Astronomy unit 7 practice test
V
Main-sequence stars are all designated by luminosity class _____.
parsec
a unit of distance equal to 3.0857 × 1013 km
pulsar
A _____ is a neutron star that emits narrow beams of energy as it spins on its axis.
binary star
A _____ is two stars orbiting a common center of gravity.
visual binary
A _____ is when both stars in a system can be seen separately through a telescope.
long-term variable
A red variable is a _____ star that is a red giant or supergiant.
helium
A star leaves the main sequence when it stops fusing hydrogen into _____ in its core.
nova
A(n) _____ is a star that suddenly flares up, then fades after a few weeks or months.
light
Almost everything we know about stars comes to us through careful analysis of the _____ they emit.
iron
Formation of _____ marks the end of a blue star's life because it cannot be fused into another element.
lower right
Stars toward the _____ of the main sequence fuse hydrogen at a slower rate because they have less internal nuclear activity.
hydrogen-helium
The _____ cycle process ends with the production of helium-4.
carbon
The _____ cycle/process begins and ends with the same element.
triple-alpha
The _____ cycle/process only occurs in really hot stars.
Hydrostatic equilibrium
_____ is a term describing fluids at rest.
Apparent magnitude
_____ is how bright a star looks in our sky.
Singularity
_____ is the point where gravity compresses an object to infinite density and to almost no volume.
Absolute magnitude
_____ measures the total energy output of a star.
Bright-line
_____ spectra indicate the presence of specific elements and confirm the heat necessary to vaporize them.
Dark-line
_____ spectra indicate the presence of specific elements because those elements absorb white light.
helium flash
occurs after helium begins to fuse with carbon in the triple-alpha process
Big Scrunch
occurs when a star's iron heart suddenly compresses its mass in tenths of a second from stellar death
Enjar Hertzsprung
plotted the absolute magnitude of individual stars within clusters against their colors
Henry Russell
plotted the absolute magnitude of stars against their spectral classes
giants and supergiants
plotted to the upper right on the H-R diagram
lattice
As a white dwarf cools, the carbon and oxygen ions lock themselves into a crystal _____, or three-dimensional pattern of atoms.
slit
The _____ permits light only from a selected source.
Our Sun is a G2 yellow star of above-average size.
Which of the following sentences best describes our Sun?
Mass
_____ dictates what characteristics a star shows throughout all stages of its activity.
White dwarfs
_____ do not shrink further because their electrons cannot get any closer together.
Pulsars
_____ spin rapidly because they are governed by the spin rate of their original star being concentrated into a drastically shrunken condition.
H-R Diagram
a chart of the absolute magnitudes of stars plotted against their temperatures
isotope
a form of an element having the same number of protons, but having more or fewer than the usual number of neutrons
black hole or neutron star
a form of degenerate matter that can occur after a star explodes
light year
approximately 9,460,000,000,000 km
luminoity
indicated by adding a Roman numeral to the letter and number that designates a star's class
Joseph von Fraunhofer
invented the spectroscope
convection
keeps helium from accumulating in the core of a red dwarf
main-sequence
the center curving line in the H-R diagram
logarithm
the exponent to which a base must be raised to produce a given number
