Term
| What is the definition of the Milky Way? |
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Definition
| The band of faint white light that encircles the entire inside of the celestial sphere. |
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Term
| In which season is the Milky way the brightest? |
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Definition
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Term
| What kind of Galaxy do we live in? |
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Definition
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Term
| What are the two parts of our flat disk like Galaxy, and what is their thickness? |
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Definition
| 1.) Thin dust ~ 1,000 L.Y. across 2.) Thick dust ~ 3000 L.Y. across |
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Term
| What are the three parts to the structure of a Galaxy? |
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Definition
| 1.) Flat wheel shaped disk 2.) Spherical, concentric halo 3.) Central bulge |
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Term
| What does the spherical, concentric halo section of the Galaxy contain? |
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Definition
| Old globular star clusters. |
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Term
| What does the central bulge section of a Galaxy contain? |
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Definition
| Older stars spaced very close together. |
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Term
| Where is the sun located in reference to our Galaxy? |
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Definition
| In the disk ~1/2 of the way out from the center, in the mid-plane. |
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Term
| Who determined the sun's location in the Galaxy, and how did he do it? |
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Definition
| Harlow Shapley ~ by using the RR Lyrae variable stars in the globular star clusters. |
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Term
| Why did Herschel greatly underestimate the diameter of galaxy? |
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Definition
| Herschel was unaware of interstellar dust. |
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Term
| What is it that Shapley found out about the spherical distribution of globular star clusters? |
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Definition
| They are with the center of the disk, on a point ~26,000 L.Y. away, in the direction of Sagittarius. |
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Term
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Definition
| Everything in a star Hydrogen and Helium. (Metals and everything else) |
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Term
| What 3 groups did astronomers put elements into? |
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Definition
| Helium, Hydrogen, and Metallicity |
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Term
| What is the name of the group of stars with very low % of “metals” and what are some examples? “1st generation stars” |
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Definition
| Population (around central bulge) `Globular star clusters, `Dim, red main sequence stars, `RR Lyr variable stars. |
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Term
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Definition
| Material that is emitting any kind of radiation, and thus is not visible at any wavelength. |
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Term
| What is a “galactic rotation curve” graph? |
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Definition
| A graph that shows that the velocity of objects do NOT fall of with increasing distance from center, but stays flat. |
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Term
| How was the presence of dark matter been confirmed? |
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Definition
| by studying the Orbital Motion of various objects in the Galaxy |
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Term
| True or False, interstellar dust is equivalent to dark matter? |
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Definition
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Term
| If the typical mass per star is ½ solar mass, then the number of stars in the Galaxy is about how many? |
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Definition
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Term
What is behind the dark mass in our Galaxy?
A) Black holes?
B) Dim red star?
C) Brown dwarfs?
D) Neutrinos, or other exotic particles?
E) WIMPS (Weakly Interacting Massive Particles)
F) We don't know yet. |
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Definition
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Term
| The age of the Universe is estimated to be about _____ billion years and the age of the Galaxy somewhat less. |
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Definition
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Term
| Soon after the formation of the Universe, from the so-called “Big Bang”, only ________ existed. Later, matter began to condense from the energy. |
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Definition
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Term
| After ___________ years, galaxies such as ours began to form from the huge collections of (mainly) hydrogen atoms. |
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Definition
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Term
| Which part is the oldest of our Galaxy? |
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Definition
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Term
| Which part of our Galaxy is the youngest? |
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Definition
| The Disk. Both young, & old stars are found in disk. |
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Term
| Where is the only part where stars are still forming in our Galaxy? |
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Definition
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Term
| What is the most numerous class of galaxies? |
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Definition
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Term
| What contracts to form the parts of the Galaxy we now know? |
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Definition
| The huge collections of gas began the gravitational contraction |
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Term
| What is the fundamental distance determination method, which uses the parallax of nearby stars? |
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Definition
Triangulation or surveying
(d = 1/p) |
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Term
| To determine GREAT distances what method is used that is standard? |
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Definition
| Standard Light Bulb method |
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Term
| How does the Standard Light Bulb method work? |
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Definition
| Find some way to estimate the true brightness of an object and then calculate how far away it has to be to look that dim. |
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Term
| What are Active Galaxies? |
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Definition
| those that have bright nuclei associated with great energy production or energetic outflows of matter. (Most emit strong radio waves). |
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Term
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Definition
| Active galaxies with more radio output than light output) |
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Term
| What are Seyfert galaxies? |
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Definition
| Spiral galaxies with bright, star-like nuclei, and strong emission lines in their spectra. |
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Term
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Definition
| 2 regions of strong radio emission occur on either side of a “peculiar” galaxy. (Peculiar means the galaxy does not fit well into the Hubble classification scheme.) |
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Term
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Definition
| A stream of material projects from the center of a galaxy. |
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Term
| What did the discovery of the Hubble Law tell us? |
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Definition
| The Universe is expanding! |
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Term
| The farther you look into space, the earlier back in time you see, why is this? |
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Definition
| The speed of light is finite. |
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Term
| What was the 1st Quasar ever discovered? |
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Definition
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Term
| We see the Sun not as it is now, but as it was about ____ minutes ago. |
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Definition
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Term
Optical photos showed “star-like” dots.
Since stars are not strong radio sources, these were called ________. |
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Definition
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Term
The _______ Law is used to measure the biggest distances.
a.k.a. “meter stick” |
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Definition
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Term
| When can the Hubble Law be used? |
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Definition
When no objects of any kind can be resolved in a galaxy
Only the spectrum can be obtained. |
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Term
| Hubble and Humason found the relation between the ______ of recession of a galaxy and its __________. |
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Definition
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Term
| How did galaxies evolve or develop with time? |
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Definition
| By colliding with each other. |
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Term
| What is the definition of Cannibalism in terms of Astronomy? |
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Definition
| A larger galaxy devours a smaller one. |
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Term
| Star-burst galaxies result when _______ trigger lots of star formation. |
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Definition
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Term
| ___________ may form in centers of clusters of galaxies by “mergers”, and then “cannibalism”. |
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Definition
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Term
| Collisions of elliptical galaxies in clusters also strip them of ______ and ________. |
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Definition
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Term
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Definition
| Looks the same in all directions |
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Term
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Definition
| Super clusters distributed uniformly throughout 3-d space |
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Term
| Various studies of the distribution of galaxies in space indicate that the Universe is __________ and __________. |
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Definition
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Term
| “On a very large scale, the universe must look the same to any observer”. This is known as the ___________. |
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Definition
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Term
| How many stars are in a Super Cluster? |
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Definition
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Term
| We are in the ______ group. |
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Definition
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Term
| The _______ Cluster galaxy is 50 MLY away and is the closest to us. |
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Definition
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Term
| What is the difference between regular and irregular galaxies? |
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Definition
Regular clusters of galaxies are symmetrical and contain mostly ellipticals.
Irregular clusters galaxies are not symmetrical and have some spirals |
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Term
| What are the empty pockets in the universe called, and how far across are they typically? |
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Definition
The empty pockets in the universe are called voids.
Voids are typically 150 MLY across. |
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Term
| Most of the universe is __________. |
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Definition
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Term
| Galaxies formed within the first _______ years of the Universe. |
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Definition
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Term
For distant galaxies we study their color:
Blue = ________
Red = ________
~~Shape:
Spiral = ______
Elliptical = ________ |
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Definition
Distance, Color:
~young
~old
~~Shape:
~young
~old |
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Term
| What is the best-known theory to explain our Universe’s being. |
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Definition
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Term
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Definition
• Population I: (around thin dust)
o Star with relatively large % of metals
o Includes our sun and other objects from spiral arms:
• Open star clusters,
• Cepheid variable stars
• Young O and B associations.
• GMCs
• Cold H I regions
• Hot H I regions |
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Term
| The Sun’s Galactic orbit has a circumference of ____ x ____ x ______ LY. |
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Definition
| 2 x (pie) x (26,000 L.Y.) |
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Term
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Definition
| `lies at the center of the Galaxy and is believed to contain a supermassive black or hole or “Big Black Hole” (BBH) |
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Term
| What is responsible for the strong radio signals in the nucleus of the Galaxy? |
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Definition
| As matter gradually falls towards this BBH, an accretion disk has formed and is responsible for the strong radio signals. |
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