AST 2002 UCF Exam 2 (Key Terms)

Angular Momentum

"circling momentum"; used to describe objects turning in circles or going around curves

chromatic aberration

"color finging" can't focus; lens is unable to bring all wavelengths of color to the same focal plane

planetesimal

"pieces of planets"; combine near the sun to form rocky planets; combine beyond frostline to form icy planetesimals which capture H/He far from sun to form gas planets

protoplanetary disk

a rotating circumstellar disk of dense gas and dust surrounding a young newly formed star

absorption spectrum

a spectrum of electromagnetic radiation transmitted through a substance, showing dark lines or bands due to absorption of specific wavelengths - if a light shines through a gas, each element will absorb those photons whose colors match their electron energy levels - used to determine which elements are present - all colors minus those that were absorbed

continuous spectrum

a spectrum that contains or appears to contain all wavelengths but notspectrum lines over a wide portion of its range - hot, dense objects give off all wavelengths - "thermal radiation"

excited state

a state of an atom that is higher in energy than the ground state

twinkling

air turbulence in the atmosphere distorts light and makes this appearance

interferometry

allows multiple telescopes to work together to achieve an angular resolution equivalent to that of a much larger single telescope; more difficult for shorter-wavelength light

neutron

an uncharged elementary particle that has a mass nearly equal to that of the proton and is present in all known atomic nuclei except the hydrogen nucleus

blueshift

if an object is coming toward us, its light is shifted to shorter wavelengths and longer frequencies - shorter wavelengths of visible light are bluer

redshift

if an object is moving away from us, its light is shifted to longer wavelengths and shorter frequencies - longer wavelengths of visible light are redder

spherical aberration

lack of focus due to the wrong shape

jovian plane

large mass and size, far from the sun, made mostly of H, He, and hydrogen compounds, rings and many moons; Jupiter, Saturn, Uranus, Neptune

frost line

marked the key transition between the warm inner regions where terrestrial planets formed and the cool outer regions where Jovian planets formed; lay between the present-day orbits of Mars and Jupiter

temperature

measures the average kinetic energy of the particles - A higher temperature means that the particles on average have more kinetic energy and are moving faster

tidal friction

strain produced in a celestial body (such as the Earth or Moon) that undergoes cyclic variations in gravitational attraction as it orbits, or is orbited by, a second body

sagging

telescope has support around the edges, but lens sags in the middle

Universal Law of Gravitation

tells us the strength of the gravitational attraction between two objects - Every mass attracts every other mass through the force called gravity - The strength of the gravitational force attracting any two objects is directly proportional to the product of their masses

doppler effect

the change in frequency or wavelength of a wave (or other periodic event) for an observer moving relative to its source

atomic mass number

the combined number of protons and neutrons in an atom - Every atom of a given element contains exactly the same number of protons, but the number of neutrons can vary

wavelength

the distance between adjacent peaks of the wave

emission spectrum

the distribution of electromagnetic radiation released by a substance whose atoms have been excited by heat or radiation - the atoms of each element have their own distinct set of electron energy levels - each element emits its own pattern of colors

weight(apparent weight)

the force that a scale measures when an object is on it; weight depends on both mass and force acting on mass (including gravity)

condensation

the general process in which solid (or liquid) particles form in a gas; particles condense out of the gas; elements and compounds began to solidify out of the nebula

tidal force

the gravitational pull exerted by a celestial body that raises the tides on another body within the gravitational field, dependent on the varying distance between the bodies

half-life

the length of time it would take for half the nuclei in a collection to decay

inhomogeneities

the lens has to be perfectly smooth

ground state

the lowest energy state of an atom or other particle

radiometric dating

the method by which we measure a rocks age; relies on careful measurement of the proportions of various atoms and isotopes in the rock

frequency

the number of waves that pass each second - Hertz is the measure of frequency

solar nebula

the particular cloud of gas from which our solar system was born

nucleus

the positively charged central core of an atom, consisting of protons and neutrons and containing nearly all its mass

electron energy levels

the possible energies of an atom

accretion

the process by which "small seeds" grew into planets; small grains stick to one another via electromagnetic force until they are massive enough to attract via gravity to form

momentum

the quantity of motion of a moving body, measured as a product of its mass and velocity - The reason Earth manages to keep rotating and going around the sun - An individual object can gain or lose momentum only when a force causes it to exchange momentum with another object

electromagnetic spectrum

the range of wavelengths or frequencies over which electromagnetic radiation extends

angular resolution

the smallest angle over which we can tell that two dots (or two stars) are distinct

kelvin scale

the temperature scale used in science; does not have negative temperatures because it starts from the coldest temperature known as absolute zero - A higher average kinetic energy for the particles in a substance means a higher total energy, so thermal energy depends on temperature

isotope

versions of an element with different numbers of neutrons; named with their element name and atomic mass number (carbon-12 or 12C)

synchronous rotation

when the rotation period of a moon, planet, or star equals its orbital period about another object

neap tide

when the tidal forces of the sun and moon counteract with each other, at first and third quarter moon, we get relatively small tides

spring tide

when the tidal forces of the sun and moon work together, at new and full moons, the water tends to "spring up" from earth

proton

a positively charged elementary particle that is a fundamental constituent of all atomic nuclei

potential energy

stored energy; may later be converted into kinetic or radiative

inverse square law

a law stating that the intensity of an effect such as illumination or gravitational force changes in inverse proportion to the square of the distance from the source; the strength of gravity between two objects decreases with the square of the distance between their centers

electron

a negatively charged subatomic particle; it can be either free (not attached to any atom), or bound to the nucleus of an atom

photon

a particle representing a quantum of light or other electromagnetic radiation - Photons of light can be counted individually and can hit a wall one at a time - Each photon travels at the speed of light and is characterized by a wavelength and frequency - Each photon carries a particular amount of energy that depends on its frequency - The higher the frequency of the photon, the more energy it carries

adaptive optics

can eliminate much of the blurring caused by our atmosphere; makes a telescope's mirrors do an opposite dance, canceling out the atmospheric distortions

plasma

consists of highly charged particles with extremely high kinetic energy

atomic number

each different chemical element contains a different number of protons in its nucleus

ion

electrically charged atoms; the escape of the electron ionizes the atom

radiative energy

energy carried by light; all light carries energy, which is why light can cause changes in matter - Light can warm the surface of a planet, or alter molecules in our eyes to allow us to see

kinetic energy

energy of motion - Falling rocks, orbiting planets, molecules moving in the air

refraction

focuses light using lens

reflection

focuses light using mirrors; used exclusively in professional astronomy today

light pollution

our atmosphere scatters the bright lights of cities which obscure the view even for the best telescopes

nebular theory of solar system formation

our solar system formed from a giant, swirling cloud of gas & dust called the solar nebula

liquid

particles are not held in a regular arrangement, but are still very close to each other

solid

particles are packed tightly together so they are unable to move about very much

gas

particles have a great deal of space between them and have high kinetic energy

terrestrial planet

planets small in mass and size, close to the sun, made of metal and rock, few moons & no rings; Mercury, Venus, Earth, Mars

asteroid

rocky bodies that orbit the sun much like planets, but they are much smaller