Image: Venus' silhouette as it crosses face of sun
Imelda B. Joson and Edwin L. Aguirre
Watching the tiny silhouette of the planet Venus slowly cross the face of the sun doesn’t evoke the same drama and excitement as experiencing a total solar eclipse, but what makes a transit so unique is its rarity and historical significance.
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updated 6/4/2012 7:37:53 PM ET 2012-06-04T23:37:53

Tomorrow's historic transit of Venus across the sun's face has astronomers and skywatchers abuzz, but how spectacular would it be to see our own planet silhouetted against the solar disk?

Venus will pass in front of the sun from Earth's perspective on Tuesday (June 5; Wednesday, June 6, in much of the Eastern Hemisphere), marking the last such Venus transit until 2117. However, there's a chance to observe an Earth transit less than two years from now using a little creative thinking, some researchers note.

In January 2014, Jupiter will witness a transit of Earth. And we can see it too, the astronomers say, by training NASA's Hubble Space Telescope on the huge planet and studying the sunlight it reflects.

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"Many people will be keen to see what a habitable, populated planet looks like in transit, and it would be a sheer delight to watch Earth pass in front of the sun," Jay Pasachoff, of Williams College, wrote in a commentary in the journal Nature last month. [ Most Amazing Hubble Discoveries ]

Searching for life
A transit of Earth would be an unprecedented skywatching spectacle, but the main allure of the event for scientists is the chance to see what the atmosphere of a habitable (and inhabited) world looks like from afar.

This information could help astronomers in their search for life on distant alien planets, Pasachoff said.

"We would try to detect Earth's atmosphere in that way, which would be a real analogue to finding an Earth-like planet around another star," he told SPACE.com.

Hubble is already gearing up for a similar observation of the coming Venus transit. The instrument is too sensitive to be pointed anywhere near the sun, so scientists will use the moon as a mirror. The goal is to see if Hubble can determine the makeup of Venus' atmosphere, which is well-studied, in a test of how well the technique can be applied to exoplanets.

A tough observation
Watching the Earth transit with Hubble, while challenging, is quite doable, according to Pasachoff.

"It's a difficult observation, but we've calculated that we can make the observation," he said.

Pasachoff and his colleagues have applied for time on Hubble to watch a September 2012 Venus transit in light reflected off Jupiter, as a sort of proof of principle. They should know by June 15 if their proposal was successful, Pasachoff said.

If they are granted Hubble time for the September Venus transit, the researchers will apply to watch the January 2014 Earth transit. The team isn't taking anything for granted, since Hubble time is so hotly contested. (It's oversubscribed by a factor of almost 10, Pasachoff said.)

"We're hopeful, but we're mindful of the oversubscription rate," Pasachoff said.

If their bid fails, Hubble likely will never get to see an Earth transit. The next one from Jupiter's perspective won't occur until 2026, and the venerable instrument — which launched in 1990 — is expected to shut its eyes before then.

"This is the last one that would happen within the lifetime of Hubble," Pasachoff said.

Editor's note: If you snap a great photo of the Venus transit and would like to share it with SPACE.com for a story or gallery, please send images and comments to SPACE.com managing editor Tariq Malik at tmalik@space.com.

You can follow SPACE.com senior writer Mike Wall on Twitter:@michaeldwall. Follow SPACE.com for the latest in space science and exploration news on Twitter@Spacedotcom and onFacebook.

© 2013 Space.com. All rights reserved. More from Space.com.

Photos: Month in Space: January 2014

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  1. Southern stargazing

    Stars, galaxies and nebulas dot the skies over the European Southern Observatory's La Silla Paranal Observatory in Chile, in a picture released on Jan. 7. This image also shows three of the four movable units that feed light into the Very Large Telescope Interferometer, the world's most advanced optical instrument. Combining to form one larger telescope, they are greater than the sum of their parts: They reveal details that would otherwise be visible only through a telescope as large as the distance between them. (Y. Beletsky / ESO) Back to slideshow navigation
  2. A balloon's view

    Cameras captured the Grandville High School RoboDawgs' balloon floating through Earth's upper atmosphere during its ascent on Dec. 28, 2013. The Grandville RoboDawgs’ first winter balloon launch reached an estimated altitude of 130,000 feet, or about 25 miles, according to coaches Mike Evele and Doug Hepfer. It skyrocketed past the team’s previous 100,000-feet record set in June. The RoboDawgs started with just one robotics team in 1998, but they've grown to support more than 30 teams at public schools in Grandville, Mich. (Kyle Moroney / AP) Back to slideshow navigation
  3. Spacemen at work

    Russian cosmonauts Oleg Kotov, right, and Sergey Ryazanskiy perform maintenance on the International Space Station on Jan. 27. During the six-hour, eight-minute spacewalk, Kotov and Ryazanskiy completed the installation of a pair of high-fidelity cameras that experienced connectivity issues during a Dec. 27 spacewalk. The cosmonauts also retrieved scientific gear outside the station's Russian segment. (NASA) Back to slideshow navigation
  4. Special delivery

    The International Space Station's Canadian-built robotic arm moves toward Orbital Sciences Corp.'s Cygnus autonomous cargo craft as it approaches the station for a Jan. 12 delivery. The mountains below are the southwestern Alps. (NASA) Back to slideshow navigation
  5. Accidental art

    A piece of art? A time-lapse photo? A flickering light show? At first glance, this image looks nothing like the images we're used to seeing from the Hubble Space Telescope. But it's a genuine Hubble frame that was released on Jan. 27. Hubble's team suspects that the telescope's Fine Guidance System locked onto a bad guide star, potentially a double star or binary. This caused an error in the tracking system, resulting in a remarkable picture of brightly colored stellar streaks. The prominent red streaks are from stars in the globular cluster NGC 288. (NASA / ESA) Back to slideshow navigation
  6. Supersonic test flight

    A camera looking back over Virgin Galactic's SpaceShipTwo's fuselage shows the rocket burn with a Mojave Desert vista in the background during a test flight of the rocket plane on Jan. 10. Cameras were mounted on the exterior of SpaceShipTwo as well as its carrier airplane, WhiteKnightTwo, to monitor the rocket engine's performance. The test was aimed at setting the stage for honest-to-goodness flights into outer space later this year, and eventual commercial space tours.

    More about SpaceShipTwo on PhotoBlog (Virgin Galactic) Back to slideshow navigation
  7. Red lagoon

    The VLT Survey Telescope at the European Southern Observatory's Paranal Observatory in Chile captured this richly detailed new image of the Lagoon Nebula, released on Jan. 22. This giant cloud of gas and dust is creating intensely bright young stars, and is home to young stellar clusters. This image is a tiny part of just one of 11 public surveys of the sky now in progress using ESO telescopes. (ESO/VPHAS team) Back to slideshow navigation
  8. Fire on the mountain

    This image provided by NASA shows a satellite view of smoke from the Colby Fire, taken by the Multi-angle Imaging SpectroRadiometer aboard NASA's Terra spacecraft as it passed over Southern California on Jan. 16. The fire burned more than 1,863 acres and forced the evacuation of 3,700 people. (NASA via AP) Back to slideshow navigation
  9. Where stars are born

    An image captured by NASA's Spitzer Space Telescope shows the Orion Nebula, an immense stellar nursery some 1,500 light-years away. This false-color infrared view, released on Jan. 15, spans about 40 light-years across the region. The brightest portion of the nebula is centered on Orion's young, massive, hot stars, known as the Trapezium Cluster. But Spitzer also can detect stars still in the process of formation, seen here in red hues. (NASA / JPL-Caltech) Back to slideshow navigation
  10. Cygnus takes flight

    Orbital Sciences Corp.'s Antares rocket rises from NASA's Wallops Flight Facility on Wallops Island, Va, on Jan. 9. The rocket sent Orbital's Cygnus cargo capsule on its first official resupply mission to the International Space Station. (Chris Perry / NASA) Back to slideshow navigation
  11. A long, long time ago...

    This long-exposure picture from the Hubble Space Telescope, released Jan. 8, is the deepest image ever made of any cluster of galaxies. The cluster known as Abell 2744 appears in the foreground. It contains several hundred galaxies as they looked 3.5 billion years ago. Abell 2744 acts as a gravitational lens to warp space, brightening and magnifying images of nearly 3,000 distant background galaxies. The more distant galaxies appear as they did more than 12 billion years ago, not long after the Big Bang. (NASA / NASA via AFP - Getty Images) Back to slideshow navigation
  12. Frosty halo

    Sun dogs are bright spots that appear in the sky around the sun when light is refracted through ice crystals in the atmosphere. These sun dogs appeared on Jan. 5 amid brutally cold temperatures along Highway 83, north of Bismarck, N.D. The temperature was about 22 degrees below zero Fahrenheit, with a 50-below-zero wind chill.

    Slideshow: The Year in Space (Brian Peterson / The Bismarck Tribune via AP) Back to slideshow navigation
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