The Sky this Week: May 17–26, 2013
Your daily digest of celestial events coming soon to a sky near you.
May 17, 2013
Friday, May 17
The days on either side of First Quarter Moon are the best time to observe our satellite because long shadows emphasize the lunar landscape. // Ziad El-Zaatari
The First Quarter Moon hangs high in the southwest as darkness falls, and then sinks steadily toward the western horizon throughout the evening hours. Our satellite reaches First Quarter phase at 12:35 a.m. EDT tomorrow morning (9:35 p.m. PDT tonight). The Moon lies in southern Leo, some 6° southwest of 1st-magnitude Regulus.
Saturday, May 18
Venus passes 6° due north of 1st-magnitude Aldebaran today. You should be able to spot the brilliant planet, which shines at magnitude –3.9, low in the west-northwest 30 minutes after sundown. Spying 1st-magnitude Aldebaran (which appears just 1 percent as bright as Venus) takes significantly more effort. You’ll need binoculars, a flat horizon, and a near-perfect sky to spot the star lurking to the planet’s lower left.
Sunday, May 19
The Blackeye Galaxy (M64) floats through the small constellation Coma Berenices and shines relatively brightly for a galaxy at magnitude 8.5. // Bernard Miller
Binoculars open a world of wonders invisible to naked eyes. Did you realize you could see several galaxies without resorting to a telescope? One of the spring sky’s best is the Blackeye Galaxy (M64) in Coma Berenices. This constellation stands high in the south during late evening hours. The 8th-magnitude spiral galaxy appears about 1° northeast of the 5th-magnitude star 35 Comae Berenices. M64 is just in the range of 50mm binoculars under a dark sky, although you’ll need 80mm or larger binocs or a telescope to spot the dark dust lane that gives the galaxy its “black eye.” To learn more about this season’s best objects for binoculars, see “Explore 11 spring binocular gems” in the May issue.
Monday, May 20
Mercury appears to be in hot pursuit of Venus this week. Tonight, the innermost planet passes 7° north of Aldebaran, just two days after Venus slid past the 1st-magnitude star. Unfortunately, those 48 hours have been enough to carry Aldebaran below the horizon and out of our sight. Mercury, however, shines brightly at magnitude –1.3 and lies 4° high in the west-northwest 30 minutes after sunset. The easiest way to spot the planet is to use binoculars and look 3° to Venus’ lower right.
Tuesday, May 21
Comet PANSTARRS (C/2011 L4) has now faded to 8th magnitude, which puts it in the range of large binoculars or small telescopes. Fortunately, its position near Polaris means that it remains on view all night for observers in the Northern Hemisphere. Tonight, it lies about 7° from the 2nd-magnitude Pole Star and just 4° from the modest star cluster NGC 188. Astronomers consider this open cluster to be one of the oldest in our galaxy.
Wednesday, May 22
Titan, Rhea, and Enceladus form a straight line the night of May 22/23. You should also see Tethys and Dione and, perhaps, dimmer Mimas. // Astronomy: Roen Kelly
Although Saturn reached opposition nearly a month ago, it still looks spectacular. It lies among the background stars of eastern Virgo and appears about one-third of the way to the zenith in the southeastern sky as darkness falls. It reaches its peak in the south by 11 p.m. local daylight time. Saturn shines at magnitude 0.3, noticeably brighter than Virgo’s brightest star, Spica, which lies 13° west of the planet. When viewed through a telescope, Saturn’s globe measures 19" across while the rings span 42" and tilt 18° to our line of sight. Several moons also should be visible. Tonight you’ll find 8th-magnitude Titan, 10th-magnitude Rhea, and 12th-magnitude Enceladus forming a straight line due south of the planet.
Thursday, May 23
Jupiter lies low in the west-northwest after sunset all week. This evening, it appears about 10° high 30 minutes after the Sun goes down and sets shortly before 10 p.m. local daylight time. Shining at magnitude –1.9, the giant planet stands out in the twilight to the upper left of Venus and Mercury. During the next week, these three planets will put on a remarkable series of conjunctions best viewed with binoculars. Tonight, Jupiter lies 5° from Venus and 6° from Mercury, but these gaps will tighten during the next few nights.
Friday, May 24
Venus (upper left) and Jupiter appeared near each other at the end of January 2008. The two brightest planets should look equally spectacular in late May. // Mike Salway
Mercury passes 1.4° north of Venus this evening (officially at midnight EDT), and the two make an attractive pair in evening twilight. They appear less than 5° to the lower right of Jupiter. From now through May 29, the three planets remain within 5° of one another.
Full Moon occurs at 12:25 a.m. EDT tomorrow morning (9:25 p.m. PDT this evening), but our satellite looks completely illuminated all night. You can find it rising in the southeast around sunset and peaking in the south around 1 a.m. local daylight time. The Moon lies among the background stars of northern Scorpius, just more than 5° from 1st-magnitude Antares. An essentially undetectable penumbral lunar eclipse also occurs tonight. A mere 1.6 percent of the Moon dips into the fringe of Earth’s outer shadow. The eclipse starts at 11:53 p.m. EDT and lasts 34 minutes.
Saturday, May 25
The three evening planets now lie within 3° of one another, with Jupiter to the left and slightly above Mercury and Venus. The trio stays packed within a 3° circle through May 27, although their positions relative to one another will change noticeably each night.
The Moon reaches perigee, the closest point in its orbit around Earth, at 9:43 p.m. EDT. It then lies 222,685 miles (358,377 kilometers) away from us. Because perigee arrives less than 24 hours after Full Moon, residents of coastal areas should expect higher than normal tides for a few days.
Sunday, May 26
The largest asteroid cuts across Gemini in May, passing less than 1° from 4th-magnitude Iota (ι) Gem late in the month. // Astronomy: Roen Kelly
Tonight offers a good opportunity to track down asteroid 1 Ceres. The solar system’s largest asteroid — it’s so big, in fact, that astronomers now also classify it as a “dwarf planet” — lies less than 0.5° west-northwest of the 4th-magnitude star Iota (ι) Geminorum. The pair stands about 15° high in the west-northwest at the end of evening twilight and make a nice target after the planetary trio sets. You’ll need a telescope to spot 9th-magnitude Ceres. To confirm your sighting, sketch the field and return to it a night or two later. The object that moved is the asteroid.
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