As a warm-up act for Mercury's jaunt across the sun in May, the speedy little planet in April provides a mid-month glow to remember. This month's planetary event will be the best view of ever-elusive Mercury we get for a long time.

A little after sunset on the evening of April 16, look to the west-northwestern horizon, where you will notice a zero-magnitude (bright) object. That is Mercury and it will be about 20 degrees above the horizon. As evening wears on, the fleet planet moves toward the horizon, and it will set after 9 p.m.

As the middle of the month approaches, the planet appears to climb higher in the heavens and stay out longer. After the planet's grand show on the same night as the full moon, Mercury begins to move back to its usual place of visual obscurity.

Mercury's spring fling is far from over, as it transits the sun on May 7. Only Mercury and Venus, planets inside Earth's orbit around the sun, can transit the sun, a rare event in which the planet appears to cross the solar disk. The last Mercury transit occurred in November 1999, when it was visible to Europe, Asia and Africa, according to Fred Espenak, an astronomer with the NASA Goddard Space Flight Center in Greenbelt. The last Venus transit happened in 1882, and the next one will be next year.

As night falls, two gaseous giants command the attention of sky gazers looking south. Saturn can be found in the constellation Taurus, and Jupiter is ensconced within Cancer.

Saturn's famous rings are tilted about as far as possible toward Earth -- about 27 degrees -- and because of the planet's high placement in the southwest sky, it provides a great show in telescopes. The zero-magnitude planet sets now around midnight, before we set our clocks forward this weekend.

Jupiter, a negative-second-magnitude object (very bright), travels the same sky path, behind Saturn, and it now sets in the 3 a.m. hour. Jupiter will set in the 2 a.m. hour by the end of April.

Down-to-Earth Events April 1-8 -- Turn off your lights and you might find a dark sky. Celebrate National Dark Sky Week, an idea created by Jennifer Barlow, a high school student from Midlothian, Va., by finding outdoor lighting systems that send fewer beams into the urban sky.

April 5 -- Every piece of rock found in space has a story. Lucy McFadden, an astronomer at the University of Maryland, explains how scientists interpret those stories in her lecture "The Colors of Rocks in Space," at the university's observatory on Metzerott Road, across from the system administration building in College Park. After the talk, enjoy the early spring sky through a telescope, weather permitting. 8 p.m. Information, 301-405-6555 or

April 10 -- Philip Christensen, a professor at Arizona State University, describes the search for life that may have existed on Mars. in his lecture "Mars in a New Light!" at the Einstein Planetarium, National Air and Space Museum, 7:30 p.m. Free, but tickets required. Tickets available at the museum's Lockheed Martin Imax Theater box office, or at or 800-529-2440. (Service fee through Information, 202-357-2700 or

April 12 -- Get hands-on astronomy experience, or learn from local experts about choosing and using telescopes and other astronomical instruments at the National Astronomy Day celebration at the Exploring the Universe gallery, National Air and Space Museum, 10 a.m.-3 p.m. Information, 202-357-2700 or

April 12 -- Alycia Weinberger, of the Carnegie Institution of Washington, will explain the formation of extrasolar planets at the regular meeting of the National Capital Astronomers, Montgomery County Bethesda-Chevy Chase Regional Center, 4805 Edgemoor Lane, next to the Bethesda Metro station., 3 p.m. Information,

April 13 -- At the regular meeting of the Northern Virginia Astronomy Club, Craig Tupper provides updated information about the RoboScope remote-controlled telescope, which will be available for club member use this summer. Enterprise Hall (Room 80, on the basement level) on the campus of George Mason University in Fairfax. Parking in lot B. 7 p.m. Information,

April 19 -- If you have no clue what the local metrication of Riemannian manifolds means, then "Black Holes: Gravity to the Max" is the lecture for you. Learn all about gravity in an extreme form at the Montgomery College Planetarium in Takoma Park, 7 p.m. Parking in the faculty lot. Information, 301-650-1463 or

April 26 -- The National Park Service and the National Capital Astronomers hold their first "Exploring the Sky" event this season. 8:30 p.m. At Rock Creek Park, near the Nature Center, in the field south of Military and Glover roads NW. Information, 202-895-6070.