Sky This Week is brought to you in part by Celestron.
Friday, June 20
The summer solstice occurs at this evening at 10:42 P.M. EDT. For those in the Northern Hemisphere, this marks the official beginning of the summer season. (For those south of the equator, of course, this is the winter solstice and marks the official beginning of winter.)
On this date, the Sun appears to sit directly above Earth’s Tropic of Cancer, which marks 23.5° latitude north. Also on the summer solstice, our daytime star appears highest overhead at local noon.
Summer is a time of longer days and shorter nights, but that doesn’t mean there’s nothing to observe. Right now, the Red Planet dominates the western sky at sunset, having recently passed Regulus, the brightest star in Leo the Lion. Shining at magnitude 1.4, Mars still matches Regulus in brightness and is now located some 2° east (to the upper left) of the star in the sky.
Through a telescope, Mars appears too small to make out surface detail. It’s just 5” across, thanks to its distance from us: nearly 172 million miles (276.8 million kilometers). Further, the planet is slowly making its way toward solar conjunction on the far side of the solar system from Earth, which it will reach early next year. Although Mars won’t offer great telescopic viewing for some time, it remains a standout point of light to enjoy after sunset and doesn’t set until roughly local midnight.
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%)
*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 21
Cassiopeia the Queen swings in a wide circle around the North Celestial Pole, visible much of (if not all of) the night for most northern observers. This evening around 11:30 P.M. local daylight time, you’ll find the famous W asterism of Cassiopeia right-side up in the north, just below the house-shaped constellation Cepheus.
Cassiopeia is home to several deep-sky delights, including Achird (Eta [η] Cassiopeiae), a fine double star that is lovely in any telescope and a great object for beginners. It’s easy to find — locate the W and find the star at the peak in the center of the celestial letter. About 4.5° to its lower right tonight (south-southwest) is the second valley (reading the letter left to right). The star at the peak is magnitude 2.2 Navi (Gamma [γ] Cas); the star at the valley to its lower right is similarly bright magnitude 2.2 Shedar (Alpha [α] Cas). Just east (to the lower left) of a line drawn between Gamma and Alpha and about two-thirds of the way from the former to the latter is mid-3rd-magnitude Eta Cas.
The two stars of this system are separated by 11”, shining at magnitudes 3.4 and 7.5. Their color contrast is quite noticeable to most observers, and is why the pair is particularly famous. The brighter primary is a yellow G-type star much like the Sun in mass and brightness, while the fainter secondary is a cooler orangey-red K-type dwarf with less than half our Sun’s mass.
Sunrise: 5:32 A.M.
Sunset: 8:32 P.M.
Moonrise: 2:06 A.M.
Moonset: 4:39 P.M.
Moon Phase: Waning crescent (19%)
Sunday, June 22
The Moon passes 7° north of Venus at 5 A.M. EDT. An hour before sunrise the pair is easy to see in the east, nearly 20° high in the constellation Aries.
Venus is the brightest point of light in the sky, shining at magnitude –4.2. To its upper left is the delicate crescent Moon, some 26 days old and 13 percent lit. As New Moon occurs later this week, the Moon is now waning, with only its westernmost limb lit. Through binoculars or a telescope, you may still catch the round, dark, flat crater floor of Grimaldi in sunlight near the terminator separating night from day.
Use your telescope to observe Venus and you’ll see it is 60 percent lit and a hefty 19” across. On the first of this month, it was 50 percent lit — did you view it then, and can you see the difference now?
Aries doesn’t offer much in the way of bright stars, but you might still spot its brightest two: Hamal and Sheratan, standing about 16° above Venus in the early-morning sky. Hamal is also cataloged as Alpha Arietis and shines at magnitude 2.0. Sheratan (Beta [β] Ari) lies to Hamal’s right (southwest) and is slightly fainter, at magnitude 2.6.
Mercury passes 5° south of Pollux in Gemini at 4 P.M. EDT and now lies to the lower left of this magnitude 1.2 star in the western sky after sunset. The planet shines at magnitude –0.1 tonight.
The Moon passes 5° north of Uranus at midnight EDT — we’ll catch up with this pair tomorrow in the early-morning sky.
Sunrise: 5:32 A.M.
Sunset: 8:32 P.M.
Moonrise: 2:39 A.M.
Moonset: 5:58 P.M.
Moon Phase: Waning crescent (11%)
Monday, June 23
The Moon reaches perigee at 12:44 A.M. EDT. This is when our satellite lies closest to our planet, and today the Moon sits just 225,668 miles (363,177 km) away.
As Luna rises early this morning, it lies to the right of Uranus in the eastern sky. Although Uranus is faint — magnitude 5.8 — and best seen with binoculars or a small telescope, the Moon is fortunately far enough away and dim enough — only 6 percent illuminated — that its light won’t interfere in finding the distant ice giant this morning.
The easiest way to find Uranus is to first center on the Pleiades open cluster in northwestern Taurus with binoculars or a small telescope. This stunning group of young stars is also known as the Seven Sisters. From here, shift your field of view about 4.7° south to find a pair of 6th-magnitude stars, separated by about 20’. These are 13 and 14 Tauri. 14 Tau is the slightly dimmer star to the east; from this star, it’s a short jaunt just 50’ farther east to land on Uranus, standing in line with the pair of suns.
The planet’s disk spans 3” — enough that it may appear circular to sharp-eyed observers, rather than more like a pinpoint, as stars do. It may also appear blush-gray, a reflection of the visual color of its upper atmosphere.
Uranus’ visibility will continue to improve through the end of June and into July. And by the last day of June, bright Venus will have moved close by, offering a much brighter signpost to find it.
Sunrise: 5:32 A.M.
Sunset: 8:33 P.M.
Moonrise: 3:21 A.M.
Moonset: 7:16 P.M.
Moon Phase: Waning crescent (4%)
Tuesday, June 24
Jupiter is in conjunction with the Sun at 11 A.M. EDT. Planets in solar conjunction are not visible from Earth, as they lie on the opposite side of the Sun from our planet as viewed from above (or below) the plane of our solar system. Don’t worry, though — it won’t be gone for long. The gas giant will reappear in the morning sky in mid-July.
Instead of focusing on the solar system’s largest planet, let’s turn to its smallest: Mercury now shines at magnitude 0 in Gemini and is visible in the western sky for about an hour and a half after sunset. The planet lines up with the heads of the Twins this evening: Looking west around 9:30 P.M. local daylight time should show you a line of three bright points about 5° high, slanted slightly toward the ground. The leftmost point, brightest and closest to the horizon, is Mercury. In the middle is the next-brightest, Pollux, which shines at magnitude 1.2 with a slightly golden glow. At the right and highest up is Castor, the dimmest at magnitude 1.6.
Through a telescope, Mercury’s disk spans 7” — a larger apparent size than Mars! Although physically Mercury is much smaller than Mars, it’s currently closer to Earth than the Red Planet, giving it that size bump. The disk of Mercury is also just over half lit, appearing as a 57-percent-lit gibbous. It is currently waning each night and will appear exactly 50 percent illuminated on the 28th.
Sunrise: 5:33 A.M.
Sunset: 8:33 P.M.
Moonrise: 4:13 A.M.
Moonset: 10:27 P.M.
Moon Phase: Waning crescent (1%)
Wednesday, June 25
New Moon occurs at 6:32 A.M. EDT. As always during this time, no Moon in the sky means it’s time to search for fainter targets. Today, we’re centering on M15, which stands 60° high in the southern sky around 3:30 A.M. local daylight time. (Nighttime observers can also catch this object, though it rises about an hour after sunset and continues to gain altitude all night, so the later you look, the better.)
M15 is a bright globular cluster in Pegasus. Binoculars or a telescope will show a 7’-wide ball of stars just 4.5° northwest of 2nd-magnitude Enif (Epsilon [ε] Pegasi), often depicted as the tip of the Winged Horse’s nose.
On its own, of course, M15 is a worthy target. Containing more than 100,000 stars, it is a dense cluster that is a favorite of observers. But there’s more: M15 was the first globular cluster in which astronomers found a planetary nebula, the illuminated bubble of gas and dust blown off by a dying Sun-like star. Called Pease 1, this particular planetary is great for observers with large (15 inches or more) scopes, as well as astrophotographers. If your sky is steady today and you’ve got a big scope at your disposal, give it a try — it glows around 16th magnitude just northeast of the cluster’s center. Use magnifications greater than 300x and an OIII filter to aid in spotting it, and keep in mind its compact size makes it easy to mistake for another star. Astronomy contributor Phil Harrington recommends passing the OIII filter in and out of your field of view, helping you to identify the nebula, as it stays bright when the filter dims the stars around it.
Sunrise: 5:33 A.M.
Sunset: 8:33 P.M.
Moonrise: 5:16 A.M.
Moonset: 9:26 P.M.
Moon Phase: New
Thursday, June 26
The planet Mercury sits 3.5° to the left of a two-day-old crescent Moon in the evening sky tonight. At magnitude 0.1, Mercury is still bring and nearly 6° high in the west an hour after sunset. It’s now located in Cancer the Crab, having left Gemini behind.
With barely 4 percent of its eastern limb illuminated, the young Moon may be challenging to see. You’ll want to get to a location with a clear horizon and opt for a viewing site slightly elevated from your surroundings if possible. If you don’t see the Moon at first, use binoculars or a small telescope — or even your finder scope — to scan the sky a few degrees to the right of Mercury and at the same altitude. The Moon lies roughly in line with Mercury to its left and Pollux in Gemini to its right. With your optics, you may be able to see even the unilluminated majority of the lunar surface. This is because light from the Sun bounces off Earth and lights up the shadowed regions of the Moon enough for us to see it — a phenomenon called earthshine.
Mercury is now some 53 percent lit, a small change from earlier this week. If you viewed it then, can you see the difference now? It’s subtle!
Also look with binoculars or a telescope to Mercury’s upper left in the darkening sky. Just over 7° east of the planet is M44, the Beehive Cluster, whose stars should begin popping into view as twilight falls, especially under magnification.
Sunrise: 5:33 A.M.
Sunset: 8:33 P.M.
Moonrise: 6:28 A.M.
Moonset: 10:22 P.M.
Moon Phase: Waxing crescent (2%)
Friday, June 27
The Moon now passes 3° north of Mercury at 2 A.M. EDT. By evening, our satellite stands some 9.5° east of the planet in the western sky. Now the Beehive Cluster is between the two, and the waxing Moon is some 9 percent lit as sunrise creeps from east to west across the lunar nearside.
Once darkness falls, cast your eye to the far upper right of this scene, in the direction of north. In fact, our target tonight lies extremely close to the North Celestial Pole — so close that we now call Polaris the North Star. You’ll find it at the very end of the handle of the Little Dipper, which is smaller and fainter than the more famous and easily found Big Dipper. Early this evening, the Little Dipper lies to the right of the Big Dipper’s cup. The Little Dipper’s handle is pointed down toward the ground, while the Big Dipper’s handle points upward.
Despite its special location in the sky — appearing fixed as all other Northern Hemisphere stars rotate around it — Polaris is not particularly bright, ranking 47th (it is magnitude 2.0). It is a Cepheid-class variable star whose magnitude changes by just 0.03 magnitude every four days.
Polaris is also a multiple-star system with two known companions. Only the farther of the two can be split from the primary; you’ll find it about 18” away, shining at magnitude 8.7.
Sunrise: 5:34 A.M.
Sunset: 8:33 P.M.
Moonrise: 7:43 A.M.
Moonset: 10:48 P.M.
Moon Phase: Waxing crescent (7%)
