earth science regents ch1

Big bang theory

The scientific explanation for the origin of the universe, proposing that all matter and energy expanded from an extremely hot, dense point approximately 13.8 billion yrs ago

Redshift

The shift of spectral lines toward longer, redder wavelengths observed in light from objects moving away from the observer, used as evidence that the universe is expanding

Nebula

A large cloud of gas and dust in space from which stars are formed through gravitational collapse

Nuclear fusion

The process by which lighter atomic nuclei combine to form heavier nuclei, releasing large amounts of energy; the longest and most stable phase of stellar evolution

Main sequence

The stage in a stars life during which it fuses hydrogen into helium in its core; the longest and most stable phase of stellar evolution

Red giant

A large, cool luminous star that forms when a man- sequence star exhausts its core hydrogen and its outer layers expand dramatically

White dwarf

The dense, earth-sized remnant of a low-to medium-mass star after it has shed its outer layers as a planetary nebula

Supernova

A catastrophic stellar explosion that occurs when a massive stars core collapses after exhausting its nuclear fuel, producing all elements heavier than iron

H-R diagram

A graph plotting stars by surface temperature and luminosity that reveals the relationship between stellar properties and evolutionary stage

Luminosity

The total amount of energy radiated by a star per unit time; a measure of the stars intrinsic brightness independent of distance

Nucleosynthesis

The process by which nuclear reactions inside stars and supernova explosions produce all elements heavier than hydrogen and helium

Electromagnetic spectrum

The complete range of electromagnetic radiation, from radio waves at the longest wavelengths to gamma rays at the shortest

Hydrostatic balence

The equilibrium in a main-sequence star between the outward pressure of nuclear fusion and the inward force of gravity