PHYS 1062: ASTRONOMY EXAM 3
80 Cards in this Set
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Many societies developed________to explain the patterns in the night (& day) sky.
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World models
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These models attempted to explain the motions of the Sun, Moon, stars, and especially the planets, or _______.
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"wanderers"
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The planets:
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(a) always move within several degrees of the ecliptic
(b) periodically undergo retrograde motion with respect to the background stars
(c) change their observed brightness, unlike the Sun & Moon.
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Retrograde motion
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this rather odd apparent motion results from the combination of the motion of earth and planets' own motion around the sun.
The observable phenomena that the direction of motion a planet has changes over time in relation to the stars. This observation must be accounted for by any serio…
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The Greeks developed the _______ model of the Universe with Earth as the center of that Universe. The Sun, Moon & stars all "circled" the Earth.
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geocentric
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The Greek astronomer _____refined the geocentric model – which became the accepted world view for 1500 years.
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Ptolemy
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The geocentric model used a series of perfect circles, termed _________ and _________, to model the motions of the planets.
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epicycles
deferents
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A few early astronomers guessed correctly that Earth was?
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NOT the center of the Universe, notably Aristarchus.
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In the 1543 Nicholas Copernicus proposed the _____________ model of the Universe — in which Earth and the other planets orbited the Sun.
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heliocentric
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The_______________________________involved more than just a model of planetary motion; conceptually it replaced the Earth as the immobile center of the Universe.
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Copernican Revolution
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Copernicus’ ideas were not accepted until?
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Observational evidence supporting the heliocentric model was discovered.
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In 1610, _________________ provided this new information by using the newly invented telescope to observe the Universe in greater detail than was possible with only the human eye.
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Galileo Galilei
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Telescope
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an instrument that collects electromagnetic radiation from the sky and concentrates it for better observation
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Tycho Brahe
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A Danish astronomer that provided decades of detailed positional and brightness data on the planets.
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Johannes Kepler synthesized Brahe’s data into three "laws" of planetary motion:
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The orbits of the planets are ellipses with the Sun at one focus of the ellipse.
Equal areas within an orbit are swept out in equal intervals of time.
The square of a planet’s orbital period is related to the cube of its semi-major axis.
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ellipses
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A closed curve enclosing two points (foci) such that the total distance from one focus to any point on the curve back to the other focus equals a constant.
Oval paths in which planets move around the Sun.
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Kepler’s laws are empirical relations:
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not derived from a theory or model; simply observed facts.
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Kepler’s mathematical explanation for the orbits of the planets, together with the new worlds revealed by the telescope, provided a?
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framework for the heliocentric model, which cemented acceptance of this new world view.
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What led to the abandonment of the geocentric or Ptolemaic world view, and the adoption of the Copernican or heliocentric world view.
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Galileo turned the newly invented telescope to the heavens and discovered entirely "new" worlds (~ 1610).
These discoveries, together with those of Kepler, led to the abandonment of the geocentric or Ptolemaic world view, and the adoption of the Copernican or heliocentric world view.…
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speed
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-describes movement from one place to another over time
-distance divided by time
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velocity
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a speed with a specific direction, so a change in speed or direction is an acceleration
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acceleration
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a change in velocity, so a change in speed or direction is an acceleration
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gravity
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a force that acts to pull pairs of objects together
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Free Fall
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Accelerated motion that happens when an object falls with only the force of gravity acting on it
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weight
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The force that results from the action of gravity on mass
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Escape Velocity
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The velocity needed to leave a body, it will enter an open orbit.
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orbit
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path an object takes as it revolves around another object
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center of mass
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The balance point of a body of system of bodies
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Tides
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Rise and fall of the ocean cause by moons gravitational pull
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Galileo
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-Natural motion
-Inertia and mass
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Newton’s Laws of Motion
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– 1st Law: law of inertia (defines natural motion)
– 2nd Law: force law (F=ma)
– 3rd Law: action-reaction law
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Law of Gravity
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gravitational force between two objects is proportional to the product of the mass of each object divided by the distance between their centers squared.
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Gravity is:
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- a universal force
- always an attractive force (every mass in universe attracts every other mass)
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The force due to gravity:
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•is always directed along the line connecting two masses
•depends on the product of the two masses
•depends on distance between the two masses squared (obeys the “inverse square rule”)
Often describe gravity in terms of a gravitational field produced by the presence of matter.
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Newton's modification of Kepler's 3rd Law
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-Center of mass
-Applications of modified 3rd Law
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Wave Speed(v)
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Wavelength(λ)xFrequency(f)
v=fλ
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Wave speed of light
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c=fλ
c= 300,000 km/s
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Relationship between energy carried by photon and frequency
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E=hf=hc/ λ
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Lenses(refractors):refraction of light
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– Bending of light as it passes from one transparent material to another.
– If varies with wavelength, known as dispersion (makes the rainbow)
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dispersion
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In optics, the process of separating a wave of different frequencies into its individual component waves
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Mirrors(reflectors): reflection of light
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Change in direction of light as it bounces off of the surface of an opaque material.
Main lens/mirror called the telescope’s objective or primary.
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Power of a Telescope
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-Light gathering power
-Resolving power
-Magnifying power
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diffraction
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Blurred fringe surrounding any image caused by the wave properties of light.
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Radio Telescopes
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Long wavelength signal
Colleceted with reflector
-Need large diameter reflector to maintain angular resolution
-Interferometry commonly used to attain high resolution
Advantages
-Travels through dust and gas
-Neutral hydrogen gas(most ommon in universe) produces a 21-cm radio emissi…
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Infarared Telescopes
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Some from Earth, but most from above the atmosphere
- Absorbed by water vapor, carbon dioxide, and oxygen in lower atmosphere
-Earth is a strong background radiator in infrared band
Used to imagine planets, comets, forming stars, other cool objects
Types: Ultraviolet, X-ray, and Gamma…
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Ultraviolet Telescopes
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-Utilize orbiting telescopes
-Absorbed by ozone layer of Earth's atmosphere
-Used to imagine hot stars and hot gas
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X-ray Telescopes
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-Utilize orbiting telescopes
-High energy photons focused using grazing-angle reflections from ultra smooth concentric mirrors
-Used to study very hot regions in stars, matter smashing into neutron stars, and other violent events
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Gamma Ray Telescopes
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-Utilize orbiting telescopes
-Photons too energetic to focus, so merely count interactions
-Used to study hottest and most violent objects in the universe: exploding stars, active galaxies, neutron stars, & black holes
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Spectroscopy
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The study of light
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Temperature
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-Measure of average velocity of particles that make up an object
-Kelvin temperature scale
-Absolute zero
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Black Body Radiation
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– Theoretical model for starlight
– Three rules for black body radiation
• Planck curve
Radiation emitted by a hypothetical perfect radiator; the spectrum is continuous, and the wavelength of maximum emission depends only on body's temperature
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Radiation Laws
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• Stefan-Boltzmann Law: luminosity depends on the surface area and (surface temperature)4 of the radiating object.
• Wien’s Law: the wavelength of radiation with the maximum intensity is related to 1/(surface temperature) of the radiating object.
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Model of the Atom
-Sub-atomic particles
-Proton
-Neutrons
-Electrons
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Protons and neutrons in nucleus, surrounded by “clouds” of electrons
Electrons bound to nucleus by Coulomb force
Binding energy can only have certain allowed values
• Each type atom has it own unique set of allowed energy levels.
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Interaction of Light and Matter
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Excitation and emission (absorption/emission of photons)
3 types of spectra and conditions necessary
• Continuous
• Emission
• Absorption
-Kirchoff’s Laws
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Information from Spectra
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– Balmer thermometer
– Spectral classification: use spectra to determine temperature of star’s surface.
• OBAFGKM (hot to cocl)
– Composition of stars from understanding of relationships between stellar
temperatures and presence/absence of spectral lines and line intensities.
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Doppler Effect
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Shift in observed frequency (or wavelength) of awave due to relative radial motion between source and receiver
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Angular resolution of a telescope
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proportional to wavelength, λ, of light studied & inversely proportional to diameter, D, of objective;
– minimum angular resolution varies as λ/D (from diffraction)
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Magnification equation
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f objective/f eyepiece
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Energy per photon of light
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constant x frequency = E = hf
Speed of light in a vacuum=c=3x108 m/s=constant
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Parallax
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The apperant motion of an object because of the motion of the observer
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What discoveries did Galileo observe through his telescope?
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-The phases of Venus
-The satilites of Jupiter now known as the Galilean moons
-The mountains of Earth's moon
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circular velocity
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The velocity needed to stay in a circular orbit
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Geosynchronous satilite
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Orbits eastward with the rotation of Earth and remains above a fixed spot-ideal for communications and weather satilites./
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Mass
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is the amount of matter in a body
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Momentum
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is a measure of a body's amount of motion, a combination of it's velocity and mass
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General theory of relativity
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says that a gravitational field is a curvature of space-time caused by the presence of a mass.
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Special general theory of relativity
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says that uniform(unaccelerated) motion is relative.
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equant
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the point off-center in the deferent from which the center of the epicycle appears to move uniformly
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neap tide
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Ocean tide of low amplitude occuring at first and third-quarter moon
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spring tide
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Ocean tide of high amplitude that occurs at full and new moon
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Wavelength
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The distance between succesive peaks or troughs of a wave; usually represented by λ
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Frequency
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The number of waves that pass a stationary point in 1 second
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Photon
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is a packet of light waves that can act as a particle or wave
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Properties of the Sun
Radius, Mass, Rotation, surface temp., luminosity, composition
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Radius: 6.96*10^5km
Mass: 1.99*10^30kg
Rotation: 24.5 Days at equator
Effective surface temp: 5800K
luminosity:3.84*10^26j/s
Composition: Photosphere, Chromosphere, Corona
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Photosphere
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A thin layer of gas from which Earth receives most of the suns light. Less than 500km deep. (The visible part of the sun from Earth)
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The Chromosphere
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Above the photosphere.
Can only be seen by the eye during a total solar eclipse.
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The Solar Corona
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The outermost part of the suns atmosphere (Greek for crown). Not visible to the Earths daytime sky.
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Most abundant elements in the Sun
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Hydrogen, Helium, Carbon, Nitrogen, Oxygen, Neon, Magnesium, Silicon, Sulfur, & Iron
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Sunspots
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*areas that appear darker because they are cooler than the surrounding areas
* the sun DOES NOT rotate as a mass. The equator rotates every 25 days, the poles rotate every 35 days.
*Solar Activity Cycle- period of time with increased and decreased amounts of sunspots
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Solar Wind
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a stream of particles that flow outward in all directions from the sun's surface. (hydrogen nuclei and free electrons)
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PHYS 1062: ASTRONOMY EXAM 3