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Friday, May 30
The crescent Moon lies in Cancer this evening, just a few degrees from the stunning Beehive Cluster (M44). If it seems that this cluster is mentioned in this column a lot — it is! The Beehive lies close to the ecliptic, the plane of the solar system in which all the major planets orbit. Thus, we see the planets — and our Moon, which also orbits Earth close to the ecliptic — pass by the same regions of the sky over and over again as they move relative to the background stars, including the Beehive.
This young open cluster is visible with the naked eye and has thus been known since antiquity. It is sometimes called Praesepe, or the Manger. M44 shines at a collective magnitude of 3.7 and spans some 95’, making it almost as large as another famous open cluster: the Pleiades (M45).
Tonight, the waxing Moon sits to the lower right of the Beehive as Cancer sinks in the west after sunset. The pair is visible for some three hours after the Sun disappears, offering plenty of time to observe both in binoculars or a telescope if you wish. Our satellite is now roughly 20 percent illuminated, with sunlight brightening its eastern limb. In particular, the dark, circular Mare Crisium should appear striking amid its lighter surroundings. Look also for the large crater Langrenus south of Crisium. This deep crater hosts a distinctive central peak.
Sunrise: 5:34 A.M.
Sunset: 8:21 P.M.
Moonrise: 8:52 A.M.
Moonset: —
Moon Phase: Waxing 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 31
Venus reaches its greatest western elongation (46°) from the Sun at midnight EDT. Earth’s sister planet is now visible in the early-morning sky, and today Venus rises in the east at 3:30 A.M. local daylight time — roughly two hours before the Sun. That gives observers plenty of time to view the bright morning planet, now shining at magnitude –4.4.
Venus is now in southeastern Pisces. It’s the brightest object in the sky, impossible to miss. Through a telescope, the planet’s disk stretches 24” and is 49 percent lit. Tomorrow, the planet officially reaches dichotomy, when it is exactly half illuminated. But see what you think this morning — how much of it do you judge is lit? How close or far is it from half?
In the late 1700s, amateur astronomer Johann Schröter noted that Venus often appeared to reach dichotomy a few days before or after calculations showed it would. Whether it was early or late depended on its elongation — while at western elongation, as it is now, it generally appeared to reach dichotomy a few days later than predicted. Now called the Schröter effect, astronomers still aren’t sure why this occurs, though it’s likely due to optical illusions caused by the way sunlight reflects off the planet’s thick clouds or in the way our eyes perceive the planet through our own atmosphere.
Make sure to return to the morning sky for a few more days to see when you feel Venus truly reaches dichotomy!
Sunrise: 5:34 A.M.
Sunset: 8:22 P.M.
Moonrise: 10:04 A.M.
Moonset: 12:19 A.M.
Moon Phase: Waxing crescent (26%)
Sunday, June 1
Venus officially reaches dichotomy, when the planet is half-lit, today. It appears in the early-morning eastern sky some two hours before the Sun and is well placed for viewing 60 to 90 minutes before sunrise. Take a look through a telescope and see whether you think it is now half-lit, or whether it has a few more days to go.
The Moon passes 1.4° north of Mars at 6 A.M. EDT; the two are visible together this evening, slowly setting in the western sky and visible for a few hours after sunset. Both now lie in western Leo, with the Moon close to the Lion’s bright heart, Regulus (Alpha [α] Leonis). This magnitude 1.4 star lies some 79 light-years away, making it one of the relatively closer star systems to our Sun. And it is indeed a system of stars: Regulus is a quadruple star. Amateur scopes can generally capture three of the stars in this system, with one companion some 175” away.
Mars lies about 8.5° west of the Moon and Regulus, closer to the border of Leo and Cancer. The Red Planet now shines at magnitude 1.2, a bit brighter than Regulus, and gives off a ruddy glow true to its name. Through a telescope, Mars spans just 5”. Any view of its surface features will be fairly impossible for some time, until our orbits bring us closer together late next year.
Sunrise: 5:33 A.M.
Sunset: 8:23 P.M.
Moonrise: 11:14 A.M.
Moonset: 12:51 A.M.
Moon Phase: Waxing crescent (36%)
Monday, June 2
First Quarter Moon occurs late this evening at 11:41 P.M. EDT, with the Moon now near the hindquarters of Leo the Lion.
But did you know there’s also a Lion Cub in the sky? The smaller constellation Leo Minor lies to the upper right (north) of Leo in the west this evening. Leo Minor appears crouched above its larger counterpart, sandwiched between Leo and Ursa Major. The easiest way to find it is to search the space between two famous asterisms: the Sickle of Leo and the Big Dipper.
From magnitude 2.3 Merak, the star that marks the lower righthand corner of the Big Dipper’s cup, draw an imaginary line all the way to Regulus, Leo’s brightest star and the base of the Sickle’s handle. Leo Minor is halfway along that line.
The Lion Cub doesn’t have an alpha star — instead, its brightest star is magnitude 3.8 46 Leonis Minoris. It does, however, have a beta star, which shines at magnitude 4.2.
Sunrise: 5:33 A.M.
Sunset: 8:24 P.M.
Moonrise: 12:19 P.M.
Moonset: 1:17 A.M.
Moon Phase: Waxing crescent (46%)
Tuesday, June 3
Asteroid 2 Pallas is stationary at 5 P.M. EDT. Rising late this evening in Delphinus the Dolphin, we’ll return to this large main-belt world tomorrow evening. Tonight, we’re taking a detour to observe the waxing Moon.
Already high in the sky at sunset, the Moon is some 45° high in the southwest an hour after the Sun disappears. Fix your telescope on the center of the Moon, near the terminator dividing lunar night and day. Just south of the lunar equator is a series of three craters, starting with Ptolemaeus. About 95 miles (153 kilometers) wide, its floor appears at first glance quite smooth except for one notable pockmark in the northeast. But Ptolemaeus is actually covered in craterlets that have been buried over time by ejecta from nearby impacts. Study its broad floor to see if you can find any telltale depressions.
Just south of Ptolemaeus is Alphonsus, nearly 70 miles (110 km) wide. This crater hosts a noticeable central peak as well as a north-south ridge spanning its entire width.
Southernmost of the trio is Arzachel. It is smallest (60 miles [96 km]) and youngest of the three, also hosting a central peak. Compare this crater’s walls and other features to Alphonsus — because Arzachel is younger, it is more sharply defined as it has had less time for impacts both near and far to affect its landscape.
Sunrise: 5:33 A.M.
Sunset: 8:24 P.M.
Moonrise: 1:22 P.M.
Moonset: 1:39 A.M.
Moon Phase: Waxing gibbous (56%)
Wednesday, June 4
Now let’s return to Pallas, visible in the late evening and overnight. Around local midnight, you’ll find this main-belt world some 16° high in the eastern sky, a few degrees east of the four-star lozenge in Delphinus also called Job’s Coffin.
This small, diamond-shaped asterism is made from four 4th-magnitude stars: Alpha, Beta (β), Gamma (γ), and Delta (δ) Delphini. You’ll find it about 14° east-northeast of bright Altair in Aquila. Once you’ve located Job’s Coffin, slide 6° east with binoculars or a telescope to land on 10th-magnitude Pallas. Previously moving eastward toward the border Delphinus shares with Pegasus, Pallas will now do an about-face and begin moving westward against the background sky, tracking back deeper into Delphinus once more.
While you’re in the area, if you’re using even a small scope make sure to skip back over to Gamma Del, the easternmost star in the Coffin. Through a telescope, this star can be split into its two binary components, which shine and 4th and 5th magnitudes. They are 10” apart.
Sunrise: 5:32 A.M.
Sunset: 8:25 P.M.
Moonrise: 2:22 P.M.
Moonset: 1:58 A.M.
Moon Phase: Waxing gibbous (65%)
Thursday, June 5
Now rising in the east after sunset is the famous Summer Triangle, so called because it sits high overhead on summer nights. As we head for the Northern Hemisphere summer solstice later this month, the three stars that make up this asterism will rise earlier and earlier each night.
Tonight around 11 P.M. local daylight time you’ll see the Summer Triangle some 30° high in the east. The lowest star, Altair, shines at magnitude 0.8 in Aquila the Eagle. To its upper left is magnitude 1.3 Deneb, which marks the tail of Cygnus the Swan. To the upper right of Deneb is Vega in Lyra the Lyre. At magnitude 0, it is the brightest star in the Summer Triangle and the highest as it is rising.
In all, the Summer Triangle covers some 415 square degrees and encompasses a portion of the plane of the Milky Way, our galaxy. The brightest region of the galaxy visible within the Summer Triangle is the Cygnus Star Cloud; also visible is the dark Great Rift, made up of light-blocking dust.
Sunrise: 5:32 A.M.
Sunset: 8:26 P.M.
Moonrise: 3:22 P.M.
Moonset: 2:18 A.M.
Moon Phase: Waxing gibbous (74%)
Friday, June 6
The Moon passes 0.5° south of Spica at 11 A.M. EDT. The pair hangs in the evening sky, located in the south an hour after sunset.
By this evening, the Moon has moved some 6.3° southeast of Spica, the star that anchors Virgo the Maiden as its alpha luminary. Spica is magnitude 1 and sits close to the ecliptic, the plane of the solar system, which is also near the Moon’s orbit through our sky. At times, the Moon will pass in front of Spica from our earthly point of view, but not this month.
To the lower right of Spica is a quadrilateral of four 3rd-magnitude stars. This is the outline of Corvus the Crow, a relatively small and overlooked constellation. If you’ve got a small telescope, skim over to Corvus’ delta star (also called Algorab) some 14.5° southwest of Spica (the closest of the four to Spica). You’ll find Delta Corvi is a nice double system, showing off a 3rd-magnitude blue-white primary and an orangey 9th-magnitude secondary. They’re about 24” apart, easily split and far enough apart that their colors are obvious, even given their difference in magnitude.
Sunrise: 5:32 A.M.
Sunset: 8:26 P.M.
Moonrise: 4:22 P.M.
Moonset: 2:38 A.M.
Moon Phase: Waxing gibbous (82%)
