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73 Cards in this Set
- Front
- Back
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Diurnal Motion
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Objects rise in the east and set in the west
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Scales in astronomy
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The moon is 30 earth diameters away
The average distance from the sun to the earth is defined to be 1 astronomical unit or 1 AU 1 AU is alos about 8 light minutes light minute is a unite of distance not time earth is 100 solar diameters away from the sun the closest star to the sun is about 20 million solar diameters away from the sun (4.2 light years away) radius of the disk of galaxy is about 75,000 LY |
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Diurnal cycle
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any pattern that recurs every 24 hours as a result of one full rotation of the Earth.
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Annual Cycle
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an annual cycle is the part of a measured quantity's fluctuation that is attributed to Earth's...
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Constellations
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patterns of stars that people make to build a map of the sky
-We measure the motion of planets and the moon against the fixed backdrop of the constellations. |
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Lunar Cycles
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A lunar phase or phase of the moon is the appearance of the illuminated portion of the Moon as seen by an observer, usually on Earth....
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John Bayer (uranometria)
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established the system of assigning a constellation name, and a greek letter to a star.
The brightest star in a constellation was "alpha", the next "beta" and so on... |
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The concept of stellar populations is used to show an association between:
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Location in the Galaxy, chemical composition, and age
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celestial poles
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points directly overhead from the earths poles
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celestial equator
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the band of sky that is directly overhead from earths equator
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horizon
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half the sky is almost above this
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zenith
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the point directly overhead
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nadir
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the point directly underfoot
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Meridian
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the line/arc that runs from zenith, due south to the horizon
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earth angles
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There are 360 degrees in a circle
1 degree = 60 arc minutes (60') 1 arc minute = 60 arc seconds (60") 1 degree = 3600" |
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Solar day
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the length of time from noon to noon. Or, more technically, the interval between consecutive meridian crossings of the Sun.
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Sideral Day
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amount of time it takes the Earth to rotate once on its axis. Or, more technically, the interval between consecutive meridian crossings of a star.
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Galieo
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discovered was that objects do not fall at a constant rate. Instead, they accelerate as they fall to the ground.
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Newton
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Newton's law of gravity is one of the most important tools we have for understanding the behavior of objects in the Universe.
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tides
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caused by the moon orbiting the Earth
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What changes light
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the acceleration of charged particles
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Disadvantages to Refracting Telescopes
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chromatic aberration: stars are surrounded by fuzzy rainbow colors
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flux
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flux, where flux is the energy emitted per unit area per unit time:
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what is luminosity:
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Luminosity is just the flux times the surface area
def a measure of the radiant power emitted by a star |
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Kirchhoff's laws
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Hot opaque bodies emit blackbody spectra
Hot diffuse gas produces an emission line spectrum Cool gas in front of a hot blackbody produces an absorption line spectrum |
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Balmer Series
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The optical spectrum of hydrogen contains a simple series of lines, called the Balmer series
often appear as steller spectra |
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Niels Henrik
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Niels Bohr is best known for the investigations of atomic structure and also for work on radiation, which won him the 1922 Nobel Prize for physics.
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The doppler Effect
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The Doppler formula can then tell us that the star is moving away from us, and the amount of the wavelength shifts tells us the recessional velocity (or "redshift"). If the lines are shifted to shorter wavelengths, then the object is approaching us (it has a "blueshift").
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Hot Stars to cool stars:
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Oh
Be A Fine Girl Kiss Me |
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temp of sun
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G2
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chemical composition of most stars
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75% hydrogen by mass
23% Helium by mass 2% everything else by mass |
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Trigonometric Parallax
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The fundamental method for measuring distances in astronomy
Trigonometric parallax is how your brain generates depth perception. |
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Proxima Centauri
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closest star besides sun
1.3 pc |
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Hipparcos satellite
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The Hipparcos satellite (1989-1992) measured parallaxes for about 120000 stars with a precision of 0.001 arcseconds.
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Absolute magnitude
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The Absolute Magnitude of a star is defined as a matter of convenience to be the magnitude the star would be if it were at a distance of 10 pc. Thus the Sun, with an apparent magnitude of -26.5, has an absolute magnitude of
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THE HERTZSPRUNG-RUSSELL DIAGRAM
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independently made plots of the luminosity and spectral type of nearby stars
The stars do not lie randomly but in a sequence or patern |
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THE HERTZSPRUNG-RUSSELL DIAGRAM cont.
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Most stars lie along the Main Sequence running from hot, luminous stars to cool, faint stars.
There are also Red Giant stars, that are luminous and cool There are Supergiant stars that are very luminous, and have a wide range of temperatures And there are White Dwarf stars that are hot, but very faint. |
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THE HERTZSPRUNG-RUSSELL DIAGRAM
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independently made plots of the luminosity and spectral type of nearby stars
The stars do not lie randomly but in a sequence or patern |
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THE HERTZSPRUNG-RUSSELL DIAGRAM cont.
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Most stars lie along the Main Sequence running from hot, luminous stars to cool, faint stars.
There are also Red Giant stars, that are luminous and cool There are Supergiant stars that are very luminous, and have a wide range of temperatures And there are White Dwarf stars that are hot, but very faint. |
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Spectroscopic Binaries
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systems in which the angular seperation between the two stars is too small to see them as seperate stars
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Eclipsing Binaries
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systems in which the orientation of the orbit is such that the orbital axis is perpendicular to our line of sight
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Gravitational compression
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acts to make the star collapse
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Thermal pressure
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supports the star against collapse
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Interstellar Medium (ISM)
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contains gas and dust and is what separates the stars
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Orion Nebula
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glowing cloud of gas, called an emission line region, an emission nebula, or an HII region
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conduction
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Conduction: Heat transport by direct contact (if you put your hand on a stove burner, conduction is the process that burns you). The density of the Solar interior is too low for this to be an important means of energy transport.
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radiation
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The classic "random walk". Photons travel some short distance in the ionized Solar interior, before they are absorbed or scattered off of ions. As there is a density gradient (lower density as you go to higher layers), there is a general tendency for energy to flow outward because photons will travel a little farther that way than they will if they radiate downward. This is the dominant mode of energy transport in the deep Solar interior.
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convection
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The rolling boil. Hot material that is covered by cooler material can become convectively unstable. In this case, the hot material physically moves upward, until it reaches a level where it cools efficiently, and then sinks down again. Observations of Solar granulation demonstrate that this is the dominant mode of energy transport in the upper layer of the Solar interior.
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Time dilation
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time passes more slowly for an object in motion
provides us with a means of testing the theory of Special Relativity. One can take a bunch of radioactive particles, and accelerate them up to very high velocities in particle accellerators |
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the event horizon
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The "surface" of a Black Hole, the boundary at which the escape velocity equals the speed of light
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singularity
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the mass that goes into the black hole will theoretically continue collapsing to zero size and infinite density
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Properties of Black Hole
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MASS *
CHARGE SPIN* |
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MILKY WAY
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a disk of stars and that the sun is a member of this disk
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Cepheid Variables
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class of variable star that turns out to be of profound importance for the study of other galaxies
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Spectroscopic observations
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measurement of the change in doppler shift of spectral lines over the course of pulsation cycle
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shapley
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said the center of the galaxy wasnt anywhere near the sun, It was, instead, in the direction of the constellation Sagittarius
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spiral arms
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lanes of interstellar gas, dust, and young stars that wind outward in a plane from the central regions of a galaxy
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spiral features of spiral arms
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natural consequence of introducing structure into a differentially rotating fluid. (adding creamer to coffee)
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density waves (wave of compression)
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in a spiral galaxy, a localized region in which matter piles up as it orbits the center of the galaxy, this is a proposed explanation of spiral structure
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disk rotation
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collection of stars and gas, all orbiting in the same direction about the galactic center, it moves differentially unlike solid body masses
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Dark Matter
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90% of the galaxy, something we cannot see by any means except gravitational effects.
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DarkMatter problem: Ideas:
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it could be neutrinos
Massive compact halo objects (MACHOS) weakly interacting massive particles (WIMPs) |
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Population I
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-metal abundances like that of the sun
- both high- and low-mass stars (high-mass stars imply young stellar ages -stars orbit in the disk of the Galaxy |
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Population II
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Metal abundances are less then .1 solar
-only low-mass stars - stars are not part of the disk of the galaxy |
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Galactic center
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cannot be observed in optical light. Only in infrared light, radio waves, x-rays and gamma rays.
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Sag A
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Sag A* is a radio source. But it really emits VERY little energy.
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Lord Rosse
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Lord Rosse, the Earl of Parsons, was the first person to write about the spiral structure of some of the nebulae. His sketch of the nebula M51 compares very well with modern images.
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ellipticals
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-no disk
-no evidence for young stars -the ISM is hot, and observable in x-rays -Red Colors -High average metal abundance |
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Spirals
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-Disk systems with spiral structure
-Clear ongoing star formation -ISM is cool/cold (neutral atomic gas and molecular gas) with dust -Blue colors -lower average metal abundance |
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Triaxial (galaxies)
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three axes of symmetry all of different lengths
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Sagittarius dwarf elliptical.
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currently going through our galaxy the milky way/will be accreted in the near future
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Seyfert Galaxies
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small fraction of nearby galaxies have very bright, unresolved nuclear point sources.
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Radio Galaxies
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typically ellipticals, the characteristic observational signature of radio galaxies is the presence of large-scale jets of radio emission.
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