June 2012

Tony Martinez

Each month I will describe sights of interest in the night skies of South Carolina.  These sights will be broken down into three sections; what you can see with the naked eye, with binoculars, and with a small telescope. The best time to view the night sky is at and around the times when the Moon is not visible, what is known as a New Moon; which will occur this month on June 19th. For June, your best viewing nights will be from June 9th to the 23rd. The Star chart below is set for Florence, SC on June 15th at 10 pm.

Venus Transit:
It is unlikely that any one alive today will ever see this astronomical event again. On June 5th, the planet Venus will pass in front of the Sun; this known as a Venus transit. The next time this occurs will be in the year 2117, and at that time, it will not be visible over most of the United States. However, I did manage to view the last Venus transit.
I have often mentioned the “Dance of the Planets.”  This “dance” is the unique relationship each planet has with the other planets as they revolve around the Sun. In general, the planets and their moons revolve on a plane counterclockwise around the Sun. However, this plane is not perfectly flat like a CD disk. The planets and moons can move above or below the plane of the solar system. A good example is the orbit of our Moon. If our Moon was perfectly aligned to the plane of the solar system, the once a month we would have a solar and lunar eclipse. The tilt of our Moon’s orbit results in somewhat rare eclipses on any given location on Earth.
Below is a diagram of the relationship of Earth’s orbit and Venus’s orbit.

The shapes of the Earth/Venus orbits results in the following sequence of Venus transits of the Sun: Every 8 years-105 years-8 years-122 years-8 years-105 years, etc. Therefore, the last Venus transit was in June 2004, followed by this year and then in 2117.
A Venus transit is not what some people would call a “wow” event. The reason is that viewing this event requires special equipment, and it is best to visit a site where trained astronomers can allow you to safely view the Sun. Of course the transit can be followed on television, and through streaming video to your laptop, smart phone or iPad. 
The actual transit of Venus across the Sun’s surface will take about six hours.  Through any safe solar viewing equipment, Venus will look like a small black disk moving over the surface of the Sun. The image below was taken during the 2004 transit.

Below on the left is a composite time exposure of the 2004 transit, and on the right is a comparison of the two most recent transits.

Finally below is a 2004 image of the “teardrop” effect seen as Venus enter or exits the Sun.

So if you would like to see firsthand this once in a lifetime astronomical event, stop by our ScienceSouth pavilion at Freedom Florence, from 6 pm to 8 pm on Tuesday June 5th. Outside our pavilion we will have three methods of viewing the transit. First is a projection method called the Sun Spotter. With this device, at least four people can view the Sun at the same time. Second we will have a traditional Dobsonian reflecting telescope equipped with a solar filter. Finally, we will have a unique solar telescope called an H-1 alpha, which is normally used to see the solar eruptions on the Sun’s surface, called prominences.  Because the H-1 alpha can see the atmosphere above the surface of the Sun, this device should be the first to detect the arrival of the Venus transit.
If we have rain or clouds, we will have streaming video of the transit inside the pavilion. We also have a digital planetarium Star Lab inside which can follow the transit by way of computer software imaging.
While this is a great amateur event, professional astronomers will be studying this transit very carefully. This transit is of special interest to the astronomers who are searching for exo-planets; planets orbiting distant stars. The primary method used by astronomers to locate planets around distant stars is to observe the effects caused by the planets as they pass in front of the distant star. These effects include diming the star’s brightness, or small gravitational tugging. The Venus transit will act as a model to add more information about the effects of planets transiting distant stars. 
As you watch the Venus transit this month, and notice how tiny the disk of Venus is compared to the massive Sun, you can imagine what little effect an Earth-like planet would have on a distant star. This is the reason most of the exo-planets discovered are much larger than Jupiter, and orbit very close to the distant star. This also explains why we seldom find Earth-like planets revolving around distant stars; not because they don’t exist, but because we can detect them. In reality, there may be thousands of Earth-like planets revolving around thousands of stars. As the late Carl Sagen often said, “Absence of evidence is not evidence of absence.”  
Naked Eye Sights: Using our projection Sun Spotter, the planet Venus transit of the Sun. Warning! Do not use your own telescopes or binoculars to project images of the Sun. Children, and also adults are often attracted to telescope eyepieces, and might unknowingly place their eyes on the eyepiece, which would lead to blindness.
Binocular Sights (7 to 10 power): As always, continue working on finding more Messier Objects to add to your list. In particular look toward the Milky Way’s center in the southern sky.
Telescope Sights (60-100mm: Only with professionally set up solar viewing scopes, the Venus transit. Also, Saturn is at a perfect position for viewing throughout this month.

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