Nuclear fusion
the process by which nuclei of small atoms combine to form a new, more massive nucleus; releases energy
radiative zone
the zone of the sun's interior that is between the core and the convective zone in which energy moves by radiation
convective zone
the region of the sun's interior that is between the radiative zone and the photosphere and in which energy is carried upward by convection
photosphere
the visible surface of the sun
chromosphere
the thin layer of the sun that is just above the photosphere and glows a reddish color during eclipses
corona
the outermost layer of the sun's atmosphere
sunspot
the dark area in the photosphere that is cooler than the surrounding areas and has a strong magnetic field
prominence
a loop of relatively cool, incandescent gas that extends above the photosphere and above the sun's edge as seen from Earth; looks like an arch
solar flare
an explosive release of energy that comes from the sun and is associated with magnetic distrubances on the sun's surface
coronal mass ejection (CME)
coronal gas that is thrown into space from the sun; violent, large explosions
auroras
colored light produced by charged particles from the solar wind and from the magnetosphere that react with and excite the oxygen and nitrogen of Earth's upper atmosphere; usually seen in the sky near Earth's magnetic poles; "Northern Lights" & "Southern L
star
a large celestial body that is composed of gas and emits light
Doppler effect
an observed change in the frequency of a wave when the source or observer is moving; red shift- moving away; blue shift- moving closer
light-year
the distance that light travels in one year
parallax
an apparent shift in the position of an object when viewed from different locations
apparent magnitude
the brightness of a star as seen from the Earth
absolute magnitude
the brightness that a star would have at a distance of 32.6 light-years from Earth
main sequence
the location on the H-R diagram where most stars lie; it has a diagonal pattern from the lower right to the upper left
nebula
a large cloud of gas and dust in interstellar space; a region in space where stars are born
giant
a very large and bright star whose hot core has used most of its hydrogen
white dwarf
a small, hot, dim star that is the leftover center of an old sunlike star
nova
a star that suddenly becomes brighter
neutron star
a star that has collapsed under gravity to the point that the electrons and protons have smashed together to form neutrons
pulsar
a rapidly spinning neutron star that emits pulses of radio and optical energy
black hole
an object so massive and dense that even light cannot escape its gravity
constellation
one of 88 regions into which the sky has been divided in order to describe the locations of celestial objects; a group of star organized in a recognizable pattern
galaxy
a collection of stars, dust, and gas bound together by gravity
quasar
quasi-stellar radio source; a very luminous object that produceds energy at high rate
cosmology
the study of the origin, properties, processes, and evolution of the universe
big bang theory
the theory that all matter and energy in the universe was compressed into an extremely small volume that 13 to 15 billion years ago exploded and began expanding in all directions
cosmic background radiation
radiation uniformly detected from ever direction in space; considered a remnant of the big bang
astronomy
the scientific study of the universe
galaxy
the collection of stars, dust, and gas bound together by gravity
astronomical unit
the average distance between Earth and the sun; AU
electromagnetic spectrum
all of the frequencies or wavelengths of electromagnetic radiation
telescope
an instrument that collects electromagnetic radiation from the sky and concentrates it for better observation
refracting telescope
a telescope that uses a set of lenses to gather and focus light from distant objects
reflecting telescope
a telescope that uses a curved mirror to gather and focus light from distant objects