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astronomy final > chapter 19 > Flashcards

chapter 19 Flashcards

1
Q
  • a gravitationally bound collection of stars, dust, gas & dark matter
  • about 2 million in the observable universe
A

galaxy

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2
Q

spiral nebulae that were separated from the Milky Way

A

island universes

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3
Q
  • spiral
  • elliptical
  • irregular
A

3 categories of galaxies

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4
Q
  • a galaxy of Hubble type ‘E’ class with a circular to eccentric outline, containing almost no disk and a population of old stars
  • subtypes ranging from nearly spherical (E0) to flat (E7)
A

elliptical galaxies

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5
Q

a galaxy of Hubble type ‘S’ class with a discernible disk in which large spiral patterns exist

A

spiral galaxies

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6
Q

the central region of a spiral galaxy that is similar in appearance to a small elliptical galaxy

A

bulge

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7
Q

a spiral galaxy with a bugle having an elongated, bar-like shape

A

barred spirals (SB)

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8
Q

the largest bulges and display tightly-wound and smooth spiral arms

A

Sa & SBa galaxies

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9
Q

small central bulges and more loosely wound spiral arms that appear more ‘knotty’ in appearance

A

Sc & SBc galaxies

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10
Q

a galaxy with a bulge and a disk-like spiral, but smooth in appearance like ellipticals

A

SO galaxies

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11
Q
  • a galaxy without regular or symmetric appearance
  • often lack symmetry in shape or structure
A

irregular galaxies

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12
Q

a small galaxy with a luminosity ranging from 1 million- 1 billion solar luminosities

A

dwarf galaxies

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13
Q

the amount of light emitted or reflected per unit area

A

surface brightness

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14
Q
  • determine galaxy shapes
  • in elliptical galaxies, stars move in random directions
  • spiral galaxies have a flattened, rotating disk traveling in the same direction
A

stellar motions

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15
Q
  • a sequence of techniques for measuring cosmic distances
  • position provides a star’s luminosity, enabling astronomers to then estimate its distance by comparing its apparent brightness
A

distance ladder

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16
Q
  1. solar system - radar (10^-3 pc)
  2. nearby stars - parallax (1 pc)
  3. milky way - spectroscopic parallax (10^3 pc)
  4. nearby galaxies - cepheid variables (10^6 pc)
  5. distant galaxies - type 1a supernova (10^9 pc)
A

distance ladder sequence

17
Q
  • objects of a particular type, such as type 1a supernovae, that have a known luminosity
  • astronomers combine the known luminosity & measured brightness of the object to find its distance
A

standard candle

18
Q
  • O stars
  • globular clusters
  • planetary nebulae
  • novae
  • cepheid variable stars
  • supernovae
A

objects used as standard candles

19
Q

a unit of distance equal to 1 million parsecs, or 3.26 million light-years

A

megaparsecs (pc)

20
Q
  • the empirical relationship between rotation velocity & luminosity
  • for spiral galaxies
  • half of the disk is blue-shifted, while the other half is red-shifted
    -faster rotations make broader lines and require more mass to hold them together
  • more massive galaxies have more stars and more luminous
A

Tully-fisher relation

21
Q

the speed at which a galaxy is moving away from Earth is proportional to the distance of that galaxy

A

hubble’s law

22
Q
  • H0
  • the constant of proportionality relating the recession velocities of galaxies to their distances
A

hubble constant

23
Q

matter in galaxies that emits light

A

luminous matter

24
Q

particles of invisible matter that move slowly enough to be gravitationally bound even in the smallest galaxies

A

dark matter

25
Q
  • a plot showing how the orbital velocity of stars & gas in a galaxy changes with radial distances from the galaxy’s center
  • astronomers measure the redshift & blueshift of individual stars and clumps of gas
A

rotation curve

26
Q

the centrally condensed, greatly extended dark matter component of a galaxy that accounts for up to 95% of the galaxy’s mass

A

dark matter halo

27
Q
  • massive compact halo object that includes brown dwarfs, white dwarfs & black holes
  • exert gravitational force & gravitational lensing
A

maCHOs

28
Q
  • weakly interactive massive particle
  • considered an ‘elementary particle’
A

WIMPS

29
Q
  • quasi-stellar radio source
  • the luminousity of the active galactic nuclei, seen only at great distances from the milky way
  • shine with a luminosity of a trillion - thousand trillion suns
A

quasars

30
Q

a highly luminous, compact galactic nucleus whose luminosity may exceed that of the rest of the galaxy

A

active galactic nucleus (AGN)

31
Q

a type of spiral galaxy with an active galactic nucleus at its center and strong emission in the radio part of the spectrum

A

seyfert galaxies

32
Q

a black hole of 1,00 solar masses or more that reside in the center of a galaxy and whose gravity powers active galactic nuclei

A

supermassive black holes

33
Q

a 3-dimensional, donut-shaped ring

A

torus

34
Q

accretion disk & a source of energy (gas & stars)

A

essential elements of AGN

astronomy final (2 decks)

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