IT'S A YEAR for rare natural phenomena. We're still scraping Brood X carcasses off our shoes, and here it is time for the transit of Venus. This infrequent planetary alignment, which occurs when Venus passes between the Earth and the sun, makes 17 years look like a coffee break: The last Venus transit took place in 1882. And, after an encore in 2012, there won't be another one for more than 100 years.
"We consider solar eclipses rarities," says University of Maryland Observatory director Elizabeth Warner, "and they happen almost once a year."
In addition to being what Edmond Halley called "by far the noblest [sight] that astronomy affords," the Venus transit has a preeminent place in the science's history. It was Halley who, in 1716, popularized the notion of using the transit of Venus to calculate the distance from the Earth to the sun -- the "astronomical unit" -- and thus of measuring the solar system. (A plan that was attempted in both the 18th and 19th centuries, ultimately yielding a surprisingly accurate measurement.)
The last Venus transit captured the public imagination in a way that seems improbable today. The surrounding hoopla included front-page headlines, sky-scanning crowds on city sidewalks and strange cultural artifacts like John Philip Sousa's "Transit of Venus" march. This year's transit, while less likely to find expression in popular music, is still capable of provoking awe.
"There's definitely a 'You can say you were there' quality to it," says Louis Mamakos, publicity chair of the Howard Astronomical League. "It's a once-in-a-lifetime -- or perhaps twice-in-a-lifetime -- opportunity."
Locally, the opportunity will present itself at several early morning gatherings in Maryland and Virginia, where astronomy club members and other volunteers will be on hand with telescopes equipped for viewing solar eclipses. At sunup Tuesday morning, the transit will be well underway: Unfortunately, the best seats in the house are in Europe and the Mideast. From the eastern half of the United States, only the final quarter of the transit will be visible. Those intent on watching the entire transit will have their choice of several live computer webcasts.
Though another Venus transit takes place in eight years -- they come in pairs -- this is the best time to see one, at least in this hemisphere. Viewing conditions in the Washington area will not be nearly as favorable in 2012, when the transit will occur at sunset. "We'll miss all the fun parts," Warner says.
Never attempt to look at the sun without eye protection. Doing so with the naked eye or with any optical device that is not fitted with appropriate solar filters can cause irreparable damage or blindness. Visit http://sunearth.gsfc.nasa.gov/eclipse/SEhelp/safety.html for information of how to view the transit safely.
WHERE TO WATCH VENUS
University of Maryland, Plant Sciences Building, fifth-floor balcony, on the campus at University Boulevard and Adelphi Road, College Park. The University of Maryland Astronomy Department hosts a free viewing of the Venus transit from 5:30 to 7:30 a.m. Tuesday. Telescopes with solar filters will be provided, and astronomy department faculty will be on hand to answer questions. For more information and a map to the viewing site and adjacent parking facilities, see the department's Web site at www.astro.umd.edu/openhouse. (In case of inclement weather, the transit will be viewed using computers in the university's Computer and Space Science Building, Computer Lab, Room 1220.)
Black Hill Regional Park, Visitor Center, 20926 Lake Ridge Dr., Boyds. Friends of Black Hill host a breakfast and viewing of the Venus transit from 5:15 to 7:30 a.m. for participants 6 and older. $5. Volunteers will provide telescopes with solar filters. 301-916-0220.
Montgomery College, Takoma Park campus, roof of the parking garage at Fenton and King streets, Takoma Park. Montgomery College astrophysicist Harold Williams hosts a free viewing of the Venus transit from 6 to 7:26 a.m. Telescopes with solar filters as well as box and projection viewers will be available for public use. (In case of inclement weather, there will be a live webcast viewing in the college's planetarium.) For more information, visit the Montgomery College Planetarium Web site at www.montgomerycollege.edu/Departments/planet.
Alpha Ridge Park, 11685 E. Old Frederick Rd., Marriottsville. The Howard Astronomical League hosts a free public viewing of the Venus transit from 5:15 to 7:30 a.m. (Participants are asked to arrive by 5:15 a.m. for an orientation session -- and bring a chair.) Viewing equipment will be provided by league members. For more information and directions, see the group's Web site at www.howardastro.org.
Observatory Park, Turner Farm, Georgetown Pike and Springvale Road, Great Falls. The Fairfax County Park Authority hosts a free public viewing of the Venus transit from sunup until 7:15 a.m. Volunteers from the Analemma Society and the Northern Virginia Astronomy Club will answer questions and provide telescopes with solar filters. For more information, see the Analemma Society Web site at www.analemma.org.
San Francisco's Exploratorium presents a live webcast from Athens at www.exploratorium.edu/venus/index.html.
The University of North Dakota presents a live webcast from New Delhi at http://people.cs.und.edu/~rmarsh/VENUS/venusindex.html.
Saturday at 9 p.m., University of Maryland Observatory director Elizabeth Warner discusses "Observing the Venus Transit" in conjunction with the observatory's bimonthly open house; weather permitting, the lecture will be followed by a viewing of the night sky through the facility's telescopes. University of Maryland Observatory, Metzerott Road, between Adelphi Road and University Boulevard, College Park. Free. 301-405-6555.
View the Smithsonian Institution Libraries' online exhibit "Chasing Venus: Observing the Transits of Venus, 1631-2004," at www.sil.si.edu/exhibitions/chasing-venus/.
Listen to Sousa's "Transit of Venus" march on the Library of Congress's "I Hear America Singing" Web site at http://memory.loc.gov/cocoon/ihas/html/venus/venus-home.html.