Sic Venus Transit Solis

Hubble Spacium Telescopium Vigilabo

There’s this event coming on June 5/6 called the “Transit of Venus” and as I read about it, the Latin translation of it jumped into my head. My mind’s funny like that. Sic Transit Gloria Venus and all that.

So, what’s it all mean? The Transit of Venus is when the planet Venus will move in its orbit between us and the Sun in a sort of mini-eclipse.  It happens very rarely. In fact, after this one, there won’t be another transit of Venus as seen from Earth until the year 2117.

This mottled landscape showing the impact crater Tycho is among the most violent-looking places on our Moon. reveals lunar features as small as roughly 560 feet (170 meters) across. The large "bulls-eye" near the top of the picture is the impact crater, caused by an asteroid strike about 100 million years ago. The bright trails radiating from the crater were formed by material ejected from the impact area during the asteroid collision. Tycho is about 50 miles (80 kilometers) wide and is circled by a rim of material rising almost 3 miles (5 kilometers) above the crater floor. The image measures 430 miles (700 kilometers) across, which is slightly larger than New Mexico.The image was taken in preparation to observe the transit of Venus across the Sun's face on June 5-6. Courtesy NASA/ESA/STScI

As you can imagine, such an event presents some cool scientific opportunities.  One of them will be for the Hubble Space Telescope, believe it or not.  Hubble, as you may know, can’t look directly at the Sun, and it has a heck of a time looking at Venus simply due to logistics, as well as brightness. It can look at the Moon, and for this reason, astronomers have come up with an ingenious method to ‘watch’ the Transit of Venus by using the Moon as a sort of “mirror”.  They tested it, coming up with the image below.  This type of observational technique isn’t new. It’s very similar to one being used to sample the atmospheres of the giant planets as they pass in front of stars as seen from our point of view on Earth.

For the Venus observations, since astronomers already know the chemical makeup of its atmosphere, they’re going to test this technique on a planet they “know” to see if it can be used on the atmospheres of distant planets around other stars. If it works the way they think it will, then it could help them tease out the very faint fingerprints of the atmosphere of an Earth-like planet, even one that might be habitable for life.

During the transit, Hubble will snap images and perform spectroscopy, dividing the sunlight into its constituent colors, which could yield information about the makeup of Venus’s atmosphere. Hubble’s main instruments will get a workout in this test.  The telescope’s Advanced Camera for Surveys, Wide Field Camera 3, and the Space Telescope Imaging Spectrograph will concentrate their attention on wavelengths of light ranging from infrared to ultraviolet.  The whole operation will take seven hours starting before the transit begins and lasting until well after it ends. Because the astronomers only have one shot at observing the transit, they had planned a practice run to see if their idea would work, which included the test observations of the Moon that resulted in the image above.

This is one of those experiments that’s so elegant and cool because it demonstrates the many-faceted ways that astronomers can study objects. You don’t always have to look directly at something; sometimes indirect observations  get you to the same place. And, that’s glorious!

If you want to do a little transit-viewing yourself, visit the Transit of Venus page for details on safe viewing (because the Sun’s involved, you really have to be careful… and NEVER look directly at the Sun. With that caveat, I recommend you check it out. This is the last time this century sky watchers can view Venus passing in front of the Sun and it’s just one of those cool things you can brag about at the next family picnic or company party.


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