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167 Cards in this Set
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Angstrom Ǻ
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A unit of distance equaling 1-billionth of a meter (10-9); commonly used to measure wavelength (λ)
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Angular diameter
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The angle formed by lines extending from the observer to opposite sides of an object
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Angular distance
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The angle formed by lines extending from the observer to two locations
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Apelion
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Orbital point farthest from the Sun
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AU
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Astronomical unit: average distance from Earth to the Sun or approximately 1.5 x 10^8 km or 93 x 10^6miles
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celestial equator
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projection of the Earth's equator on the celestial sphere
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Chromosphere
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Bright gases just above the photosphere of the sun
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closed orbit
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an orbit that returns to the same starting point over and an over- either circular or elliptical
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Constellation
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One of the stellar patterns identified by name
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Corona
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The faint outer atmosphere of the sun, composed of low-density, high temperature gas
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Diamond-ring effect
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During total solar eclipse, the momentary appearance of a spot of photosphere at the edge of the moon producing a brilliant glare set in the silvery ring of the corona
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ecliptic
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apparent pathway of the Sun against the stars as seen from Earth - a projection of the Earth's orbit
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ellipse
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A closed curve around two points called foci such that the total distance from one focus to the curve and back to the other focus remains constant
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epicycle
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the small circle followed by a planet in the Ptolemaic theory. The center of the epicycle follows a larger circle (derant) around the Earth
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equinox
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day with equal amounts of sunlight / darkness
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Evening star
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any planet first visible in the evening (sunset) sky
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eyepiece
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a short forcal length lens used to enlarge the image in a telescope; lens nearest the eye
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false-color image
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A representation of graphical data with added or enhanced color added to reveal detail
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Geocentric Universe
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A model universe with Earth at the center. -i.e. Ptolemaic Universe
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How is resolution determined?
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wavelength / diameter of telescope
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Intensity
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A measure of the light energy from a star that hits one square meter in one second (m2/s)
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Kepler's 2nd law
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Speed of the planets varies depending on it's orbit; it covers equal areas in equal intervals of time
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ly
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Light year: a unit of distance that light travels in one year- approximately 10^13 km or 63,000 AU
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Mars: distance / orbital period
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1.5 AU from the Sun, Orbital period approximately 2 years
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Minute of arc
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An angular measure: 1/60th of a degree
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Morning star
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any planet visible shortly before sunrise
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nanometer (nm)
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Perihelion
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Orbital point of closest approach to the sun
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Photon
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A quantum of electromagnetic energy; carries an amount of energy that depends inversely on its wavelength
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Photosphere
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The bright visible surface of the sun
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Second of arc
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An angular measure: 1/60th of a minute of arc
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solar eclipse
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An event that occurs when the moon passes directly between the Earth and the Sun, blocking our view of the sun
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Spring tide
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Ocean tide of high amplitude that occurs at full and new moon; at this point the moon is aligned with the Earth and Sun so the sun's gravity works with the moon'sand amplifies the tide
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synodic period
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The time a solar system body takes to orbit the sun once and return to the same orbital relationship with the Earth
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Vernal equinox
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The place on the celestial sphere where the sun crosses the celestial equator moving northward
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March 20; Spring begins
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Zodiac
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band around the sky extending 9 degrees above and below the ecliptic
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λ
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symbol for wavelength
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Geosynchronous satellite
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A satellite that orbits eastward around the Earth with a period of 24 hours and remains in the same spot above the Earth's surface
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center of mass
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The balance point of a body or system of masses; the point about which a body or system of masses rotates in the absence of external forces
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refracting telescope
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A telescope that forms images by bending (refracting) light with a lens
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Milankovitch hypothesis
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Suggestions that Earth's climate is determined by slow periodic changes in the shape of it's orbit, the angle of it's axis and percession
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reflecting telescope
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A telescope that uses a concave mirror to focus light into an image
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chromatic aberation
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A distortion ofund in refracting telescopes because lenses focus different colors at slightly different distances. Consequently images are surrounded by color finges
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achromatic lens
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A telescope lens composed of 2 lenses ground from different kinds of glass and designed to bring 2 selected colors to the same focus and correct for chromatic abberation
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light-gathering power
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the ability of a telescope to collect light - proportional to the area of the telescope's objective lens or mirror
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revolving power
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The ability of a telescope to reveal fine detail - depends on the diameter of the telescope's objective
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1 mile = ?km
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1 mile = 1.609 km
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diffaction fringe
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blurred fringe surround any image, caused by the wave properties of light
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north celestial pole
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point on the celestial sphere directly above the Earth's north pole
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Seeing
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Atmospheric conditions on a given night
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Magnifying power
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The ability of a telescope to make an image larger
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light pollution
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The illumination of the night sky by wasted light from cities and outdoor lighting which prevents the observation of faint objects
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prime focus
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The point at which the objective mirror forms an image in a reflecting telescope
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secondary mirror
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In a reflecting telescope a mirror that directs the light from the primary mirror to a focal point
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Cassegrain focus
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The optical design in which the secondary mirror reflects light back down thruough a tube that lies in a hole in the center of the objective mirror
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Newton's Law of Gravity- equation
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F = (-G) * Mm/r² Mm: masses of 2 orbiting objects r²: distance between centers of objects -G: gravitational constant F: force of gravity between 2 objects
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Umbra
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The region of shadow that is totally shaded
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Penumbra
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The portion of a shadow that is only partially shaded
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Newtonian focus
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The optical design in which a diagonal mirror reflects light out the side of the telescope tube for easier access
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Schmidt-Cassegrain focus
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The optical design that uses a thin corrector plate at the entrance to the telescope tube - allows wide angle viewing
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Sidereal drive
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The motor and gears on a telescope that turn it westward to keep it pointed at a star
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escape velocity
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The initial velocity an object needs to escape from the surface of a celestial body
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Asterism
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A named grouping of stars that is not one of the recognized constellations
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Node
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The points where an object's orbit passes through the plane of the Earth's orbit
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Prominence
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Eruption on the solar surface; most visible during the total solar eclipse
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Summer solstice
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The point on the celestial sphere where the sun is at it's most northernly point
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Objective lens or mirror
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In a refracting telescope, the long-focal length lens that forms an image of the object viewed; lens closest to the object. In a reflecting telescope, the principal mirror that forms an image of the object viewed.
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Primary lens or mirror
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The largest lens or mirror in the telescope
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Nadir
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Point on the celestial sphere directly below the observer
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wave length
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The distance between successive peaks or troughs of a wave; represented by λ
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electromagnetic radiation
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Changing electric and magnetic fields that travel through space at the speed of light and transfer energy from one place to another
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example: Lightwaves, radio waves
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zenith
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Point on the celestial sphere directly above the observer
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circular velocity
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The velocity an object needs to stay in orbit around another object
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Neap tide
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Ocean tide of low amplitude occuring in the 1st and 3rd quarters of the moon. Moon and sun's gravity work against each other, decreasing the size of the tides
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Natural law
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A theory that is almost universally accepted as true
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Group 2A
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Alkaline Earth metals: +2 charge
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Paradigm
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A commonly acceptd set of scientific ideas and assumptions
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South celestial pole
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Point on the celestial sphere directly above the Earth's south pole
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This planet is slightly bigger than the moon and .39 AU from the Sun
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Mercury
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Atmospheric window
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Wave length region in which our atmosphere is transparent - @ visual, infrared and radio wavelengths
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Focal length
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The focal length of a lens is the distance from the lens to the point where it focuses parallel rays (light rays from very great distances) of light
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Beta particle
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high speed electron
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Mass
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The measure of the amount of matter making up an object
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Retrograde motion
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The apparent backward (westward) motion of planetsas seen against the background of stars
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Weight
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Measure of gravitational forces acting on an object
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achromatic lens
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A telescope lens composed of two lenses ground from different kinds of glass and designed to bring two selected colors to the same focus and correct for chromatic abberation
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Speed of light
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300,000 km/s
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Open orbit
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An orbit that carries an object away, never to return to it's starting point
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Horizon
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Circular boundary between the sky and the earth
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How to determine magnitude / intensity
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Mb-Mb = 2.5 lgo (Ia/Ib) or Ia/Ib = 2.512^Mb-Ma
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Morning start
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any planet visible in the sky just before sunrise
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Sidereal period
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The time a celestial body takes to turn once on its axis or revolve once in its orbit relative to the stars
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Celestial sphere
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An imaginary sphere of very large radius surrounding the Earth and to which the planets, stars, sun and moon SEEM attached
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Magnitude scale
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astronomical brightness cale; the larger the number, the fainter the star
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Scientific notation
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System of recording very large or very small numbers by using powers of 10
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Solar system
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The sun, its planets, asteroids, comets and so on
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Planet
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A small nonluminous body that shines by reflected light
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Star
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A globe of gas held together by its own gravity and supported by the internal pressures of it's hot gases which genreate energy by nuclear fusion
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Astronomical unit (AU)
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The average distance from Earth to the Sun; 1.5 x 10^8 or 93 x 10^6
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Circular velocity equation
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Vc = sqrt of GM/r
Vc= velocity G=gravitational contant 6.67 x 10^-11 m^3/s^2kg m: mass of central body r: radius of the orbit in meters |
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Comparison spectrum
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a spectrum of known spectral lines used to identify unknown wavelengths in an objects spectrum
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Adaptive optics
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a computer controlled optical system used to partially correct for seeing in an astronomical telescope
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Active optics
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Thin telescope mirrors that are controlled by computers to maintain proper shape as the telescope moves
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Density
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Mass/Volume
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Interferometry
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The observing technique in which separate telescopes are combined to produce a virtual telescope with a resolution of a telescope of a much larger diameter
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Alt-azimuth mounting
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a telescope mounting that allows the telescope to move in altitude (perpendicular to the horizon) and azimuth (parallel to the horizon)
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Equant
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In Ptolemaic theory, the point off the center in the deferent from which the center of the epicycle appears to move uniformly
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Uniform circular motion
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The classic belief that the perfec heavens could only move by the combination of uniform motion along circular orbits
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Winter solstice
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Point on the celestial sphere where the sun is farthest south
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Evening star
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Any planet visible in the sky just after sunset
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Precession
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The slow change in the direction of Earth's axis of rotation
One cycle takes approximately 26,000 years |
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Parallax
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The apparent change in positoin of an object due to a change in the location of the observer
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spectral line
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A line a spectrum at a specific wavelength produced by the absorption or emission of light by certain atoms
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nucleus
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The central core of an atom containing protons and neutrons; carries a positive charge
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proton
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a positively charged atomic particle contained in the nucleus of an atom; sometimes refers to the nuceus of the hydrogen atom
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neutron
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an atomic particle with no charge and approximately the same mass as a proton
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electron
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low-mass atomic particle carrying a negative charge
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Isotope
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an atom that has the same number of protons but a different number of neutrons
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Ionization
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the process in which atoms gain or lose electrons
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ion
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an atom that has lost or gain electrons
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molecule
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two or more atoms bonded together
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Coulomb forces
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the electrostatic force of repulsion or attraction between charged bodies
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Binding energy
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the energy needed to pull an electron away from its atom
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Quantum mechanics
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the study of the behavoir of atoms and atomic particles
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Permitted orbit
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one of the energy levels in an atom that an electron may occupy
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Energy level
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one of the number of states an electron my occupy in an atom, depending on its binding energy
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excited atom
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an atom in which an electron has moved from a lower to a higher energy level
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ground state
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the lowest permitted electron energy level in an atom
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heat
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the flow of thermal energy
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temperature
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a measure of the agitation among the atoms and molecules of a material: aka the intensity of atomic motion
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Kelvin temperature scale
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a temperature scale using Celsius degrees and based on zero at absolute zero
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absolute zero
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the theoretical lowest possible temperature at which a material contains no extractable heat energy; established as zero onthe Kelvin temperature scale
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black body radiation
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radiation emitted by a hypothetical perfect radiator. The spectrum is continuous, and the wavelength of maximum emission depends on the body's temperature
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Wavelength of maximum intensity
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the wavelength at which a perfect radiator emits the maximum amount of energy. Depends only on the object's temperature
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Joule
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A unit of energy equivalent to the force of 1 newton acting over a distance of 1 meter: 1 joule per second equals 1 watt of power
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continuous spectrum
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a spectrum in which there are no absorption or emission lines
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absorption spectrum
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spectrum that contains absorption lines caused by photons being absorbed by atoms or molecules
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emission spectrum
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a spectrum containing emission lines
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length of 1 light year (ly)
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63, 000 AU
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emission line
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a bright line in a spectrum caused by the emissio of photons from atoms
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spectrograph
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a device that separates light by wavelengths to produce a spectrum - a fingerprint of the source of the light
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absorption line
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a dark line in a spectrum; is produced by the absence of photons absorbed by atoms or molecules
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Kirchoff's laws
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a set of laws that describe the absorption and emission of light by matter
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transition
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the movement of an electron from one atomic energy level to another
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Lyman series
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Spectral lines in the ultraviolet spectrum of hydrogen produced by transitions whose lowest energy level is the ground state
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Balmer series
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A series of spectral lines produced by hydrogen in the near-ultraviolet and visible parts of the spectrum
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Paschen series
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Spectral lines in the infrared spectrum of hydrogen produced by the transitions whose lowest energy level is third
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spectral class or type
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A star's positoin in the temperature classification OBAFGKM; is based on the appearance of the star's spectrum
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Spectral sequence
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the arrangement of spectral classes ranging from hot to cool
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Celcius to Kelvin
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K = C + 273.15
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L dwarf
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a main sequence star cooler than an M star
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T dwarf
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a very cool, low-mass star or brown dwarf located below the L stars on the main sequence
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Doppler effect
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the change in the wavelength of radiation due to the relative radial motion of source and observer
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Blueshift
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A Doppler shift twoard shorter wavelengths caused by a velocity of approach
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Redshift
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A Doppler shift toward longer wavelengths caused by a velocity of recession
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radial velocity (Vr)
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a component of an object's velocity directed away from or toward Earth
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charged coupled device (CCD)`
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an electronic device consisting of a large arrange of light-sensitive elements used to record very faint images
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Absorption spectrum
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Produced when radiation passes through a cooler gas: results in dark lines in a spectrum
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Autumnal Equinox
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The point on the celestial sphere where the sun crosses the celestial equator going southward.
Sept 22 Fall begins |
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Ecliptic
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The apparent path of the sun around the sky
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Eccentricity
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A number between 1 and 0 that describes the shape of an ellipse:
Distance of 1 focus to center of ellipse divided by semimajor axis In a circle: 0, while in an oval: close to 1 |
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Saros cycle
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An 18 year, 11.33 day period after which the pattern of lunar and solar eclipses repeats
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Gamma particles
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high energy light
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Aphelion
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Orbital point of greatest distance from the sun
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Scientific model
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a tentative description of a phenomenon for use as an aide to understanding
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Sunspots
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relatively dark spots on the sun that contain intense magnetic fields
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Granulation
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the fine structure of bright grains covering the sun's surface
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