365daysDate: July 7, 2009

Title: The Mysterious Epsilon Aurigae


Podcaster: Mike Simonsen of AAVSO

Organization: AAVSO

Description: In this episode Mike interviews Rebecca Turner from the AAVSO to find out all about the strange star Epsilon Aurigae and the AAVSO’s Citizen Sky project to study it. This will be the largest citizen science research project in history, and the goal is to understand one of the most enigmatic stars in the sky.

Bio: The AAVSO is an international non-profit organization whose mission is: to observe and analyze variable stars; to collect and archive observations for worldwide access; to forge strong collaborations between amateur and professional astronomers; and to promote scientific research and education using variable star data.

Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by the American Astronomical Society, the major organization for professional astronomers in North America, whose members remind everyone that One Sky Connects Us All. Find out more or join the AAS at


Hi and welcome to the Restless Universe, the podcast of the American Association of Variable Star Observers. You can visit us on the web at

Mike: I’m Mike Simonsen, and today I’ll be talking with Rebecca Turner. Rebecca is the coordinator of the AAVSO’s special project for the International Year of Astronomy 2009. This project revolves around the mysterious and strange star, Epsilon Aurigae. Hi Rebecca!

Rebecca: Hi Mike, thanks for having me! We are very excited about our new citizen science project called “Citizen Sky”. I hope that everyone will take some time to check out our website at We are excited to see what we can learn about this very interesting star.

Mike: Epsilon Aurigae is a variable star, an eclipsing binary. But there are thousands of eclipsing binaries. What are some of the things that are so unusual about Epsilon Aurigae?

Rebecca: – Well, its very bright object – bright enough to be seen with the unaided eye in even the largest, light polluted cities
– It has a very long period, it only eclipses every 27.1 years. It’s due for an eclipse this summer so that means the last time Epsilon Aur had an eclipse we were all rockin’ big hair and sporting shoulder pads in all of our clothes
– Based on the shape of the light curve and the spectra that have been taken of the system, astronomers can’t figure out what exactly is eclipsing the primary F star
– Another strange feature of the light curve is that there is a slight brightening in the middle of the eclipse

Mike: So, every 27 years Epsilon Aurigae is eclipsed by a very large object, but astronomers still don’t know for sure what that object is. What are some of the leading theories?

Rebecca: The leading theory is that the secondary is surrounded by a large opaque disk, which would explain why light from the secondary doesn’t seem to be showing up in spectra. The disk seems to have a hole in the center, which would account for the mid-eclipse brightening. Current thinking is that perhaps the center of the disk is home to 2 less luminous, tightly orbiting stars. This tight orbit could create what astronomers are calling a gravitational eggbeater effect – creating that hole in the disk. Theories of a large planet falling into the stars at the center of the disk have also been introduced.

Mike: When does the next eclipse begin, and how long does the eclipse last?

Rebecca: That is a very good question. Eclipse is predicted to begin in August. Some properties of the eclipse have been changing over time. The overall duration of the eclipse, which has ranged from 730 days down to 640 days over the years, seems to be getting shorter and shorter. Also, the fading and brightening at the beginning and end of the eclipse are getting faster, so that even thought the whole eclipse is shorter the time at minimum is actually getting longer. The mid-eclipse brightening we mentioned earlier also seems to be getting brighter. So things are changing in this system on a time scale of decades!

Mike: Because this star is so bright it makes it hard for some professional observatories to study it. So the AAVSO is recruiting Citizen Scientists to help study the next eclipse. What exactly are citizen scientists?

Rebecca: Citizen Scientists are volunteers, many of whom have no prior scientific training, who work with trained scientific researchers to answer real-world science questions.

Mike: Just to be clear, it’s not just amateurs with fancy telescopes and CCDs or photoelectric photometers that are needed for this experiment. People with just their eyes or a pair of binoculars can contribute to understanding this weird star by observing Epsilon Aurigae over the next two years and reporting their observations to AAVSO, right?

Rebecca: Yes, anyone can participate regardless of background, training, or equipment: with just good pair of eyes and a finder chart (which we will give you,) you can monitor this eclipse.

Mike: Is there training available? How will people learn how to make variable star estimates?

Rebecca: Yes, there is definitely training available. Right now, you can visit the citizen sky web site at and download the 10 star training tutorial. This tutorial will guide you through the process of collecting data on variable stars. By the time you complete the tutorial you will be an experienced variable star observer contributing real data to professional scientists!

Mike: How do they report their observations? Is this all online in a website or something?

Rebecca: In the coming weeks we will roll out the data section of the citizen sky website which will allow observers to easily submit their data online, view their data alongside all of the other participants’ data, and even download variable star data for further study.

Mike: Do you have to be an AAVSO member to participate in Citizen Sky?

Rebecca: Absolutely not, this project is open to everyone. You don’t have to be a member of any astronomy club or organization – or even have any prior experience with astronomy to be involved. We really do welcome anyone who is interested.

Mike: There is going to be a workshop held in August at the Adler Planetarium in Chicago. How can people participate in that? Is there grant money for people to cover travel expenses?

Rebecca: Yes, we are having a workshop Aug 4-7 in Chicago. This workshop will be focused on observing Epsilon Aurigae and on education and public outreach. We expect to have small travel grants available to workshop participants and the application is available on the Citizen Sky website right now. Space is limited, but as we’re talking right now there are slots still available so we encourage those who are interested to visit the web site and apply.

Mike: What if they just can’t go. Will that workshop be recorded or available on YouTube or something?

Rebecca: Yes, after each workshop, video of all of the workshop presentations will be posted on the Citizen Sky website, so even if you can’t attend you can benefit from these talks. DVDs will also be made available for local clubs to use in outreach activities.

Mike: What happens after the data is collected?

Rebecca: In scientific research data collection is followed by: analyzing data, creating and testing your own hypotheses, collaborating with others on theories, or writing papers for publication.

Mike: There is going to be a workshop on that topic as well, right?

Rebecca: Yes, we will be holding a second workshop in the spring of 2010 at the California Academy of Sciences focused on data analysis and scientific paper writing. Updates on plans for that workshop will be posted on the cit sky website.

Mike: What are the science goals of the experiment? What do we hope to learn this time around?

Rebecca: There is so much to learn about this star. We are hoping that during this eclipse we can answer questions like:

  • What is the mass of the system?
  • What are the evolutionary states of the stars?
  • What exactly is at the centre of the disk?
    What is the geometry of the system?
  • Will the shape of the light curve continue to change as it has over the years and what can this tell us about physical changes going on in the system?

Mike: What are the education and outreach goals of the project?

Rebecca: We hope to get a whole new group of people interested in astronomy in general and science as a whole. We hope to help participants experience the value of teamwork – through scientific collaboration in our case. We are also placing a strong emphasis on participation in the full scientific method, not just data collection. We will guide participants through all of the steps from collection, to analysis, to publication in a special addition of the peer-reviewed journal of the AAVSO.

Mike: This is really set up to be the biggest citizen science project of all time. Who are some of the other organizations and people that are helping to make this a success?

Rebecca: AAVSO is spearheading and organizing the project. Adler Planetarium and California academy of sciences; each hosting workshops, creating visualizations and a planetarium show trailer for the project. Staff helping with web site development from Johns Hopkins University. And our lead astronomer and resident Eps Aur expert is from The University of Denver.

Mike: And as we record this, we’re assuming we got a giant grant from the national Science Foundation to pay for all this.

Rebecca: Exactly, we have received informal word that we have been fully funded and we are just waiting for the official stamped, signed letter to arrive in our mailbox, which w expect at any moment.

Mike: That’s good, because otherwise next month we’ll be crying about “We didn’t get the money and now our plans have all been changed.”

Rebecca: Yes, we’ll be singing the blues next month.

End of podcast:

365 Days of Astronomy
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