Unit 5Light years,

Theories and Characteristicsof the Universe

THEORY is: An idea that is the best explanation of many observations and helps make new predictions

Light year is: Distance that light travel in a vacuum in one year, about 9.5 trillion km- which is used to record distances between stars and galaxies

SPEED of LIGHT is: The speed at which light travels:About 186,282 miles per second or 299,792 kilometers per second

TIME NOT DISTANCE !

BIG BANG THEORY is: A theory that states that about 12 billion to 15 billion years ago, the universe began with a huge, fiery explosion.

UNIVERSE is: the totality of everything that exists, including all matter and energy, the planets, stars, galaxies, and the contents of intergalactic space.

Galaxy is: Large group of stars, dust and gas held together by gravity; can be elliptical, spiral, and irregular

Irregular Galaxy

BLACK HOLE is: Final stage in the evolution of a supernova, in which the core’s mass collapses to a point that it has no volume and whose gravity is so strong that not even light can escape

STAR is: A huge object in space made up of gas and giving off light and heat from nuclear reactions; the sun is a star

MAIN SEQUENCE STAR is: A "main sequence star" is not really a type of star but a period in a stars life. When a star is in "main sequence" it is converting hydrogen into energy. This is the longest period in a stars lifetime.

STELLAR NEBULA is: is an interstellar cloud of dust, hydrogen, helium and other ionized gases.

WHERE A STAR IS BORN!

made up of gas and plasma, they are made by certain types of stars when they die.

PLANETARYNEBULA

Luminosity is:  a measure of the radiant power emitted by a star.

 a scatter graph of stars in which the absolute magnitude (intrinsic luminosity) of stars is plotted vertically against their surface temperature (or corresponding spectral types)

Hertzsprung-Russell diagram

ABSOLUTE MAGNITUDE a measure of the star's luminosity---the total amount of energy radiated by the star every second.

APPARENT MAGNITUDEThe apparent brightness of a star observed from the Earth

Electromagnetic SpectrumFull range of electromagnetic waves

TROUGH is:the lowest part of a wave; the part of a wave with the least magnitude.

CREST is:the highest part of a wave; the part of a wave with the greatest magnitude.

WAVELENGTH is:The distance between successive crests of a wave

FREQUENCY is:the number of occurrences of a repeating event per unit time.

NANOMETER is:1 billionth of a meter, written 10⁻⁹ m

Hertz is:Measurement of wave frequency equal to vibrations per second

Spectroscope is:Instrument used for producing and observing spectra.