// THIS IS A DRAFT SCRIPT - MAY BE DIFFERENT FROM ON AIR SCRIPT //

Title: Saturn as a Litter Box
Written By: Aaron
Castdate: 0511??
Voices: Pamela & Travis

Pamela:	Welcome to another edition of Slacker Astronomy. Each week we bring you a recent news event from the world of astronomy. And when there is nothing new to report in astronomy we will continue searching for venture funding for our new astronomy music video channel - AMTV.
	(MTV rift)
Travis:	All MC Hawking, all the time.
	(short mc hawking clip introducing himself from track #1 which I uploaded to the library maybe :56-1:08? your call...)
Pamela:	Recently we added our back catalog of shows to our XML feed. This means you can now listen to every Slacker Astronomy show with your podcast client, except for the infamous April Fools Day show.
Travis:	While putting the shows online we took a trip down memory lane and realized we have been neglecting one of our most popular subjects in those early days.
Pamela:	Sex and drugs?
Travis:	What does that have to do with astronomy?
Pamela:	Tsk. Tsk. If you have to ask, you'll never know. 
Travis:	Today we bring some interesting news about Saturn. While not groundbreaking, the method behind the discovery is pretty clever and turns out to be pretty fundamental to astronomy as a whole. 
Pamela:	And we get to reference another one of our infamous early shows, the one about Mira and the Magic 8 ball. People either loved it or hated it.
Travis:	Or you loved to hate it, but I don't think anyone hated to love it.
Pamela:	Well for this episode, we hope you simply love to love it.
Travis:	Just remember it's okay to love us, just don't LOOOVVVEE us, to quote a bad 90's movie.
Pamela:	We wouldn't be slacker astronomy if we quoted a GOOD 90's movie. 
Travis:	Speaking of good movies, did you know 2001 was originally meant to take place at Saturn instead of Jupiter? Kubrick was worried the special effects of the time couldn't do justice to Saturn, so he moved the story to Jupiter instead.
Pamela:	What makes Saturn so beautiful, and hard to render in 1960's F-X technology, are its rings. They were among the many things discovered by Galileo when he first turned the telescope to the night sky. 
Travis:	There is a dark division in the rings called the Cassini division, after Giovannna Cassini, who discovered it in 1675 while at the Royal Observatory in Paris. It can be seen with a very large amateur telescope and good stable seeing conditions. 
Pamela:	Astronomers, once again the masters of creativity, have come up with names for different sections of the rings. The inside of the Cassini division is called the B ring, the outside division? Wait for it.. (game show host voice) yup, it's the A ring. The A ring. Circle gets the square.
Travis:	So the Cassini division separates ring A from ring B. The ring system is divided into lots of smaller rings with similar names. But the largest are those A and B rings. 
Pamela:	Recently astronomers discovered thin parallel spokes in the rings, most notably on the A ring. They resemble cat scratches. These thin, parallel stripes are just 100 meters wide, roughly the length of a football field. They are so small that they cannot be directly seen by any instrument currently in existence.
Travis:	How they were detected is pretty clever. The Cassini spacecraft is currently orbiting Saturn. From a distance of a whopping 1.6 million kilometers, it took some pictures which detected the 100 meter wide stripes. 
Pamela:	Astronomers Phil Nicholson and Matt Hedman at Cornell University realized ahead of time that, when viewed from Cassini, Saturn's rings were going to eclipse a bright star named Omicron Ceti, also know as Mira the Wonderful.
Travis:	Mira is a bright star which can be seen with the naked eye in the constellation Cetus, the whale. In the show notes at slackerastronomy.org we link to an earlier show we did on Mira.
Pamela:	Not only were the rings going to eclipse Mira, but they were going to do it at a really shallow angle of 3.5 degrees, making it almost an edge-on eclipse.
Travis:	When an astronomical body moves in front of a star it is often called an occultation.  Amateur astronomers have been measuring occultations and using some basic geometry to map mountain ranges on the Moon.
Pamela:	Sometimes a background star will just barely graze the surface of the Moon. When it does, if the Moon has some high mountains on that edge, then the peaks of the mountains may block the starlight from reaching Earth.
Travis:	So the star blinks in and out as it passes behind the mountain range. If the blinking is carefully timed by many observers across the Earth, astronomers can make maps of the mountains more accurate than any of our current maps made from spacecraft orbiting the Moon.
Pamela:	Occultation was used recently to detect parts of Pluto's atmosphere. We have a link to that story too in our show notes. It is a technique used often in solar system astronomy to map other bodies.
Travis:	Nicholson and Hedman applied the technique to Saturn's rings and the star Mira. Except, of course, they made it much more complicated. Instead of looking at the entire light of the star, they monitored the infrared *spectra* of the star. 
Pamela:	This allowed them to look for very subtle changes in the star's light as the rings passed in front of it. During a three hour observation window, Cassini took 100,000 spectra observations of Mira while it was passing behind the rings. And it did this four times between May and August of 2005.
Travis:	That is an awful lot of spectra. Many astronomers dislike working with spectra. It is a very time consuming process sensitive to tiny details in the processing of the images. So a small error can lead to a large change in the result. So our slacker hats off to them for processing almost half a million spectra images of Mira. That alone is worthy of our respect.
Pamela:	Don't get us wrong, we love spectra. It provides a wealth of information. Having reduced spectra before, we are just in awe with the amount of work that must have gone into this.
Travis:	As Mira moved behind the rings, its angle changed. When the angle was shallow, more light was allowed in. When it became larger, less light was allowed in until the star was almost completely occulted.
Pamela:	This is how your window blinds work at home. When you open them, you orient the panels to be parallel with the sky. 
Travis:	And when you close them, you make the panels perpendicular and they block out most of the outside light. When you are spying on neighbors, you make them perpendicular and then force a tiny hole open with your hands!
Pamela:	It would take big hands to force a hole into Saturn's rings. 
Travis:	I know who can do it.
Pamela:	Oh no you don't...
Travis:	I do!
Pamela:	No... you don't! 
Travis:	The almighty...
Pamela:	I won't allow you to bring him up again.
Travis:	Flying spaghetti monster!
Pamela:	This is a spaghetti monster free show!
Travis:	Too late!
(Doh! sample)
Pamela:	If you bring him up one more time...
Travis:	Her.
	(pause - suddenly interested) 
Pamela: It's a her? 
Travis: Indeed, she is a her. 
Pamela: Hmm. I quite like the sound of that. Tell me more after the show. 
Travis: I will always be happy to talk about her-pasta'ness. 
Pamela: Okay, so by mapping these changes in Mira's light, the astronomers were able to visualize the cat scratch markings on the rings. Pictures are in the show notes on our web site. 
Travis: They believe these rings are caused by the conflict between Saturn's tidal forces and the gravitational attraction of the ring particles themselves. The astronomers refer to the lines as gravitational wakes. 
Pamela: The wakes have been theorized since the 1970's and other astronomers claim to have independent evidence for their existence in separate data. We'll keep an eye on the journals to see if and when the other evidence is published. 
Travis: These wakes will play a role in astronomers' understanding of Saturn's ring system and how the particles interact with each other, which is a complex process not well understood.  
Pamela: The particles in the rings are very small. Most of them are similar to grains of sand and ice, although larger pieces exist as well. So many particles make simulations complicated. 
Travis: This discovery also helps to narrow down the thickness of the rings, now estimated at only 10 meters. Remember from now on when you see those beautiful pictures of Saturn, that those rings are only 10 meters deep and consist mainly of dust and ice grains.  
Pamela: They also performed one observation of the star Antares. This was at a much higher angle of 32 degrees so 50% of the star's light was blocked. This allowed for fine mapping of some portions of the A ring. 
Travis: So in summary, these two astronomers had to predict what the field of view would be of the Cassini spacecraft, when a bright star would be in the background, schedule the instruments, reduce almost half a million observations and then take the results and come up with a model explaining them which just happens to be accurate enough to measure the thickness of Saturn's rings to an accuracy of meters.
Pamela: All while in their cushy chairs at Cornell in beautiful upstate New York and over a billion kilometers away from their instrument. Not a bad day's work. 
Travis: We award them the slacker astronomy seal of approval, an image of an astronomer asleep at the telescope. 
Pamela: I thought it was that of an astronomer proudly holding up a physics report card with all C's. 
Travis: Let's ask our listeners. If any designers out there want to design a small slacker astronomy seal of approval, send it to info@slackerastronomy.org and we'll post it on the site. Who knows maybe we'll use it for something! 
Pamela: As always, more info is available in the show notes on our web site. You can also post comments and questions there too. Visit us at slackerastronomy.org. 
Travis: For Pamela and our author Aaron, I'm Travis.  
Pamela: You've been listening to Slacker Astronomy, a podcast for you, for fun, for the voices in our heads.