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24 Cards in this Set

  • Front
  • Back

Front (Term)


Everything we see with the naked eye belongs to our galaxy, the Milky Way Galaxy, except for our satellite galaxies, the _________ Clouds and M-31, the Andromeda Galaxy of the fall sky; the latter is a huge spiral a little larger than our own Galaxy, but 2.5 million light years distant

Back (Definition)


Magellanic

Front (Term)


The key to measuring galactic distances lies with the discovery by Henrietta Leavitt that certain giant stars are unstable and pulsate regularity. Their periods of pulsation are tied to their masses and thus their luminosities. On the H-R diagram this "________" strip occurs mainly in classes F through M with luminosities ranging from 100 to 10,000 suns.

Back (Definition)


Instability

Front (Term)


Harlow Shapley used RR Lyrae variables in globular clusters to plot their positions in space. He found they were not centered around us, as earlier models of our Galaxy had proposed, but spherically symmetrical around a galactic nucleus in _______. Also, his distances proved our Milky Way was far larger than any previous model had proposed. The earlier models were thrown off by the vast amounts of dust in the plane of the Galaxy which hide over 90% of it from our eyes.

Back (Definition)


Sagittarius

The Milky Way and similar spirals have two main components; the disk component includes the Sun and other stars close to the plane of the Milky Way; the open star clusters, and the gas and dust which hide most of the disk from visual observation. The disk is about ________ light years across, and we lie about ___________ light years from it's center.

80,000, 25,000

The Milky Way and similar spirals have two main components; the disk component includes the Sun and other stars close to the plane of the Milky Way; the open star clusters, and the gas and dust which hide most of the disk from visual observation. The disk is about ________ light years across, and we lie about ___________ light years from it's center.

80,000, 25,000

The brightest portion of the disk is the spiral arms, where ______ of hot, young (O-B type) stars light the leading edge of the density wave.

Associations

The ________ component has a distribution much like the globular star clusters which are its most obvious members. On the outside, the ________ is a thin cloud of old stars and globular clusters which extends far beyond the visible disk. H-R diagrams shows these are old stars. Much more concentrated, the nuclear bulge appears yellow, but like the halo, is generally lacking in gas and dust from which new stars could be made.

Spherical, halo

While the disk stars move in almost ________ orbits in the _______ plane, much like planets in the solar system, the halo stars move in highly elliptical orbits at random inclinations to the plane of the Milky Way, much like the orbits of long period _______.

Circular, galactic, comets

While the disk stars move in almost ________ orbits in the _______ plane, much like planets in the solar system, the halo stars move in highly elliptical orbits at random inclinations to the plane of the Milky Way, much like the orbits of long period _______.

Circular, galactic, comets

Front (Term)


Motions of stars in our vicinity lead us to believe that it takes our sun about ______ million years to revolve completely around the Galactic nucleus. Using Kepler's and Newton's laws, we thus estimate that the mass between us and the Galactic Nucleus must be about __________ solar masses.

Back (Definition)


240, 100 billion

Front (Term)


Kepler's laws note that as we go farther out from the Sun, the great concentration of mass in the center of the solar system, the speed of the planets decreases. But observations of stars farther out than the Sun in our galaxy shows that they revolve much faster than we expected. This in turn means that much mass lies beyond us out in the Galactic __________, in the form of mysterious dark matter; some predict as much as 90% of the mass of the universe is in some form still unknown to us at present, although white dwarfs, brown dwarfs of less than 8% of the sun's mass and black holes of over 3 solar masses are also popular ca issues on the "missing mass" or "darker matter" problem.

Back (Definition)


Corona

The galactic nucleus lies toward ______ and is the stronger ________source in the entire sky. Infrared observations reveal the stars must be very close together in this region, and, x-Ray, and gamma rag observations suggest that perhaps a black hole of 4 million solar masses is the power supply for the violence we observe there. Energetic as our own core is. In the next chapters we will find even more energy coming from the cores of quasars, Seyfert Galaxies, and radio galaxies. If you feed mass into a black hole, a great deal of that mass can be converted into energy according to Einstein; such energy sources may power quasars in the cores of active galaxies.

Sagittarius, radio

The disk stars are called Population 1; in age they are ______, and richer in metals. They move in planet-like orbits, like the sun's. The open clusters and associations are their most obvious groupings.

Younger

But the spherical component is Population 2; confusingly it came first, as these stars are far older in age and made of almost nothing but hydrogen and ________. These older stars move in comet-like orbits. Their most obvious members are in globular clusters. We interpret these distributions to suggest our Galaxy began as a spherical cloud of H and He from which population 2 stars condensed first. But further condensation enhanced rotation, forming the galactic disk from which Population 1 stars formed now enriched in metals from previous ______ explosions.

Helium, super nova

As Edwin Hubble realize the other galaxies or separate entities from our own Milky Way he also categorize them into three major groups ______ like the two companions to M-31 and _____ like our satellites the Magellanic clouds

Spirals ellipticals irregulars

As Edwin Hubble realize the other galaxies or separate entities from our own Milky Way he also categorize them into three major groups ______ like the two companions to M-31 and _____ like our satellites the Magellanic clouds

Spirals ellipticals irregulars

In Hubbells tuning fork diagram the most circular ellipticals are type ______ while the most flattened are ______

E0, e7.

As Edwin Hubble realize the other galaxies or separate entities from our own Milky Way he also categorize them into three major groups ______ like the two companions to M-31 and _____ like our satellites the Magellanic clouds

Spirals ellipticals irregulars

In Hubbells tuning fork diagram the most circular ellipticals are type ______ while the most flattened are ______

E0, e7.

Transitory between E and S or the S0 then the diagram branches into normal And barred spirals. Within each type of spiral the degree of winding of the spiral arms assigns letters from SA to SC with the type ______ being the most open. M31 and our own Milky Way are both large Sb type galaxies; some recent studies hit the Milky Way may be an SBb. Irregulars lack either type of structure and appear chaotic

Sc

As Edwin Hubble realize the other galaxies or separate entities from our own Milky Way he also categorize them into three major groups ______ like the two companions to M-31 and _____ like our satellites the Magellanic clouds

Spirals ellipticals irregulars

In Hubbells tuning fork diagram the most circular ellipticals are type ______ while the most flattened are ______

E0, e7.

Transitory between E and S or the S0 then the diagram branches into normal And barred spirals. Within each type of spiral the degree of winding of the spiral arms assigns letters from SA to SC with the type ______ being the most open. M31 and our own Milky Way are both large Sb type galaxies; some recent studies hit the Milky Way may be an SBb. Irregulars lack either type of structure and appear chaotic

Sc

In color ellipticals appear ________ throughout much like the core of spirals and are usually pouring gas and dust so little New star formation occur in them; all their stars are population _______. Compared to the flattened spirals, the ellipticals rotate ________.

Yellow, II, slowly