The Eta Aquarid meteors peak on the night of May 5/6. The Moon will not interfere. Expect up to 20 meteors per hour as seen from a dark-sky location.   

• ---

• The Planets

•  

  Mercury goes through superior conjunction – passing “behind” the Sun - on May 11, and becomes visible in the evening sky shortly thereafter. On the 19th, it sets an hour after the Sun; in a telescope, it appears as a disk 5.4 arc-seconds in diameter and 90% illuminated. By month’s end, it is setting an hour and three-quarters after sunset; its angular diameter is then 6.4” across and 65% lit up. But the most interesting aspect of Mercury this month is its close approach to its fellow planets Venus and Jupiter; see our “What’s New” page for more.

   

   

  Venus is starting to climb higher in the west after sunset. It sets about 45 minutes after the Sun on the 1st and an hour and 20 minutes after sunset on the 31st. The planet remains at magnitude -3.9 and in a “full Venus” phase throughout; its diameter increases only slightly from 9.8” to 10.2” in diameter. See below for its conjunction with other evening planets.

   

    

  Jupiter becomes visible shortly after sunset; it sets three hours after the Sun on May 1st, but just an hour after sunset by the 31st. During May, Jupiter remains in Taurus. The planet’s distance from us increases from 546 million to 567 million miles, and it dims accordingly from magnitude -2.0 to -1.9. A telescope shows a disk with an equatorial diameter of 34 arc-seconds on the 1st and 32” on the 31st. See its conjunctions below.

   

   

  Saturn, had just reached opposition on April 27/28, when it was at its nearest, brightest, and largest this year. However, during May, the planet is only marginally more distant; its distance increases from 1.319 billion kilometers (820 million miles) to 1.344 billion km. (835 million miles) from Earth. It dims slightly from magnitude +0.1 to +0.3. At the beginning of May its globe appears 18.8” across, while it visible rings are 42.7” wide; on the 31st, the disk is 18.5” across, while the rings span 42.0” across. The ring system is inclined toward our line of sight by about 18°. On the 12th, the planet moves from Libra into Virgo. Spica lies about 14° to its west.   

   

   

  By the end of May, Neptune rises four hours before the Sun. The magnitude-7.9 planet lies in Aquarius. In a telescope, it appears as a bluish disk just 2.3’ across.

   

   

  Uranus, in Pisces, rises two and a half hours before sunrise at month’s end. Due to its low altitude and faintness (magnitude 5.9, it remains a challenging target. If you do catch it in a telescope, you’ll see a green-grey disk 3.4’ in diameter.

   

   

  Mars remains too close to the Sun to be visible this month. Radio interference from the Sun, however, will be markedly reduced; accordingly, the precautionary communication blackout affecting the spacecraft at Mars – Curiosity, Opportunity, Mars Reconnaissance Orbiter, Mars Odyssey, and Mars Express – will be lifted.

   

   

   

  Dwarf Planets/Asteroids:

   

   

  Pluto, in Sagittarius, is highest around 4 AM. Even then, as seen from mid-Northern latitudes, it gets no higher than about 30° above the horizon.

   

   

  The dwarf planet/Main-Belt-asteroid 1 Ceres is in Gemini; on May 26th, it passes within a quarter degree of the 4th-magnitude star Iota Geminorum. The asteroid itself is of about magnitude 8.8.

     

• ---

   

  What's New

•  

•  

• A Planetary Trio 

   

  Just after sunset on May 19th, three planets – Mercury, Venus, and Jupiter form a rough line, with Mercury the lowest; Venus lies 4° to the east (upper left) of Mercury, and Jupiter in turn about 9° to the east (upper left) of Venus. Over the next few days, Mercury continues to climb higher; it passes 1.3° to the upper right of Venus on the 24th. Two days later, Mercury lies just 2.5° to the upper right of Jupiter. From the 24th to the 29th, Mercury, Venus, and Jupiter form a “trio” (defined as three objects that fit into a circle 5° across or smaller). The three planets are the closest together on the 26th; on this evening, the three planets fit into a circle just two and a half degrees across. On the 28th, Venus and Jupiter are only 1 degree apart.

•  

  

   

•  A Planetary Trio: Mercury, Venus, and Jupiter at their closest.

  May 26th, 8:39 PM EDT

  (One-half hour after sunset)

  (Click to enlarge)*

   

  After the 29th, the trio disperses. By May 31st, Venus is 3.5° to the upper left of Jupiter, and Mercury is 4° to the upper left of Mercury.

   

• 

   

  Close-up of A Planetary Trio

  May 26th, 2013, 8:39 PM EDT

  (One-half hour after sunset)

  (Click to enlarge)*

•  

       

•    

• The Correct Relative Sizes (though NOT distances) and Phase Angles of Jupiter, Venus, Mercury.

  May 26th, 8:39 PM EDT

  (One-half hour after sunset)..

   (Click to enlarge)*

   

•