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- 1. Citizen Science with epsilon Aurigae Brought to you by the AAVSO, the 2009 InternaFonal Year of Astronomy, the NaFonal Science FoundaFon and Your Universe Astronomers need your help! A very bright star in the sky changes in brightness every 27 years and no one knows why! The star is too bright for professionals to look at with most large telescopes. So, we need your help to watch this star as it dims and brightens over the next several years. This guide will help you find this bright star, Ci#zenSky is a known as epsilon Aurigae (Eps Aur), measure its collaboraFon of the American AssociaFon of brightness and then submit the measurement to Variable Star Observers assist professional astronomers (AAVSO), the University of Denver, the Adler Planetarium, the Johns Hopkins University and the ParFcipate in one of the largest ciFzen science California Academies of Science with support from projects in history! Thousands of people just like the NaFonal Science you will also be helping out. Astronomers need FoundaFon. large numbers of people to get the amount of precision they need to do their research. You are the key. Header artwork is reproduced with permission from Sky & Telescope magazine (www.skyandtelescope.com)
- 2. What is epsilon Aurigae? Epsilon Aurigae is an enigma. It looks like a single, bright star from Earth. However, it consists of at least two stars (and possibly more) in the same solar system. Unlike our relaFvely stable and clean solar system, this one is very complex and dusty. Every 27 years, epsilon Aurigae is eclipsed by a very large object. Astronomers don't know what the star's colossal partner is, but one leading theory suggests it's a gas cloud more than a thousand Fmes as wide as the sun that harbors two small stars at its core. AlternaFvely, the object at the center of the cloud may be a black hole or a single larger star that has somehow siphoned gas from epsilon Aurigae to create an enveloping cloak of darkness. Each eclipse lasts nearly two years, by far the longest in any known binary star system. The next eclipse begins in August, 2009 and is expected to last unFl May, 2011. Astronomers need your help to monitor this eclipse. The star is too bright for telescopes. If astronomers can get thousands of reports from people monitoring the star, they can use staFsFcal techniques to analyze the star’s behavior with high precision. * Top Illustration by Citizen Sky participant Nico Comargo This is a light curve. It shows how Epsilon Aurigae’s brightness changes over Fme. Each of these data points is a single brightness esFmate of the star made by an amateur astronomer
- 3. Using a Star Chart It’s easier than it looks! A star chart is just a map of the sky. You use it to match a pa^ern of stars in the sky with a pa^ern of stars on the chart, just like you’d match a pa^ern of streets with those on a street atlas. 1. First, find the constellaFon that the variable star is in. 2. On the next page is a map of constellaFons in the northern sky. 3. Face North and rotate the chart so the current season is at the bo^om. 4. Hold the map up against the sky and look for the constellaFons. 5. For epsilon Aurigae: We suggest starFng with Cassiopeia, which is usually easy to find because it looks like a “W” hanging in the sky. 6. Once you have found that, look for Capella. It is a very bright star near it but lower in the sky. Once you have Capella, you have found Aurigae! 7. Go to page 5 to learn how to make your observaFon. N This is a photograph of an This is the same area of the sky around photograph, with Aurigae Aurigae outlined in yellow
- 4. Capella This sky chart is reprinted with permission from Sky & Telescope magazine. Visit www.skyandtelescope.com to customize the chart for your locaFon and Fme. Purchase a copy of the magazine at your local newsstand for an easy-‐to-‐use, fold-‐out sky chart in each issue. Reprinted by CitizenSky.org with permission from Todd Salat.
- 5. Using a Variable Star Chart This is also known as “star hopping”. You found the constellaFon, now find the variable star. This star chart is a li^le different from the last one. It is “zoomed in” on the constellaFon Aurigae. It also has some informaFon you’ll need to make a brightness esFmate of a star. 1.Find the stars in the constellaFon that look like the ones on the chart. Be paFent, the first Fme you do this it may take a long Fme. It will be much easier ajer the first Fme. By the forth or fijh observaFon, you won’t even need the chart! 2. Find the variable star by locaFng the star at the cross hairs on the chart. 3. Next, find the comparison stars – the stars with numbers on them. 4. That’s it! Now turn to the next page to make an esFmate of the variable star’s brightness. The variable star Comparison stars Brighter stars in the sky will have bigger Other stars in the sky dots on the chart, like this one
- 6. Measuring a Star’s Brightness a.k.a. making an “observa?on” To measure a star’s brightness, you simply compare it to other stars in the sky. Those other stars are called “comparison stars” because you use them to make the comparison. Astronomers have carefully measured the brightness of the stars and assigned them a number according to the brightness. The smaller the number, the brighter the star. In this example, Betelgeuse will In this example, Betelgeuse will be close to the same brightness as be close to the same brightness Rigel, which has a 01 brightness. as the star labeled 21. So one So one may esFmate Betelgeuse may esFmate it at brightness at brightness 01. 21. In this example, Betelgeuse is somewhere in the middle between the 01 and the 21 comparison stars. So one may esFmate it somewhere in between the two numbers, say, brightness 11.
- 7. ReporFng Your ObservaFons Once you have made an esFmate, write it down in a journal. Record the day, the Fme and the brightness esFmate. Don’t try to memorize and recall it later. This is scienFfic data so we need it to be as accurate as possible. There are two ways to report your data to professional astronomers: via postal mail or the Internet. • Internet: We highly recommend submiong your observaFons via the Internet. By doing so, your observaFons get sent to astronomers very quickly. Also, you can compare your observaFons to other observers immediately ajer you have submi^ed them. To submit online. 1. Go to hLp://www.ci#zensky.org/submitdata It will take about 10 minutes to submit your data for the first Fme. Once your data is submi^ed, the web site will show you other data submi^ed by other observers, with your data highlighted. This way you can see how you compare with others and with any other data you had previously turned in. Ajer that it should take no more than five minutes to submit your data. • Postal Mail: If you prefer to submit your esFmates via postal mail, fill out the form at the bo^om of this page and mail it to the AAVSO. If you would like more forms, just ask and we will mail you new copies. Your Full Name: ______________________________________________________________ Your Address (if you want confirmaFon): __________________________________________ E-‐Mail Address (opFonal): ______________________________________________________ Sample Observa#on Name of Star: Alpha Ori Date & Time of ObservaFon: January 1, 2009 9:15pm EsFmated Brightness: 22 Comparison Stars Used: 20, 25 Observa#on #1 Name of Star: Date & Time of ObservaFon: EsFmated Brightness: Comparison Stars Used: Observa#on #2 Name of Star: Date & Time of ObservaFon: EsFmated Brightness: Comparison Stars Used: Observa#on #3 Name of Star: Date & Time of ObservaFon: EsFmated Brightness: Comparison Stars Used: Observa#on #4 Name of Star: Date & Time of ObservaFon: EsFmated Brightness: Comparison Stars Used: Observa#on #5 Name of Star: Date & Time of ObservaFon: EsFmated Brightness: Comparison Stars Used: You can mail this report at any Fme. All five observaFons do not need to be filled out. Please mail this report to: AAVSO 49 Bay State Road Cambridge MA 02138.
- 8. Ten Star Training Program Observing a variable star takes pracFce. We have designed a training program that begins with stars that are easy to find and observe. Slowly the stars become more challenging as you go down the list. By the Fme you reach Epsilon Aurigae at the bo^om of the list, you’ll be an expert variable star observer contribuFng real data to professional scienFsts! Begin by observing the stars at the top of the list and then move your way down. Charts for finding these stars are available at the back of this packet. Some of these stars can only be seen during certain seasons of the year. If a star is currently “out of season” for you, just skip it and come back to it later when the Fme is right. Star Name Season Notes 1 alpha Orionis Fall, Winter a.k.a. Betelgeuse, a red star in the “armpit” of Orion 2 eta Geminorum Fall, Winter Cassiopeia is an easy constellaFon to find -‐ it looks 3 gamma Cassiopeia All Year like a giant “W” wri^en on the sky. This star has an enFre eclipse in one night! See 4 beta Persei Winter chart for more info. Very easy to find in the summer – it’s next to the 5 beta Lyrae Summer bright star straight overhead! 6 R Lyrae Summer Note the spelling of “miu”. This is intenFonal-‐ to 7 miu Cephei All Year replace the greek character “mu”. 8 delta Cephei All Year 9 eta Aquilae Summer Winter, 10 epsilon Aurigae Our VIP star! Spring Note: The seasons listed are when the star’s constellaFons are easily seen in the evening northern hemisphere sky. If you stay out later, or get up very early, then the next season’s constellaFons are viewable. For example, ajer midnight in the spring you can see many of the summer constellaFons.
- 9. Last Steps Keep observing! Please make an observaFon of these stars at least once per month and submit your data as soon as you can. This project will conFnue unFl 2012. Please conFnue to make observaFons unFl then. Get a Cer?ficate! When you have made and submi^ed ten observaFons to the AAVSO, a cerFficate will be mailed to you cerFfying your contribuFon to real science. Itching for a Bigger Challenge? The AAVSO has many ciFzen science projects that range the gamut from introductory to advanced. ParFcipants in the more advanced projects can even get their names published in professional journals. Our projects don’t always involve making observaFons. Some involve programming, educaFon & public outreach, data mining, data analysis and more. Contact us if you would like more informaFon on these projects. For More Informa?on… Visit www.ciFzensky.org for more informaFon on variable stars and how you can contribute to more ciFzen science projects. We also have a complete manual and curriculum about variable stars called Variable Star Astronomy (VSA). It is available at: h^p://www.aavso.org/educaFon/vsa/ Illustration by Citizen Sky participant Brian Thieme
- 10. Star Chart for alpha Orionis and eta Geminorum Notes: Alpha Orionis (Betelgeuse) is very easy to find. Orion’s belt consists of three very bright stars that can be seen from almost any city. Once you find the belt, the rest of the constellaFon is easy to recognize. Alpha Orionis is a very red star, but someFmes it is hard to see the color from city locaFons. It is also a very large star. If it was placed in the center of our solar system, it would engulf all planets out to Jupiter – including Earth! Alpha Orionis varies in brightness from 05 to 15 on our brightness scale over a course of a few weeks. At first it can be hard to noFce the change, be paFent and you’ll see it.
- 11. Star Chart for gamma Cassiopeia and beta Persei Notes: Beta Persei (Algol – the Demon Star) is an interesFng star. Around every 3 days it goes into an eclipse that lasts around 8 hours. This means if you can someFmes see the star get dim and then bright again in a single evening! It happens very quickly, so for this star we recommend making one observaFon every 30 minutes. Ajer only a few observaFons, you’ll see it noFceably dimmer than when you started. Here are some upcoming dates and midpoint Fmes (EDT) for 2009 eclipses: Nov. 10-‐11 at midnight; Nov. 13-‐14 at 8:30pm, Dec. 3-‐4 at 10:30pm, Dec. 6-‐7 at 7pm, Dec. 23-‐24 at midnight. Start observing about 4 hours before midpoint. More predic?ons are at h^p://www.aavso.org/observing/programs/eclipser/ebephem.shtml
- 12. Star Chart for beta Lyrae and R Lyrae Notes: Lyrae is a very easy constellaFon to recognize in the summer. Vega is the brightest star in the summer sky and is usually near the top of the sky in the early to mid evening hours. The constellaFon looks somewhat like an hourglass and is relaFvely small compared to most of the other constellaFons in these charts. Beta Lyrae usually varies from 34 to 44 on our brightness scale. It takes about 13 days to see a complete cycle.
- 13. Star Chart for miu Cephei and delta Cephei Miu Cep Notes: On our brightness scale, Delta Cephei changes from a 33 to a 45 and back again over the course of a li^le over 5 days. Observe this star every night for a week and you can watch a complete cycle. A star of 33 brightness can be seen from most urban locaFons. However, a 45 star may be a challenge due to light polluFon washing it out. Therefore, if you are living in an area with bright nighome skies it may look like Delta Cep disappears when it dims down to 45 and then it may seem to reappear when the star returns to 33!
- 14. Star Chart for eta Aquilae Notes: Eta Aquilae is similar to Delta Cephei. It varies in brightness from 35 to 44 over the course of about a week.
- 15. Star Chart for epsilon Aurigae