Astrophysics Fundamentals Flashcards
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Read the first 6 Astrophysics Fundamentals flashcards as text
What is Wien's displacement law?
Answer: It states that the peak wavelength of blackbody radiation is inversely proportional to temperature
Wien's displacement law states that the peak wavelength (λmax) of blackbody radiation is inversely proportional to the absolute temperature: λmax × T = 2.898 × 10⁻³ m·K, explaining why hotter objects appear bluer.
What is the Stefan-Boltzmann law?
Answer: A law stating that a blackbody radiates power proportional to the fourth power of its temperature
The Stefan-Boltzmann law states that the total energy radiated per unit surface area of a blackbody is proportional to the fourth power of its temperature (E = σT⁴), explaining why small temperature increases cause huge luminosity increases.
What is Kepler's third law of planetary motion?
Answer: The square of a planet's orbital period is proportional to the cube of its semi-major axis
Kepler's third law states that P² ∝ a³, where P is the orbital period and a is the semi-major axis, meaning planets farther from the Sun take disproportionately longer to complete an orbit.
What is the Doppler effect and how is it used in astronomy?
Answer: The change in observed frequency of waves from a moving source; used to measure radial velocities of celestial objects
The Doppler effect is the change in observed frequency or wavelength of waves emitted by a moving source; in astronomy, spectral line shifts reveal radial velocities of stars, galaxies, and gas clouds.
What is the inverse square law of light?
Answer: The apparent brightness of a source decreases with the square of the distance from the observer
The inverse square law states that the apparent brightness (flux) of a light source decreases proportional to the square of the distance (F = L/4πd²), because light spreads over an ever-growing spherical surface.
What is the virial theorem in astrophysics?
Answer: A theorem stating that the average kinetic energy of a gravitationally bound system equals half the magnitude of its average gravitational potential energy
The virial theorem states that for a gravitationally bound system in equilibrium, the total kinetic energy equals −½ the total gravitational potential energy, used to estimate masses of clusters from velocity dispersions.