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Astronomy > Lecture 12 > Flashcards

Lecture 12 Flashcards

1
Q

definition of galaxies

A

stellar and interstellar matter isolated in space and bound together by its own gravity

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2
Q

types of galaxies

A
  1. spiral
  2. barred spiral
  3. irregular
  4. peculiar
  5. lenticular
  6. elliptical
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3
Q

What type of galaxy is the milky way

A

spiral

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4
Q

All spiral galaxies include what?

A

a flattened disc, central galactic bulge with a dense nucleus and an extended halo of old faint stars

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5
Q

How are spiral galaxies divided

A

by the size of the central bulge (subdivided into a, b or c)

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6
Q

Elliptical galaxies have little___

A

structure

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7
Q

How are elliptical galaxies divided

A

depending on how elliptical they are (E0 is circular, E7 is elongated)

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8
Q

what are the problems with dividing galaxies based on their appearance

A

what a galaxy looks like depends on the position of the observer or their view point

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9
Q

when viewed edge on the patchiness of the milky way is due to

A

interstellar material blocking our view

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10
Q

structure of spiral galaxies

A

halo-bulge-disk

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11
Q

By measuring the distance and direction to many globular clusters in the halo it is found that

A

the globe is spherical and not centered on the sun

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12
Q

Disc stars orbit in ____ and are ___ in color, meaning the stars age is ___

A

circles; blue-ish; younger

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13
Q

Halo stars orbit in __ orbits, stars are __ in color meaning the stars are __ in age

A

random; yellow; older

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14
Q

Bulge stars orbit in a ___ and are __ in color

A

somewhat ordered pattern; yellow

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15
Q

How do we know halo stars are old?

A

they have a redder color and a lack of dust or gas, meaning no new star formation

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16
Q

2 types of pulsating variable stars

A

RR Lyrae variables and Cepheid variables

17
Q

RR Lyrae variables have a __ period

A

short

18
Q

Cepheid variables have a __ period

A

longer

19
Q

Where are pulsating variable stars plotted on the HR diagram

A

in the instability strip

20
Q

Pulsations are due to…

A

intrinsic variations in the star (increase and decrease in size as the outer layer expands and contracts)

21
Q

direct relationship between period of ___ and ___

A

pulsations; luminosity

22
Q

by measuring the periodicity of a pulsating star what can be determined?

A

its luminosity

23
Q

galaxies often occur in clumps called

A

galaxy clusters

24
Q

distance to galaxies can be determined using

A

variable stars

25
Q

Standard candles

A

objects with a well defined luminosity (very birght)

26
Q

Tully-Fisher relation

A

rotation speed and luminosity of spiral galaxies found to be closely related ( rotation speed is related to mass, mass is related to luminosity)

27
Q

by measuring rotation speed a galaxies ___ can be estimated and used to find its ___

A

luminosity; distance

28
Q

Hubble’s Law

A

galaxies within a cluster move in a random way but galaxy clusters and galaxies themselves move in a very ordered way

29
Q

virtually every individual galaxy and cluster has a __ spectrum

A

red-shifted

30
Q

the further away a galaxy is from us…

A

the faster it is receding

31
Q

from the amount of ___ the velocity at which an object is moving away can be determined

A

red-shift

32
Q

plot of __ and recessional __ show a straight line

A

distance; velocity

33
Q

the rate at which a galaxy __ is directly proportional to its __ from us

A

recedes; distance (recessional velocity= distance)

34
Q

Cosmological redshifts

A

redshifts of large clusters of objects at huge scales

35
Q

Hubble’s constant

A

to convert a proportionality relationship to an equality relationship[ we must include a constant of proportionality

36
Q

Hubble’s constant equations

A

recessional velocity= Ho x distance

distance=velocity/Ho

37
Q

if we can measure ____ of a galaxy cluster we can determine the __ to it

A

recessional velocity;distance

Astronomy (5 decks)

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