Date: March 22, 2011

Title: A Sneak-Peak on Variable Stars

Podcaster: Julio Vannini

Links: Personal Blog: http://ungaman.wordpress.com
Southern Gems Team page: http://www.citizensky.org/teams/southern-gems/
ANASA´s web: http://www.anasa.org.ni

Description: A quick review about variable stars, their importance and what can we do about it.

Bio: Julio Vannini, an amateur astronomer from Nicaragua, serving as secretary for the Nicaraguan Amateur Astronomers Society, ANASA; and member of the Southern Gems team from the Citizen Sky project. His main interest: public outreach, variable stars and the Moon.

Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by Jeff Barr .To my children – Stephen, Andrew, Tina, Bianca, and Grace. Your future is in the stars! Keep learning and keep looking up.

Transcript:

Hello!

Welcome to another program from the “365 Days of Astronomy” podcast series. My name is Julio Vannini, an amateur astronomer from Nicaragua; and I will be your host for today’s program.

The date is March 22nd, 2011.

Today, we will talk about one of the most interesting phenomena in the Cosmos: Variable Stars; what they are, and what can we do with them.

Let’s get started.

The simplest definition for such stellar object is that a variable star is a star the varies in brightness in a certain period of time and as in most cases, in well defined cyclic patterns.

As seen from Earth, we can see the stars “twinkling”, giving us the impression that their brightness is actually changing. That apparent change in brightness is known as stellar scintillation, and is only a “visual trick” performed by the refraction of the thin beam of light coming from the stars and passing through the thick layers of our always moving atmosphere. That is not what a variable star is. If we manage to go outside our atmosphere, we would see the stars as steady points of light, with no apparent variation at all.

The range of variation for a variable star could be measured in tenths of a magnitude or even in several magnitudes, bringing many “invisible” stars to the visual range of many amateur telescopes, and in many cases, to the naked eye.

Variable stars are catalogued in two major categories: Intrinsic variables and Extrinsic variables.

Intrinsic variables are those whose variation is due to events that are directly linked to the star’s behavior and nature, such as solar flares, swelling and shrinking of the stellar radius, eruptions, acretion disk formed by material coming from a companion star, and many other factors.

Classical examples of Intrinsic variables are: Cepheids, omicron Ceti type, protostars, novae and 1A supernovae stars.

Extrinsic variables are those whose variation obeys to external factors, such as eclipsing caused by companion stars or dark unseen objects.

Classical examples of Extrinsic stars are: beta Persei (Algol) and epsilon Aurigae.

The study of these stars might be traced back to the the year 1006, with the first written record of an “appearing” star, registered by Chinesse astronomers and native American tribes. By studying these stars, we are able to learn more and more about their physical and chemical structures. It also allows us to better understand and to discover many exciting events happening around such stars.

Let’s see an example:

The star epsilon Aurigae is what is called a long period variable: every 27 years it is eclipsed by an unknown dark object that revolves around the star. This eclipse lasts some 17 months, dimming the star in a very noticeable way to the naked eye. By makig observations to such eclipse with the naked eye and by instrumentation, it would be possible to uncover the hidden secrets of such a dark object.

Another interesting example is omicron Ceti, or Mira. This is a pulsating star; very faint when its stellar radius is shrinking but when it grows back, it turns out very bright and noticeable to the naked eyes.

Not all variable are visible without optical aid, but many of them are within the range of binoculars and médium to large amateur telescopes. Remember, by makig these observations, one can learn a lot about these stars and contribute by helping professional astronomers to gather valuable information.

You can participate too by making visual or telescopic observations. There are several groups of amateur and professional astronomers working hard measuring variable stars. One of them is the Citizen Sky project, a very special initiative that provides several tutorials for the begginers. There is also the American Association of Variable Star Observers, AAVSO. This group provides a lot of information a tools for locating, measuring and recording observations.

You can visit these projects on internet at CitizenSky.org and aavso.org websites.

Well, that’s all for today. I hope you have enjoyed the program and hope to see you soon, making observations of variable stars, and watching the Universe change right in front of your eyes.

My name is Julio Vannini and you can reach me by visiting my Blog at ungaman.wordpress.com.

Have a nice and day and clear skies!

End of podcast:

365 Days of Astronomy
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