Transit of Venus

Big Story: Annular solar eclipse, transit of Venus and other non-doomsday celestial phenomena

By Vera H-C Chan 

Supermoon May 5, 2012Doomsday, schmoomsday.

Why settle for dusty ol' Mayan calendars and 12/12/12 apocalyptic visions, when 2012 has been offering up so many stellar—and planetary—sightings? We Earthlings have already been treated to nice meteor showers as well as a magnificent supermoon, and this weekend brings an annular solar eclipse.

That's not even the best treat: Venus will be ambling between Earth and the sun in a rare (though non-earth-shattering) planetary alignment. Sure, the event might look like a black pimple floating across the face of the sun, but this celestial rarity once guided adventurous astronomers in their quest to determine the size of the solar system and yielded the first-ever global scientific collaboration. Don't blink—Venus doesn't cross our path again until December 2117.

Annular Solar Eclipse, Jan. 4, 2011An annular solar eclipse and that ring of fire: A solar eclipse happens this Sunday, except for the Eastern seaboard (sorry). It's an "annular" eclipse rather than a total one, which means the sun's edges peek out from behind the moon, creating the illusion of a ring of fire. (The word "annular" comes from the Latin word for ring.) The lower 48 states will have to wait until Aug. 17, 2017, for a total shutout. This weekend's eclipse

begins at dawn in southern China. It then sweeps across the Pacific Ocean, passing south of Alaska, and makes landfall on the Pacific coast near the California-Oregon border. It ends near Lubbock, Texas, at sunset. Partial phases of this eclipse will be visible over most of western North America. (May 9, Space.com)

Those of you in the annular path should head to higher ground (avoiding clouds and light pollution) and put solar filters either over your eyes or on your equipment. Thirty-three national parks will be hosting solar gatherings. Lucky Coloradans get to hang out for free at the University of Colorado at Boulder's Folsom stadium, starting 5:30 p.m. local time, thanks to the Fiske Planetarium.

Below, a chart of solar eclipse times. (Credit: Geoff Gaherty/Starry Night Software/SPACE.com)

May 2012 solar eclipse times

What kind of solar glasses to get: Designer sunglasses don't cut it. At this late date, check telescope stores or call your local planetarium. No. 14 welder's glass, carried in specialty welding stores, works too. Don't forget solar filters for your camera equipment. Then there's the cardboard method:

The safest and simplest technique is perhaps to watch the eclipse indirectly with the solar projection method. Use your telescope, or one side of your binoculars, to project a magnified image of the sun's disk onto a shaded white piece of cardboard.

The image on the cardboard will be safe to view and photograph. But make sure to cover the telescope's finder scope or the unused half of the binoculars, and don't let anybody look through them. (May 9, Space.com)

If you don't buy binoculars for this weekend, you may want to consider ordering a pair for the transit of Venus.

Transit of Venus, June 8, 2004Measuring the solar system with the transit of Venus: Yes, there's an app. With just the tap of a finger on a screen, people can do in hours what 18th-century scientists needed years to do: measure the solar system. This year's transit of Venus—the second of a pair—begins on the evening of June 5 for North Americans. Our previous glimpse was in June 2004, and before that, back in the 19th century. An explanation of this planetary alignment:

Mercury and Venus are the only planets closer to the Sun than Earth, both moving faster in their orbits and passing us regularly. But rather than crossing directly between us and the Sun, these planets are usually slightly above or below the Sun as we see them. When they line up just right we see the round, black silhouette of the planet slowly crossing the Sun, an even referred to as a "transit." Mercury transits the Sun 13 or 14 times each century. But Venus transits happen in pairs—two transits eight years apart—with more than 100 years between each pair. (Transit of Venus, Astronomers Without Borders)

How to see the transit of Venus: Astronomy Without Borders will stream a webcast from Mount Wilson Observatory. See above about solar glasses.

Measuring the solar system the old-fashioned way: In 1761 and 1769, obsessed stargazers undertook glorious, and sometimes fatal, journeys, in an orchestrated effort that took 45 years to coordinate.

In 1716, British astronomer Edmond Halley had called upon scientists to unite in a project spanning the entire globe. He predicted that on June 6, 1761, Venus would traverse the burning disc of the sun for about six hours.

At a time when it took six days to travel from London to Newcastle, dozens of them travelled to remote outposts of the world to observe the phenomenon, laden with clocks, huge telescopes and other instruments.

Many risked their lives. With the Seven Years' War [1756-63] tearing Europe apart, they were even sent into war zones. (May 12, The Daily Mail)

Most were not swashbuckling men by any measure, but they risked traveling with instruments and rum, barely surviving shipwrecks and warship attacks. In 1761 Venus didn't quite cooperate and messed up the calculations. The second transit—on June 3, 1769—saw more success. Sharing the information took years, but the calculated distance between Earth and the sun wasn't far off the 92,960,000 miles that scientists agree on today.

More to come: Put this on your night calendar or monitor: Sea and Sky. Marshall Space Flight Center astronomer Mitzi Adams recommends the Perseids in August, which always has very bright meteors. "The conjunction of Venus and Saturn in November (27) should be pretty spectacular and complements the conjunction of Venus and Jupiter that occurred in March," she tells Yahoo!.