Astronomy Test 4 (Em’s) – Flashcards
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Galaxy type containing the highest percentage population I stars?
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Irregular
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Used to measure the distance to nearby stars
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Parallax
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When supernovae promote more star formation, this is called ______
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Self- propagating star formation
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Still a mystery because we don't have a theory of quantum gravity?
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Planck Epoch
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Atoms exist, but stars don't
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Dark Ages
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How many years does it take the Sun to orbit the Milky Way?
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230 million years
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Approximately how many stars are in our Galaxy?
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Two Hundred Billion
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A galaxy with very little or no interstellar gas and dust
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elliptical
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Why are infrared and radio telescopes the instruments of choice for studying the galactic center?
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Dust in the plane of the Milky Way obscures observations at other wavelengths
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The Virgo Cluster is an example of a
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Rich cluster
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Properties of Elliptical galaxies:
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NOT fast; population II stars (yellow); very little gas/dust; old
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Properties of Irregular galaxies:
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High concentration of gas/dust; lots of star activity/production; not big
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Subcategories of each galaxy type indicate:
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How wrapped the spiral arms are or how flat the elliptical is
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Poor cluster
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Not many galaxies Ex: Milky Way in the Local Group
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Rich cluster
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100s, 1000s of galaxies and large ones; large chance of colliding Ex: Virgo cluster (closest to us)
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Technique used to measure distances within our solar system:
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Radar ranging
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Technique used to measure distances to nearby stars:
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Parallax
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Technique used to measure distances in the Milky Way:
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Main-sequence fitting
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Technique used to measure distances in nearby galaxies:
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Cepheids - use pulsing to measure distance
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Technique used to measure distances in galaxy clusters:
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1) White dwarf supernovae 2) Tully-Fisher relation
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Planck Epoch:
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A mystery partly because we lack a quantum theory of gravity.
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A Grand Unification Epoch:
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Forces except gravity are unified
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The Inflationary Epoch:
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Universe expands rapidly smaller than a proton to bigger than a melon - Supported experimentally
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Electroweak Epoch:
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Weak and electromagnetic forces act as one.
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The Quark, Hadron, and Lepton Epoch:
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What we think of a "normal" elementary particle form and survive.
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Photons, Nucleosynthesis and the Cosmic Background Radiation
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Atoms form (Hydrogen and Helium) and Cosmic Background radiation ' decouples ' from matter
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"Modern" Era
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Stars form - Quantum fluctuations at the time of inflation determines the distribution of matter in the universe. Denser areas are where stars will form. Gravity is the major large-scale force
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Which feature of a galaxy contains the most Population II stars?
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Halo - virtually no blue stars, not around gas/dust
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Which feature of a galaxy is at the center of the galaxy?
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Bulge - football shape; population II stars, little gas/dust
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What is a main characteristic of the bulge?
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A supermassive black hole at the center
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Which feature of a galaxy is in a flattened shape?
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Disk - spiral arms
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Which feature of a galaxy has both Population I and II stars?
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Disk
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What are Population I stars associated with?
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Spiral arms
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Density-wave theory
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traffic jam; cars = stars; stars move to denser regions; in and out, but spiral arm remains; young stars
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Self-propagating star formation
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one generation dies, new ones come; waves of stars; requires supernova explosions
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Shapely used these objects to determine the location of the center of the Milky Way
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globular clusters
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Example of spiral galaxy
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Milky Way Galaxy and Andromeda
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Spiral galaxy qualities:
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Contain flattened galactic disk in which spiral arms are found; central galactic bulge with a DENSE NUCLEUS, extended halo of faint, old stars
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Globular clusters trace out the structure of the Galactic disk.
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FALSO
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Herschel's attempt to map the Milky Way by counting stars led to an inaccurate estimate of the Galaxy's size because he was unaware of absorption by interstellar dust.
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VERDAD
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What kind of orbit do Stars and gas in the Galactic disk move in around the Galactic center?
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Roughly circular
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A telescope searching for newly formed stars would make the most discoveries if it were pointed
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Within a spiral arm
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What did a major discovery made by Harlow Shapley using RR Lyrae stars and globular clusters establish?
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The size of the Galaxy and the Sun's position in it
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What kind of motion do stars in the halo have?
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Randomly-oriented
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What kind of motion do stars in the disk have?
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Generally stay confined to moving in the disk
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Oldest component of the galaxy?
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Halo
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Best possible scenario for the formation of our Galaxy?
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Began as a number of "dwarf galaxies," which merged under the influence of gravity to form our Galaxy
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Common star in spiral arms (almost no where else)?
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High mass O and B stars
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What effect does a spiral density wave have on the material it encounters?
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It slows the material down, causing it to compress and heat up, assisting gravity in forming stars.
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What kind of orbit does the Solar System have around the Galaxy?
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similar to that of a planet, almost circular and in the galactic plane
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Orbits of stars within most elliptical galaxies?
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They have random orbits in three dimensions.
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Which type of galaxy exhibits the largest range of sizes and masses?
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Elliptical
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Which of these STANDARD CANDLES has been used to determine distances to the most distant galaxies?
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Type I supernovae
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What is the criterion for a group of galaxies to be considered a cluster?
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Galaxies in a cluster are bound together by their mutual gravitational pull
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Unlike spirals, elliptical galaxies do not contain a flattened disk.
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true
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Cause of Irregular II galaxies?
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result of a collision, or close encounter, of two normal galaxies.
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Most stars found in Irregular galaxies are:
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Young/blue
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Richer star-forming galaxies
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Irregular > Spiral > Elliptical
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M31 in Andromeda is:
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A bigger version of our Galaxy, and the largest member of the Local Group.
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Property common to spiral galaxies?
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ongoing star formation and emission nebula in the arms
