Sometimes Too Much Light Can Be A Bad Thing (sad funeral music in background fades out instead of the regular theme) Pamela: Welcome to Slacker Astronomy; a podcast about astronomy and just about anything else that floats over our heads. Travis: Each week we bring you a recent news event from the world of astronomy. But, this week we almost brought you nothing. Why? Because we were in mourning. Pamela: That's right, we were sad over the loss of Aaron. Rebecca: What!? Travis: Aaron will be missed! He brought humor, grace, and a certain note of drama to entertainment. Rebecca: No way. I just got here! Pamela: Aaron passed away on June 23, 2006. Rebecca: But... I just saw him. Pamela: At the ripe old age of 83. Rebecca: Damn did he look good for 83. Travis: Plastic surgery, Rebecca. Rebecca: He doesn't seem the type... (questioning) Travis: Everyone's doing it these days. Rebecca: Have you? Travis (offended): Of course not! How could you suggest that I would even need... Pamela: Let's not spoil this day with bickering. It should be a day of joy. A day to remember all of the wonderful episodes Aaron brought us. Travis: Hmmm. My favorite was when Gopher and Isaac got drunk and did donuts with the loveboat. Rebecca: Boy I think I missed some wild times around here... Pamela: I think I liked the one where Farah Fawcet and Kate Jackson locked Jaclyn Smith in the bathroom and forced her to listen to Don Pamela: What was your favorite show by Aaron? Rebecca: Ummmm. It must be the one I was in. Travis and Pamela (unison): You were in an Aaron Spelling TV show?!?!!? Travis: We new you were a professional actor, but we had no idea. Pamela: What's he like? Did you get his autograph? Rebecca (whistles): Hold on! You're talking about Aaron SPELLING, the TV producer - not Aaron PRICE, of Slacker Astronomy? Pamela: Of course! Aaron's just fine. He's in the other room playing with his blocks. Rebecca: Aye, aye, aye. Let's just get on with the show. Travis: The star of today's show is magnetic. Pamela: More precisely, a magnetic cataclysmic variable star, often referred to as polars. Travis: Which means they have wild mood swings? Pamela: Exactly. Polars are wildly variable and completely unpredictable. Their brightness in the sky can change on the order of minutes, days, weeks, months and years. But most of the time their activity can be put into one of two categories, the high state and the low state. Travis: High state meaning it is bright with lots of activity and low state meaning it is relatively dim and quiet. Pamela: EF Eridanus, or EF Eri for short, has been monitored by astronomers since its discovery in 1978. Most of that time it has been in a high state. In 1995, it entered a low state and has remained there ever since. This is by far the longest low state on record for this star, and astronomers couldn't be happier. Travis: Cataclysmic variable star systems are made of two stars -- a white dwarf and another, usually less massive donor star Pamela: And it gets even better. In March 2006, EF Eri finally returned to its active state after its 9 year slumber. So astronomers can no longer see the white dwarf, and observations of the secondary will be very difficult. However, they can now test this new theory by following the activity of emission lines in the secondary and the accretion stream. Travis: It is also interesting to note that in the Acknowledgements section of the paper, the astronomers thank an australian amateur astronomer, Rod Stubbings, for tirelessly monitoring this star on their behalf over the time of the quiet period. Rod Stubbings has over 100,000 thousand observations of variable stars recorded and submitted to official organizations. All of them were done visually, without a photographic camera or CCD. Aaron: I've had the fortune of meeting Rod once and he is one of the nicest, most unassuming persons I've ever met in astronomy. Kudos to Rod! Or better yet, Good on ya, Rod. Travis: And its a good reminder of things amateurs can do to help the pros. Pamela: As always, more info on this discovery is available in the show notes on our web site and a picture is in the album art. You can also post comments and questions there too. Visit us at slackerastronomy.org. Travis: For Pamela, Rebecca, and our author Aaron, I'm Travis. β Pamela: You've been listening to Slacker Astronomy, a podcast for you, for fun, for the voices in our heads. € “ that orbit each other. Pamela: The donor star gets its name from its bad habit of feeding the white dwarf gas from its atmosphere. Travis: The white dwarf uses its gravity to tear this material off the donor. As material leaves the donor star, it forms an accretion disc around the white dwarf. Pamela: Accretion! Accretion! Accretion! All we ever talk about on this show is accretion! Travis: It's a vital phenomenon on astronomy. Pamela: Do we have to explain it *every* time? Travis: What about our new listeners? Pamela: NEW listeners? Hahahahaa! Good one.. I need a tissue. Travis: We need to come up with a FAQ, and put accretion disks in it. Then instead of explaining it every time, we can just say: SEE FAQ #17. Pamela: Better yet, let's just have fun with it. Let's make it our word of the day and just keep sending people back to this episode. Travis: You got it. So this ACCRETION DISK (celebration!) glows brightly. In fact, it drowns out the light from the white dwarf, making it hard for astronomers to see it. Pamela: Polars, though, have no accretion disk (celebration!) because their intense magnetic fields steal the material that normally goes into the accretion disk (celebration!) and directs it to the poles of the star, where the material impacts the surface at tremendous speed, releasing huge amounts of energy at high energy wavelengths - including optical. Travis: Normally this activity also masks the white dwarf, just like the accretion disk (celebration!) would if it existed,. However, when a polar goes into a low state - with little or no material striking the surface, there is little or no extra light from either an accretion disk (celebration!) or from material striking the surface. Pamela: In this low state, astronomers can see down onto the white dwarf because there is no glare to get in the way. Travis: One particular polar, EF Eri, has been in this low state for about 9 years. In the beginning, the spectra of the star showed no emission lines. This is expected, since lines normally appear from an accretion disc or from the material impacting the surface of the white dwarf - both of which are missing in this low state. Pamela: These low states are technically called quiescence, which is just a really cool nerd word. A few years after EF Eri entered quiescence, some of the emission lines came back, but the lines weren β € ™t coming from the normal sources. Instead, they were coming from the secondary star. This gives astronomers yet another unique opportunity. Not only can astronomers see the white dwarf, but now they can directly detect the secondary star as well. Travis: Astronomers have seen this before with cataclysmic variables, but rarely - and the observations usually require extremely large telescopes and hordes of grad students and postdocs to do the dirty work. With EF Eri no giant telescopes are required. Pamela: So now, astronomers have two new easy to observe tools to answer a big question about polars: why do they go into these low states? Is there some astrophysics or geometry we don't understand? Is there a problem with our models of the stars? Did one of the stars say something mean to the other? Travis: Past theories have focused on the secondary star, which is the star that donates material to the white dwarf. Astronomers have wondered if the secondary star could undergo solar type cycles. By that, they mean cycles like our own Sun's 11 year cycle of activity. Pamela: Every 11 years the sun goes from being active, to relatively quiet, to active again. The difference appears dramatically in the amount of flaring, prominences and sunspots we see on the Sun. In a quiet state, the Sun may have no sunspots at all. In an active state, it may have more spots than a teenager who washes his face in bacon grease. Travis: Ewwwwww! Pamela: In theory, such a cycle could cause a low state in a polar system by lowering the amount of material ejected from the donor star that can be captured by the white dwarf. Travis: It could also, theoretically, cause a low state when a star spot, similar to our Sun β € ™s spots, moves into the stream of material from the donor to the white dwarf. Star spots are cooler regions on the surface of the star, so this could diminish the material streaming to the white dwarf. Or cut it off entirely. Pamela: A collaboration of astronomers from a bunch of institutions in the United States have studied the new spectra of EF Eri and determined that it is none of these theories are right. The primary author of the group's paper is Dr. Steve Howell of the National Optical Astronomy Observatories. We have an interview with Steve from last Winter on the SA Extra feed. Travis: They conclude that the tremendous magnetic field of the white dwarf is reaching out, across space, and dipping into the surface of the secondary star. They got this idea by looking at extrasolar planet research, where it has been reported that in a few hot Jupiter type planets show variation in certain emission lines that match the variation of the same lines in their parent star. Pamela: They also note that in another type of magnetic white dwarf, named AM Herculis, the active side of the secondary star always faces the white dwarf in the system. Travis: Slacker Astronomy likes these kinds of discoveries because they reflect out-of-the-box thinking. Astronomers took discoveries from very different fields and applied them to come up with a theory to address an unsolved problem. Pamela: And it gets even better. In March 2006, EF Eri finally returned to its active state after its 9-year slumber. So, astronomers can no longer see the white dwarf, and observations of the secondary will be very difficult. However, they can now test this new theory by following the activity of emission lines in the donor star and the accretion stream. Travis: It is also interesting to note that in the Acknowledgements section of the paper, the astronomers thank an Australian amateur astronomer, Rod Stubbings, for tirelessly monitoring this star on their behalf during quiescence. Rod Stubbings has over 100,000 thousand observations of variable stars recorded and submitted to official organizations. He made all this observations by eye, without any aid from a photographic camera or CCD. Aaron: I've had the fortune of meeting Rod once and he is one of the nicest, most unassuming persons I've ever met in astronomy. Kudos to Rod! Or better yet, Good on ya, Rod. Travis: Wow β € “ Aaron can talk as well as play with crayons and blocks! Pamela: And he can talk to us and to amateur astronomers! Talking to amateurs is an important thing for all astronomers to do - Rod is an excellent example of the scientifically powerful things amateurs can do to help the pros. Travis: As always, more info on this discovery is available in the show notes on our web site and a picture is in the album art. You can also post comments and questions there too. Visit us at slackerastronomy.org. (Fade in theme from the Love Boat or other Spelling show if findable) Pamela: And that brings another episode to a close. Sadly, Aaron wasn β € ™t here to direct and produce, so there are no podcasting Emmy β € ™s in our future. Travis: But hey, at least we can say we β € ™re the best sleep aid on the market! Sweet dreams sweet listeners β € “ May you not be driving and dozing. For Pamela, Rebecca, 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.