21 terms

Ch 30 & 31 Stars & Universe

Electromagnetic Spectrum (EM Spectrum)
Includes gamma rays, x-rays, UV, visible, microwave, radio waves. The shorter the wavelengths (gamma rays) are most dangerous.
Gamma Rays
Shortest wavelength and most damaging part of EM Spectrum. It is the energy given off during nuclear fusion in the center of a star.
Radio Waves
Longest wavelength and least damaging part of EM Spectrum.
The number of waves that pass by in a given amount of time.
The distance it takes for a wave to repeat itself. The distance from crest to crest or trough to trough.
Magnitude - Apparent
How bright a star LOOKS without taking into account its distance.

Low magnitudes = Bright.
High Magnitudes = Dim.
Example: A star with a magnitude of +1 is 100 times brighter than a star with a magnitude of +6.
Magnitude - Absolute
The ACTUAL brightness of a star. (Closely related to Luminosity)
The amount of LIGHT ENERGY given off by a star. (Closely related to Absolute Magnitude)
The change in wavelength of light as a star moves away from an observer.
HR Diagram (Hertzsprung-Russell)
Graph/diagram that shows the relationship between magnitude, temperature, and color of stars.

Allows classification into Main Sequence, Giants, Dwarfs, etc. (See Figure 30-17 p.819)
Main Sequence
90% of stars in an H-R diagram that fall along a broad strip from upper-left corner diagonally to lower right. They are stars undergoing nuclear fusion.
Light Spectra
Lines of color given off or absorbed by a star that are used to determine the star's composition (elements) and temperature.
Fusion - Nuclear
The process of taking light elements and converting them into heavier elements. Ex: Hydrogen to Helium
Type of particle in an atom's nucleus. The number of protons is used to identify the element on the periodic table.
Nebulae/Interstellar Cloud
A cloud of gas and dust that is present at the beginning of every star's life.
Hot, condensed object at the center of a nebula (disk of gas & dust) that will become a star when fusion begins.
See Figure 30-19 p.822
Planetary Nebula
The blown away outer atmosphere of a star that has run out of fuel.
A star that suddenly increases greatly in brightness because of a catastrophic explosion that ejects most of its mass.

This occurs after the red super-giant stage when a massive star stops performing nuclear fusion and runs out of fuel.
Neutron Star
If the remaining mass of the star after a supernova explosion is about 1.4 times that of our Sun, the core is unable to support itself and it will collapse further to become a neutron star.

The matter inside the star will be compressed so tightly that its atoms are compacted into a dense shell of neutrons.
Black Hole
If the remaining mass of the star is more than about three times that of the Sun, it will collapse so completely that it will literally disappear from the universe.

What is left behind is an intense region of gravity called a black hole.
Big Bang Theory
Theory that says the universe began as a tiny, hot, dense point and has been expanding ever since. As it expanded it cooled, forming stars, galaxies, etc.