Variable Stars
The most familiar star to everyone on Earth is Sol, our sun. From everyday life, we know that the sun changes very little from day to day. With the exception of changing atmospheric conditions, we see the sun to be a constant intensity everyday. This behavior of our star, which we have come to expect and depend on, is not typical of all stars. Our sun is increasing in luminosity… but with an increase of merely two hundredths of a percent every million years, no human will live long enough to notice the change. There are, however, stars that undergo more short-term changes, these stars can be seen to vary, and these variations can be tracked and studied. Such stars are called variable stars, and to those of us used to the regularity of our sun, they can be quite strange indeed. The Night Sky Live Project offers a unique way to study a cosmic zoo of star types.
Variable Types
There are two major classes of variable stars, intrinsic and extrinsic. Intrinsic Variables change due to actual physical variations in the star, such as pulsations or eruptions. Extrinsic Variables change due to rotation, or binary companionship. Within these two categories are many subcategories, all with unique properties that can be tracked and studied.
Since most variables undergo changes in light emissions due to their variability, CONCAM data can be used to watch these stars and collect information to help better understand their behavior.
Intrinsic Variables
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The two major types of Intrinsic Variables are pulsating and eruptive. Pulsating stars vary due to vibrations or changes in size and shape. One type of pulsating variables are Cepheid Variables, which are further divided into Classical Cepheids (long period) and RR Lyrae type cepheids. The regularity of some Cepheids makes the useful as markers to estimate distances in space (Estimating Distances) Another type of intrinsic variables are eruptive stars, which can often undergo dramatic changes, as demonstrated by a Supernova in which a star releases all of its final energy in a large burst. Other eruptive types are Recurrent Novae and Symbiotic Stars. Polaris is a Cepheid variable, it is the center star in the CONCAM image on the right.
Extrinsic Variables
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Extrinsic variables are stars that do not physically change in luminosity. Changes seen in these types of stars are only perceived changes due to eclipses or rotation. Eclipsing stars show a drop in magnitude, when one pair of a binary system passes in front of the other. Stars that change in magnitude due to rotation often have surface irregularities that lead to a perceived change in luminosity. This image, taken from Night Sky Live, shows an eclipsing binary Beta Persei (bright star, top left). |
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Night Sky Live and Variable Stars
Night Sky Live uses continuous cameras (CONCAMS) equipped with a fish eye lens to capture the entire sky each night. By tracking photometry, variability in stars can be observed and measured. Many variable stars can be seen in CONCAM images. Due to the large amount of data collected by the Night Sky Live project, not every star can be completely explored. With a bit of practice and some basic understanding of data analysis, ANYONE can find interesting things in the night sky. If you have an interest in a particular star, you should feel free to look at the data; you never know what you may find! The CONCAM for scientists page will help you get started, happy hunting.