Spectroscopy of Variable Stars:

Background for Variable Star Research Program

The Eta Carina Nebula

Scattered across the night sky is a class of stars that are similar to our Sun in surface temperature, but up to 1000 times larger than the Sun and 1000 to 5000 times brighter. These giant and supergiant stars are pulsating variable stars, but their pulsations are erratic: sometimes predictable, and sometimes not. Computer models of stellar evolution suggest that these strange variables are in the last stages of life and will shortly change dramatically, perhaps ejecting their outer layers to form planetary nebulae with remnant cores that will become white dwarfs, or possibly exploding violently as supernova We refer to the entire group as semi-regular variables or RV Tau stars. They exhibit complex, non-periodic changes in their brightness as well as dramatic changes to their spectra over relatively short time scales. Changes in the spectra of these variables can be quite rapid and dramatic. Some of the stars show such significant changes over a few weeks, or even days, that they appear to be completely different stars. The spectral changes in nearly all of these stars are poorly studied and their connection to the light changes is generally unknown.

In this research project we will use our new and archival spectroscopy to begin to correlate spectral changes over time with their brightness variations. We will use these same data to study the star’s surface temperature, radius, luminosity and age. The research goal is to improve our understanding of the RV Tauri stars, their physical state and the nature of their changes. We will use simple calculations to determine fundamental parameters for a number of different stars

Types of analysis and calculations you will do in this project include:

Student level: this project is appropriate for high school or advanced middle school (requires algebra)

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The Astronomy RBSE program is administered by the National Optical Astronomy Observatory with funds from the National Science Foundation.