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94 Cards in this Set
- Front
- Back
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What time is it?
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I don't know
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Who cares?
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I DO
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What are the primary functions of any telescope?
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To collect and concentrate weak signals from space, and to allow us to see the structure in astronomical objects
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What are the two main designs of telescopes?
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Refracting and Reflecting
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What is a reflecting telescope?
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Primary mirror, small mirror, eyepiece
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What is a refracting telescope?
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Larger glass lens, smallers lens eyepiece
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What is Chromatic Aberration
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Red and blue light have different speeds and do not go into the same focus
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Do reflecting telescope have chromatic aberration?
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No
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Why have reflecting telescopes replaced refractors?
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Reflectors have much greater light gathering power
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What are the design limitations of refractors?
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The lense can sag in the middle from its own weight
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Is there any limit on the diameter of a telescope mirror?
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No
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What is the Light Gathering Power of a Telescope?
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How many photons can be collected and concentrated from a faint source.
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How is LGP calculated?
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LGP= d^2
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What is the LGP of a 6m telescope?
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6^2=36
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What is the LGP of a 2m telescope?
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2^2=4
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What is the Angular Resolution of a telescope?
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The finest detail a telescope can see in an object.
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How does earth's atmosphere affect AR?
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It causes the twinkling star effect.
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How can you adjust for earth's atmosphere in a telescope?
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Use an adaptive optics system
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What are the advantages of putting your telescope in space?
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No atmosphere
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What are the three detectors that have been used in astronomy?
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Human eye, photographic plates, electronic detectors (CCDs)
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Why is the eye bad for astronomy?
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It can fool itself
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Distance is ____ to angular shift
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Inversely proportional
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Distance equals what?
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1/p, parallax, distance in parsecs
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If p=0.1 arcsecs…
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D=1/0.1=10 parsecs
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If p=0.5 arcsecs…
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d=1/0.5=2 parsecs
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How do we determine diameters of stars using Lunar occultations
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Measuring the light curve for the star to pass behind the moon
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Is the sun a normal size?
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Slightly below average
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What is the easiest way to determine stellar temperatures?
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Color (red/blue)
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When can we determine mass of stars?
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Only if they are in binary systems, we can determine their orbits, and know their distances
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How do the masses of near stars compare with our Sun's?
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Our sun has more mass, usually
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More massive stars have:
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Far greater luminosities, larger diameters, shorter lifetimes
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What quantities are plotted on the vertical & horizontal axes?
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Luminosity and Surface Temperature
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What is trig. Parallax?
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The distances to distant stars and how we calculate it
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How do we determine the distances to near stars?
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Nearby stars shift their position more than farther-away stars.
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Where is the Main Sequence on the H-R diagram?
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The gray line
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Where is the Red Giant on the H-R diagram?
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Top right
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Where is the white dwarf on the H-R diagram?
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Bottom left
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What is the composition of the interstellar medium?
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90% Hydrogran, 9% helium, 1% everything else
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What does Cold Atomic Hydrogen Gas emit?
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Photos
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What temperature is Cold Atomic Hydrogen Gas?
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100-200 degrees, K
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What is the distribution of the Cold Atomic Hydrogren gas?
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Center of milky way deficient, spiral arms apparent
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What are the kinds of molecular gas molecules?
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Simple and complex
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Where are Molecular Gas molecules found?
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Dense, cold clouds
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What is the most abundant common molecule?
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Molecular hydrogen (2 hydrogen atoms)
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Where is Interstellar dust found?
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Throughout the Milky Way, especially in concentrated cold molecular clouds
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Why can't we see the Milky Way center at optical wavelengths?
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Interstellar dust
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What is the shape of a typical dust grain?
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Oblong
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What does dust do to help stars form?
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Molecular hydrogen forms on grain surfaces, dust grains absorb UV radiation and re-emits infrared photons, dust grains absorb UV radiation that destroys H2
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What is the center of the Milky Way Galaxy rich in?
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Molecular gas
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What kind of gas dominates the outskirts of the Milky Way Galaxy
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Atomic H gas
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What are young stars closely associated with?
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Dense, cold, molecular ISM
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What is the ISM
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Interstellar Medium
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Molecular clouds are (---) forces
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Balanced forces
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What forces try to collapse a cloud?
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Gravity and external pressure
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What forces try to support a cloud?
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Magnetic field, rotation, internal pressure
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Why do clouds collapse?
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Force of collapse becomes greater than the Force of support
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What happens when molecular clouds collapse?
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They fragment into smaller, denser sub-regions. These collapse faster
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Why are Brown Dwarfs "failures"?
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Their core is not hot enough for fusion
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Are brown dwarfs common?
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Yes
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What is Hydrostatic Equilibrium?
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At every point in a star, the gravity is balanced by the outward pressure of hot gasses
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What does Hydrostatic Equilibrium imply for the Sun's core?
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High temperature and density
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What is the T of the Sun's core?
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15-million K
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What Is the density of the Sun's core?
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20x that of Iron
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What mass does a star reach the Main Sequence?
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15x the Sun's
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Describe the Proton Proton chain
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Protons collid with sufficient speed to fuse
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How much hydrogen must be converted to Helium per second in the Sun?
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600-million tons of Hydrogen
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How long can the Sun maintain its energy output?
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5-6 billion more years
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What do stars spend most of their lives on?
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Main Sequence
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What byproducts start accumulating in the core of the Sun on Main Sequence
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Helium
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What does moving out of the Main Sequence do to the star?
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Increases luminosity and color (redder)
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When Helium core heats up to 100-million degrees, Helium can fuse to what?
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Carbon
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What is the Helium Flash?
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The helium core explodes
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After the Helium flash, where does a star appear on the HR Diagram?
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More to the left
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Where is a white dwarf in a planetary nebula?
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The center
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What is a white dwarf?
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The remnant core of a star
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Describe a white dwarf
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Very small and hot, entirely carbon
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Why do low-mass stars never fuse He to Carbon/
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They don't get hot enough in their cores
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What do stars in a star cluster share?
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Birthdays
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What is a neutrino?
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Proof of Fusion in a Sun
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Why was Ray Davis' neutrino experiment wrong?
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It didn't count the right amount
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Novae can be how much brighted than the original white dwarf?
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10,000x
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Describe the death of a massive star
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Each fusion reaction creates less energy, ironi is formed and doesn't generated energy, the sun collapses
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What are the events of the collapse of the Iron core of a massive star?
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Photo-disintegration, neutron-ization, bounce once and die
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Why are radio telescopes so big?
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Radio photons carry little energy
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How big must a radio telescope be to have 1 AR?
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50,000 meters
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What would I view atomic hydrogen gas with?
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Radio waves
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What would I view supernova remants with?
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Radio/Xray
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What would I view cold clouds of gas with dust?
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Infrared
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What would I view distant galaxies with
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infarer
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What are the two types of super nova?
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Type 1 and 2, which are different in light curves and spectra
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What is Si + He?
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Sulphur
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What is Sulphur plus He?
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Argon
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What is Argon plus He?
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Calcium
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Do the combinations with He require high temperatures?
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No
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