23 terms

Glencoe Earth Science, Chapter 30

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chromosphere
layer of the Sun's atmosphere above the photosphere and below the corona that is about 2500 km thick and has a temperature around 30,000K at its top.
corona
top layer of the Sun's atmosphere that extends from the top of the chromosphere and ranges in temperature from 1 million to 2 million K.
fission
process in which heavy atomic nuclei split into smaller, lighter nuclei.
fusion
process in a star's core in which lightweight hydrogen nuclei combine into heavier helium nuclei.
photosphere
lowest layer of the Sun's atmosphere that is also its visible surface, has an average temperature of 5800 K, and is about 400 km thick.
prominence
arc of gas ejected from the chromosphere, or gas that condenses in the Sun's inner corona and rains back to the surface, that can reach temperatures over 50,000 K and is associate with sunspots.
solar flare
violent eruption of radiation and particles from the Sun's surface that is associated with sunspots.
solar wind
wind of charged particles that flows throughout the solar system and begins as gas flowing outward from the Sun's corona at high speeds.
spectrum
arrangement of visible light ordered according to wavelength.
sunspot
dark spot on the surface of the photosphere that typically lasts two months, occurs in pairs, and has a penumbra and an umbra.
absolute magnitude
brightness an object would have if it were placed at a distance of 10 pc; classification system for stellar brightness that can be calculated only when the actual distance to a star is known.
apparent magnitude
classification system based on how bright a star appears to be; does not take distance into account so cannot indicate how bright a star actually is.
binary star
Describes two stars that are bound together by gravity and orbit a common center of mass.
constellation
group of stars that forms a pattern in the sky that resembles an animal, mythological character, or everyday object.
Hertzsprung-Russel diagram
graph that relates stellar characteristics—class, mass, temperature, magnitude, diameter, and luminosity.
luminosity
energy output from the surface of a star per second; measured in watts.
main sequence
in a H-R diagram, the broad, diagonal band that includes about 90 percent of all stars and runs from hot, luminous stars in the upper-left corner to cool, dim stars in the lower-right corner.
parallax
apparent positional shift of an object caused by the motion of the observer.
black hole
small, extremely dense remnant of a star whose gravity is so immense that not even light can escape its gravity field.
nebula
large cloud of interstellar gas and dust that collapses on itself, due to its own gravity, and forms a hot, condensed object that will become a new star.
neutron star
collapsed, dense core of a star that forms quickly while its outer layers are falling inward, has a rdius of about 10 km, a mass 1.5 to 3 times that of the Sun, and contains only neutrons.
protostar
hot, condensed object at the center of a nebula that will become a new star when nuclear fusion reactions begin.
supernova
massive explosion that occurs when the outer layers of a star are blown off.