Ast-A 105 Test #3

Front 1

Stars form in ___ , ____ interstellar clouds

Back 1

Cold, Dense

Front 2

Dark Nebula-

What does it do?

Back 2

Dense cloud of gas and dust

Absorbs visible light + Obscures Stars Behind It

Front 3

1) What happens when a could collapses?

2) What triggers a collapse?

3) What happens when it contracts?

Back 3

1) Gravity causes cloud to collapse if it is compressed by a shock wave, and it goes out of hydrostatic equilibrium

2) Nearby Supernova, Cloud passing through spiral arm of galaxy, cloud collision

3) Gas is heated + compressed

Front 4

1) Protostars are formed and surrounded by what?

2) What are they best observed in? Why?

3) What happens when the star is on main sequence?

Back 4

1) dense gas and dust clouds from which they form

2) Infrared, less absorbed by dust than visible light

3) It stops contracting

Front 5

1) What is reflection Nebulae?

2) Why is it blue?

3) Do stars behind dust appear redder?

Back 5

1) bluish haze seen around hot, young stars due to interstellar dust.

2) b/c dust reflects blue light more effectively than right light

3) YES

Front 6

1) Interstellar Reddening is what?

2) Light reflected by dust cloud appears what?

Back 6

1) when dust clouds b/w star and observer scatter more blue light that red light out of beam

2) Blue

Front 7

1) Why is the Earth's sky appear blue?

2) Why does the Sun look red when near the horizon?

Back 7

1) because air molecules reflect more blue than red light

2) Because more blue light than red light has been removed

Front 8

1) What are the main sequence mass limits?

2) Why are these the limits

Back 8

1) From .08 MoS to 100 MoS

2) <.08 is too low to fuse, >100 pressure blows star apart

Front 9

Evolution of a 1 MoS Star

Back 9

1) Main Sequence
2) Red Giant
3) Helium Flash
4) Horizontal Branch
5) Second Red Giant
6) Planetary Nebula
7) White Dwarf

Front 10

1) What happens when a star leaves the main sequence?

2) How long does the sun spend on the Main Sequence?

Back 10

1) It leaves when H is used up in core from H Fusion

2) 10^10 Years

Front 11

1) What happens to a star in the Red Giant Phase?

2) Outer region of star ____ and ___

Back 11

1) H fusion ends in core, but continuous in shell around core. Gravity causes core to contract and heat.

2) expands, cools

Front 12

1) Red Giant is B___, B____, and C___

2) What happens in a Helium Flash?

3) What is the triple-a process?

Back 12

1) Big, Bright, Cool

2) Central T= 10^8 K, He fusion begins in core.

3) 3He ---> C + energy, C= carbon nucleus.

Front 13

1) What happens in the Horizontal Branch Phase?

2) L is _____ than for sun

3) What do they form in the HR diagram

Back 13

1) He Fuses to C in core, core expands and cools, envelope contracts and becomes bluer.

2) Higher

3) Horizontal grouping

Front 14

1) What happens in the Second Red Giant Phase?

2) The Core ___; envelope ____

Back 14

1) No He left in core, core is now Carbon (C), No nucleur fusion occurs in core

2) Contracts, expands

Front 15

Structure of ejected gas can be non-spherical due to....

Back 15

- Star orbiting a binary companion
- or a disk around star- produces hourglass shape

Front 16

1) What happens in a White Dwarf Phase?

2) What is the structure?

3) Does it contract anymore once a white dwarf?

Back 16

1) Hot, dense core becomes white dwarf= collapsed star about size of Earth, NO nuclear burning

2) Very Dense (10^6 X density of water). Electrons are packed as closely as possible.

3) NO, T and L decrease in time

Front 17

1) What happens in the Planetary Nebula Phase?

2) What is the structure like?

3) Is it related to planets?

Back 17

1) Envelope pulsates unstably. Envelope is ejected, core exposed.

2) Expanding spherical gas, Shell around small, hot star, appears as bright ring sky.

3) NO, but it may look like a planet when using a small telescope

Front 18

1) What is the Mass Limit for White Dwarf? Discovered by who?

2) What happens when this mass limit is breached?

3) What are more highly collapsed stars?

Back 18

1) 1.4 MoS, Chandra

2) gravity overcomes electron pressure and then collapse to smaller size and higher density.

3) Neutron Star, Black Hole

Front 19

1) Where are open star Cluster's found? And how can you describe them?

2) Where are most of the stars? How old?

Back 19

1) in disk of Galaxy (i.e. Pleiades), young, recently formed stars.

2) Near main sequence, 2X10^7 Years

Front 20

1) Where are globular star clusters found? And how can you describe them?

2) They have moved to next ____

Back 20

1) Found in bulge/halo of our galaxy, contain only old stars >10^10 years

2) Phases

Front 21

1) The younger the cluster, the ____ the mass of the turnoff stars

2) The ____ of the turnoff determines the ___ of the cluster

Back 21

1) higher

2) location, age

Front 22

1) In High Mass Stars what happens in nuclear fusion?

2) Core is only the size of ____

Back 22

1) Produces elements up to Iron, growing iron does NOT undergo fusion

2) Earth

Front 23

1) What happens in a supernova?

2) What type of particles are produced? And in what way?

Back 23

1) Gravity overcomes outward electron pressure in iron core, causing rapid collapse. Electrons and protons combine to form neutrons.

2) Neutrinos, through a pulse

Front 24

1) What happens in a supernova blast?

2) What types of elements are produced?

Back 24

1) Energy released by core collapse causes shock wave to travel out.

2) Elements heavier than iron

Front 25

1) Elements heavier than H and He are produced in ____ stars, where do they go?

Back 25

1) Massive, Return to interstellar gas

Front 26

1) What are some observations of Supernova 1987A?

Back 26

1) Blue supergiant exploded, L increased by a few 1000X, Neutrino Pulse seen in 2 underground detectors- confirmed stellar core collapse

Front 27

1) What does the Chandra X-ray provide?

2) What is the central source for the X-ray?

Back 27

1) Provides much more detail than previous x-ray telescopes.

2) Neutron Star formed in supernova

Front 28

1) What are neutron stars?

2) Neutron Stars are _____ , ____ gas

3) What do they emit?

Back 28

1) ultra-collapsed stellar cores, produced by SuperNova, made of tightly packed neutrons.

2) expanding, hot

3) all forms of EM radiation: radio - gamma rays

Front 29

1) What is pulsar? How was it discovered?

2) What was the first explanation?

Back 29

1) pulsing source of radio, visible, or X-rays. By using radio telescope in 1967.

2) alien signals

Front 30

1) Pulsar Model is a...

2) What are not aligned?

3) What is the radiation beamed along?

4) Lighthouse Effect-

Back 30

1) Magnetized, rapidly rotating neutron star.

2) Magnetic and rotation axis

3) The magnetic axis

4) see flash when beam sweeps past us

Front 31

1) Why is Rotation so fast?

2) As core collapses spin rate ____

Back 31

1) "Ice Skater Effect"

2) Greatly Increases, fastest =42000

Front 32

1) How are accretion disks formed?

2) What happens to gas in the disk?

Back 32

1) When gas escapes from normal star and is attracted by gravity of collapsed star and then it forms

2) it spirals inward, releasing gravitational energy, then heated to High T by friction and radiaties UV and X-ray

Front 33

1) What is the maximum mass for a neutron star?

Back 33

1) 3 MoS

Front 34

1) What is Cygnus X-1

Back 34

Visible star is B supergiant with strong wind, it is a Black Hole M= 5-10 MoS

Front 35

1) What is a black hole?

2) What happens to its density?

Back 35

1) Object with such strong gravity that NOTHING can escape from its vicinity- even light

2) It has infinite density- a singularity

Front 36

1) Explain Curved Space

Back 36

1) Mass causees space to curve. High mass concentration caused surrounding space to pinch off from rest of universe, nothing can escape from this region.

Front 37

1) What is the event horizon?

2) What happens to something that goes into event horizon?

3) What is the escape speed?

Back 37

1) Location of BH surrounded by spherical surface. "Sphere of no escape"

2) merges into BH, and increases event horizon and BH mass

3) faster than speed of light

Front 38

1) Photons follow ___ paths in curved space

2) The more collapsed a star, the more it ____ the surrounding ____

Back 38

1) Curved

2) curves, space

Front 39

1) Where are Black Holes located?

2) How do BH's power active galaxies and quasars?

Back 39

1) In binary star systems (we have about 20) and at centers of galaxies

2) through gravitational energy release

Front 40

What are the properties (endstate,mass,Radius) of stars with...

1) M<10 MoS
2) M>10 MoS
3) M>25 MoS

Back 40

1) white dwarf, 1.4 MoS, Radius of Earth

2) neutron star, < 3 MoS, 10 Km

3) black hole, > 3 MoS, 9km

Front 41

1) Where is the sun located in the Milky Way?

Back 41

1) in the disk, left of the galactic center from top view, midway b/w center and edge

Front 42

1) When looking at the Milky Way through Infrared, compare the wavelength of Dust and Stars and their Temp

Back 42

1) Dust- Longer Wavelength IR, LOWER T. Stars- Shorter Wavelength IR, HIGHER T

Front 43

1) What is the shape of the Milky Way?

2) How many LY's in diameter, thickness?

Back 43

1) Disk, Frisbee shaped

2) 100,000 LY, 2000 LY

Front 44

1) What paths do stars and gas follow in the disk.

2) What is the orbital period of the sun?

3) How many orbits has it completed?

Back 44

1) Circular orbits (like planets)

2) 2X 10^8 Years

3) Age/Period= 25 orbits

Front 45

1) What happens in the evolution of the disk with respect to each stellar generation?

2) Do young or old stars have high metal content in the atmosphere, why?

Back 45

1) Each generation adds "metal" to interstellar gas, from supernova explosions

2) Young because they are formed from enriched gas

Front 46

1) Give details about the Halo

2) What are the motions like in the spheroid?

Back 46

1) It is spherical and extends well beyond disk, contains individual stars, global star clusters, and dark matter. OLD STARS only- no gas and dust

2) no common orbital plane or direction

Front 47

1) What did the old view of the galactic center not account for?

2) How did Shapley develop the modern view of the galactic center?

Back 47

1) Dust, which obscures distant stars

2) Used globular clusters, and these are found near galactic center

Front 48

1) What is a standard candle?

2) Where is the milky way and the galactic center located?

3) How far is the Sun from the galactic center?

Back 48

1) an object of known luminosity

2) Sagittarius

3) 25,000 LY