In The Sky This Month

Read about the most important celestial activities visible in this month's sky. This monthly summary highlights lunar phases, planets, meteors showers, auroras and more.

BLOOMINGTON, Ind.—Venus, Jupiter and Mercury will have a spectacular series of conjunctions in evening twilight during the last half of May. Skywatchers will need a clear view of the western horizon to see the stately dance of the planets as it unfolds.

The month will begin with Jupiter high and Venus low in the west-northwest soon after sunset. Each evening Jupiter will settle lower while Venus drifts higher as they move toward conjunction on May 28.

Mercury will be out of sight for the first half of May as it passes behind the sun, but it will reappear in the evening sky on May 19, forming a line with Venus and Jupiter low in the west-northwest. Venus will be 4 degrees to the upper left (south) of Mercury, and Jupiter 9 degrees to the upper left of Venus. Binoculars may be needed to pick Mercury out of the bright twilight.

The line will be shorter each evening as Mercury appears higher and Jupiter lower. Then from May 24 to 29, Venus, Jupiter and Mercury will form a triangle that fits within a circle less than 5 degrees wide. Binoculars will show all three planets in the same field of view. The trio will be most compact on the evening of May 26 in North and South America. On May 28, Venus and Jupiter, the two brightest planets, will be only 1 degree apart. Try to see these planets immediately after sunset, when they will be highest above the horizon.

By May 31 the three planets will again be in a line, but this time it will be getting longer, with Venus to the lower right of Mercury and Jupiter to the lower right of Venus. An animation of the three planets' changing configurations can be seen at skypub.com/may2013planets.

As evening twilight fades during May, bright yellow Saturn will come into view in the southeastern sky. It will be highest in the south around midnight. The white star Spica will be about 15 degrees to Saturn's right (west) and not as bright. Saturn's rings will be tilted 18 degrees to our line of sight. Its largest moon, Titan, will be due south of the planet on May 6 and 22 and due north on May 14 and 30.

Mars will be too close to the sun to be seen during May.

Meteor Shower
This month Earth will encounter a stream of dust left behind in space by Comet Halley, causing the Eta Aquarid meteor shower that will peak before dawn on May 6. The shower will be active for a few days before and after the peak as well. The meteors will appear to come from a point called the radiant in the constellation Aquarius, which will rise in the east about two hours before the start of morning twilight. The higher this point is above the horizon, the more meteors will be visible. The waning crescent moon will not rise until around 4 a.m. local time that night, providing a moonless sky for viewing meteors.

Observers in the Northern Hemisphere may see around 25 meteors per hour, because Aquarius will be close to the eastern horizon. Those watching in the Southern Hemisphere will see Aquarius much higher in the sky, and there may be twice as many meteors per hour at the peak.

Moon Phases
The moon will be at third quarter on May 2, new on May 9, at first quarter on May 18, full on May 25 and at third quarter again on May 31.