Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Flashcards > Astronomy Final > Flashcards

Astronomy Final Flashcards

1
Q

What is an elliptical galaxy

A
  • centrally concentrated balls of old stars
  • reddish color
  • very little gas and dust
  • very little star formation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is a spiral galaxy, what is a bar

A

Spiral Galaxies: “Rotating Disk Systems”
-actively forming stars
-disks rich in gas and dust
Barred Spiral Galaxies:
-Gas and dust travel down bar to inner-nucleus to (feed supermassive black hole?)
-“Dust lanes” may arise from collisions with other galaxies or spontaneously if halo is not massive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is a merging galaxy? Do stars collide? What does collide? What is a starburst?

A

Merging Galaxy: when a galaxy is found in rich clusters and loose groups by gravitational tides
-Stars do not collide in merging galaxies
-galaxy clusters collide
Starburst: when large spiral galaxies form 1-3 stars like the sun each year “Starburst Galaxies” are peculiar/interacting

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the difference between a group and a cluster

A

Group: small collection- “galaxy poor” like Milky Way
Cluster: large collection- “galaxy rich” like Virgo cluster

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

The Milky Way is a member of the Local Group – which galaxy type is most common? How many spiral galaxies are in the Local Group?

A
  • Spiral galaxy is most common

- there is only 1 spiral galaxy in the local group (The Milky Way)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

The H-alpha line for a galaxy is observed at λ= 700nm. λrest= 656.3nm. What is the redshift of the galaxy? What is the recessional velocity?

A

[z = 0.07; v = 2 x 104 km/s]

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Galaxies are not distributed randomly in space. They like company. Using Hubble’s Law, large surveys of galaxies have pieced together maps showing how galaxies are distributed. Galaxy distribution is “frothy” – large regions with very few galaxies (“Voids”) and large “Sheets” or “Walls” of galaxies, spanning many Mega-parsecs (Mpc – million parsecs). Especially dense concentrations of galaxies – called galaxy clusters – stand out. Most galaxies lie on sheets surrounding large voids.

A

Study the material on back of card

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What causes galaxies to have long tidal tails? How are tidal dwarf galaxies formed?

A

-gravitational tidal interaction forces cause galaxies to have long tidal tails
Tidal Dwarfs:
-formed in the tidal tail
-once two blue galaxies merge the spawn a large number of new dwarf galaxies (small/red)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How do you create a ring galaxy like the Cartwheel Galaxy?

A
  • Star formation, gas distribution
  • Through special collisions (peculiar galaxy)
  • “Feeding the monster”: galaxy collides and flied through the center of another making a splash
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is found at the centers of massive galaxies

A

-Bulge/ Supermassive Black Holes are found at the centers of massive galaxies

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How can a galaxy-galaxy collision trigger an Active Nucleus

A

Center of some galaxies emit large amounts of energy

  • Outshine entire galaxy- “Active Galactic Nuclei”
  • Power source is gas flowing in to black hole
  • Interactions send gas to inner-most regions, therefore “feeding the monster”
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What happens during a high-speed collision? (Note what happens to the intra cluster gas when there are high speed collisions between galaxies in a large cluster)

A
  • Galaxy is stripped of its gas and dust

- very hot intracluster X-ray emitting gas heated by collision

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What happens during a near-miss/low speed collision? (For example in M82)

A

During near-miss low speed collision:

  • Prolific star formation occurs at center of galaxy
  • Powerful winds form young stars cause M82 to expel gas and dust at a prodigious rate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What do we think happened to Centaurus A – the giant elliptical with a big dust lane?

A

-It gained a dust land via a collision with a spiral (gas/ dust rich) galaxy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Make a list of what can happen during a tidal interaction. Is the Milky Way undergoing any tidal interactions with nearby dwarfs? Will it merge with Andromeda in the future?

A
  1. May create spiral arms
  2. Galactic Cannibalism
    - The Milky Way is not undergoing tidal interactions with nearby dwarfs
    - Yes, the Milky Way will merge with Andromeda in about 6 billion years or so
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What type of galaxy collisions/mergers form elliptical galaxies? Spiral galaxies?

A
  • If a galaxy “eats” another galaxy larger than itself, it forms and elliptical galaxy
  • If a galaxy “eats” another galaxy smaller than itself, it forms a nice spiral
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Sub galactic unites merge to form a protogalaxy. What happens next to form a spiral or elliptical galaxy? How does the stellar birth rate differ for elliptical and spiral galaxies?

A
  • Stars form gradually, gas not involved in star formation collapses to form a disk, and a spiral galaxy happens
  • Stars form rapidly, gas quickly consumed to make stars, and an elliptical happens
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is a quasar?

A
  • distant supermassive black holes within an active distant galaxy, Quasi-stellar radio source, easier to discover radio than optical
  • Bright red- shifted hydrogen emission lines
  • none local
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How does the number of quasars per unit volume in the early universe compare with the number today? How many billion years after the Big Bang did the number per unit volume reach its peak? What physical argument do we use to explain why there are no nearby quasars?

A
  • The number of quasars are not as common as they were during the first 3 billion years
  • The number per unit volume reached its peak roughly around 2 or 3 billion years after the Big Bang
  • The argument used is: The Universe expands even after light leaves, moving volume per unit measurement, distant and very luminous. Absorption lines- cold gas through other galaxies or gas clouds
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What types of galaxies contain radio loud quasars? Nearby radio-quiet quasars?

A
  • Elliptical galaxies contain radio loud quasars

- Spiral galaxies contain radio quiet quasars

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is a Seyfert galaxy – what is the difference between Type 1 and Type 2? Can you recognize each type from an optical spectrum (see slides 22 & 23)

A

Seyfert Galaxy:
-Large spirals with unusually luminous nuclei
-Active nucleus, they look ordinary, though big, spiral galaxies
Type 1:
-Optical Spectrum: broad hydrogen lines
Type 2:
-Optical Spectrum: narrow hydrogen lines

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is a radio galaxy – draw a sketch labeling the main components

A
  • A radio galaxy is where a radio lobe jets outward from both ends
  • the visible galaxy in center >200,000pc
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what is a blazar?

A

-a compact source of synchrotron emission: highly variable radio emission

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What powers an AGN?

A
  • material (gas/dust) spiral down to a supermassive black hole at center of galaxy
  • spirals faster as it neats the center and heats up the accretion disk
  • the released energy powers jets of magnetic fields and high-speed electrons moving away in two direction emitting synchrotron radiation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

what is the AGN Unification scheme and the components

A
  • Radio Jet- Broad line clouds

- Dusty torus-narrow line clouds-Sy1- Sy2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What is the Eddington Limit?

A

-Lower limit to the mass of a black hole

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

The mass of a supermassive black hole is 1 million solar masses. What is the Eddington luminosity for this source?

A

[3x1010 Lsun]

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What is NuSTAR?

A
  • its a mission that has developed the first orbiting telescopes to focus light in the high energy X-ray region of the electromagnetic spectrum
  • Nuclear Spectroscopic Telescope Array
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What is Olber’s paradox and how is it resolved?

A
  • If the universe is in static and infinite all likes of sight will lead to a star
  • The entire night sky should be as bright as the sun, but due to the red shift at a constantly increasing rate of the universe the stars appear to go into infrared which masks the stars to appear dark because it is outside of our visual
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What was Einstein’s Greatest Blunder?

A
  • He applied his general relativity to structure to the Universe
  • Calculations could not produce static universe by adding a “cosmological constant” which basically forced the universe to remain static in physics
  • Later, tis was proven wrong by universal expansion and he said this was the greatest mistake of his career
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What is Hubble’s Law? Use Hubble’s law to calculate the distance to a galaxy observed to have a recessional velocity of 10,000 km/s.

A
  • the further away a galaxy is the faster it appears to be moving away from us, it implies that 14 billion years ago all galaxies were in the same place
  • [137.0 Mpc]
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Use Hubble’s law to calculate the recessional velocity of a galaxy t a distance of 99 Mpc.

A

[7227 km/s ]

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What is a cosmological redshift how does it differ from a Doppler shift?

A

-Its a redshift caused by the expansion of the universe (objects do not move, space time does

34
Q

What are the three cosmological principles?

A
  1. Law of Physics stay the same throughout the universe and does not change with time, EXCEPT in black holes
  2. The universe is “Isotropic”- looks the same in every direction
  3. The universe is “Homogeneous”-should be the same everywhere
35
Q

Does the Universe have a center or an edge?

A

-No

36
Q

Who proposed the Big Bang theory? i.e. that the universe began as a cosmic singularity .
After what period of time did “space and time” behave according to the physics that we know and love today?

A
  • George Henri Lemaitre

- 380,000 years after the big bang

37
Q

Why is the Helium abundance so important – how is this used to support the theory of a Big Bang?

A
  • There is far more Helium in the Universe than could have been created by fusion of Hydrogen in stars
  • if early universe was hot as the sun’s core, it could have made lots of Helium
38
Q

Penzias and Wilson discovered the cosmic microwave background radiation using a radio telescope. Why were the follow-up COBE and WMAP satellite results so important?

A

-Some people thought CMB was not blackbody, but COBE found the CMB to be a Blackbody with T=2.735K, which fits COBE with blackbody spectrum perfectly

39
Q

photons out number atoms by roughly a billion to one. The mass density of radiation dominated the early universe. Look at the evolution of density – does matter or radiation dominate today?

A

-Matter dominates

40
Q

What happened during the era of recombination?

A

-The formation of the first atoms

41
Q

Describe the primordial fireball

A

Before recombination:

  • no atoms
  • plasma is opaque
  • the universe was too hot and dense for light to travel, therefore, we cannot see before the period of 380,000 years after the Big Bang
42
Q

How long was the Helium window?

A

-200 seconds to 300 seconds

43
Q

What are the three pillars of the Big Bang?

A
  • Hubble’s law
  • The cosmic background radiation
  • The abundance of deuterium and helium
44
Q

We live in a flat universe. What will happen to two parallel laser beams?

A

-Two beams of light would remain perfectly parallel

45
Q

The critical density defines the geometry of Space. If the average density is greater than the critical density what is the geometry of space? If it is less, or equal to?

A

“Po>Pc” Spherical

-Less than

46
Q

The WMAP observations of the cosmic microwave background show that it is very smooth to one part in 10,000. However there are very small temperature fluctuations and astrophysicists measure the angular sizes of these hot and cold spots and compare them to models of the universe. The observed angular size peaks at about 1 degree – what type of universe do we live in, why does this imply the universe is filled with dark energy?

A
  • A dark energy dominated flat accelerating universe
  • it is implied by the model cosmic fireball- dominant hotspots have an angular size of 1 degree. This is what we see from BOOMERANG, MAXIMA, and WMAP. Todays matter dominates .0002 the rest is dark energy.
47
Q

How was structure formed in the Universe – what came first perturbations in the dark matter or in ordinary matter?

A
  • Distribution grows in size and mass as they attract more and more dark matter via gravity
  • Perturbations in the dark matter came first
48
Q

Has the universe always expanded at the same rate? In the early universe was the rate of expansion increasing or slowing – why? In the universe today is the rate of expansion increasing or decreasing – why?

A
  • No, it speeds up over time
  • first 9 billion years mutual gravitational attraction slowed the expansion of the universe
  • Today, (past 5 billion years), the universe expansion is increasing because dark energy dominates and the expansion speeds up
49
Q

What is significant about the dark energy density in the last 5 billion years?

A

-It dominated the Universe causing its expansion to speed up

50
Q

What do we predict will happen in 30 billion years time?

A

-We will have expanded so that only a thousand or so of the nearest galaxies will still be visible

51
Q

What is the isotropy problem?

A

-Why the cosmic microwave background is so uniform (flat)

52
Q

What is the flatness problem?

A
  • tiny deviations in value of “Po” would lead to, if “Po” slightly less than “Pc”=> expansion too rapid for clumping: no galaxies no us
  • If “Po” slightly greater than “Pc”=> gravitational collapse and a Big Crunch no us
  • Immediately after the Big Bang “Po=Pc” to 50 decimal places (rapid expansion instant)
53
Q

What is the inflationary model? Does it provide a solution for the isotropy and flatness problems? When did the inflation occur? By what factor did the universe expand? What happened to the temperature of the Universe during inflation?

A

Inflation model:

  • After the Planck time the Universe experienced a brief period of inflation: the universe doubles in size a hundred times and expanded by factor of 10^3 in all directions
  • FINISH ANSWERING THIS QUESTION
54
Q

What are the four fundamental forces – which two have a range of infinity? Which two have a range limited to the size of a nucleus? What are the four exchange particles? Photon, gluon ….

A 
Four Fundamental Forces:
1. gravitational-(Gravitons)
2. Electromagnetism (Photons)
3. Strong- (binds protons and neutrons together; Gluons)
4. Weak- (enables quarks to change; Intermediate Vector Bosons)
Range of infinity:
-Electrometric
-Gravitational
Limited size nucleus:
-Strong
-Weak
Four Exchange Particles:
1.Gluons
2.Photons
3.Intermediate Vector Bosons
4.Gravitons
55
Q

What is the Grand Unified Theory

A
  • Predicts that the strong force becomes unified with the weak and electromagnetic forces (but not gravity) at energies above 10^14 GeV
  • the strong, weak, and electromagnetic interactions would all be long-range forces and would be indistinguishable from each other
  • strong and weak act as one force
56
Q

What is TOE?

A

-Theory of everything: everything unidentified

57
Q

As the Universe expands and cools the four forces freeze out. In what order did the spontaneous symmetry breaking occur? At what time did Gravity freeze out? When happened when the strong force froze out? After how many symmetry breakings did the universe finally behave as we know it today?

A
  1. No new photons and neutrons formed by pair production: matter content DOWN radiation content UP.
  2. Protons and neutrons form- energy collision: quarks are now able to stick together.
  3. Threshold Temp- collisions of photons no longer energetic enough to produce a given particle/anti-particle pair, annihilation could still proceed.
  4. Primordial Fireball- gains energy from annihilation of particles during the first second of the universe and will dominate the universe for the 380,000 years.
58
Q

During inflation all the mass and energy in the universe burst forth from vacuum space. Describe how this happens (hint: virtual particles)

A

-A virtual antiparticle pair that appears just before the inflationary epoch is pulled so far apart during inflation that the particles cannot recombine, leaving a pair of real particles

59
Q

What is pair production? Annihilation?

A

Pair Production:
-formation of two electrons from a pulse of electromagnetic energy; a direct conversion of radiant energy to matter
Annihilation:
-when a particle and its antiparticle collide and disappear

60
Q

What is the Threshold Temperature? – is the threshold temperature/energy higher or lower for a pair production of more massive particles?

A
  • When temperature becomes so low that the gamma rays no longer have enough energy to create particular kinds of particles and antiparticles
  • Temperature drops below particular particle’s threshold temperature
  • Lower energy dependent
61
Q

The existence of us (matter) implies what for the original ratio of particles to antiparticles? If the number of particles equaled the number of anti-particles what would happen?

A
  • No new protons and neutrons formed by pair production: matter content DOWN radiation content UP
  • No new electrons and positrons: matter content DOWN radiation content UP
  • Universe continued to expand and gammaoray photons became increasingly redshifted. The temp radiation field fell
  • If perfect symmetry the matter content of the universe would be zero after 1 second
62
Q

What are population III stars? why are they so massive?

How

A
  • formed from gas clouds but no dust and metals, so higher internal temperatures… creating bigger stars
  • purely hydrogen and helium; these re-ionize the universe
63
Q

How many dimensions do theorists predict there are in the universe?

A

[11]

64
Q

What is a Higg’s Boson (brief answer!!)

A

explains why the other elementary particles, except photon and gluon are massive

65
Q

What is a string (brief answer)

A

String theory- each particle has more finer levels of structures. Looks like string, vibrating producing particles

66
Q

Which photon has a greater energy a radio photon or a gamma ray photon?

A

Radio

67
Q

Which photon has the longer wavelength a radio photon or a gamma ray photon

A

-Radio

68
Q

What powers the Sun?

A

fusion- gas in our sun is hydrogen and helium

69
Q

Will the Sun go supernova?

A

No- turn into a red giant and then white dwarf

70
Q

What is a type II supernova?

A

-rapid collapse and violent explosion of a massive star

71
Q

What is a type Ia supernova?

A

-Occur in binary systems (two stars orbiting each other) in which one is a white dwarf and the other can vary from giant star to a smaller white dwarf

72
Q

What is a constellation of stars?

A
  • Images in the sky made up of patterns in the stars

- refer to the zodiac as well

73
Q

Why are telescopes placed on the tops of mountains?

A

-Because of pollution from lights and within the earth’s atmosphere as well as weather

74
Q

What is the angular resolution of a telescope? How can you improve it for a radio telescope?

A
  • angular resolution is the smallest angle over which we can see two stars are distinct (depends their actual separation and distance from us)
  • interferometry is a way of improving the angular resolution of a radio telescope (linking two or more telescopes to achieve higher angular resolution)
75
Q

Stars form when a massive cloud collapses – does just one star form?

A

-yes

76
Q

Does a star spend most of its life as a protostar, a main sequence star or a giant? Is this true for stars of all masses?

A
  • Main sequence star

- no

77
Q

How is gold formed in the universe? How is Hydrogen formed? How is helium formed?

A
  • collisions of stars
  • after the big bang the resulting elemental matter was about 3/4 hydrogen and 1/4 helium (cooling after the initial Big Bang) hydrogen is the most abundant in the universe
78
Q

Most of the mass in the Milky Way is Dark matter – what are the dark matter candidates?

A

MACHOS and WIMPS

79
Q

Does hot ionized hydrogen gas emit the 21cm radio line? What is the 21cm line?

A
  • no, cold atomic hydrogen gas (H1) 100- 30000K temp
  • refers to the electromagnetic radiation spectral line that is created by a change in the energy state of neutral hydrogen atoms
80
Q

Use Wien’s law to calculate the peak wavelength for a blackbody of temperature T = 6000K

A

[λmax = 4.8 x 10-7 m]

Flashcards (4 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions