Introduction
Photometry is a branch of optics that deals with measuring light in terms of brightness and is vital to astronomical research. By focusing light from a distant object in space, one can quantify the brightness coming from the object and use various methods to deduce meaningful information from it. In the case of variable stars, photometry can be used to analyze the period of a variable star’s period of pulsation, which can be used to derive other physical properties of the star.
One form of photometry commonly used in astronomy is aperture photometry. This method is used to specifically study and compare the amount of light coming from stars that are close to each other in the sky. In this method, the values returned by the pixels within a pre-defined radius of the center of a star can be added together. By comparing the aperture of a pulsating variable star to the aperture of a static reference star at different times over multiple pulsation cycles, one can fit a light curve to the data and find the period of the curve.
An ideal environment for photometry would be “diffraction-limited”. This means the light from a source is affected only by the natural spreading out of the light as it travels through space. Telescopes in space such as the James Webb Space Telescope and Hubble Space Telescope are as close as possible to being diffraction-limited. However, light will necessarily interact with an atmosphere when traveling through one. Light will either be scattered off of its original trajectory or absorbed by particles in the atmosphere, causing the image in a telescope to appear blurry and noisy. This is what causes an observatory to be “seeing-limited”. All ground-based telescopes, including the UMBC Observatory, are seeing-limited, as there will always be an atmosphere to interfere with sources of light.
To ensure that the facility is capable of adjusting for this noise, the Observatory Group will collect photometric data from variable stars, and compare our calculations to those taken by other facilities. Some properties of these stars, such as their distances and luminosities, can be calculated using the data collected from these stars. This project aims to reproduce known measurements of variable stars to better understand the UMBC Observatory’s capabilities and data calibration pipeline.
Author: Connor Kragh
Editor: Jacob Rubinstein
Date: 20241024