The Expanding Universe

Question 1

what did 20th century astronomers photograph?

Answer 1

the spectra of galaxies

Question 2

what did the photos of spectra of galaxies allow astronomers to measure?

Answer 2

Doppler shift, and thus the radial velocity

Question 3

Vesto Slipher

Answer 3

1912: obtained 1st measurement of Andromeda galaxy

- determined it was moving toward us at 300 km/s

Question 4

how many galaxies were redshifted (moving away from us)

Answer 4

21 out of 25 galaxies

Question 5

what did Hubble work to obtain?

Answer 5

distances to the galaxies

Question 6

what did Hubble use to measure distances to galaxies?

Answer 6

Cepheid variable stars

Question 7

Hubble’s 1929 Discovery

Answer 7

the further away a galaxy was, the larger the recessional velocity

Question 8

what two things did Hubble deal with?

Answer 8

recessional velocity and distance

Question 9

Spectra

Answer 9

the combined light of many stars

Question 10

what measurement can you get from the spectra of a galaxy?

Answer 10

you can derive the recession velocity

Question 11

what is the most fundamental method for distance?

Answer 11

stellar parallax

Question 12

brightness formula

Answer 12

luminosity/4 x pi x d^2

Question 13

what are 3 standard candles

Answer 13

main sequence stars
cepheid variable stars
type 1a supernovae

Question 14

type 1a is related to what kind of star

Answer 14

white dwarf

Question 15

what are cepheid variable stars

Answer 15

pulsating stars that vary in light output

Question 16

combining brightness and lumin. gives you

Answer 16

the distance

Question 17

key project for Hubble space telescope

Answer 17

using Cepheids to determine distance to galaxies (w/in 25 Mpc)

Question 18

what do type 1a supernova result from

Answer 18

detonation of white dwarf stars

Question 19

when do white dwarf stars detonate

Answer 19

slightly after mass exceeds 1.4 solar masses

Question 20

Type 1a luminosity

Answer 20

very luminous 9detected at over 1 billion pc)

Question 21

what can be serve as cosmological probes?

Answer 21

type 1a supernova, since they can be detected from billions of parsecs away

Question 22

Hubble’s law

Answer 22

relation b/w distance and velocity

Question 23

Hubble Law formula

Answer 23

v = H x d

Question 24

what is the Hubble law telling us about the universe?

Answer 24

that it’s expanding

Question 25

are we in a preferred location in the universe?

Answer 25

NO

Question 26

Einstein’s cosmological constant

Answer 26

opposes gravity and makes Universe static

Question 27

George Lemaitre

Answer 27

proposed that the observed recession of galaxies was evidence for the expansion

Question 28

Big Bang Universe

Answer 28

A universe w/ a well defined beginning

-time where separation of galaxies was very small

Question 29

Nature of the Expansion of Universe

Answer 29

doesn’t have a center, but rather the “fabric” of space time carrying the galaxies is expanding

Question 30

If fabric of space/time expands by a factor of two, the distance b/w galaxies will…?

Answer 30

increase by a factor of 2

Question 31

why are galaxies redshifted?

Answer 31

not due to doppler shift, but due to expansion of space

Question 32

cosmological redshift

Answer 32

wavelength of light is stretched as Universe expands

Question 33

redshift

Answer 33

shift of spectral lines to longer wavelengths

Question 34

redshift formula

Answer 34

z = obs wav - emitted wav/emitted wav

Question 35

when you measure cosmological redshift, we often express it as…?

Answer 35

a recession velocity

Question 36

What to use to measure distance to very distant galaxies?

Answer 36

Hubble law

v = H x d

Question 37

redshift can be used as a measure of what?

Answer 37

distance

Question 38

what device performed the largest redshift survey of galaxies?

Answer 38

SDSS

Sloan Digital Sky Survey

Question 39

cosmic web

Answer 39

non uniform distribution of galaxies and galaxy clusters