Using Radiation To Investigate Stars Flashcards
Why do stars emit a continuous spectrum of radiation?
The dense gas at the star’s surface emits radiation across all wavelengths.
What happens to the light from a star as it passes through its atmosphere?
Atoms in the atmosphere absorb specific wavelengths, creating absorption lines in the spectrum.
What is a line absorption spectrum?
A spectrum with dark absorption lines where specific wavelengths of light have been absorbed by gases in a star’s atmosphere.
What is a black body?
A surface that absorbs all electromagnetic radiation that falls upon it and is the best possible emitter at any wavelength.
How do stars approximate black bodies?
Stars emit electromagnetic radiation almost perfectly, making them good approximations of black bodies.
Why don’t we see a perfect continuous spectrum from stars?
Some wavelengths are absorbed by atoms in the star’s atmosphere, resulting in an absorption spectrum.
What is the luminosity of a star?
The total energy emitted per second in the form of electromagnetic radiation (measured in watts, W).
How does Stefan’s Law describe luminosity?
AσT⁴, where:
• P = luminosity (W)
• A = surface area of the star
• σ = Stefan-Boltzmann constant
• T = temperature (K)
What is the equation for intensity of radiation?
I = P / (4πR²)
What do the symbols in the intensity equation represent?
• I = intensity of radiation (W/m²)
• P = power (luminosity) of the star (W)
• R = distance from the star (m)
What is multiwavelength astronomy?
The study of galaxies using telescopes that detect different wavelengths of the electromagnetic spectrum.
Why is multiwavelength astronomy important?
Different wavelengths reveal different features of astronomical objects, such as temperature, composition, and structure.
What does Wien’s Law describe?
The relationship between the temperature of a black body and the wavelength of peak emission.
What is the equation for Wien’s Law?
λ_max = W / T
What do the symbols in Wien’s Law represent?
• λ_max = wavelength of peak emission (m)
• W = Wien’s constant (2.898 × 10⁻³ mK)
• T = absolute temperature of the object (K)
What does Wien’s Law tell us about hotter stars?
Hotter stars emit peak radiation at shorter wavelengths, meaning they appear bluer.
What does Wien’s Law tell us about cooler stars?
Cooler stars emit peak radiation at longer wavelengths, meaning they appear redder.
