot. An hour after sunset, Mars is still 15° high, just 1.1° south of 4th-magnitude Sigma (σ) Leonis. Note how Mars’ disk appears only half the size of Mercury’s through a telescope, thanks to the difference in Earth’s current distance from each planet. 

Last Quarter Moon occurs at 8:30 P.M. EDT. During this phase, our satellite rises after midnight and is visible in the early-morning sky. Keep an eye out for it tomorrow morning if you’re up early to watch Titan’s shadow transit Saturn.

Sunrise: 5:46 A.M.
Sunset: 8:26 P.M.
Moonrise: —
Moonset: 1:11 P.M.
Moon Phase: Waning gibbous (54%)

Friday, July 18
Titan’s shadow transits the cloud tops of Saturn this morning, beginning around 2:50 A.M. EDT. At that time, Saturn (in the constellation Pisces) should be above the horizon for most of the U.S., with the Last Quarter Moon a good distance away, straddling the border of Pisces and Aries. 

Saturn, at magnitude 0.9, is the brightest object in its vicinity, below the Circlet of Pisces. Center it in your telescope and note how Titan itself is still some 20” from the planet’s northeastern limb, where its shadow will appear. It’s a long transit, with the shadow reaching roughly midway across the saturnian disk around 4:30 A.M. CDT, as the East Coast is now losing its view to the sunrise. The shadow continues across for more than two hours and leaves the northwestern limb as dawn is breaking for those along the western coast of the U.S. Make sure to keep an eye on the time and stop your observations several minutes before sunrise. 

You’ll note that the entire time, Titan remains well away from the planet — it will appear to pass well north of the ringed world during daylight, around noon Eastern daylight time. The moon won’t appear to transit Saturn from our point of view until later this year. 

Sunrise: 5:47 A.M.
Sunset: 8:25 P.M.
Moonrise: 12:08 A.M.
Moonset: 2:25 P.M.
Moon Phase: Waning crescent (42%)