The Sky This Week: May 18 – May 22
Wednesday, May 18
• Neptune rises shortly before 3 a.m. local daylight time this week and appears low in the southeast before dawn. The distant world glows at magnitude 7.9, so you’ll need binoculars or a telescope to spot it. Fortunately, it lies near a brighter star that will help guide you. Look for the planet 0.4° south-southeast of 4th-magnitude Lambda (l) Aquarii. You can confirm a sighting of Neptune through a telescope, which reveals the planet’s 2.3″-diameter disk and blue-gray color.
• The Moon reaches apogee, the farthest point in its orbit around Earth, at 6:06 p.m. EDT. It then lies 252,235 miles (405,933 kilometers) from Earth’s center.
Thursday, May 19
• Brilliant Mars passes 1.0° due north of the 2nd-magnitude double star Delta (d) Scorpii this evening. Binoculars or a telescope at low power will afford the best views of this conjunction.
Friday, May 20
• Although Saturn will reach opposition and peak visibility two weeks from today, observers will be hard-pressed to see it as inferior this week. The ringed planet rises shortly after 9 p.m. local daylight time and appears highest in the south around 2 a.m. Saturn shines at magnitude 0.1 and stands out against the relatively dim background stars of southern Ophiuchus. If you target the beautiful world through a telescope, you’ll see its 18″-diameter disk surrounded by a ring system that spans 42″ and tilts 26° to our line of sight.
Saturday, May 21
• The Moon looks completely illuminated all night as it reaches Full phase at 5:14 p.m. EDT. You can find our satellite rising in the east around sunset and peaking in the south at 1 a.m. local daylight time. The Moon passed 6° due north of Mars during the afternoon hours, and those two form a dramatic quadrilateral with Saturn and the 1st-magnitude star Antares throughout the night.
Sunday, May 22
• Mars lies opposite the Sun in our sky today as it reaches peak visibility for 2016. The Red Planet appears low in the southeast as darkness falls and grows more prominent as the evening wears on and it climbs higher. By 1 a.m. local daylight time, it stands one-third of the way to the zenith in the southern sky against the backdrop of stars in northern Scorpius. The world shines at magnitude –2.1, brighter than it has been since 2005. When viewed through a telescope, the planet’s ocher-colored disk spans 18.4″ and shows subtle dark markings along with a whitish north polar cap. The Red Planet actually will come closest to Earth eight days from now, when its disk will swell to 18.6″ across. For more details on viewing the planet, see “Observe Mars at its best” in the May Astronomy.
• The Moon’s eastward motion relative to the background stars carries it 3° north of Saturn in this evening’s sky.
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