Most of you probably saw or heard about our partial lunar eclipse yesterday morning. If you missed it, I actually captured some video right as the sun was rising. http://www.heartlandconnection.com/weather/video.aspx?id=761618 While these events are fairly common over the years, a much more interesting event will be taking place as we head through the day today, June 5th, 2012.
It is a pretty cool day; Venus will pass across the face of the sun, producing a silhouette that no one alive today will likely see again. This is actually called a “transit.”
A transit is the passage of a smaller celestial body or its shadow across the disk of a larger celestial body. As observed from Earth, Mercury and Venus are the only planets of the solar system that make transits of the Sun, because they are the only planets with orbits that lie between Earth and the Sun.
It will begin to be visible around 5:04 p.m. across the heartland. It will slowly progress across the sun through sunset and actually exit the sun after sunset. The entire journey will take about 7 hours. We will be able to see it from 5:04 this evening until sunset.
THE HISTORY
Transits of Venus first gained worldwide attention in the 18th century. In those days, the size of the solar system was one of the biggest mysteries of science. The relative spacing of planets was known, but not their absolute distances. How many miles would you have to travel to reach another world? The answer was as mysterious then as the nature of dark energy is now.
Venus was the key, according to astronomer Edmund Halley. He realized that by observing transits from widely-spaced locations on Earth it should be possible to triangulate the distance to Venus using the principles of parallax.
In retrospect, the experiment falls into the category of things that sound better than they actually are. Bad weather, primitive optics, and the natural “fuzziness” of Venus’s atmosphere and other factors prevented those early observers from gathering the data they needed. Proper timing of a transit would have to wait for the invention of photography in the century after Cook’s voyage. In the late 1800s, astronomers armed with cameras finally measured the size of the Solar System as Edmund Halley had suggested
What Venus will look like as it crosses in front of the sun.
THE SCIENCE
Transits of Venus are very rare, coming in pairs separated by more than a hundred years. This June’s transit, the bookend of a 2004-2012 pair, won’t be repeated until the year 2117. Fortunately, the event is widely visible. Observers on seven continents, even a sliver of Antarctica, will be in position to observe it.
Because Venus's orbit is considerably large, transits of Venus are much rarer. Indeed, only six such events have occurred since the invention of the telescope (1631, 1639, 1761,1769, 1874 and 1882). Transits of Venus are only possible during early December and June when Venus's orbital nodes pass across the Sun. Transits of Venus show a clear pattern of recurrence at intervals of 8, 121.5, 8 and 105.5 years. The following table lists all transits of Venus during the 800 year period from 1601 through 2400.
Transits of Venus: 1601-2400
Date Universal Separation
Time (Sun and Venus)
1631 Dec 07 05:19 940"
1639 Dec 04 18:25 522"
1761 Jun 06 05:19 573"
1769 Jun 03 22:25 608"
1874 Dec 09 04:05 832"
1882 Dec 06 17:06 634"
2004 Jun 08 08:19 627"
2012 Jun 06 01:28 553"
2117 Dec 11 02:48 724"
2125 Dec 08 16:01 733"
2247 Jun 11 11:30 693"
2255 Jun 09 04:36 492"
2360 Dec 13 01:40 628"
2368 Dec 10 14:43 835"
The nearly 7-hour transit begins at 3:09 pm Pacific Daylight Time (22:09 UT) on June 5th. The timing favors observers in the mid-Pacific where the sun is high overhead during the crossing. In the USA, the transit will be at its best around sunset.
A map of where it is visible across the world.
HOW CAN I SEE IT
It is just possible to see without optical magnification (but using solar filter protection) as it crosses the Sun. Nevertheless, the planet appears to be only 1/32 of the Sun's apparent diameter so a pair of binoculars or a small telescope at modest power will offer a much more satisfying view. All binoculars and telescopes must be suitably equipped with adequate filtration to ensure safe solar viewing.
Observing tip: Do not stare at the sun. Venus covers too little of the solar disk to block the blinding glare. Instead, use some type of projection technique or a solar filter. A welder’s glass #14 or greater is a good choice.
If you do not have any of the protective materials needed to see it by looking at it, you can also see it by creating a pin-hole camera. The simple way of doing this is to puncture a small hole in a piece of paper and then holding that up to the sun. Hold another piece of paper a few feet behind it and it will show Venus crossing the sun on the piece of paper. This is a safe way to see it. For a more elaborate pin-hole camera, check this link out! http://www.lifeslittlemysteries.com/2443-solar-eclipse-viewer.html
This is a picture of what it looks like using a pin-hole camera.
WEAHTER WISE
It will begin to be visible around 5:04 p.m. across the heartland. It will slowly progress across the sun through sunset and actually exit the sun after sunset. The entire journey will take about 7 hours. We will be able to see it from 5:04 this evening until sunset.
It does look like we have a pretty good shot of being able to see it weather wise. While most of the day will be Mostly Sunny, more clouds will be working in as we head through the evening. We should be just Partly Cloudy through sunset with enough breaks to be able to attempt to see Venus cross the sun.
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Futurecast Cloud Cover This Evening.
So give it a try! If anyone captures some cool pictures feel free to post them on our facebook, website, or email them.
Have a great day everyone!
-Brian
TV Station Profiles & Public Inspection Files forKTVO