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Ch 17 Stars Part 1
Vocabulary
| Term | Definition |
|---|---|
| Stellar Parallax | a star's apparent motion with respect to more distant background objects as the observer's location changes |
| Astronomical Unit | average distance between the Earth and the Sun (AU) |
| Proxima Centauri | nearest star to the Sun, one of three in the Alpha Centauri system about 4 light-years away |
| Solar Neighborhood | stars within about 15 light-years of the Sun; mostly red dwarfs |
| Parsec | distance equivalent to 206,000 AUs or 3.26 light-years |
| Proper Motion | angular movement of a star across the sky, seen from Earth, in seconds of arc per year |
| Radial Velocity | motion either towards or away from an observer, measured via the Doppler Effect |
| True Space Motion | actual motion, taking into account both transverse and radial motion according to the Pythagorean Theorem |
| Transverse Velocity | sideways motion relative to an observer |
| Constellation | group of stars in the sky with a recognizable pattern as seen from Earth |
| Alpha Star | brightest star in a constellation |
| Celestial Coordinates | used to locate objects on the celestial sphere via declination and right ascension |
| Luminosity | total energy radiated by a star each second, at all wavelengths |
| Absolute Brightness | brightness a star would have if it were at 10 parsecs from Earth |
| Absolute Magnitude | magnitude a star would have if it were at 10 parsecs from Earth |
| Energy | must be transferred in order to do work on, or to heat, an object |
| Flux | total amount of energy that crosses an area per unit of time |
| Apparent Brightness | brightness that a star appears to have, as measured by an observer on Earth |
| Apparent Magnitude | apparent brightness of a star, expressed using the magnitude scale |
| Magnitude Scale | inverted, logarithmic system of ranking stars by apparent brightness |
| Inverse-Square Law | a field's strength rapidly decreases with the square of the distance (e.g. gravity, light, etc.) |
| Temperature | amount of heat in an object, and an indication of how fast its particles are moving |
| Blackbody Radiation | thermal electromagnetic radiation within or surrounding an object |
| Blackbody Curve | spread of intensity of radiation emitted by any object over all possible frequencies |
| Kelvin | absolute zero temperature scale where all motion ceases at 0, unlike Fahrenheit or Celsius |
| Wavelength | distance from one wave crest/peak to the next |
| Frequency | number of wave crests passing a given point per second |
| Photometry | when the brightness (# of photons) of a light source is measured through a set of filters |
| Stellar Spectra | separation of a star's light into its component colors, revealing Fraunhofer lines |
| Annie Cannon | Harvard "computer" who devised THE classification scheme for stellar spectra in the late 19th century (OBAFGKM) |
| Power | amount of energy transferred or converted per unit of time |
Created by:
john_bailey720
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