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PLANET: From Venus With Love: A Once-in-a-Lifetime Celestial Show

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PLANET: From Venus With Love: A Once-in-a-Lifetime Celestial Show

Post by Naseem Abbas Malik on Sun Jul 01, 2012 6:17 am

From Venus With Love: A Once-in-a-Lifetime Celestial Show







Report by Katherine Noyes



Transits of Venus come in pairs separated by
more than a hundred years. Tuesday's transit is the "bookend" of an
eight-year pair, with the last occurring in June 2004. For that last
one, no one alive at the time had seen a Transit of Venus with their own
eyes. Modern solar telescopes captured an unprecedented view of the
event then -- and this time around the view should be even better.
The planet Venus will create a rare spectacle on
Tuesday when it passes directly in front of our sun, creating an image
for viewers on Earth that won't be repeated until the year 2117.




Known as "the 2012 Transit of Venus," the nearly seven-hour journey
will begin at 3:09 p.m. Pacific Daylight Time (22:09 UT) Tuesday and
will be widely visible around the globe. Observers on seven continents
will be in a position to see it, in fact -- including even a sliver of
Antarctica.

Ideal viewing conditions will be in the mid-Pacific, where the sun is
high overhead during the crossing. In the United States, the transit
will be best viewed at sunset, treating those on Earth to a rare view of
what
NASA describes as "the swollen red sun 'punctured' by the circular disk of Venus."

To avoid burning their eyes, viewers of the event must not watch the
transit directly. Instead, they can watch using a projection technique
or a solar filter. A No. 14 welder's glass can also work well, according
to NASA.

NASA Television will air a
live program starting at 5:30 p.m. EDT on Tuesday showcasing the celestial phenomenonThe Relative Tilt of the Orbit'



"These transits are rare," Scott Austin, associate professor of astronomy and director of the astronomical facilities at the
University of Central Arkansas, told TechNewsWorld.

Venus actually ends up between Earth and the sun every 1.6 years, Austin pointed out.

The majority of those conjunctions don't result in transits, however,
"due to the relative tilt of the orbit of Venus relative to the orbit
of the Earth," he explained.


http://youtu.be/-nXv9YvkNyA




'This Doesn't Happen Often'




Indeed, "the way the orbits of the planets wobble and the fact that
Earth has to be in exactly the right position with respect to the sun
and Venus mean this doesn't happen that often," noted Paul Czysz,
professor emeritus of aerospace engineering at
St. Louis University.

Venus and Earth are roughly the same size, Czysz told TechNewsWorld,
but Venus goes around the sun faster than Earth does because it's closer
to it.

"You have to be exactly in the right place and at the right time" to
see the transit, he added. So does the sun, for that matter, so that
Venus's transit can be made visible by daylight.




A Long History




Humans have long been entranced by Transits of Venus, not just for their beauty and rarity but also for scientific reasons.

The Babylonians and Mayans were able to predict exactly when such
events would happen on the basis of observation alone, Czysz pointed
out.

Later, in the 18th century, "observations of the transit were used to get estimates of distances within the solar system,"
Mario Livio, senior astrophysicist with the Space Telescope Science Institute, told TechNewsWorld.

At that time, the size of the solar system was one of science's biggest mysteries.

"Venus transits have been historically scientifically significant for
determining the apparent diameter of Venus and its distance," noted
Austin.




'Layers of the Venusian Atmosphere'




This year's transit may not be quite as central to our understanding of
distances in the solar system, but it's by no means devoid of scientific
import.

"This transit will allow planetary scientists to study certain layers
of the Venusian atmosphere by observing the light from the Sun passing
through those layers," Austin explained.

"This will help refine this technique when applied to extrasolar
planets that are observed to transit their parent stars," he added.




'No One Alive Had Seen a Transit'




Transits of Venus come in pairs separated by more than a hundred years.
Tuesday's transit is the "bookend" of an eight-year pair, with the last
occurring in June 2004.

For that last one, no one alive at the time had seen a Transit of
Venus with their own eyes, NASA noted, and the hand-drawn sketches and
grainy photos of previous centuries scarcely prepared them for what was
about to happen.

Modern solar telescopes captured an unprecedented view of the event then -- and this time around the view should be even better.




Looking at 'Moonshine'




This year's transit will be observed by NASA's Solar Dynamics
Observatory, and it will also be observed indirectly by the Hubble Space
Telescope, Livio pointed out.

"Hubble will be observing the moon to look at 'moonshine' -- the
reflection of the sun's light by the lunar surface," he explained.

"By comparing data in and out of transit, information will be gathered on Venus' atmosphere," Livio noted.

Astronaut Don Pettit will also photograph Tuesday's Transit of Venus from the International Space Station, with photos
posted to Flickr along the way. Pettit and the Expedition 31 crew will be the first people in history to see a Venus transit from space.




'You'd Burn a Hole'




Perhaps most important of all is that viewers don't try to watch the
transit directly, because tiny Venus covers too little of the sun to
block out its blinding glare.

"If you use binoculars, you could burn your eyes," Czysz warned.
"With telescopes as large as they are today, you'd burn a hole right
through a piece of wood."

Instead, viewing must be done through special solar filters or at a
planetarium or observatory that's equipped for solar viewing and open
for the event, noted Austin, whose observatory at UCA is among those
hosting a special viewing.

At such facilities, the image of the transit is "run through a series
of lenses" and projected, Czysz pointed out, so "you're not looking at
any image directly."




Our 'Last Chance'




In any case, there's no doubt taking the necessary safety precautions will be well worth the trouble.

"Given that the next transit is not until December of 2117," Livio
said, "this is most probably the last chance of anybody alive today to
actually see a transit."
















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