Saturday, December 3, 2011

Photometry for Astronomers

Photometric results of VAO Observations on 11/21/2011
Astronomers interested in the variability of stars need a tool to understand how they vary in time.   This tool is called photometry and it is widely used by astronomers to study not only intrinsic star variability but the more familiar exoplanet transit searches.    It is also used to study galaxies and other extended objects.  So why study changes in "brightness"?

Changes in brightness can lead to the discovery of eclipsing binaries, transiting exoplanets, exotrojans and exomoons.   It can tell you about the morphology of Active Galactic Nuclei and about the properties of supernovae explosions.  You can infer from the data when you collect it over time about the physical properties of the object you are studying.

The plots to the right are examples of light curves or in other words many measurements of the intensity of stars over a period of time.  On the horizontal axis you have number of exposures. On this particular case each tick on the axis is roughly 80 seconds.  On the vertical we have the instrumental magnitude of the star.   As you can tell by the graphs there are stars on this ensemble that vary on time scales of hours.  These measurements were taken on VAO in Webster NY and the graphs are the results of the photometric pipeline I setup for this particular field.