Astronomy Final Exam Flashcards
Galactos is the Greek word for _____
milk
What makes up the milky way?
stars, dust, and gas
The middle of a galaxy is called a _____
bulge
The Milkyway is how “tall”?
1000 light years`
How wide is the Milkyway?
100,000 light years
3 main categories of galaxies
elliptical, spiral, irregular
Spiral galaxies are normally what color?
blue
Giant ellipticals are often found in _____ consisting of hundreds or thousands of galaxies.
rich clusters
The Milkyway and Andromeda are each a collection of _____ and _____
small dwarf spheroidal and irregular glaxies
Nearest cluster to ours
Virgo
Distance to Virgo
52 Mly
The 4 brightest galaxies are ______ galaxies
giant elliptical
The nearest “rich” cluster is _____
Coma, as many as 10,000 galaxies
Measuring galaxy distance
Step 1: __________
determine size of the solar system using radar
Measuring galaxy distance
Step 2: _________
determine the distances of stars out to a few hundred light years using parallax
Measuring galaxy distance
Step 3: ________
main sequence fitting of star clusters
Measuring galaxy distance
Step 4: _________
Because the period of cepheid variable stars tell us their lumosities, we can use them as standard candles
Inverse square law
M = L / 4(3.14)d^2
Cepheid variables and Type 1a supernovae can be used as _______
standard candles
Hubbles Law
v = Ho d v = velocity Ho = hubbles constant d = distance
More distant galaxies are moving at a much _____ rate
faster
this is given by hubbles law
We have detected galaxies from when the universe was only ________ years old
1 to 2 billion years old
Physical cosmology
The use of the laws of physics to study the formation and fate of the universe
The early universe must have been _______
hot and dense
Known forces in the universe
- Gravity
- strong force
- electromagnetism
- weak force
Plank era lasted
10^-43
Gut era lasted
less than a trillion trillion trillionth of a second
We have detected leftover ______ from the big bang theory
radiation
WMAP gives us ________
detailed pictures of the universe
How old is the universe?
13.7 billion years old
An undetected form of mass that emits little or no light, but whose existence we infer from its gravitational infulence
Dark matter
An unknown form energy that seems to be the source of a repulsive force causing the expansion of the universe to accelerate
Dark energy
A plot of orbital velocity, v, versus orbital radius, r,
rotation curve
A galaxy cluster is made up of:
85% dark matter
13% hot gas
2% stars
Three methods of measuring a clusters mass:
- galaxy motions
- x-ray gas temp
- gravitational lensing
(MACHOS) Ordinary dark matter:
dead or failed stars in halos of galaxies
(WIMPS) extraordinary dark matter:
mysterious neutrino-like particles
