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Transcript of Sun-Earth Day 2007 Podcast, Program 3

We live in the atmosphere of a dynamic magnetic star that interacts with the Earth, the solar system, and space beyond. My name is Troy Cline, and you are listening to the third in a series of NASA podcasts for Sun-Earth Day, 2007: Living in the Atmosphere of the Sun.

On November 8th 2006, a rare crossing of the planet Mercury across the face of the sun will take place for observers in North and South America, Australia, and parts of Asia. This event will be captured on a LIVE WEBCAST focusing on science, technology, and history as well as our most current knowledge of the Sun and space weather. The Webcast will Air at 1:30 Eastern Standard Time and will run for 1 full hour. We will feature:

  • A panel of scientists live from NASA's Goddard Space Flight Center with an additional panel of educators and amateur astronomers live from Langley Research Center.
  • Interacting with these panelists will be 2 NASA Explorer Schools ready to ask there very own questions about the transit and of course space weather.
  • You will also see an important telescope ‘safety viewing’ demonstration with instructions on how to view the transit using a classroom solarscope.
  • Live images of the transit will also be included from 2 satellites, SOHO and TRACE. We will also tap into real-time ground based images from Kitt Peak and Hawaii!

For more specific information about the webcast and how to connect, just visit the home page of this year's Sun-Earth Day website at . [Music Interlude]

As a side note, I recently received an email with some pretty amazing information pertaining to the Mercury transit that I simply have to share with you. This email came from, Steele Hill, the education and public outreach specialist for the SOHO spacecraft. In his email he wrote: "An instrument aboard SOHO ,LASCO C3, will begin seeing Mercury in its field of view beginning on November 5. It will be pretty bright. It will disappear from our view on November 12. Incidentally, Venus and Mars will be visible in the frame ...and then on November 11-12, a 4th planet, Jupiter will appear. This is only the 2nd time that SOHO has seen 4 planets at once". You can view these images by visiting the SOHO website at or by opening the Sun-Earth Media viewer found in the multimedia section of the Sun-Earth Day 2007 website. Now for the rest of the show! [Music Interlude]

In today's podcast, Lou Mayo will give us a crash course on the Mercury transit, when it will begin and how you can safely view the event. Then Sten Odenwald will tell us about this year's technology through time lineup which will include more information about the upcoming Transit. All of this can be found by visiting this years Sun-Earth Day home page. [Music Interlude] Lou Mayo is a planetary scientist and member of the Sun-Earth Day team. He not only provides our team with science content but he also coordinates community based astronomy programs for groups such as amateur astronomers and girl scouts. Last but certainly not least, he runs a national network of after school astronomy clubs. In his interview I first asked him to answer the basic question, "what is a transit?"

Lou: First thing that you need to know is that astronomers get really excited whenever any two things come even close together in the cosmos. So anytime two planets, a planet and a star, or moon come together, it's a big deal. A transit is when a small body moves across the face of a larger body. And in this case, the Mercury transit is when Mercury moves across the face of the Sun as we see it from Earth. And this is a fairly rare event. It's going to happen about 13 times this century. It will happen on November 8th, and then it won't happen again until the year 2016. So, you know, it has some importance.

I asked Lou to tell us how to safely view the transit of Mercury.

Lou: Mercury is smaller than Venus, and it's also roughly twice as far away as Venus. So you won't be able to see Mercury with just a set of solar glasses. You'll need a telescope fitted with a good filter, I would recommend at least a 500 millimeter focal length viewing 50 to 100 power or more. And you can see the transit that way. Another way to view the transit might be with a solarscope or other projection method in order to view the transit that way because Mercury is so small. Sitting on top of the disc of the Sun, you're going to have to have pretty favorable viewing conditions. But if the conditions are good, and the Sun is high in the sky, you should be able to see Mercury that way we think. Another great way to view the transit is to get on the internet and go to any one of a number of ground based solar telescopes.

Now that we know what a transit is it makes sense to ask when and where will the transit be visible?

Lou: Well, of course the transit occurs on November 8th, and it occurs at about 19:12 universal time which is going to be about 2pm eastern time. The transit will take 5 hours, so it's fairly slow. You'll have plenty of time to view it. Now, observers in the middle U.S. and eastern U.S. will see the first and second contacts of the planet Mercury on to the disc of the Sun as the Sun will set with Mercury still in transit. Viewers in the western United States however will be able to see the entire transit.

Lou also began to talk about the historical significance of the Mercury transit.

Lou: The Venus transit was very important, because that was used as a tool to scale the size of the solar system. So this was a big deal - the Venus transit that is. The Mercury transit has some historical signifigance. It was the first transit viewed, and it was viewed in 1631 by Pierre Gassendi . And I think only 3 people at that time because of weather conditions actually viewed that transit using Kepler's tables of planetary motion to predict the timing. Mercury is too far away, too small and too close to the Sun to be able to use it very easily for paralax measurements. But what they could do is they could measure the angular diameter of Mercury against the Sun and get a pretty good measure of the angular size of Mercury. I think Casandi estimated it was about 20 arcseconds, and we know that that's not bad when Mercury is at inferior conjunction. In other words, when it moves kind of between the Earth and the Sun, it should have a size of about 11 arcseconds. So while not as important in the scientific community, it was the first transit viewed and we were able to get an angular size of the planet Mercury out of it, so it does have some important historical signifigance.

Troy: How often does this happen with Mercury?

Lou: Mercury transits happen more frequently than Venus transits. We will see 13 of them this century.

Troy: So if I miss this one, chances are ...

Lou: Chances are you will be able to see the next one in the year 2016.

Be sure to visit the Amateur Astronomer section of the Sun-Earth Day website. [Music Interlude]

My next interview was with Sten Odenwald. Sten is an award-winning astronomer at the NASA Goddard Space Flight Center. His work has included being the education and public outreach director for the NASA IMAGE satellite program. Currently he plays an active role in the Themis, Solar-B and Sun-Earth Day education programs where he develops new NASA education resources and works with teachers at national conventions and workshops across the country.

I first asked Sten to tell us about the Technology Through Time feature on the Sun-Earth Day website and about what we can expect to see in this year's new Lineup!

Sten: A couple of years ago, we did this series of essays, about a couple of times a month. At that time, the theme was ancient observatories. So we decided to sort of look at all the different ancient observatories and monuments that featured the Sun and Sun observations and seasonal observations. Basically we did all of the ancients that we know about. Stonehenge, Chichen itza, and Machu picchu, and a variety of other things. Teachers really liked that format. So last year what we did is, we decided to focus in a little bit more on the development of the technology that we use today. We don't use stones and knives that much in observing the Sun, but we do use telescopes and a variety of equipment that derives from telescopic observations. So those essays last year had to do with the first telescopic observations of the Sun, the first spectroscopic observations where we figured out the elements and magnetic fields, and leading all the way up to satellite observations towards the end of the school year. Then we discovered that well ... you know ... wow! You know we've talked about the Sun from the standpoint of the ancients, and we've talked about the Sun from the standpoint of the development of this technology, but (laughs) reading through all these essays you will never really get a good sense for all the phenomena that go along with the Sun. We didn't really cover Sunspots too much. We didn't cover solar flares, prominences, the solar wind, the heliosphere, and the interactions with the planets. So this year's essays are mainly going to be about filling in those details so that by the end of this year, you'll have a pretty good idea of what the different phenomena are that we are so interested in.

I asked Sten to tell us about the essay he wrote in support of the Transit of Mercury.

Sten: The Mercury Transit or the transit of Mercury, you know, it doesn't directly tie in with Space weather and solar activity and stuff like that, but it's basically neat. You know, it's neat in the same way that the Transit of Venus was back in 2004. I always get a sort of a chilling feeling every time I see, you know, the dark disc of a planet passing in front of a star because it just gives you a very dramatic visual impression of just how small the planet is (laughs). And Mercury is going to be so small you won't see it with the naked eye, you'll need a telescope to see it. But still, in it's 3 or 4 hour passage across the disc of the Sun, you know, you'll be looking at it, but then you'll also be sort of looking at the disc of the Sun, with maybe an occasional Sunspot. So again, it sort of focuses your view on the Sun, you know, sort of through the back door, but hey, in this business, you take what you can get (laughs).

All of the Technology Through Time essays and associated resources are still available on the Sun-Earth Day website. [Music Interlude]

Sun Earth Day is a program sponsored by the NASA Sun-Earth Connection Education Forum at the Goddard Space Flight Center, and at the UC Berkeley Space Sciences Laboratory.

To find out more about the Sun Earth Day program, visit our website at:

This is Troy Cline signing off.

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