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48 Cards in this Set

  • Front
  • Back
Stars form in ___ , ____ interstellar clouds
Cold, Dense
Dark Nebula-

What does it do?
Dense cloud of gas and dust

Absorbs visible light + Obscures Stars Behind It
1) What happens when a could collapses?

2) What triggers a collapse?

3) What happens when it contracts?
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
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?
1) dense gas and dust clouds from which they form

2) Infrared, less absorbed by dust than visible light

3) It stops contracting
1) What is reflection Nebulae?

2) Why is it blue?

3) Do stars behind dust appear redder?
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
1) Interstellar Reddening is what?

2) Light reflected by dust cloud appears what?
1) when dust clouds b/w star and observer scatter more blue light that red light out of beam

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

2) Why does the Sun look red when near the horizon?
1) because air molecules reflect more blue than red light

2) Because more blue light than red light has been removed
1) What are the main sequence mass limits?

2) Why are these the limits
1) From .08 MoS to 100 MoS

2) <.08 is too low to fuse, >100 pressure blows star apart
Evolution of a 1 MoS Star
1) Main Sequence
2) Red Giant
3) Helium Flash
4) Horizontal Branch
5) Second Red Giant
6) Planetary Nebula
7) White Dwarf
1) What happens when a star leaves the main sequence?

2) How long does the sun spend on the Main Sequence?
1) It leaves when H is used up in core from H Fusion

2) 10^10 Years
1) What happens to a star in the Red Giant Phase?

2) Outer region of star ____ and ___
1) H fusion ends in core, but continuous in shell around core. Gravity causes core to contract and heat.

2) expands, cools
1) Red Giant is B___, B____, and C___

2) What happens in a Helium Flash?

3) What is the triple-a process?
1) Big, Bright, Cool

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

3) 3He ---> C + energy, C= carbon nucleus.
1) What happens in the Horizontal Branch Phase?

2) L is _____ than for sun

3) What do they form in the HR diagram
1) He Fuses to C in core, core expands and cools, envelope contracts and becomes bluer.

2) Higher

3) Horizontal grouping
1) What happens in the Second Red Giant Phase?

2) The Core ___; envelope ____
1) No He left in core, core is now Carbon (C), No nucleur fusion occurs in core

2) Contracts, expands
Structure of ejected gas can be non-spherical due to....
- Star orbiting a binary companion
- or a disk around star- produces hourglass shape
1) What happens in a White Dwarf Phase?

2) What is the structure?

3) Does it contract anymore once a white dwarf?
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
1) What happens in the Planetary Nebula Phase?

2) What is the structure like?

3) Is it related to planets?
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
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?
1) 1.4 MoS, Chandra

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

3) Neutron Star, Black Hole
1) Where are open star Cluster's found? And how can you describe them?

2) Where are most of the stars? How old?
1) in disk of Galaxy (i.e. Pleiades), young, recently formed stars.

2) Near main sequence, 2X10^7 Years
1) Where are globular star clusters found? And how can you describe them?

2) They have moved to next ____
1) Found in bulge/halo of our galaxy, contain only old stars >10^10 years

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

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

2) location, age
1) In High Mass Stars what happens in nuclear fusion?

2) Core is only the size of ____
1) Produces elements up to Iron, growing iron does NOT undergo fusion

2) Earth
1) What happens in a supernova?

2) What type of particles are produced? And in what way?
1) Gravity overcomes outward electron pressure in iron core, causing rapid collapse. Electrons and protons combine to form neutrons.

2) Neutrinos, through a pulse
1) What happens in a supernova blast?

2) What types of elements are produced?
1) Energy released by core collapse causes shock wave to travel out.

2) Elements heavier than iron
1) Elements heavier than H and He are produced in ____ stars, where do they go?
1) Massive, Return to interstellar gas
1) What are some observations of Supernova 1987A?
1) Blue supergiant exploded, L increased by a few 1000X, Neutrino Pulse seen in 2 underground detectors- confirmed stellar core collapse
1) What does the Chandra X-ray provide?

2) What is the central source for the X-ray?
1) Provides much more detail than previous x-ray telescopes.

2) Neutron Star formed in supernova
1) What are neutron stars?

2) Neutron Stars are _____ , ____ gas

3) What do they emit?
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
1) What is pulsar? How was it discovered?

2) What was the first explanation?
1) pulsing source of radio, visible, or X-rays. By using radio telescope in 1967.

2) alien signals
1) Pulsar Model is a...

2) What are not aligned?

3) What is the radiation beamed along?

4) Lighthouse Effect-
1) Magnetized, rapidly rotating neutron star.

2) Magnetic and rotation axis

3) The magnetic axis

4) see flash when beam sweeps past us
1) Why is Rotation so fast?

2) As core collapses spin rate ____
1) "Ice Skater Effect"

2) Greatly Increases, fastest =42000
1) How are accretion disks formed?

2) What happens to gas in the disk?
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
1) What is the maximum mass for a neutron star?
1) 3 MoS
1) What is Cygnus X-1
Visible star is B supergiant with strong wind, it is a Black Hole M= 5-10 MoS
1) What is a black hole?

2) What happens to its density?
1) Object with such strong gravity that NOTHING can escape from its vicinity- even light

2) It has infinite density- a singularity
1) Explain Curved Space
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.
1) What is the event horizon?

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

3) What is the escape speed?
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
1) Photons follow ___ paths in curved space

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

2) curves, space
1) Where are Black Holes located?

2) How do BH's power active galaxies and quasars?
1) In binary star systems (we have about 20) and at centers of galaxies

2) through gravitational energy release
What are the properties (endstate,mass,Radius) of stars with...

1) M<10 MoS
2) M>10 MoS
3) M>25 MoS
1) white dwarf, 1.4 MoS, Radius of Earth

2) neutron star, < 3 MoS, 10 Km

3) black hole, > 3 MoS, 9km
1) Where is the sun located in the Milky Way?
1) in the disk, left of the galactic center from top view, midway b/w center and edge
1) When looking at the Milky Way through Infrared, compare the wavelength of Dust and Stars and their Temp
1) Dust- Longer Wavelength IR, LOWER T. Stars- Shorter Wavelength IR, HIGHER T
1) What is the shape of the Milky Way?

2) How many LY's in diameter, thickness?
1) Disk, Frisbee shaped

2) 100,000 LY, 2000 LY
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?
1) Circular orbits (like planets)

2) 2X 10^8 Years

3) Age/Period= 25 orbits
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?
1) Each generation adds "metal" to interstellar gas, from supernova explosions

2) Young because they are formed from enriched gas
1) Give details about the Halo

2) What are the motions like in the spheroid?
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
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?
1) Dust, which obscures distant stars

2) Used globular clusters, and these are found near galactic center
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?
1) an object of known luminosity

2) Sagittarius

3) 25,000 LY