IB Physics: Astrophysics (Option E)
Luminosity
how bright a star will be in relation to the sun if all star were the same distance from the observer
Light Year
the distance light travels in one year
Ellipse
A elongated circle, or oval shape, the shape of the planets orbit.
Astronomical Unit
The average distance between Earth and the sun, about 150 million kilometers (1.5 x 10^11)
Stellar Cluster
A group of stars that are physically near each other in space, created by the collapse of the same gas cloud.
Relative Density
The density of a star or planet relative to another star or planet.
Stefan – Boltzmann Law
Total Energy Radiated per Unit Time (W) = Stefan – Boltzmann Constant 5.67 x 10^-8 (Wm^-2K^-4) x Surface Area of Body x Temperature of Black Body ^ 4
Wien’s Displacement Law
Peak Wavelength (m) = (2.90 x 10^-3) / Distance from star to earth.
Absorption Spectrum
the spectrum of electromagnetic radiation that has passed through a medium that absorbed radiation of certain wavelengths
Taotao He
He + Absence = Homo/Dual-sexuality
Doppler Effect
change in the apparent frequency of a wave as observer and source move toward or away from each other
Red-Shift
occurs when a light source is moving quickly away from an observer
Blue-Shift
occurs when a light source is moving quickly toward and observer
H-R Diagram
about 90% of stars lie on the main squence. It plots intrinsic brightness and temperature
Main Sequence
a diagonal area on an H-R diagram that includes more than 90 percent of all stars
Red Giant
a very large red star with little energy produced (eg. Felix Tang)
Red Supergiant
a very large star of high luminosity (eg. Benjamin Tang)
White Dwarfs
remnants of burn out stars. very hot and small. difficult to find b/c they are so faint (eg. Harmony Hsia)
Black Hole
a region of space resulting from the collapse of a star (eg. D-Wang)
Eclipsing Binary Stars
a star system in which one star periodically blocks the light from another
Spectroscopic Binary Stars
Two stars whose presence that can be decuded by the stellar spectra.
Exploding Star
Star that ends its life through a cataclysmic outward explosion (eg. Ammar Nasir)
Parallax Method
A triangle that is created by Earth, Sun, and a star.
Absolute Magnitude
The actual brightness of a star
Apparent Magnitude
the brightness of a star when viewed from Earth
Spectroscopic Parallax
a methos of determining a star’s distance from the Earth by measuring its surface temperature, luminosiry, and apparent magnitude
Cepheid Variable
A star of variable luminosity. The luminosity increases sharply and falls off gently with a well-defined period. The period is related to the absolute luminosity of the star and so can be used to estimate the distance to the star.
Olber’s Paradox
If the universe has infinite time and space, there would be an infinite number of stationary stars, making the night sky bright, which is not the case.
Big Bang Theory
(cosmology) the theory that the universe originated 13.7 billion years ago from the cataclysmic explosion of a small mass of matter at extremely high density and temperature
Constellations
a group of stars that forms a shape or pattern