Sky This Week is brought to you in part by Celestron.
Friday, June 13
Mercury is making its way through Gemini, passing close to the star Mebsuta (Epsilon [ε] Geminorum) this evening. Visible for more than an hour after sunset, the magnitude –0.8 planet shines brightly in the west. Through binoculars or a telescope, you’ll be able to spot 3rd-magnitude Mebsuta just 20’ east of Mercury in the darkening sky. Start your search about 30 to 45 minutes after sunset, when the pair is still some 5° high.
To the upper left of Gemini stands the constellation Cancer, which currently hosts no planets. Its standout deep-sky target is the Beehive Cluster, also cataloged as M44. Swinging your binoculars or telescope up to the middle of the constellation should easily show this magnitude 3.7 open cluster, which spans nearly 100’ on the sky.
Keep looking to the upper left and beyond Cancer you’ll find Leo, which is now the home of magnitude 1.4 Mars. The Red Planet is just 2.1° northwest of Leo’s brightest star, Regulus, which shines at the same magnitude as the planet. Mars will continue to slide closer to the star over the next few days, passing less than a degree from the luminary on the 16th. We’ll come back to Leo to observe the close pairing then!
Sunrise: 5:31 A.M.
Sunset: 8:30 P.M.
Moonrise: 10:59 P.M.
Moonset: 7:11 A.M.
Moon Phase: Waning gibbous (94%)
*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, June 14
The Moon passes 0.1° south of Pluto in the constellation Capricornus at 1 P.M. EDT. Unfortunately, the tiny, dim dwarf planet is so faint — magnitude 14.5 — that it requires a large telescope and dark skies to see. Even experienced observers will find it incredibly hard to spot, especially with the bright Moon spreading its light nearby.
But the Moon doesn’t rise until late tonight, leaving a dark window after sunset to explore the sky. Back in Leo in the west this evening, you might try your luck with Comet 29P/Schwassmann-Wachmann, also known as Schwassmann-Wachmann 1.
Now around 13th magnitude, the comet is sliding through southwestern Leo. Today, Schwassmann-Wachmann 1 is roughly 2° from magnitude 3.5 Subra (Omicron [ο] Leonis), often depicted as Leo’s front foot. You’ll need a medium to large scope for the job, given the comet’s faintness. Without a tail to really speak of, Schwassmann-Wachmann 1 will look more like a round, fuzzy glow a few arcminutes across at most. Astronomy contributor Alister Ling recommends practicing on nearby galaxy NGC 3049, which shines at magnitude 12.5, using powers above 150x. To find NGC 3049, slide a little farther east of Omicron — the barred spiral lies 3.4° east of this star.
You should be able to to get good views of Schwassmann-Wachmann 1 through the rest of the month, as the now-waning Moon will rise later and later, leaving the evening sky dark. You’ll still need to be ready shortly after sunset, though, as this region will set a little earlier each day. The comet, however, is tracking slightly upward in the sky, heading for Pi (π) Leonis as the month progresses.
Sunrise: 5:31 A.M.
Sunset: 8:30 P.M.
Moonrise: 11:33 P.M.
Moonset: 8:18 A.M.
Moon Phase: Waning gibbous (89%)
Sunday, June 15
Two hours after sunset, the sky is dark and the constellation Canes Venatici is high in the west, nestled beneath the curve of Ursa Major’s long tail, which also creates the handle of the Big Dipper asterism.
Located in northern Canes Venatici is M51, famously known as the Whirlpool Galaxy. It’s easy to find just 3.5° southwest of magnitude 1.9 Alkaid, also cataloged as Eta (η) Ursae Majoris, the star at the very end of the Big Dipper’s handle.
The Whirlpool is a face-on spiral galaxy that shows off both its bright nucleus and winding arms. Shining at magnitude 8.4, it’s a bright galaxy and any small scope will capture it as a circular glow that brightens toward the center, but larger telescopes (6 inches or more) will, as always, reveal more detail — in this case, resolving its individual spiral arms from some 31 million light-years away.
You’ll also notice a smaller, more compact bright object just north of the main galaxy’s glow. This is M51’s companion galaxy, magnitude 9.6 NGC 5195. Astronomers have determined that NGC 5195 appears to be passing behind M51 from our point of view; the two galaxies have been interacting for hundreds of millions of years. This has enhanced the spiral structure of the Whirlpool, contributing to its standout appearance in our sky.
Sunrise: 5:31 A.M.
Sunset: 8:31 P.M.
Moonrise: —
Moonset: 9:27 A.M.
Moon Phase: Waning gibbous (81%)
Monday, June 16
Early risers can catch a transit of Titan’s shadow across the cloud tops of Saturn this morning. There aren’t many of these events, as conditions need to be just right for us here on Earth to see Titan or its shadow cross the face of the planet. But given the recent ring-plane crossing, we’ve still got several shadow transits left to enjoy before the current series comes to an end in October.
Saturn is visible in the early-morning sky, now rising around 1:30 A.M. local daylight time. Shining at magnitude 1.0, the ringed planet stands out in southern Pisces, southeast of the Circlet asterism. Center Saturn in a telescope and you’ll certainly enjoy its gorgeous ring system, currently tilted at an angle of just 3.4°, with its southern face now visible.
Titan itself, shining around magnitude 8.5, is located just northeast of Saturn. Tethys and Dione, fainter 10th-magnitude moons, cluster just southeast of the planet early this morning, while Rhea (also 10th magnitude) lies west of Saturn.
Titan’s shadow transit begins around 4:20 A.M. EDT, as the shadow slips onto the northeastern limb. It then moves east to west across the cloud tops, reaching midway across the planet about two and a half hours later, at 5 A.M. MDT. (Note the time zone change, as sunrise has already occurred for those in the Eastern and Central time zones.) The shadow continues its trek, visible to North American observers progressively farther west, with the transit continuing through sunrise on the West Coast. Titan remains northeast of Saturn the entire time.
Saturn’s much smaller moon, Enceladus, is also transiting with its shadow during this event, but this pair will likely be invisible given their size and dimness in contrast with the bright disk of the planet.
If you’re not an early riser, though, don’t worry — there some action in the evening sky today, too. Mars will pass 0.8° north of Regulus at midnight EDT, and both are visible for several hours after sunset for evening observers to enjoy.
In the post-sunset sky, look west to find the two standing close together, with Mars just to the upper right of Regulus. Both star and planet are the same magnitude (1.4) but their colors will give them away. Regulus is a hot, blue-white star whose temperature reaches some 15,400 kelvins, more than twice our Sun’s surface temperature of nearly 5,800 kelvins. Mars, however, shines with a ruddy, orange-red light. This is not because of its temperature, but instead because of sunlight reflecting off the oxidized (rusty) red material on its rocky surface.
In addition to enjoying the pair with your naked eyes, you can also capture them together in the field of view of any telescope or binoculars. The pair is 40° high at sunset and will remain visible above the horizon until local midnight.
Sunrise: 5:31 A.M.
Sunset: 8:31 P.M.
Moonrise: 12:02 A.M.
Moonset: 10:36 A.M.
Moon Phase: Waning gibbous (72%)
Tuesday, June 17
Night owls looking southeast late this evening should easily be able to find the Teapot of Sagittarius, a large asterism that lies close to the plane of the Milky Way. The top of the Teapot’s lid is marked by magnitude 2.8 Lambda (λ) Sagittarii, and just 2.5° northeast of this star is tonight’s target: globular cluster M22.
Shining at magnitude 5.1, M22 is one of the brightest globulars in our sky. It’s best seen with binoculars or a small telescope, although observers with dark skies and a clear horizon can catch its fuzzy glow with the naked eye as well. M22 spans about the same size on the sky as the Full Moon and contains at least 70,000 stars. It stands roughly 10,000 light-years away, making it a relatively close globular cluster, and is physically some 200 light-years across.
M22 is visible through midnight and into the early-morning hours of the 18th as Sagittarius arcs low through the southern sky. It transits, or reaches its highest point in the sky, around 2 A.M. local daylight time, which will be the best time to catch it if you’re looking to study it in detail.
Sunrise: 5:31 A.M.
Sunset: 8:31 P.M.
Moonrise: 12:28 A.M.
Moonset: 11:46 A.M.
Moon Phase: Waning gibbous (62%)
Wednesday, June 18
Asteroid 4 Vesta is stationary at 3 P.M. EDT. Now located in the constellation Virgo, Vesta is mid-6th-magnitude — easy to find in just a few minutes from any location using binoculars or a small telescope.
Step outside this evening an hour or two after sunset to find the large constellation Virgo hovering above the southwestern horizon. The Maiden’s brightest star is magnitude 1.0 Spica, easy to pick out some 30° above the horizon.
Vesta now lies to the far upper left of this star, near Virgo’s eastern border with Libra. Look for 4th-magnitude Iota (ι) Virginis, some 13.5° northeast of Spica. From Iota, Vesta is just a short 1.5° jump to the east tonight. If you are using larger binoculars or a telescope, look also for the globular cluster NGC 5634. This small, 5’-diameter faint cluster glows at magnitude 9.6 and tonight lies just under 2° east-southeast of Vesta’s position.
Previously moving west (or retrograde) through the sky before tonight, Vesta will now start traveling east — more specifically, it will move to the southeast against the background stars, heading for Libra.
Last Quarter Moon occurs at 3:19 P.M. EDT; our satellite then passes 3° north of Saturn and 2° north of Neptune at midnight EDT. The pairing will be visible in the early-morning sky tomorrow before sunrise, so keep reading for more details.
Sunrise: 5:31 A.M.
Sunset: 8:32 P.M.
Moonrise: 12:51 A.M.
Moonset: 12:56 P.M.
Moon Phase: Waning gibbous (51%)
Thursday, June 19
Saturn and Neptune rise together just before 1:30 A.M. local daylight time, with the waning Moon nearby. You can catch them in the few hours before local sunrise — the pair of planets is 23° high in the east two hours before dawn, with the Moon close by to their left. The crescent Moon is now just over 40 percent lit.
First-magnitude Saturn is visible to the naked eye, but 8th-magnitude Neptune is not. You’ll need binoculars or a telescope to find the distant ice giant, located 1.1° north of the ringed planet. In a little over a week, the two planets will undergo an official conjunction.
Saturn’s disk spans a hefty 17”, with its rings stretching nearly 40” from end to end. The planet’s brightest moon, Titan, is now 2.5’ west of the planet. This moon will reach its greatest western elongation tomorrow.
North of Saturn, Neptune will be a bit harder to discern, looking like a small, “flat” blue-gray star amid the pinprick white of background stars. At its vast distance of 2.87 billion miles (4.48 billion kilometers), Neptune’s disk now appears just 2” wide.
Sunrise: 5:31 A.M.
Sunset: 8:32 P.M.
Moonrise: 1:15 A.M.
Moonset: 2:07 P.M.
Moon Phase: Waning crescent (40%)
Friday, June 20
The summer solstice occurs at 10:42 P.M. EDT, marking the official beginning of summer for those in the Northern Hemisphere. On this date, the Sun is located directly above the Tropic of Cancer at 23.5° north, taking its most northerly path through the sky. It is also the longest day of the year north of the Tropic of Cancer.
Although the night is short, it’s still an excellent opportunity to try viewing a summertime phenomenon called noctilucent clouds. These clouds are unusual in that they form very high in the atmosphere, when ice crystallizes around aerosol particles some 50 miles (80 km) high — that’s roughly 10 times higher than the more familiar cirrus clouds. To see them, look toward the north. Your chances are higher if you live at a higher latitude, as these clouds are most often seen by observers between about 50° and 65° north, though this is not a hard cutoff.
Noctilucent or night-glowing clouds appear exactly that — to glow long after the Sun has set. This is because they’re floating so high up that sunlight reflects off them long after sunset from an observer’s location, thanks to the curvature of Earth. These clouds can be visible even around midnight, offering a dazzling show even if the stars aren’t visible. You’ll know you’re seeing noctilucent clouds because of their glow, rather than the dark blotches associated with much lower clouds. And although these clouds appear static over short periods of time, if you spend a while watching or photographing them, you’ll see their shapes transform, ebb, and flow throughout the night.
Sunrise: 5:31 A.M.
Sunset: 8:32 P.M.
Moonrise: 1:39 A.M.
Moonset: 3:22 P.M.
Moon Phase: Waning crescent (29%)
