Date: February 11, 2011
Title: Super Sun Day
Podcaster: Bob Hirshon
Organization: American Association for the Advancement of Science (AAAS)
Description: While last Sunday was Super Sunday to American football fans, it was Super Sun Day to solar physics fans, because NASA released the first images of both sides of the sun taken simultaneously. It was made possible by the STEREO (Solar TErrestrial RElations Observatory) and today’s podcast features Terry Kucera, the mission’s Deputy Project Scientist.
Bio: Bob Hirshon is Senior Project Director at the American Association for the Advancement of Science (AAAS) and host of the daily radio show and podcast Science Update. Now in its 24th year, Science Update is heard on over 300 commercial stations nationwide. Hirshon also heads up Kinetic City, including the Peabody Award winning children’s radio drama, McGraw-Hill book series and Codie Award winning website and education program. He oversees the Science NetLinks project for K-12 science teachers, part of the Verizon Foundation Thinkfinity partnership. Hirshon is a Computerworld/ Smithsonian Hero for a New Millennium laureate.
Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by the Education and Outreach team for the MESSENGER mission to planet Mercury. Follow the mission as the spacecraft helps to unlock the secrets of the inner solar system at www.messenger-education.org.
Transcript:
Super Sun Day
Hirshon:
Welcome to the 365 Days of Astronomy Podcast. I’m Bob Hirshon, host of the AAAS radio show and podcast Science Update. For many Americans, this past Sunday was Super Sunday, the day when the two top football teams face one another to see who is the best. And of course, the venerable Green Bay Packers came out on top this year. But for space scientists, it was also Super Sun Day: the day when NASA scientists released the first picture of the entire sun—both halves, imaged at the same time.
It was made possible by the STEREO, or Solar TErrestrial RElations Observatory, mission. Terry Kucera is Deputy Project Scientist for the mission, and she says Sunday’s achievement was put into motion over four years ago, when a pair of STEREO spacecraft, dubbed Ahead and Behind, were launched into space.
Kucera:
And they were put into an orbit in which one is going around the sun a little faster than earth and the other is going around the sun a little slower than earth, and as a result they separate at the rate of about 45 degrees per year. So now, four years later, they’ve reached the point where they are opposite each other on either side of the sun and that means we can just about see the entire sun. And as they move further on in back of the sun relative to the earth, we’ll be able to see the whole thing for the next 8 years, when combined with observations from earth orbit.
Hirshon:
Now the sun does rotate – it takes about 27 days—so unlike the moon, we already see the entire surface of the sun each month. So why do we need to send up spacecraft to see the side facing away from us? Well, Kucera says scientists are interested in seeing transient phenomena on the sun, analogous to weather on earth.
Kucera:
Being able to see the entire sun means we will be able to see all solar activity, not just the stuff we can see from earth. If you think about only a point of view from earth, that’s like studying weather patterns on the—if you wanted to study the earth, its atmosphere is constantly changing, you could only study weather half of the day, but never at night. Now we’re able to see the entire sun, meaning we can study all the solar activity all the time and not just watch it for a couple of weeks while that side is facing us and then not know what’s going on on the other half of the sun.
Hirshon:
So it’s really solar phenomena they are interested in seeing in real time, around the entire star.
Kucera:
There are a number of different kinds of solar activity. There’s bright solar flares, which give off lots of x-rays. There are also coronal mass ejections, which are these huge magnetic structures, which actually blow out of the sun into the solar system. And those affect us here on earth, especially our technology, it can affect communications, navigations, power systems, spacecraft, so we’re interested in it from that point of view, that’s something that’s called space weather. Understanding how the sun can affect our technologies and how space changes in a way that can affect our spacecraft and things like that.
Hirshon:
She says they’re also interested in solar events that affect other planets.
Kucera:
So another really neat thing about being able to see the entire sun is because it lets us understand space weather throughout the solar system. Things that happen on the sun affect planets. Right now, the MESSENGER spacecraft is very soon going to be in orbit around Mercury. And they for instance are quite interested in what’s going on in the sun because, again, solar activity can affect spacecraft and communications. And so they were quite interested a week or two ago when there wa a coronoal mass ejection that went off and was headed off in that direction.
Hirshon:
Fortunately, there was no damage to MESSENGER. But Kucera says these events can threaten spacecraft operations. They can also be dangerous for humans working in space.
Kucera:
In general, the astronauts that we have up on the space station right now are in low earth orbit. So they are largely protected by the earth’s magnetic field. However, if they have reason to believe there is going to be substantial solar activity, they would avoid doing something like a walk outside of the station.
Hirshon:
Kucera says that in addition to tracking events like coronal mass ejections, STEREO will also allow scientists to monitor sunspots, the dark areas where the sun’s magnetic field is exceptionally strong.
Kucera:
And if you look at the sun the way STEREO looks at the sun, in ultraviolet light, then these are bright areas. And then there are a number of other features on the sun that are maybe less well known. But these various dark areas tell us things about the magnetic field of the sun. And you can see these rotate as the sun goes around. And these do change and it’s entirely possible for you to look at some part of the sun that looks blank at one time and then 27 days, 28 days later when that same part of the sun is facing you, there can suddenly be a whole bunch of new active regions right there.
Hirshon:
Now the most astute of you will probably have realized already that with the Ahead spacecraft traveling faster than the Behind spacecraft, in another four years they will be back together again. And really, it’s already difficult to tell if Ahead or Behind is Ahead. Luckily, there is a third spacecraft looking at the sun from earth orbit, called the Solar Dynamic Observatory or SDO. Kucera says that between the three spacecraft, we’ll have a full view of the solar surface for many years.
Kucera:
Now, with the STEREO spacecraft and SDO, we can basically see it all the time. We’ll be able to get images say, every ten minutes of the entire surface.
Hirshon:
If you visit the STEREO mission home page, you can see the latest images of the sun, and Kucera says over the coming weeks, they’ll be providing updated, sharper images. That’s all for now. For the 365 Days of Astronomy Podcast, I’m Bob Hirshon.
End of podcast:
365 Days of Astronomy
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