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Astronomy - Exam 1-Bennett
Ch 1, 3-6 Bennett Columbus State University Rosa Williams
148
Astronomy
Undergraduate 1
02/08/2012

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Term
solar system
Definition
The sun and all the material that orbits it, including planets, dwarf planets, and small solar system bodies. Although the term solar system technically refers only to our own star system, it is often applied to other star systems.
Term
Milky Way Galaxy
Definition
Term
galaxy
Definition
A great island of stars in space, containing from a few hundred million to a trillion or more stars, all held together by gravity and orbiting a common center.
Term
Local Group
Definition
The group of about 40 galaxies to which the Milky Way belongs.
Term
Superclusters
Definition
A gigantic region of space where many individual galaxies and and many groups and clusters of galaxies are packed more closely together than elsewhere in the universe.
Term
Universe (or cosmos)
Definition
The sum total of all matter and energy - that is, all galaxies and everything in between them.
Term
Big Bang
Definition
The name given to the event thought to mark the birth of the universe.
Term
nuclear fusion
Definition
The process in which two (or more) smaller nuclei slam together and make one large nucleus.
Term
star
Definition
A large, glowing ball of gas that generates heat and light through nuclear fusion in its core.
Term
planet
Definition
A moderately large object that orbits a star and shines primarily through by reflecting light from its star. According to a definition approved in 2006, an object can be considered a planet only if: 1. orbits a star, 2. is large enough for its own gravity to make it round, and 3. has cleared most other objects from its orbital path. An object that meets the first two criteria but has not cleared its orbital path, like Pluto, is designated a dwarf planet.
Term
moon (or satellite)
Definition
An object that orbits a planet. The term satellite can refer to any object orbiting another object.
Term
asteroid
Definition
A relatively small and rocky object that orbits a star.
Term
comet
Definition
A relatively small and ice-rich object that orbits a star.
Term
small solar system body
Definition
An asteroid, comet, or other object that orbits a star but is too small to qualify as a planet or dwarf planet.
Term
Star system
Definition
A star (sometimes more than one star) and any planets and other materials that orbit it.
Term
cluster
Definition
(or group of galaxies) A collection of galaxies bound together by gravity. Small collections (up to a few dozen galaxies) are generally called groups, while larger collections are called clusters.
Term
observable universe
Definition
The portion of the entire universe that can be seen from Earth, at least in principle. The observable universe is probably only a tiny portion of the universe.
Term
Astronomical Unit (AU)
Definition
The average distance between Earth and the Sun, which is about 150 million kilometers. More technically, 1 AU is the length of the semimajor axis of Earth's orbit.
Term
Light year
Definition
The distance that light can travel in 1 year, which is about 9.46 trillion kilometers.
Term
rotation
Definition
The spinning of an object around its axis, which is an imaginary line connecting the North Pole and the South Pole through the center of Earth.
Term
expansion of (the universe)
Definition
The increase in the average distance between galaxies as time progresses.
Term
orbit (revolution)
Definition
The orbital motion of one object around another. For example, Earth orbits around the sun once a year.
Term
ecliptic plane
Definition
The plane of Earth's orbit around the sun.
Term
axis tilt (of a planet in our solar system)
Definition
The amount by which a planet's axis is tilted with respect to a line perpendicular to the ecliptic plane.
Term
models
Definition
A representation of some aspect of nature that can be used to explain and predict real phenomena without invoking myth, magic, or the supernatural.
Term
geocentric model
Definition
Any of the ancient Greek models that were used to predict planetary positions under the assumption that Earth lay in the center of the universe.
Term
Ptolemaic model
Definition
A geocentric model of the universe developed by Ptolemy in about 150 A.D.
Term
Copernican Revolution
Definition
The dramatic change, initiated by Copernicus, that occurred when we learned that Earth is a planet orbiting the Sun rather than the center of the universe.
Term
ellipse
Definition
A type of oval that happens to be the shape of bound orbits. An ellipse can be drawn by moving a pencil along a string whose ends are tied to two tacks; the locations of the tacks are the foci (singular:focus) of the ellipse.
Term
semimajor axis
Definition
Half the distance across the long axis of an ellipse, in this text, it is usually referred to as the average distance of an orbiting object, abbreviated a in the formula for Kepler's third law.
Term
eccentricity
Definition
A measure of how much an ellipse deviates from a perfect circle; defined as the center-to-focus distance divided by the length of the semimajor axis.
Term
Kepler's 1st Law
Definition
Law stating that the orbit of each planet about the Sun is an ellipse with the Sun at one focus.
Term
Kepler's 2nd Law
Definition
The principle that, as a planet moves around its orbit, it sweeps out equal areas in equal times. This tells us that a planet moves faster when it is closer to the Sun (near perihelion) than when it is farther from the Sun (aphelion) an its orbit.
Term
Kepler's 3rd Law
Definition
The principle that the square of a planet's orbital period is proportional to the cube of its average distance from the Sun (semimajor axis), which tells us that more distance planets move more slowly in their orbits; in its original form, written p2=a3.
Term
pseudoscience
Definition
Something that purports to be science or may appear to be scientific but that does not adhere to the testing and verification requirements of the scientific method.
Term
paradigm
Definition
A general pattern of thought that tends to shape scientific study during a particular time period.
Term
theory
Definition
A model of some aspect of nature that has been rigorously tested and has passed all tests to date.
Term
speed
Definition
The rate at which an object moves. It's units are distance divided by time, such as m/s or km/hr.
Term
velocity
Definition
The combination of speed and direction of motion; it can be stated as a speed in a particular direction, such as 100km/h due north.
Term
acceleration
Definition
The rate at which an object's velocity changes. Its standard units are m/s2.
Term
acceleration of gravity
Definition
The acceleration of a falling object. On Earth, the acceleration of gravity, designated by g, is 9.8 m/s2.
Term
momentum
Definition
The product of an object's mass and velocity.
Term
force
Definition
Anything that can cause a change in momentum.
Term
net force
Definition
The overall force to which an object responds; the net force is equal to the rate of change in the object's momentum, or equivalently to the object's mass x acceleration.
Term
angular momentum
Definition
Momentum attributable to rotation or revolution. The angular momentum of an object moving in a circle of radius r is the product m x v x r.
Term
torque
Definition
A twisting force that can cause a change in an object's angular momentum.
Term
mass
Definition
A measure of the amount of matter in an object.
Term
weight
Definition
The net force that an object applies to its surroundings; in the case of a stationary body on the surface of the Earth, it equals mass x acceleration of gravity.
Term
free-fall
Definition
The condition in which an object is falling without resistance, objects are weightless when in free-fall.
Term
weightless
Definition
A weight of zero as occurs during free-fall.
Term
Newton's 1st Law
Definition
Principle that, in the absence of net force, an object moves with constant velocity.
Term
Newton's 2nd Law
Definition
Law stating how a net force affects an object's motion. Specifically, force = rate of change in momentum, or force = mass x acceleration.
Term
Newton's 3rd Law
Definition
Principle that, for any force, there is always an equal and opposite reaction force.
Term
conservation of momentum
Definition
The principle that, in the absence of net force, the total momentum of a system remains constant.
Term
conservation of angular momentum
Definition
The principle that, in the absence of net torque, the total angular momentum of a system remains constant.
Term
conservation of energy
Definition
The principle that energy (including mass-energy) can be neither created nor destroyed, but can only change from one form to the other.
Term
kinetic energy
Definition
Energy of of motion, given by the formula 1/2mv^2.
Term
radiative energy
Definition
Energy carried by light; the energy of a photon is Planck's constant times its frequency, or h x f.
Term
potential energy
Definition
Energy stored for later conversion into kinetic energy; includes gravitational potential energy, electrical potential energy, and chemical potential energy.
Term
joule
Definition
The international unit of energy, equivalent to about 1/4000 of a Calorie.
Term
thermal energy
Definition
The collective kinetic energy, as measured by temperature, of the many individual particles moving within a substance.
Term
temperature
Definition
A measure of the average kinetic energy of particles in a substance.
Term
Kelvin
Definition
The most commonly used temperature scale in science, defined such that absolute zero is 0k and water freezes at 273.15k.
Term
gravitational potential energy
Definition
Energy that an object has by virtue of its position in a gravitational field; an object has more gravitational potential energy when it has a greater distance that it can potentially fall.
Term
mass-energy
Definition
The potential energy of mass, which has an amount E=MC^2
Term
bound orbits
Definition
Orbits on which an object travels repeatedly around another object; bound orbits are elliptical in shape.
Term
unbound orbits
Definition
Orbits on which an object comes in towards a large body only once, never to return; unbound orbits may be parabolic or hyperbolic in shape.
Term
center of mass
Definition
The point of at which two or more orbiting objects would balance if they were somehow connected; it is the point around which the orbiting objects actually orbit.
Term
Newton's version of Kepler's Law
Definition
A generalization of Kepler's third law used to calculate the masses of orbiting objects from measurements of orbital period and distance, usually written as "refer to formula"
Term
orbital energy
Definition
The sum of an orbiting object's kinetic and gravitational potential energies.
Term
gravitational encounter
Definition
An encounter in which two (or more) objects pass near enough so that each can feel the effects of the other's gravity and they can therefore exchange energy.
Term
escape velocity
Definition
The speed necessary for an object to completely escape the gravity of a large body such as a moon, planet, or star.
Term
tidal force
Definition
A force that occurs when the gravity pulling on one side of an object is larger than that on the other side, causing the object to stretch.
Term
tidal friction
Definition
Friction within an object that is caused by tidal force.
Term
synchronous rotation
Definition
The rotation of an object that always shows the same face to an object that it is orbiting because its rotation period and orbital period are equal.
Term
spectrum
Definition
Term
power
Definition
The state of energy usage, usually measured in watts. (1 watt=1 joule/s)
Term
watts
Definition
The standard unit of power in science.
Term
emission
Definition
A light bulb emits visible light; the energy of the light comes from electrical potential energy supplied to the light bulb.
Term
Absorption
Definition
When you place your hand near an incandescent light bulb, your hand absorbs some of the light, and this absorbed energy warms your hand.
Term
Transmission
Definition
Some forms of matter, such as glass or air, transmit light, which means allowing it to pass through.
Term
Reflection/scattering
Definition
Light can bounce off matter, leading to what we call reflection (when bouncing is all in the same general direction) or scattering (when the bouncing is more random.)
Term
wavelength
Definition
The distance between adjacent peaks or troughs between waves.
Term
frequency
Definition
The rate at which peaks of a wave pass by a point, measured in units of 1/s, often cycles per second or hertz.
Term
cycles per second
Definition
The rate at which peaks of a wave pass by a point, measured in units of 1/s, often cycles per second or hertz.
Term
hertz
Definition
The standard unit of frequency for light waves; equivalent to units of 1/s.
Term
field
Definition
An abstract concept used to describe how a particle would interact with a force. For example, the idea of a gravitational field describes how a particle would react to the local strength of gravity, and the idea of an electromagnetic field describes how a charged particle would respond to forces from the other charged particles.
Term
electromagnetic wave
Definition
A synonym for light, which consists of waves of electric and magnetic fields.
Term
speed of light
Definition
The speed at which light travels, which is about 300,000 km/s.
Term
photons
Definition
An individual particle of light, characterized by the wavelength and a frequency.
Term
visible light
Definition
The light our eyes can see, ranging in wavelength from about 400 to 700nm.
Term
electromagnetic spectrum
Definition
The complete spectrum of light, including radio waves, infrared light, visible light, ultraviolet light, X-rays, and gamma rays.
Term
electromagnetic radiation
Definition
Another name for all types of light, from radio waves through gamma rays.
Term
infrared
Definition
Light with wavelength that falls in the portion of the electromagnetic spectrum between radio waves and visible light.
Term
Radio wave
Definition
Light with very long wavelengths (and hence low frequencies) - longer than those of infrared light.
Term
microwaves
Definition
Light with the wavelengths in the range of micrometers to millimeters. Microwaves are generally considered to be a subset of the radio wave portion of the electromagnetic spectrum.
Term
ultraviolet
Definition
Light with wavelengths that fall in the portion of the electromagnetic spectrum between visible light and X rays.
Term
gamma rays
Definition
Light with very short wavelengths (and hence high frequencies) - shorter than those of X rays.
Term
X rays
Definition
Light with wavelengths that fall in the portion of the electromagnetic spectrum between ultraviolet light and gamma rays.
Term
atoms
Definition
Consists of a nucleus made from protons and neutrons, surrounded by a cloud of electrons.
Term
element
Definition
A substance made from individual atoms of a particular atomic number.
Term
protons
Definition
Particles found in atomic nuclei with positive electrical charge, built from three quarks.
Term
neutrons
Definition
Particles with no electrical charges found in atomic nuclei, built from three quarks.
Term
electrons
Definition
Fundamental particles with negative electric charge; the distribution of electrons in an atom gives an atom its size.
Term
nucleus
Definition
The compact center of an atom made from protons and neutrons.
Term
electrical charge
Definition
A fundamental property of matter that is described by its amount and as either positive or negative, more technically, a measure of how a particle responds to the electromagnetic force.
Term
atomic number
Definition
The number of protons in an atom.
Term
atomic mass number
Definition
The combined number of protons and neutrons in an atom.
Term
isotopes
Definition
Forms of an element that have the same number of protons but a different number of electrons.
Term
molecules
Definition
Technically, the smallest unit of chemical element or compound; in this text, the term refers only to combinations of two or more atoms held together by chemical bonds.
Term
compounds
Definition
A substance made from molecules consisting of two or more atoms with different atomic numbers.
Term
solid
Definition
The phase of matter in which atoms or molecules are held tightly in place.
Term
liquid
Definition
The phase of matter in which atoms or molecules are held together but move relatively freely.
Term
gas
Definition
The phase of matter in which atoms or molecules can move essentially independently of one another.
Term
chemical bond
Definition
Term
evaporation
Definition
The process by which atoms or molecules escape into the gas phase from a liquid
Term
sublimation
Definition
The process by which atoms or molecules escape into the gas phase from a solid.
Term
molecular dissociation
Definition
The process by which a molecule splits into its component atoms.
Term
ions
Definition
Atoms with a positive or negative charge.
Term
ionization
Definition
The process of stripping an electron from an atom.
Term
plasma
Definition
A gas consisting of ions and electrons.
Term
pressure
Definition
The force (per unit of area) pushing on an object. In astronomy, we are generally interested in pressure applied by gas (or plasma). Ordinarily, such pressure is related to the temperature of the gas (see thermal pressure). In objects such as white dwarfs and neutron stars, pressure may arise from a quantum effect. Light can also exert pressure - radiation pressure.
Term
energy level transitions
Definition
Term
spectroscopy
Definition
The process of obtaining spectra from astronomical objects.
Term
continuous spectrum
Definition
A spectrum of light that spans a broad range of wavelengths without interruption by emission or absorption lines.
Term
emission lines
Definition
The process by which matter emits energy in the form of light.
Term
emission line spectrum
Definition
A spectrum that contains emission lines.
Term
absorption lines
Definition
The process by which matter absorbs radiative energy.
Term
absorption line spectrum
Definition
A spectrum that contains absorption lines.
Term
thermal radiation
Definition
Term
thermal radiation spectrum
Definition
The spectrum of radiation produced by an opaque object that depends only on the object's temperature; sometimes called blackbody radiation.
Term
blueshift
Definition
A Doppler shift in which spectral features are shifted to shorter wavelengths, observed when an object is moving toward the observer.
Term
redshift (Doppler)
Definition
A Doppler shift in which spectral features are shifted to longer wavelengths, observed when an object is moving away from the observer.
Term
rest wavelengths
Definition
The wavelength of a spectral feature in the absence of any Doppler shift or gravitational redshift.
Term
image
Definition
A picture of an object made by focusing light.
Term
focal plane
Definition
The place where an image created by a lens or mirror is in focus.
Term
detector
Definition
Term
CCDs (charge coupled device)
Definition
A type of electronic light detector that has largely replaced photographic film in astronomical research.
Term
pixels
Definition
An individual "picture element" on a CCD.
Term
light-collecting area
Definition
The area of the primary mirror or lens that collects light in a telescope.
Term
angular resolution
Definition
The smallest angular separation that two pointlike objects can have and still be seen as distinct points of light.
Term
diffraction limit
Definition
The angular resolution that a telescope could achieve if it were limited only by the interference of light waves; it is smaller (i.e. better angular resolution) for larger telescopes.
Term
reflecting telescope
Definition
A telescope that uses mirrors to focus light.
Term
light curves
Definition
A graph of an object's intensity against time.
Term
light pollution
Definition
Human-made light that hinders astronomical observations.
Term
turbulence
Definition
Rapid and random motion.
Term
adaptive optics
Definition
A technique in which telescope mirrors flex rapidly to compensate for the bending of starlight caused by atmospheric turbulence.
Term
grazing incidence mirrors
Definition
Reflections in which light grazes a mirror surface and is deflected at a small angle; commonly used to focus high-energy ultraviolet light and X-rays.
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