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Chapter 12
Chapter 12
20
Astronomy
Undergraduate 2
04/08/2013

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Term
The star with twice the Sun's radius and the same surface temperature
Definition
is four times more luminous than the Sun
Term
The star with the surface temperature of 20,000K emits most of its power in
Definition
the blue part of the spectrum
Term
The star with twice the Sun's surface temperature is
Definition
16 times more luminous
Term
The luminosity class of a star determines its
Definition
size
Term
The star of O5 spectral class ______ the star of F5 spectral class
Definition
is hotter than
Term
Our Sun belongs to the
Definition
luminosity class V (the Main sequence)
Term
Cooler stars are
Definition
more abundant that hotter stars and are less massive than hotter stars
Term
Spectral classification is based on the star's
Definition
absorption spectrum
Term
More luminous stars are
Definition
more massive and younger than less luminous stars
Term
A star's spectral class defines
Definition
its surface temperature
Term
To discriminate between a giant and a dwarf star of the same spectral class astronomers use
Definition
the widths of absorption lines in their spectra
Term
The Hertzsprung-Russell diagram uniquely describes
Definition
the star's mass, the star's temperature, the star's color, and the star's radius
Term
The star's luminosity depends on
Definition
its mass, temperature, radius, and color
Term
From measurements of the apparent and absolute stellar magnitudes astronomers can directly measure
Definition
the star's distance to us
Term
Trigonometric parallax defines
Definition
the star's distance to Earth
Term
Absolute stellar magnitude does NOT depend on the star’s
Definition
distance to us
Term
A star of the apparent magnitude of m=5 is ___than the star of 6th apparent magnitude
Definition
about 2.5 times brighter
Term
The hotter the star, the greater its
Definition
luminosity
Term
The Main Sequence stars in the H-R diagram contribute
Definition
over 90% of the total population in our Galaxy
Term
A star’s color is uniquely characterized by its
Definition
temperature
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