Test 3 Flashcards
RR Lyraes stars
Round a 1/2 day period. Old stars Low mass Low metallicity Usually found in globular clusters
Instability strips
Region on the HR diagram where variable stars are found.
Cepheid variable stars
1-100 day period Young stars High metallicity High mass Found in open clusters or disk
Constellation at middle of Milky Way galaxy
Sagittarius
Shapely
He found RR Lyrae stars in globular clusters and determined we are not at the center of the galaxy
Edwin Hubble
Used the hooker telescope and found cepheid variable stars in andromeda galaxy proving it was a whole nother galaxy not just a star forming region within our galaxy
Used to map the spiral arms of the Milky Way galaxy
Hydrogen spin-flip transition
Halo
No gas and dust Old stars Metal poor Population II stars Globular clusters
Disk
Gas and dust Young stars Emission nebulas Star formation, GMCs Open clusters Population I stars Metal rich Sun
Bulge
Contains population I and II stars
Forming spiral arms
1) star formation propagation
2) density wave theory
Milky Way rotation
Use Doppler effect
V = 230 km/sec
Galactic year
The time it takes to go around the center of the galaxy.
One galactic year for the sun: t= 200,000,000 - 250,000,000 years
So sun is about 22 galactic years old
Mass of Milky Way
m = 9.4 * 10^10 solar masses
Number of stars in the Milky Way.
200,000,000,000 stars
Dark matter
For the outside of the galaxy to be goin as fast as the center of the galaxy there must be more mass that can’t be seen.
Missing mass.
The effects of it’s gravity can be seen but not what’s causing it.
WIMP: Google
Center of Milky Way
Super massive black hole.
Sgr A: 3,000,000 solar masses
There’s that much mass in a spot smaller than the solar system
Spiral galaxies
Gas and dust Orbits with a plane Young O&B stars Open and globular clusters Blue Metal-rich
Elliptical galaxies
Very little gas and dust Random orbits Old stars Globular clusters Red Metal poor
Poor clusters
About 30 galaxies in a group
Local group: MW, andromeda, etc (about 25)
Rich clusters
1000s of galaxies
Giant ellipticals usual found at center
Super clusters
Clusters of galaxy clusters
Large scale structure of the universe
Voids: regions without galaxies
Galaxies cluster together in long filaments
What type of galaxy cluster is the Milky Way apart of?
Poor
What are the 2 closest galaxies to the Milky Way?
Large and small Magellanic Clouds.
What is a quasar seen from the side called?
Radio galaxy
What type of star cluster contains population type II objects?
Globular cluster
What type of galaxy contain the least gas and dust?
Ellipticals
Who was the first to determine the distance to the Andromeda galaxy by using Chepheid variable stars?
Edwin Hubble
Which galaxy type is the oldest?
All are the same age
Can two colliding elliptical galaxies make a spiral?
No
What type of variable stars are found in globular clusters and were used by Harlow Shapely in determining distances to globular clusters?
RR Lyraes
What is the size of a black hole with 10 solar masses of material?
R= 3(10) = 30 km
What type of galaxy is the Milky Way?
Spiral
Which type of galaxy is the reddest?
Ellipticals
Which is true for a semi-detached binary system?
A) both stars fill their Roche lobes
B) matter is being transferred from one star to the other through the L1 point.
C) both stars share a common envelope.
D) the stars can be used to determine distances to other galaxies
E) none of the above
B
Which of the following characteristics do all cluster stars not have in common?
A) mass
B) age
C) composition
D) distance
E) all of the above are common to cluster stars
A
Which galaxy type used up most of its gas and dust early in it’s history?
Ellipticals
Which of the following is true about the large scale structure of the universe?
A) galaxies are uniformly distributed in the universe
B) all galaxies are at the center of the universe with only a few at the edges
C) the galaxies are distributed on the edge of bubbles with nothing in some regions
D) the nearby quasars are much more numerous than the distant quasars
E) none of the above
C
Which of the following is not true about quasars?
A. they have high redshifts
B. They emit a lot of energy
C. They are equivalent to radio galaxies just seen from a different angle.
D. They are much more numerous when the universe was much younger.
E. All the the above are true about quasars.
E.
What is it called when distant light is bent by closer objects?
Gravitational lensing
Which of the following is not true of spiral galaxies?
A. The disk of the galaxy has circular orbits all in the same direction.
B. gas and dust are only found in the halo of the galaxies.
C. They have a bluer colour.
D. They contain population I and II stars.
E. All of the above are true for spiral galaxies.
B.
Hubble law
The further a galaxy is away from us, the faster it is moving away.
LaGrangian points
Points of gravitational equilibrium in a 3 body system
Large and small Magellanic Clouds
Companion galaxies of the Milky Way.
Z value
Change in wavelength over rest wavelength.
Light element abundances
The amount of H, He, Li, Be in the universe matches the prediction of the Big Bang theory.
Harlow shapely
First one to determine the center of the Milky Way using globular clusters
Center of Milky Way
In Sagittarius where a super massive black hole resides
Forming spiral arms
Two methods:
Star formation
Density wave
Which are the largest galaxies in the universe?
Giant ellipticals
What is the group of galaxies containing over a thousand galaxies called?
Rich cluster
What does quasar stand for?
Quasi stellar radio source
Which region of the galaxy contains globular clusters?
Halo
What’s the current temperature of the background radiation?
3 K or 2.72 K
What type of stars did Shapely use to determine the distance to globular clusters?
RR Lyraes
What is the suspected classification of the Milky Way galaxy?
SBb
What is it called when a small galaxy collides with a large galaxy?
Galactic cannibalism
What is the name for a binary star system in which both stars fill their Roche lobes?
Contact binary
What is the name for a galaxy which is currently showing a large amount of star formation?
Starburst
Who was the first to determine the shape of the Milky Way galaxy and that we weren’t at the center?
Harlow shapely
Who first determined the distance to the Andromeda galaxy?
Hubble
Which galaxy type has the most gas and dust?
Irregulars
Which galaxies formed first?
All formed at the same time
How many years does it take the sun to orbit the Milky Way?
250,000,000
Which type of galaxy has almost all population II stars?
Ellipticals
Which of the following is not a method for determining distances?
A. Cepheid variable stars
B. galactic parallax
C. Brightest stars in a galaxy
D. Supernova type I
E. All are methods for determining distances
B.
Collision between galaxies can:
A. Turn ellipticals into spirals
B. cause all the stars in both galaxies to collapse into super massive black holes
C. Cause bursts of star formation
D. Cause large numbers of stars to collide and explode.
E. All of the above
F. None of the above
C.
What is it called when distant light is bent by nearer objects? A. Space-time distortions B. large-scale warping C. Einstein field equations D. Relativistic bending E. None of the above
E.
What allows astronomers to map the positions of the Milky Way’s spiral arms?
The spin-flip transmission of a hydrogen atom
Quasar
Quasi stellar radio source. Objects which look like stars but are actually extremely distant galaxies
Dark matter
Matter who’s gravitational influence can be detected but it can’t be seen
Algol paradox
The more massive star in the binary star system is the least evolved
Population II objects
Old objects
Metal poor
Found in halo and globular clusters
Open cluster
Cluster of young stars with about 100 stars lying in the disk of the galaxy
Event horizon
Point around a black hole where escape velocity equals the speed of light
Galactic cannibalism
When a larger galaxy swallows a smaller one
Write Hubble’s law and explain what it implies
Further a galaxy is, the faster it’s moving.
Implies the universe is expanding
What is usually found in the center of rich clusters of galaxies?
Giant ellipticals
Which region of the galaxy contains open clusters?
Disk
What did Penzias and Wilson discover with their microwave antenna?
Background radiation
Who invented the tuning fork diagram to classify galaxies?
Hubble
Which is not true of giant elliptical galaxies?
A. They have many globular clusters
B. they are found at the centers of rich clusters of galaxies
C. They are most likely formed by the collision of other galaxies
D. They are redder in colour than spiral galaxies
E. All of the above are true
E.
Which is the most likely theory for the formation of galaxies?
A. Many smaller clumps merged into galaxies
B. one large clump collapsed into a galaxy
A.
In the GUTs (grand unified theory) which of the four forces was the first to seperate?
Gravity
Colliding galaxies
Gas and dust hits each other
Stars rarely collide
starburst galaxies
High amount of star formation.
Occurs after galactic cannibalism
Galaxy formation theories
- Start with a large cloud of gas and dust that collapses
2. Many small clouds come together. Most likely theory!!!
Hubble’s constant
H = V/D H = 67.80 + or - .77 km/sec/mpc
Age of universe
t = 1000/H t = about 13 billion years
Distance to galaxies
- Variable stars
- Brightest stars
- Brightest globular cluster
- Supernova explosions
- Brightest galaxy in clusters
- Hubble’s law
Sky at many wavelengths
Radiowaves: detects gas
Microwaves: everywhere
Infrared: dust
Optical (visible)
Ultraviolet: everywhere. Hot gas.
X-rays: gas at millions of degrees
Gamma rays: supernova explosions. Collision of black holes
Quasars are:
Really small
Very far
Very powerful
Radio galaxies
Giant streams of stuff shooting out of galaxies perpendicular to the disk.
Gravitational lensing
When mass bends light.
Proves dark matter because there isn’t enough mass to bend the light
Cosmology
Study of the universe as a whole
Who discovered background radiation?
Penzias and Wilson
Temperature of background radiation?
3 degrees Kelvin
3 pieces of evidence for the Big Bang theory
- Universe is expanding so it had to start from a single point
- Background radiation
- Light element abundances
GUTs
Grand unified theory
the 4 natural forces were at one time unified as one force.
4 natural forces
- Strong nuclear force
- Weak nuclear force
- Electromagnetic force
- Gravity
Big Bang theory
10^-43 : gravity seperates from the one force.
10^-36 : inflationary epoch. Strong force separates.
10^-34 : leptons, quarks, etc.
10^-10 : weak and electromagnetic forces separate
3 min ABB : H –> He
500,000 ABB : background radiation is created
100,000,000 ABB : first stars
1,000,000,000 ABB : galaxies
Equation to get distance
H (Hubble’s constant) = V/D
