Unit 10: Invisible Astronomy Flashcards
(136 cards)
1
Q
A
2
Q
What type of light have most astronomy discoveries focused on?
A
Visible light
3
Q
What part of the electromagnetic spectrum is visible light?
A
The portion that spans the colors of the rainbow
4
Q
Are radio waves visible to the human eye?
A
No, they are invisible
5
Q
Why are radio waves easier to detect from space than visible light?
A
They can be detected with the right instrumentation and operate 24/7
6
Q
What do radio telescopes look like?
A
They resemble large satellite dishes
7
Q
Where can radio telescopes be located?
A
Anywhere on Earth, even at sea level or in sheep paddocks
8
Q
Do radio telescopes need domes or high mountain locations?
A
No
9
Q
Why can radio telescopes operate during the day and through clouds?
A
Because radio waves have long wavelengths that pass through clouds and daylight
10
Q
What collapsed in 2020?
A
The Arecibo Observatory in Puerto Rico
11
Q
How does the atmosphere affect visible light vs. radio waves?
A
Visible light is mostly blocked by clouds; radio waves are not
12
Q
What is atmospheric opacity?
A
A measure of how much light is blocked by the atmosphere
13
Q
Why are visible telescopes placed on mountains?
A
To minimize atmospheric interference and see fainter objects
14
Q
What molecules block infrared light?
A
Water vapor and other atmospheric molecules
15
Q
What is special about radio waves and atmospheric opacity?
A
There is a large window where atmospheric opacity is 0% for radio waves
16
Q
What materials can be used to build radio dishes?
A
Any metal like iron, aluminum, steel
17
Q
Why can radio dishes have a wire mesh surface?
A
Because radio waves are large enough to pass through the holes
18
Q
Why can we see further in radio than visible light?
A
Radio waves are not blocked by interstellar dust
19
Q
Why do we detect more radio light from distant galaxies?
A
Because they emit more radio than visible light
20
Q
What are radio jets?
A
Enormous streams of radio light emitted from galaxies
21
Q
What allows us to probe more distant regions of space?
A
The ability to detect strong radio emissions from distant galaxies
22
Q
Why did the military begin using radio communication before WWII?
A
Radio waves travel easily through media and don’t require expensive equipment
23
Q
How did WWII contribute to radio astronomy?
A
Trained engineers and surplus equipment helped launch radio astronomy
24
Q
Who accidentally discovered radio waves from space in the 1930s?
A
Karl Jansky
25
Where did Jansky work?
Bell Labs in New Jersey
26
What was Jansky originally investigating?
Sources of radio static that interfered with transatlantic voice transmission
27
What were Jansky’s two sources of static?
Thunderstorms and a faint hiss from the sky
28
Where did Jansky find the strongest radio signal coming from?
The direction of the Sagittarius constellation
29
What does Sagittarius mark in our galaxy?
The center of the Milky Way
30
Why did Jansky’s radio signal rise and fall every 24 hours?
Because the Milky Way center rises and sets due to Earth's rotation
31
What did Jansky discover?
The first cosmic radio emission from the Milky Way
32
Who built a backyard radio telescope in 1937?
Grote Reber
33
What did Reber's map reveal?
Radio emission from the Milky Way and discrete sources elsewhere
34
What are contour maps in radio astronomy?
Maps showing levels of radio intensity with lines
35
What are diffuse and discrete radio sources?
Diffuse sources are spread out; discrete are compact and localized
36
What did Reber’s discovery prompt?
Further investigation into the sources of radio emission
37
Who theorized that hydrogen emits 21cm radio waves?
Hendrik van de Hulst
38
What causes the 21cm emission in hydrogen?
Electron spin-flip in hydrogen atom releasing a radio photon
39
Why is the 21cm flip rare in lab conditions?
Hydrogen is very stable; flips happen over millions of years
40
Why can we detect 21cm waves in space?
Galaxies contain massive amounts of hydrogen, ensuring flips occur somewhere
41
What does a 21cm radio map of the galaxy show?
The distribution of hydrogen gas
42
What structure did 21cm maps help confirm?
The Milky Way is a spiral galaxy
43
How many spiral arms are in the Milky Way?
Four main spiral arms
44
Where is the Sun located in the galaxy?
On the Orion Spur, a minor arm of the Milky Way
45
Why are some spiral arms in the map drawn as dashed lines?
They lie behind the galactic bulge and are not directly observable
46
What causes the Milky Way's widespread radio emission?
Hydrogen gas between stars in the galaxy's disk
47
Who discovered solar radio interference during WWII?
Stanley Hey
48
What did Stanley Hey correlate radio surges with?
Solar flares from sunspots
49
What do sunspots look like in radio images?
Bright spots indicating intense radio emission
50
What did the connection between sunspots and radio emission reveal?
Radio bursts follow the sun’s magnetic field lines
51
What generates the Sun’s magnetic field?
Differential rotation of its metallic, plasma-like body
52
What is differential rotation?
Faster spin at the equator than at the poles
53
How often does the sun's magnetic field reset?
Every 11 years
54
What did Samuel Schwabe discover in the 1840s?
The 11-year sunspot cycle
55
What happens during solar maximum?
Many sunspots, solar flares, and radio bursts
56
Why do sunspots appear dark?
They are cooler regions caused by magnetic field eruptions
57
Why do sunspots appear in pairs?
Magnetic field lines loop out and back into the sun
58
What causes radio bursts during solar maximum?
Charged particles moving along magnetic field lines
59
What causes solar flares?
Magnetic field loops snapping and releasing trapped particles
60
What Earth phenomena follow the 11-year solar cycle?
Auroras and magnetic storms
61
What are auroras?
Glowing light shows from solar particles hitting Earth's atmosphere
62
Where are auroras most commonly seen?
At high latitudes near the poles
63
What are magnetic storms?
Disturbances in Earth’s magnetic field caused by solar activity
64
How do solar flares cause magnetic storms?
Charged particles distort Earth's magnetic field upon arrival
65
What happens to compass needles during magnetic storms?
They spin erratically
66
What is the solar wind?
Charged particles emitted from solar flares
67
Why are auroras seen near the poles?
Earth's magnetic field channels particles to the poles
68
What causes different colors in auroras?
Particles hitting different atmospheric molecules like oxygen and nitrogen
69
What is the lowest latitude aurora ever seen?
In the Caribbean, in 1921
70
Do other planets have auroras?
Yes, planets like Jupiter also have auroras
71
What are discrete radio sources?
Compact locations emitting large amounts of radio light
72
What device enabled the study of compact radio sources?
Radio arrays
73
Why use radio arrays instead of one giant dish?
They are cheaper, easier to build and steer, and provide better resolution
74
Who built the first radio array?
Martin Ryle in the 1960s
75
What is the VLA and where is it located?
Very Large Array in New Mexico, with 27 dishes
76
What is the Very Long Baseline Array?
An international array with 10 dishes across Earth for high-resolution imaging
77
What is the SKA?
Square Kilometer Array, a massive future radio array project
78
Where is the SKA being built?
Australia and South Africa
79
What did Jocelyn Bell Burnell and Anthony Hewish discover in 1967?
Pulsars – pulsing radio sources
80
Why were pulsars initially thought to be alien signals?
Because of their regular, fast, and constant pulses
81
What is the Crab Nebula?
A supernova remnant emitting pulses from a neutron star
82
What is a neutron star?
A dense core left behind after a supernova of a high-mass star
83
Why do neutron stars spin so fast?
Because of conservation of angular momentum as they shrink
84
What creates the radio beams in a neutron star?
Spinning charged particles creating strong magnetic fields
85
Why do pulsars appear to pulse?
Their magnetic axis is tilted from the spin axis, sweeping beams across space
86
What is a good analogy for a pulsar?
A lighthouse whose beam sweeps past the observer
87
Are all neutron stars pulsars?
No, only if their radio beam points toward Earth
88
Why are pulsars useful for science?
They act as precise cosmic clocks
89
How can pulsars help test general relativity?
By measuring time dilation in strong gravitational fields
90
What is time dilation?
Time slows down in stronger gravitational fields
91
How do binary pulsar systems prove time dilation?
Their pulse rate slows near massive stars and speeds up farther away
92
What does the change in pulsar pulse timing confirm?
That time, not spin rate, is affected by gravity
93
What major theory is confirmed by pulsar timing?
General relativity
94
What are quasars?
Quasi-stellar objects emitting intense radiation, powered by supermassive black holes
95
Who discovered broad absorption line quasars?
Studied by astronomers like the one in the transcript; not specified
96
What is Cygnus A?
A strong radio source matched to a faint galaxy with large radio lobes
97
What are radio lobes?
Large regions of radio emission extending from galaxies
98
What type of galaxy is typically a radio galaxy?
Elliptical galaxy
99
What distinguishes quasars in visible light?
They appear like stars, but are actually galaxies with high redshifts
100
Who identified the true nature of quasars?
Martin Schmidt in the 1960s
101
What tool did Martin Schmidt use?
5-meter Hale telescope
102
What did the spectra of quasars reveal?
Emission lines with huge redshifts indicating they are distant galaxies
103
What does a high redshift indicate?
The object is moving away quickly and is very distant
104
Why are quasars called quasi-stellar?
Because they look like stars in visible light
105
What powers a quasar?
A supermassive black hole with an accretion disk
106
What is an accretion disk?
A disk of matter spiraling into a black hole, glowing intensely
107
What creates quasar radio jets?
Strong magnetic fields from the accretion disk around the black hole
108
How are radio galaxies related to quasars?
They may be less active quasars with smaller accretion disks
109
What is NGC 4261?
A nearby elliptical radio galaxy with a visible accretion disk
110
Why do we only see quasars far away?
They existed in the early universe and have since quieted down
111
What do quasars indicate about early galaxies?
They were highly active with consuming black holes
112
What can reactivate dormant black holes?
Galaxy interactions pushing material into the black hole
113
Do all galaxies have supermassive black holes?
Yes, likely left over from their formation
114
What is Sagittarius A?
The supermassive black hole at the center of the Milky Way
115
Is the Milky Way’s black hole active?
Mildly active, occasionally feeding on nearby dwarf galaxies
116
Is Sagittarius A dangerous to us?
No, its gravitational and radiation effects are minimal from our location
117
Why can't we observe X-ray light from the ground?
Earth's atmosphere blocks X-rays
118
What was NASA's first X-ray observatory?
Einstein Observatory
119
What are two major X-ray observatories launched in 1999?
Chandra and XMM-Newton
120
What is the Cygnus Loop?
A 20,000-year-old supernova remnant observed in X-rays
121
What is a stellar black hole?
A collapsed core of a massive star forming a singularity
122
Why can't we see black holes directly?
They do not emit light and are too small and far away
123
How do we detect black holes?
By observing their gravitational effects on nearby stars
124
What is an accretion disk?
Matter spiraling into a black hole, glowing from high-speed collisions
125
What type of light does matter near a black hole emit?
X-ray light
126
What is Cygnus X-1?
A strong X-ray source and the first black hole ever identified
127
Who discovered Cygnus X-1's binary nature?
Tom Bolton
128
How was Cygnus X-1 confirmed as a black hole?
By detecting a star orbiting an unseen, massive X-ray source
129
What telescope was used to confirm Cygnus X-1?
David Dunlap Observatory near Toronto
130
Why was Tom Bolton important?
He provided the first observational evidence of a black hole
131
Where is the David Dunlap Observatory located?
Richmond Hill, near Toronto, Canada
132
What kind of telescope does the David Dunlap Observatory have?
A 2-meter reflecting telescope
133
What happened to the David Dunlap Observatory in 2008?
It was sold by the University of Toronto
134
Who maintains the observatory now?
Royal Astronomical Society of Canada
135
What does the Royal Astronomical Society of Canada do?
Hosts tours, viewing sessions, and star parties
136
Can you visit the David Dunlap Observatory today?
Yes, it’s open for public visits and events
