Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
343 Cards in this Set
- Front
- Back
|
Horizon
|
The boundary between earth and the sky
|
|
|
Asterisms
|
Patterns formed by bright stars
|
|
|
Constellations
|
Recognizable patterns, informal names derived from ancient legends (Orion)
|
|
|
Pointer Stars
|
The two stars of the bowl farthest from the Big Dipper’s handle
|
|
|
Celestial Sphere
|
A sky map with a coordinate system
|
|
|
Winter Triangle
|
Three of the brightest stars: Sirius, Procyon, Betelgeuse; constellations: Orion, Canis Major, and Canis Minor
|
|
|
Summer Triangle
|
Deneb, Vega, and Altair; constellations: Cygnus—northern cross—Aquila, Lyra
|
|
|
Celestial Equator
|
The earth’s equator expanded onto the celestial sphere, which divides the sky into Northern and Southern hemispheres
|
|
|
Declination (Dec)
|
The equivalent to latitude (degrees)
|
|
|
Right Ascension (r.a.)
|
The equivalent to longitude (hrs)
|
|
|
Prime Meridian
|
Zero longitude on earth
|
|
|
Vernal Equinox
|
Zero right of ascension (equal to the Prime Meridian on Earth);
March 21st. The point on the ecliptic where the Sun crosses the celestial equator from North to South. |
|
|
Diurnal Motion
|
Daily motion of the celestial bodies—rising and setting of stars
|
|
|
Revolution
|
Motion of any astronomical object around another astronomical object
|
|
|
Circumpolar
|
Stars and constellations that never go below the horizon
|
|
|
Zenith
|
Directly overhead
|
|
|
Ecliptic
|
Path the sun traces on the celestial sphere or the plane where earth orbits the sun
|
|
|
Equinox
|
Latin meaning equal night. When the sun is directly over the Earth’s equator resulting in 12 hours of day and 12 hours of night everywhere on Earth for that day
|
|
|
Winter Solstice
|
Dec 22nd. Sun is furthest South of the celestial equator. In the northern hemisphere, it is the day with the fewest daylight hours and the sun is the lowest at noon.
|
|
|
Summer Solstice
|
June 21st. The Sun is furthest North of the celestial equator. In the northern hemisphere it is the day with the most daylight hours and the Sun is highest at noon.
|
|
|
Autumnal Equinox
|
September 22nd. Sun crosses celestial equator moving North to South.
|
|
|
Zodiac
|
The constellations which the sun moves throughout the year as it travels along the celestial ecliptic. 13 in all, including Ophiuchus the Serpent Holder.
|
|
|
Solar Day
|
Suns motion through the sky. 24 hour day; time between the Sun at its zenith (noon) or when it crosses the meridian
|
|
|
Time Zones
|
Every 15 degrees of longitude
|
|
|
Sidereal Day
|
The length of time from when a star is in one place in the sky until it is next in the same place (view from Earth)
OR Time when Earth makes one complete rotation of 360 degrees. Which is 23 hours, and 56 minutes long. The sidereal day is shorter than the solar day by 3.9 minutes or 0.986 degrees |
|
|
Tropical year
|
Time interval from one vernal equinox to the next; time between successive equinoxes; 365.2422 solar days
|
|
|
Geocentric
|
A view of the universe based on the observed motion of the celestial sphere and believe that the sun, moon, stars and planets, revolve around the earth.
|
|
|
Cosmology
|
A theory of the overall structure and evolution of the universe
|
|
|
Retrograde motion
|
When planets stop and move backwards for several weeks or months
|
|
|
Heliocentric
|
Sun centered cosmology
|
|
|
Configurations
|
Geometric arrangements between earth, another planet, and the sun
|
|
|
Inferior conjunction
|
When Mercury or Venus is directly between the Earth and the Sun
|
|
|
Superior conjunction
|
When Mercury and or Venus are on the opposite side of the Sun from the Earth
|
|
|
Elongation
|
The angle between the Sun and a planet as viewed from earth. Varies from 0 degrees to a maximum value depending on where we see it in its orbit around the Sun; Elongation is zero if planets are aligned
|
|
|
Conjunction
|
When planets further from the Sun than Earth (outer planets) are located behind the Sun (as seen from Earth).
|
|
|
Opposition
|
When the outer planet is opposite the Sun in the sky,
OR When Earth is between the Sun and an outer planet. |
|
|
Sidereal Year
|
The time it takes a planet to make one complete orbit around the Sun
|
|
|
Sydonic Period
|
The time that elapses between two successive identical configurations as seen from Earth
|
|
|
Parallax
|
The apparent displacement of an object relative to more distant objects caused by viewing it from different locations
|
|
|
Major Axis
|
The longest diameter across an ellipse that passes through both foci
|
|
|
Semimajor Axis
|
Half of the major axis’s distance
|
|
|
Kepler’s first law
|
The orbit of a planet around the Sun is an ellipse with the Sun at one focus.
|
|
|
Orbital Eccentricity
|
The shape of a planet’s orbit around the Sun, designated by the letter e which ranges from 0 (circular orbit) to just under 1 (nearly a strait line); The Sun is one foci point on the Major Axis (longer diameter) and there is nothing at the other focus
|
|
|
Perihelion
|
When a planet moves most rapidly nearest the Sun (refers to this point in orbit).
|
|
|
Aphelion
|
A planets point of orbit that is most slow, furthest away from the Sun
|
|
|
Kepler’s Second Law
|
A line that joins the planet and a Sun sweeps out equal areas in equal intervals of time.
|
|
|
Kepler’s Third Law
|
The square of a planet’s sidereal period around the Sun is directly proportional to the cube of the length of its orbital semimajor axis/ p^2 = a^3
|
|
|
Astronomical Units (AU)
|
The average distance from the Earth to the Sun
|
|
|
Galilean Moons
|
Jupiter’s four moons
|
|
|
Newton’s First Law—The Law of Inertia
|
Inertia is the property of matter that keeps an object at rest or moving in a strait line at a constant speed unless acted upon by a net external force.
|
|
|
Newton’s Second Law—The Force Law
|
The acceleration of an object is directly proportional to the net force acting on it and is inversely proportional to its mass.
|
|
|
Acceleration
|
The rate at which velocity changes with time
|
|
|
Newton’s Third Law—The Law of Action and Reaction
|
Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first object.
|
|
|
Velocity
|
Speed and direction of motion
|
|
|
Angular Momentum
|
A measure of how much energy is stored in an object due to its rotational revolution
|
|
|
Newton’s Law of Universal Gravitation
|
Two objects attract each other with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.
|
|
|
Parabolas
|
An open curve formed by cutting a circular cone at an angle parallel to the sides of the cone/ another form of orbital path.
|
|
|
Hyperbola
|
An open curve obtained by cutting a cone with a plane/ another form of orbital path
|
|
|
Fusion
|
A process that transforms hydrogen into helium through the gravity compressing matter at the central core of a star
|
|
|
Stellar Winds
|
Outer layers of stars are expelled in a continuous outflow
|
|
|
Nebula
|
Luminous shells of gas ejected from old, low-mass stars
|
|
|
Supernova
|
A stellar explosion during which a star suddenly increases its brightness roughly a million fold
|
|
|
Metals
|
All the elements in the universe except hydrogen and helium
|
|
|
Solar Nebula
|
The region of the cloud from which the solar system developed; has a diameter of at least 100 AU and the total mass of 2-3 times that of the Sun
|
|
|
Protosun
|
A concentration of matter resulting from the increase in density, pressure, and temperature, at the center of the nebula
|
|
|
Protoplanetary Disks or Proplyds
|
Disks of gas and dust surrounding young stars
|
|
|
Planet
|
An object that directly orbits a star has enough mass to create a sphere, enough gravitational force that it has cleared its orbital neighborhood of most of the smaller debris there.
|
|
|
Moons or natural Satellites
|
Bodies that orbit larger objects which in turn orbit stars.
|
|
|
Planetismals
|
Dust and pebbles accumulated over a few million years that coalesced into larger objects; diameter of a few Km or Mi
|
|
|
Protoplanets
|
When planetismals mutual gravitational attraction brought each other together to form this larger object
|
|
|
Accretion
|
The coming together of smaller pieces of matter to form larger ones
|
|
|
Core-accretion Model
|
The traditional theory of giant planet formation; while the inner regions of the solar system were heating up, temperatures in the outer regions remained cool
|
|
|
Dwarf Planet
|
Do not have enough mass/gravitational force to clear their orbital neighborhoods of debris.
|
|
|
Gravitational Instability Model
|
A second theory based on complex computer simulations that indicate that the giant planets condensed into existence within 100 thousand years without massive terrestrial cores acting like seeds of their formation
|
|
|
Orbital Inclinations
|
The angles of orbital planes of other planets with respect to the ecliptic; 7 degrees or less
|
|
|
Asteroid Belt
|
Between the orbits of Mars and Jupiter’s lies millions of asteroids
|
|
|
Asteroids
|
Bodies composed of mostly rock and metal; typically less than 1 km across
|
|
|
Meteoroids
|
Pieces of rocky and metallic debris even smaller than asteroids
|
|
|
Comets
|
Chunks of rock and ice with elongated orbits
|
|
|
Kuiper belt
|
The comet orbit, beyond Neptune’s orbit, centered on the ecliptic; 50 AU
|
|
|
Oort Comet Cloud
|
Spherical distribution of comets, very far from the sun, 50,000 AU
|
|
|
Average Density
|
The chemical composition of any object; how much mass an object has in one unit of volume; p = m/v
|
|
|
Terrestrial Planets
|
The four inner planets have densities similar to Earth and are composed of the same chemicals—Earth, Mercury, Venus and Mars
|
|
|
Jovian Planets/ Giant Planets
|
The four outer planets that are low in density, high in mass and mostly composed of hydrogen and helium—Jupiter, Saturn, Uranus and Neptune
|
|
|
Atmospheric pressure
|
14.7 pounds per square inch = 1 ATM; pressure is defined as p = force/ area
|
|
|
Troposphere
|
Lowest layer of the atmosphere; first 15 KM; contains all weather; heated by Earth and dense air; temperature decreases with altitude
|
|
|
Stratosphere
|
Extends from 15 to 50 KM—second layer; contains Ozone layer; temperature increases with altitude
|
|
|
Ozone Layer
|
In the stratosphere, composed of o3; efficiently absorbs ultraviolet rays from the Sun
|
|
|
Mesosphere
|
Above the stratosphere; 50-90 Km; cooling with lower pressure; temperature decreases with altitude
|
|
|
Ionosphere / Thermosphere
|
Begins at 80KM; the Sun’s ultraviolet light heats and ionizes atoms producing charged particles that reflect radio waves; absorbs more energy; temperature increases with altitude
|
|
|
Crust
|
Earth’s outermost layer; composed of low density rock that floats on denser material below it
|
|
|
Nuclear Fission
|
The process of radioactive atoms breaking apart, creating heat/ energy
|
|
|
Nuclear Fusion
|
Energy generated by the Sun, wherein lighter atoms are fused together
|
|
|
Planetary Differentiation
|
Iron and other dense materials sink toward the center of liquid earth and less dense materials are forced upwards towards the surface; produced the layered structure within the Earth
|
|
|
Seismic Waves
|
Vibrations that travel through Earth either as ripples (ocean waves) or by compressing matter (sound waves)
|
|
|
Convection
|
A liquid or gas is heated from below, expands, becomes buoyant, rises, carrying the heat it receives with it, releases heat, cools, condenses, sinks, repeats
|
|
|
Convection Current
|
Fluid motion of a circular currant; process of the Earth’s mantle
|
|
|
Dynamo Theory
|
The convection of molten iron in Earths outer core combined with our planets rotation creates electric currents which in turn create Earth’s magnetic field
|
|
|
Solar Wind
|
An erratic flow of electrically charged particles ejected from the Sun’s upper atmosphere
|
|
|
Van Allen Radiation Belts
|
Earth’s magnetic field traps some of the charged particles creating these two huge doughnut shaped rings which surround the Earth
|
|
|
Northern Lights/ Aurora Borealis and Southern Lights/ Aurora Australis
|
When the Van Allen belts overload with particles, they leak through the magnetic fields near the poles and cascade down into Earth’s upper atmosphere, colliding with gases there creating fluoresce
|
|
|
Coronal Mass Ejection
|
A violent event on the Sun’s surface that sends a burst of protons and electrons strait through the Van Allen belts and into the atmosphere; they disturb radio waves, damage communications satellites, and electric transmission lines; they also create Auroras everywhere
|
|
|
Small Solar System Bodies/ SSSB’s
|
All objects that are not planets, dwarf planets, or moons
|
|
|
Minor Planet
|
Planetismals or asteroids
|
|
|
Kirkwood Gaps
|
Gaps in the asteroid belt created by Jupiter’s gravitational attraction
|
|
|
Meridian
|
North- South line
|
|
|
Altitude
|
Vertical angle above the horizon
|
|
|
Axis tilt
|
23.5 degrees relative to the ecliptic
|
|
|
Polaris
|
North star
|
|
|
Sidereal Year
|
Time for exactly one revolution; 365.2564 solar days
|
|
|
Ellipse
|
Elongated circle; orbital path
|
|
|
Coma
|
Vaporized gases that surround a comet's nucleus
|
|
|
Hydrogen Envelope
|
Surrounds a comet's nucleus
|
|
|
Ion Tail
|
Ionized gases from a comet that points directly away from the Sun due to Solar Wind
|
|
|
Dust Tail
|
The curved second tail of a comet that points in the direction combining motion and photon pressure
|
|
|
Radar
|
Time it takes for light to hit an object and come back
|
|
|
Subduction
|
Occurs when continental granite pushes down oceanic basalt into the Earth's mantle
|
|
|
Primary Atmosphere
|
Earth's first atmosphere composed of helium and hydrogen, which escaped gravitational pull as they got hot and blown away by solar wind
|
|
|
Secondary Atmosphere
|
Earth's second atmosphere that consisted mostly of Nitrogen, Water, and Carbon Dioxide out gassed by volcanic activity
|
|
|
Magnetosphere
|
Surrounds and protects Earth by trapping ionized particles from Solar Wind; created from the solid core spinning at a faster rate than the outside Earth which creates convective currents in the liquid core-- motion of electric charges; Earth's north pole is the magnetic south pole; magnetic field axis is tilted 12 degrees away from the Earth's rotational axis
|
|
|
Synchronous Rotation
|
The Moon rotates once per revolution; Rotation and Revolution at the same time; this is why we only see one side of the moon
|
|
|
Maria
|
Impact basins on the Moon created by ancient impacts that were so large they penetrated into the hot molten mantle, subsequently filling the crater with lava
|
|
|
Mare Basalt
|
Denser rock on the Moon originating from the mantle due to volcanic activity; 3.1- 3.8 billion years old
|
|
|
Anorthosite
|
Lighter rock on the Moon in the highly cratered highlands; 4-4.3 billion years old; original Moon crust
|
|
|
Regolith
|
Fine powdery dust on the surface of the Moon due to billions of years of micrometeor bombardment
|
|
|
Lunar Syndoic Month
|
29.5 days; phases go through one full cycle
|
|
|
Lunar Sidereal Month
|
27.3 days; Moon rotates 360 degrees around the Earth
|
|
|
Terminator
|
The line dividing the dark side and the bright side of the Moon
|
|
|
Lunar Eclipses
|
Occurs when the Moon crosses the ecliptic during a full phase; the Earth, Moon, and Sun must be aligned; the 5.2 degree angle to ecliptic of the Moon's orbit prevents frequent eclipses
|
|
|
Solar Eclipse
|
Occurs during the new Moon phase, when the shadow of the Moon crosses in front of the Earth
|
|
|
Partial Solar Eclipse
|
Only part of the Sun is blocked out (in penumbra)
|
|
|
Annular Solar Eclipse
|
In the umbra and the Moon is far from Earth
|
|
|
Total Solar Eclipse
|
In the umbra and the Moon is close to earth;covers all of the Sun except the Sun's atmosphere which can be observed
|
|
|
Umbra/penumbra
|
Different levels of shadow due to the relative size and distance of the sun
|
|
|
Penumbral Lunar Eclipse
|
The Moon passes only through Earth's penumbra; Difficult to detect
|
|
|
Partial Lunar Eclipse
|
Only part of the umbra covers the Moon
|
|
|
Total Lunar Eclipse
|
The umbra covers the Moon completely
|
|
|
Tides
|
Occur due to the difference in gravitational force between the the closer vs. farther side of the Earth
|
|
|
Lunar Phases
|
The moons position relative to the Sun changes, and as a result we see these phases: Waxing Crescent, First Quarter, Waxing Gibbous, Waning Gibbous, Third Quarter, and Waning Crescent
|
|
|
Precession
|
Our sidereal year differs from the time between consecutive equinoxes primarily due to Earth's rotation axis slowly changing direction in space.
|
|
|
Line of Nodes
|
Where the Moon crosses the ecliptic.
|
|
|
Solar Corona
|
Hot gases surrounding the Sun; the
Sun's upper atmosphere |
|
|
Eclipse Path
|
As Earth turns and the Moon orbits during a solar eclipse, a shadow path is traced on the Earth by the Moon's umbra
|
|
|
Visible Light
|
White light that contains a combination of all rainbow colors, and is a form of electromagnetic radiation.
|
|
|
Electromagnetic Radiation
|
Radiation consisting of oscillating electric and magnetic fields, namely gamma rays, x rays, visible light, ultraviolet and infrared radiation and radio waves.
|
|
|
Photons
|
A discrete unit of electromagnetic energy
|
|
|
Refraction
|
The change in direction as light travels through one medium into another, resulting in a spread of colors, or wavelengths of visible light.
|
|
|
Spectrum
|
A spread of colors created from refraction, complete or with colors missing
|
|
|
Wavelength
|
The distance between two successive wave crests.
|
|
|
Blueshift
|
All of the colors in the spectrum of an approaching source are shifted toward the short wavelength--blue-- end of the spectrum regardless of it's distance.
|
|
|
Redshift
|
All the colors in the spectrum of a receding source are shifted toward the longer wavelength -- red-- end of the spectrum, regardless of it's distance.
|
|
|
Doppler Shift
|
Blueshift or Redshift-- the amount of Doppler shift varies directly with approaching or receding speed.
|
|
|
Frequency
|
The number of wave crests that pass a given point per second. Unit is Hertz.
|
|
|
Intensity
|
How bright an object appears to be due to the total number of photons passing per second from that source with a given energy
|
|
|
Infrared Radiation
|
Electromagnetic radiation with wavelengths slightly longer than red light. We detect this light as heat.
|
|
|
Radio Waves
|
Electromagnetic radiation a few centimeters in wavelength
|
|
|
Ultraviolet Radiation
|
Wavelengths shorter than those of visible light, extends from 400 nm to 10 nm.
|
|
|
X Rays
|
Electromagnetic radiation with wavelengths shorter than 10 nm
|
|
|
Gamma Rays
|
The most energetic form of electromagnetic radiation with the shortest wavelength
|
|
|
Electromagnetic Spectrum
|
The full range of all possible wavelengths.
|
|
|
Refracting Telescopes
|
- Uses two converging lenses to collect and focus light
-Uses an objective lens that focuses and an eyepiece that magnifies - Suck because of chromatic aberration which makes the different wavelengths of light travel at different speeds because it had to go through a medium (the glass) -Suck because they absorb and reflect a percentage of light -Suck because they can have density variations or bubbles |
|
|
Reflecting Telescopes
|
Collect light through mirrors.
|
|
|
Light Ray
|
A flow of photons
|
|
|
Reflection
|
The angles between the incoming light ray and the perpendicular is always equal to the angle between the outgoing, reflected light ray and the perpendicular.
OR The angle of incidence equals the angle of reflection. |
|
|
Focal Point
|
When light rays hit a concave mirror in the shape of a parabola, all parallel incoming light rays strike the mirror to converge into this focal point, where the image is formed.
|
|
|
Primary Mirror
|
The large, concave, light-gathering mirror in a reflecting telescope, analogous to the objective lens on a refracting telescope
|
|
|
Focal Length
|
The distance between the primary mirror and the focal point (where the image is formed).
|
|
|
Focal Plane
|
The plane at the focal length of a lens or concave mirror on which an extended object is found
|
|
|
Secondary Mirror
|
A small, flat mirror placed between the primary mirror and the focal point that reflects light rays to one side of the telescope.
|
|
|
Eyepiece lens
|
Where the astronomer views the image through a telescope.
|
|
|
Newtonian Reflector
|
An optical arrangement in a reflecting telescope in which a small secondary mirror reflects converging light rays to one side of the telescope tube.
|
|
|
Cassegrain Focus
|
An optical arrangement in a reflecting telescope in which light rays are reflected by a secondary mirror through a hole in the primary mirror
|
|
|
Coude Focus
|
A reflecting telescope in which a series of mirrors direct light into a remote focus away from the moving parts of the telescope
|
|
|
Spectrographs
|
Instruments that separate light from objects into its individual colors to determine the objects' chemistry, surface temperature, and motion towards or away from us.
|
|
|
Prime Focus
|
An observing device is located at the undeflected focal point, directly in front of the primary mirror.
|
|
|
Light-gathering Power
|
The power of a telescope to gather light that is directly related to the area of the telescope's primary mirror.
|
|
|
Extended objects
|
more than just points of light
|
|
|
Angular Resolution
|
Measures the clarity of images by the arc angle between two adjacent stars whose images can just barely be distinguished by the telescope. The smaller the angle, the sharper the image.
|
|
|
Magnification
|
Makes objects appear larger. Associated with resolution because the larger the image the more detail you could potentially see. The magnification of a reflecting telescope is equal to the focal length of the primary mirror divided by the focal length of the eyepiece lens.
|
|
|
Charge Coupled Devices (CCD's)
|
Highly efficient electronic light detectors that typically respond to 70 percent of the light falling on them, making their resolution much better than film. Divided into light sensitive squares called pixels.
|
|
|
Objective Lenses
|
Large convex lenses used in telescopes instead of primary mirrors
|
|
|
Convex lenses
|
Lenses that are thicker at their centers than at their edges, which force light to converge as it passes through
|
|
|
Concave lenses
|
Lenses thinner at their center than at their edges which cause light rays to diverge
|
|
|
Refractor
|
An arrangement of two lenses used to gather light-- has an objective lens rather than a primary
|
|
|
Chromatic Aberration
|
When different colors of light are refracted at different amounts so different colors have different focal lengths, resulting in a blurred image.
|
|
|
Spherical Aberration
|
When different parts of a spherically concave mirror reflect light to slightly different focal points which cases image blurring.
|
|
|
Schmidt Corrector Plate
|
A thin lens with a spherical mirror placed in front of the telescope--used to correct Spherical Aberration
|
|
|
Twinkling
|
When the stars appear to change brightness and position rapidly because the air density changes rapidly changing refraction
|
|
|
Seeing Disk
|
The angular diameter of a star's smeared out image
|
|
|
Active Optics
|
Finds the best orientation for the primary mirror in response to changes in temperature and the shape of the telescope mount
|
|
|
Adaptive Optics
|
Uses sensors to determine the amount of twinkling created by atmospheric turbulence
|
|
|
Interferometry
|
Combines images from different telescopes to increase resolution
|
|
|
Radio Telescopes
|
Record radio signals from the sky
|
|
|
Very-long-baseline-interferometry (VLBI)
|
Radio telescopes separated by thousands of kilometers linked together
|
|
|
Scintillators
|
Devices that detect the visible light created as X rays pass through them
|
|
|
Calorimeters
|
Devices that detect heat generated by X rays passing through them
|
|
|
Blackbodies
|
A hypothetical perfect radiator that absorbs and reemits all of the electromagnetic radiation that strikes it
|
|
|
Blackbody Curves
|
The curve obtained when the intensity of radiation from a blackbody at a particular temperature is plotted against it's wavelength
|
|
|
Wein's Law
|
The peak wavelength of radiation emitted by a blackbody is inversely proportional to its temperature
|
|
|
Stephan-Boltzmann Law
|
An object emits energy per unit area at a rate proportional to the fourth power of its temperature in Kelvins
|
|
|
Planck's Law
|
A relationship between the energy carried by a photon and its wavelength
|
|
|
Absorption Lines
|
A dark line in a continuous spectrum created when photons of a certain energy are absorbed by atoms or molecules
|
|
|
Emission Line
|
A bright line of electromagnetic radiation
|
|
|
Spectroscope
|
A device that consists of a narrow slit, a prism, and several lenses that straiten the light rays and magnify the spectrum so it can be closely examined.
|
|
|
Spectral Analysis
|
The identification of chemical substances by their spectral lines
|
|
|
Spectrograph
|
A device for photographing a spectrum-- the astronomers most important tool
|
|
|
Diffraction grating
|
A piece of glass that has thousands of closely placed parallel groves cut
|
|
|
Kirchoff's first law
|
A solid, liquid, or dense gas produces a continuous spectrum (also called a continuum)-- a complete rainbow of colors without any spectral lines. This is a blackbody spectrum.
|
|
|
Kirchoff's second law
|
A rarefied (opposite of dense) gas produces an emission line spectrum-- a series of bright spectral lines against a dark background.
|
|
|
Kirchoff's third law
|
The light from an object with a continuous spectrum that passes through a cool gas produces an absorption line spectrum-- a series of dark spectral lines among the colors of the rainbow
|
|
|
Radioactive
|
An element that naturally and spontaneously transforms into another element by emitting particles at a considerable speed
|
|
|
Nucleus of an Atom
|
Consists of particles called protons and neutrons-- dense enough for radioactive alpha particles to bounce off of
|
|
|
Atom
|
The smallest particle of a chemical element that still has the properties of that element
|
|
|
Electrons
|
Particles with a negative charge that orbit the atomic nucleus based on its attraction to positively charged protons
|
|
|
Protons
|
Particles with a positive charge in the nucleus of an atom
|
|
|
Neutron
|
A particle in the nucleus of an atom with no electrical charge
|
|
|
Strong Nuclear Force
|
The force that binds protons and neutrons together in an atoms' nucleus
|
|
|
Weak Nuclear Force
|
A nuclear interaction involved in certain kinds of radioactive decay
|
|
|
Atomic Number
|
The number of protons in an atoms nucleus that determines the element of that atom
|
|
|
Electromagnetic Force
|
The interaction between charged particles; the second of four fundamental forces in nature
|
|
|
Isotope
|
Atoms that all have the same number of protons (atomic number) but different number of neutrons. Their nuclear properties often differ greatly.
|
|
|
Ion
|
When an atom contains a different number of electrons than protons
|
|
|
Ionization
|
The process of creating an ion
|
|
|
Molecules
|
Atoms share electrons with each other; groups of atoms
|
|
|
Quantum Mechanics
|
The branch of physics dealing with the structure and behavior of atoms and their interactions with with each other and with light
|
|
|
Transition
|
The change in energy and orbit of an electron around an atom or molecule
|
|
|
Ground State
|
The lowest energy allowed orbit or energy level of an electron (n = 1)
|
|
|
Excited State
|
When an electron is in an orbit with more energy than the lowest energy state available to it
|
|
|
Photoionization
|
When an electron orbiting in a hydrogen atom encounters a photon with more than 13.6 eV (electron volt) that photon is absorbed and knocks the electron completely out of orbit and away from the atom
|
|
|
Radial Velocity
|
The speed of an abject toward or away from us
|
|
|
Transverse Velocity
|
The portion of an object's velocity perpendicular to our line of sight to it
|
|
|
Proper Motion
|
The change in the location of a star on the celestial sphere
|
|
|
Limb
|
The Sun's edge
|
|
|
Limb Darkening
|
When the Suns Photosphere appears darkest at the limb (edge) of the solar disk which occurs because we see regions of different temperatures at different depths of the photosphere
|
|
|
Photosphere
|
The region in the solar atmosphere from which most of the visible light escapes into space
|
|
|
Granules
|
Lightly colored convection features about 1000 km in diameter seen constantly in the solar photosphere
|
|
|
Chromosphere
|
Immediately above the photosphere is a dim layer of less dense stellar gas
|
|
|
Spicules
|
Narrow jets of gas rising in the solar chromosphere
|
|
|
Supergranules
|
Enormous regions of rising and falling chromospheric gas
|
|
|
Transition Zone
|
Region between the Sun's chromosphere and corona where the temperature skyrockets to about 1 million K
|
|
|
Coronagraph
|
A specially designed telescope that artifically blocks the photosphere during a total eclipse
|
|
|
Heliosphere
|
A bubble in space created by the solar wind contains the sun and planets
|
|
|
Genesis Spacecraft
|
Launched to collect pristine solar wind particles outside magnetosphere. Although the parahute failed, we still collected important neon isotopes that revealed that the Sun has nearly retained a onstant temperature
|
|
|
Sunspots
|
Regions of the photosphere that appear dark because they are cooler than the rest of the Sun's lower atmosphere
|
|
|
Sunspot Maximum
|
The time during the solar cycle when the number of sunspots is greatest
|
|
|
Sunspot Minimum
|
The time during the solar cycle when the number of sunspots is least
|
|
|
Sunspot Cycle
|
The semiregular 11 year period with which the number and location of sunspots fluctuate
|
|
|
Umbra/Penumbra of Sunspots
|
Each sunspot has two parts: a dark central region (umbra) and a brighter ring that surrounds that (penumbra)
|
|
|
Differential Rotation
|
The rotation of a nonrigid object in which parts at different latitudes or different radial distances move at different speeds
|
|
|
Zeeman Effect
|
A splitting of spectral lines in the presence of a magnetic field
|
|
|
Plasma
|
A hot, ionized gas
|
|
|
Helioseismology
|
The study of vibrations on the solar surface
|
|
|
Solar Cycle
|
A 22 year cycle during which the Sun's magnetic field reverses it's polarity twice
|
|
|
Magnetic Dynamo
|
A theory that explains phenomena of the solar cycle as a result of periodic winding and unwinding of the Sun's magnetic field in the solar atmosphere
|
|
|
Maunder Minimum
|
A period where the Sun has no sunspots resulting in extreme old and drought in parts of the world
|
|
|
Plages
|
A bright spot on the Sun believed to be associated with an emerging magnetic field
|
|
|
Filaments
|
A dark curve seen above the Sun's photosphere that is the top view of a solar prominence
|
|
|
Prominences
|
Flame like protrusions seen near the limb of the Sun and extending into the solar corona. The side view of a filament.
|
|
|
Solar Flare
|
A violent eruption on the Sun's surface
|
|
|
Coronal Hole
|
A dark region of the Sun's inner corona as seen at X ray wavelengths
|
|
|
Thermonulear Fusion
|
A reaction in which the nuclei of atoms are fused together at a high temperature
|
|
|
Hydrogen Fusion
|
The thermonuclear fusion of hydrogen to produce helium
|
|
|
Solar Model
|
A set of equations that describe the internal structure and energy generation of the Sun
|
|
|
Hydrostatic Equilibrium
|
The balance between the inward force of gravity and the outward force of motion of the hot gas
|
|
|
Radiative Zone
|
A region inside a star where energy is transported outward by the movement of photons through a gas from a hot location to a cooler one
|
|
|
Radiative Transport
|
The outward movement of energy by photons hitting particles and thereby reemit photons
|
|
|
Convective Zone
|
A layer in a star where energy in transported outward by means of convection
|
|
|
Neutrino
|
A subatomic particle, with no electric charge and little mass, that is important in many nuclear reactions and super novae
|
|
|
Cerenkov Radiation
|
Radiation produced by particles traveling through a substance faster than light
|
|
|
Stellar Parallax
|
The apparent motion of nearby stars among the background of more distant stars, due to the Earth's motion around the Sun
|
|
|
Apparent Magnitudes
|
The brightness of stars measured without regard to their distances from Earth
|
|
|
Absolute Magnitude
|
The apparent magnitude that a star would have if it were ten parsecs from Earth
|
|
|
Parsec
|
A unit of distance equal to 3.26 light-years
|
|
|
Inverse Square Law
|
Apparent brightness decreases inversely with the square of the distance between the source and the observer
|
|
|
Luminosity
|
The rate at which electromagnetic radiation is emitted from a star or other object
|
|
|
Photometry
|
The measurement of light intensities
|
|
|
Stellar Spectroscopy
|
The study of the properties of stars encoded in their spectra
|
|
|
Balmer Lines
|
Visible hydrogen lines on a spectra
|
|
|
Spectral Types
|
A classification of stars according to the appearance of their spectra
|
|
|
OBAFGKM sequence
|
The sequence of stellar spectral classifications from hottest to coolest stars
|
|
|
Hertzsprung-Russel (HR) Diagram
|
A plot of the absolute magnitude or luminosity of stars versus the surface temperatures or spectral classes
|
|
|
Main Sequence
|
A grouping of stars on the HR diagram extending diagonally across the graph from the hottest brightest stars to the dimmest coolest stars
|
|
|
Main Sequence Star
|
A star, fusing hydrogen to helium in its core, whose surface temperature and luminosity place it on the main sequence on the HR diagram
Stars in hydrostatic equilibrium in which nuclear reactions fuse hydrogen into helium in their cores at nearly constant rates. |
|
|
Giant Star
|
A star whose diameter is roughly ten to 100 times that of the Sun
|
|
|
Red Dwarf
|
A low-mass main sequence star
|
|
|
Red Giants
|
A large, cool star of high luminosity
|
|
|
Supergiants
|
A star of very high luminosity
|
|
|
White Dwarf
|
A low-mass stellar remnant that has exhausted all its thermonuclear fuel and contracted to a size roughly equal to the size of Earth
|
|
|
Luminosity Class
|
The classification of a star of a given spectral type according to its luminosity and density; the classes are supergiant, bright giant, giant, subgiant, and main sequence
|
|
|
Spectroscopic Parallax
|
A method of determining a star's distance from Earth by measuring its surface temperature, luminosity, and apparent magnitude
|
|
|
Optical Double
|
A pair of stars that appear to be near each other but are unbound and at very different distances from Earth
|
|
|
Binary Star
|
Two stars revolving about each other; a double star
|
|
|
Center of Mass
|
The point around which a rigid system is perfectly balanced in a gravitational field; also, the point in space around which mutually orbiting bodies have elliptical orbits
|
|
|
Visual Binary Star
|
A double star in which the two components can be resolved through a telescope
|
|
|
Eclipsing Binary
|
A double star system in which stars periodically pass in front of each other as seen from Earth
|
|
|
Light Curve
|
A graph that displays variations in the brightness of a star or other astronomical object over time
|
|
|
Close Binary
|
A binary star whose members are separated by a few stellar diameters
|
|
|
Mass-Luminosity Relation
|
The direct relationship between the masses and the luminosities of the main sequence stars which is that low mass stars have low luminosity and high-mass stars have high luminosity
|
|
|
Spectroscopic Binary
|
A double star whose binary nature can be deduced from the periodic Doppler shifting of lines in its spectrum
|
|
|
Radial-Velocity Curve
|
A plot showing the variation of radial velocity with time for a binary star or variable star
|
|
|
Interstellar Medium
|
Interstellar gas and dust-- the material between stars that contains at least 10% of all observed mass in our Galaxy
|
|
|
Reflection Nebula
|
A comparatively dense cloud of gas and dust in interstellar space that is illuminated by a star between it and Earth
|
|
|
Molecular Clouds
|
Nebulae that are often embedded in much larger bodies of gas and dust
|
|
|
Giant Molecular Clouds
|
A large interstellar cloud of cool gas and dust in a galaxy
|
|
|
Dark Nebula
|
A cloud of interstellar gas and dust that obscures the light of more distant stars
|
|
|
Emission Nebula
|
A glowing gaseous nebula whose light comes from fluorescence caused by a nearby star
|
|
|
Interstellar Extinction
|
The dimming of starlight as is passes through the interstellar medium
|
|
|
Interstellar Reddening
|
The reddening of starlight passing through the interstellar medium resulting from the scattering of short wavelength light more than long wavelength light
|
|
|
Supernova Remnants
|
Gas and dust left over from dead stars
|
|
|
Bok Globules
|
A small, roundish, dark nebula in which stars are forming
|
|
|
Dense Cores
|
Any of the regions of interstellar gas clouds that are slightly denser than normal and destined to collapse to form one or a few stars
|
|
|
Jeans Instability
|
The condition under which gravitational forces overcome thermal forces to cause part of an interstellar cloud to collapse and form stars and planets
|
|
|
Open Cluster
|
A loosely bound group of young stars in the disk of the galaxy; a galactic cluster
|
|
|
Pre-main-sequence Star
|
The stage of star formation just before the main sequence that involves slow contraction of the young star
|
|
|
Evolutionary Track
|
On the HR diagram, the path followed by a point representing an evolving star
|
|
|
Birth Line
|
A line on the HR diagram corresponding to where stars with different masses transform from protostars to pre-main-sequence stars.
|
|
|
T Tauri Stars
|
Young, variable, pre-main-sequence stars associated with interstellar matter that show erratic changes in luminosity
|
|
|
Brown Dwarf
|
Any of the planetlike bodies with less than 0.08 the mass of the Sun and and more than about 13 the mass of Jupiter; such bodies do not have enough mass to sustain fusion in their cores
|
|
|
H II Region
|
A region of ionized hydrogen in interstellar space
|
|
|
OB Association
|
An unbound group of very young, massive stars predominantly of spectral types O and B
|
|
|
Zero-age Main Sequence (ZAMS)
|
The positions of stars on the HR diagram that have just begun to fuse hydrogen in their cores
|
|
|
Hydrogen Shell Fusion
|
Hydrogen fusion that occurs in a thin shell surrounding the core of a star
|
|
|
Pauli Exclusion Principle
|
Formulated by Wolfgang Pauli. States that nature does not allow two identical particles to exist in the same place at the same time that have the same momentum or position
|
|
|
Electron Degeneracy Pressure
|
A powerful pressure produced by repulsion of closely packed degenerate electrons
|
|
|
Core Helium Fusion
|
The fusion of helium to form carbon and oxygen at the center of a star
|
|
|
Helium Flash
|
The explosive ignition of helium fusion in the core of a low-mass giant star
|
|
|
Instability Strip
|
A region on the HR diagram occupied by pulsating stars
|
|
|
Variable Star
|
A star whose luminosity varies
|
|
|
RR Lyrae Variables
|
A type of pulsating star with a period of less than one day
|
|
|
Cepheid Variable Star
|
One of two types of yellow, supergiant, pulsating stars
|
|
|
Period-luminosity Relation
|
A relationship between the period and average luminosity of a pulsating star
|
|
|
Type I Cepheids
|
A population I Cepheid variable star found in the disks of spiral galaxies-- brighter metal rich
|
|
|
Type II Cepheids
|
A population II Cepheid variable star found in elleptical galaxies and in the halos of disk galaxies, that is 1.5 magnitudes dimmer than type I Cepheid. -- dimmer, metal poor
|
|
|
Globular Cluster
|
A large spherical cluster of gravitationally bound stars usually found in the outlying regions of the galaxy
|
|
|
Horizontal-branch Stars
|
A group of post-helium-flash stars near the main sequence on the HR diagram of a typical globular cluster
|
|
|
Turnoff Point
|
The location of the brightest main-sequence stars on the HR diagram of a globular cluster that are just beginning to exhaust the hydrogen in their cores (thus turning away from the main sequence to become Red Giants)
|
|
|
Population I Stars
|
A star, such as the Sun, whose spectrum exhibits spectral lines of many elements heavier than helium-- a metal rich star
|
|
|
Population II Star
|
A star whose spectrum exhibits comparatively few spectral lines of elements heavier than helium-- a metal poor star
|
|
|
Roche Lobe
|
The teardrop shaped regions around each star in a binary star system inside which gas is gravitationally bound to that star
|
|
|
Detached Binary
|
A binary system in which the surfaces of both stars are inside their Roche Lobes
|
|
|
Semi-detached Binary
|
A close binary system in which one star fills or is overflowing its Roche Lobe
|
|
|
Overcontact Binary
|
A close binary system in which the two stars share a common atmosphere
|
|
|
Accretion Disk
|
An orbiting disk of matter spiraling in toward a star or black hole
|
