June's Featured Variable: Finder Chart Y Canum Venaticorum in Canes for Y Canum Venaticorum Venatici the Hunting Dogs It is easy to estimate the brightness I bet you have seen a star twinkling —the air (magnitude) of a star, but first note: surrounding Earth makes it look like the star • in finder charts like below, brighter is sparkling! Even if we went to outer space, are indicated by larger dots we could see many stars change brightness. • the brighter the star, the lower the magnitude number “Variable stars" continuously dim, brighten, magnitudes are written to the nearest and dim. Some complete this pattern in • tenth—but without a decimal point, under a second, while others take . to enable anyone, anywhere, to which could be confused as a star. So, 42 = magnitude 4.2 participate in scientific discovery One YOU can see this month is Y through variable star astronomy Canum Venaticorum in the • in this chart, magnitudes for comparison , "The Hunting Dogs." stars—nearby stars to compare a given star's brightness to—are noted American Association of Variable Star Observers 49 Bay State Road, Cambridge, MA 02138, USA Y Canum Venaticorum, formally nick-named Find two comparison stars close to your given Telephone: +1 (617) 354-0484 "La Superba," is located about a third of the variable star's brightness—one brighter and www.aavso.org | [email protected] way from Chara (Beta Canum Venaticorum) one dimmer. Then observe in the night sky: is toward the famous pair Alcor and Mizar in the variable's brightness half-way between the handle of the Big Dipper. the two comparisons'? A quarter? Really close? Apply that fraction to the difference In dark skies, La Superba is just barely visible between the two magnitudes and you to the naked eye, but its red color makes it estimated the star's brightness for that time! obvious in binoculars. La Superba is one of This comparison and finder chart for Y Canum the reddest stars known. It is a semi-regular Venaticorum (YCVn) will help you estimate its variable star whose brightness drops by 75% brightness. over a period of every 157 days. The icon indicates the location of Y CVn. It is the brightest of the giant red stars —stars that have a fairly high concentration of carbon in their atmosphere. It is such a large star that if it replaced the Sun, its outer atmosphere would extend beyond . Time Magnitude ______AAVSO can help YOU About the AAVSO Connect with the AAVSO become a citizen astronomer!

The American Association of Variable Star Who are AAVSO Members? Discover the benefits of membership and Observers (AAVSO) is an international join us! nonprofit organization of citizen and A citizen scientist—contributes to science professional astronomers interested in stars by acquiring data on variable objects and https://www.aavso.org/join-aavso#benefits that change in brightness—variable stars. submitting them to our databases, or other activities, such as data mining. Benefits include being able to participate in From its earliest days in 1911, AAVSO An educator or mentor—teaches our mentor program: beginners are paired members have included some of the most observing skills to fellow AAVSO observers, with an experienced observer for guidance prolific astronomers of the 20th & 21st through instructing AAVSO CHOICE courses and techniques: centuries. or being a mentor. https://www.aavso.org/mentor-program

AAVSO Databases A student—is learning how to find a star, * * * * * set up a telescope, observe, submit data, or AAVSO International Database (AID): The is increasing their astronomy knowledge AAVSO Tools for Beginner Observers: largest and most comprehensive digital variable star database in the world, with over A professional astronomer— uses AAVSO Beginner Tutorials: aimed at those with 43 million variable star observations—a free data and services to advance their research absolutely no experience, these introduce resource for the entire scientific community An AAVSO Ambassador—a student or variable star science basics and then provide Variable Star Index (VSX): a collection of up- young professional representing AAVSO "challenges" for you to apply the concepts: to-the-minute data on over 200,000,000 through astronomy education and activities https://www.aavso.org/tutorials specific variable stars Interested in becoming an ambassador? AAVSO Online Forum: talk to peers for Spectroscopy Database: spectroscopic • www.aavso.org/ambassador-program advice: https://www.aavso.org/forum observations of stars • Email [email protected] Solar Database: Sudden Ionospheric * * * * * Observing Manuals: each one is dedicated Disturbance (SID) Database, and data relating You, your friends, and colleagues are also to a type of observing, including visual, CCD, to sunspot observations invited to join us for: DSLR, Spectroscopy, Solar, and more: https://www.aavso.org/observing-manuals Database: long-term follow-up AAVSO's free-to-all 2021 Webinar Series! information on planets orbiting other stars Come to one or all! Most Saturdays of the . CHOICE Courses: peer-taught informal See the schedule and sign up: online observing courses: https://www.aavso.org/choice-astronomy https://www.aavso.org/2021-webinars Community Explore Education Let’s connect and explore