IB Physics E.5.3 Measuring Stellar Properties Key Definitions

Dark lines in a stellar spectrum at specific wavelengths where photons have been absorbed by atoms in the star's outer atmosphere. Each element produces a unique set of lines, allowing astronomers to identify the chemical composition of a star.

Luminosity measures the amount of radiated electromagnetic energy per unit time.

The parallax angle $p$ is defined as half the total angular shift of the star.

Stellar parallax refers to the apparent shift in the position of a nearby star against the background of distant stars when observed from two opposite points in Earth’s orbit around the Sun, six months apart.

The relationship between a blackbody's peak emission wavelength $\lambda_\text{max}$ and its surface temperature $T$: $\lambda_\text{max} T = 2.90 \times 10^{-3}\,\text{m K}$. A hotter star peaks at a shorter (bluer) wavelength.