Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
169 Cards in this Set
- Front
- Back
|
conv. 1 Astronomical Unit to km
|
1AU = 1.5 x 10^8 km
|
|
|
Light speed
|
3x10^5 km/sec
|
|
|
Light travel time over Earth-Sun distance
|
8 minutes
|
|
|
When we look at the sun, we see it as it was _______ minutes ago.
|
8 minutes
|
|
|
The universe that we observe is the universe of the ______.
|
past
|
|
|
Distance of moon (light-seconds).
|
1 light-second
|
|
|
Talking to people on the moon, how long is the delay between responses?
|
2 seconds; 1 second for the signal to arrive at moon, 1 second for signal to travel back
|
|
|
Distance of mars (light-minutes).
|
4 light-minutes
|
|
|
A space ship moving to the center of Jupiter would be...
|
crushed by the atmospheric pressure
|
|
|
Jupiter's dark spot
|
1. Larger than the continental United States
2. Caused by a comet about 500 meters wide. The comet exploded, sending Jupiter's innards to the surface. |
|
|
Distance to Pluto (light-years)
|
5 light-hours
|
|
|
Pluto is now considered a _____________.
|
dwarf planet
|
|
|
Why was Pluto "demoted"?
|
Consistency; astronomers found other objects with size and mass of pluto in the system -- some estimate 50 to 100 similar objects.
|
|
|
Alpha Centauri, distance away
|
4.3 light-years
|
|
|
"Alpha" designates
|
brightest start in a constellation; ex. Alpha Centauri
|
|
|
Number of stars in the galaxy
|
300 billion stars
|
|
|
the sun is a mass of incandescent gas/a gigantic nuclear furnace/where hydrogen is built into helium/at at a temperature of millions of degreeeeees
|
a song.
|
|
|
Tallest Eagle dust pillar is about _______________ in length.
|
4 light-years
|
|
|
Length of Milky Way
|
100,000 light-years
|
|
|
Thickness of Milky Way
|
1,000 light-years
|
|
|
Distance of sun to galactic center
|
28,000 light-years
|
|
|
How many stars can we see via unaided eyesight?
|
3,000
|
|
|
What cosmic objects can we see with unaided eyesight?
|
1. Stars in our galaxy
2. Three galaxies (1 in Northern hemisphere; 2 in Southern hemisphere) |
|
|
Andromeda Galaxy, distance away
|
2 million light-years
|
|
|
Intergalactic space, characteristics
|
1. Hardly any gas and dust
2. A few stars; occasionally one gets thrown out of a galaxy |
|
|
Virgo Cluster, distance
|
60 million light-years
|
|
|
Nearest rich cluster of galaxies
|
Virgo Cluster
|
|
|
Hubble Ultra Deep Field: how big was the piece of the sky it took?
|
1/10 the diameter of the full moon
|
|
|
mok tabak
|
Cosmic Microwave Background
|
|
|
In what five ways do we obtain information about the universe?
|
1. Light: almost everything
2. Meteorites: mostly solar system 3. Cosmic rays 4. Neutrinos: Elusive, very fast, very low mass particles produced in nuclear reactions 5. Gravitational waves: not detected yet... |
|
|
Wavelength
|
λ, Linear distance between 2 successive wave crests.
|
|
|
1) Define Frequency in terms of light
2) What symbol denotes it? |
1) The number of wavecrests that go past a point in a given time
2) ν |
|
|
Speed of light equation
|
c=λ ν
speed of light = (wavelength)(frequency) |
|
|
Angstroms, define
|
Å, measurement often used to express the length of optical light wavelengths
.1 nanometre 100,000,000Å = 1 cm |
|
|
How many Angstroms are in 1 cm?
|
10^8 Å
|
|
|
Wavelength/frequency relationship
|
the shorter the wavelength, the higher the frequency
|
|
|
Hertz, define
|
1. Measure of frequency
2. Means cycles/sec (Frequently used for sound, but can be used for any repeated subject, like light waves) |
|
|
Electromagnetic rays, lowest wavelength to highest wavelength
|
Gamma Rays, X-rays, Ultraviolet, Visible, Infrared, Microwave, Radio
|
|
|
Relationship between wavelength, frequency and energy
|
Lower wavelength = higher frequency = higher energy
|
|
|
What electromagnetic waves can we detect from the ground?
|
Visible, infrared, radio
|
|
|
What electromagnetic waves can’t we detect from the ground?
|
Gamma, X-rays, Ultraviolet, (Microwave?)
|
|
|
Compared to a blue object, a red object would emit more photons at (higher/lower) wavelengths?
|
Higher
|
|
|
Compared to a red object, a blue object would emit more photons at what wavelengths?
|
Lower (shorter wavelengths)
|
|
|
The hotter a blackbody is...
|
1. The bluer its spectrum
2. The shorter its wavelengths 3. The more light of all wavelengths it emits - even though a 7500 blackbody is much bluer than a 4500K blackbody, it emits more red light |
|
|
Wein’s Law
|
λ(sub max) T = (a constant)
In other words, as peak emission (wavelength) goes up, temperature goes down (an inverse relationship). |
|
|
How can we measure a star's temperature?
|
By recording its spectra.
|
|
|
Brightness
|
the number of photons
|
|
|
A radiating solid, liquid, or highly pressurized gas emits what kind of spectrum?
|
continuous spectrum
|
|
|
A cool gas cloud emits what kind of spectrum when observed with a blackbody behind it?
|
an absorption-line spectrum
|
|
|
A cool gas cloud emits what kind of spectrum when look against a cold, dark background like space?
|
Emission-line
|
|
|
A gas of ions is called
|
plasma
|
|
|
The energy between level 1 and 2 of a Hydrogen atom has the energy of what?
|
Photon at 1216 Å.
|
|
|
Hydrogen atoms “eat” photons at what angstrom?
|
1216Å photons.
|
|
|
Process of absorption lines
|
1. Photons pass through material 2. The atoms of the material “eat” certain photons at certain wavelengths (Å) 3. You don’t see light at these wavelengths
|
|
|
Process of emission lines
|
1. Photons pass through material
2. The atoms of the material “eat” certain photons at certain wavelengths (Å) 3. The atoms reemit these photons in other directions 4. You see light at these wavelengths that stick out on a black, dark background. |
|
|
Hydrogen transition that radiates UV
|
Lyman Series
|
|
|
Hydrogen transition that radiates optical light
|
Balmer series
|
|
|
Doppler Effect
|
the measured wavelength (λ) of the light emanating from a source depends on the relative motion of the source and the observer
|
|
|
Object moving away from you, light gets
|
redder
|
|
|
Object moves toward you, light gets
|
bluer
|
|
|
Doppler equation
|
(observed shift) / (rest wavelength) = (radial velocity of source) / (speed of light)
|
|
|
Earth's rotation
|
diurnal motion
|
|
|
Earth, axis of rotation
|
23.5 degrees
relative to the plane of Earth's revolution |
|
|
plane of Earth's revolution
|
ecliptic plane
|
|
|
Imagined sphere around the Earth and the sky
|
celestial sphere
|
|
|
Celestial equator
|
an extension of the Earth's equator in the celestial sphere
|
|
|
Why conceptualize a celestial sphere?
|
Helps us understand the geography of the sky.
|
|
|
Zenith
|
Direction pointing directly above your head
|
|
|
Nadir
|
Direction pointing directly below your feet
|
|
|
To see the South celestial pole, where must you be?
|
Southern Hemisphere
|
|
|
To see the North celestial pole, where must you be?
|
Northern Hemisphere
|
|
|
Why is Polaris important?
|
(1) Happens to be a very bright star near the north celestial pole.
(2) The angle that it subtends above the northern horizon is the same as your latitude on Earth |
|
|
When the earth rotates, the sky appears to rotate around what cosmic object?
|
Polaris (North Star)
|
|
|
Polaris is also known as...
|
The North Star
|
|
|
Southern Hemisphere's equivalent to the North Star.
|
There is none. (Trick question, bitch)
|
|
|
The sky that you see is a function of what?
|
Of where you are on Earth.
|
|
|
If you're standing right at the North Pole, what is at your Zenith?
|
Polaris
|
|
|
The dome of stars makes one revolution how often?
|
Every 24 hours (the stars revolve because of Earth's rotation)
|
|
|
Where must you stand to see all of the stars in the sky in the course of a year?
|
At the equator.
|
|
|
Stars that never set
|
Circumpolar stars
|
|
|
Sextant
|
Instrument used to measure the altitude of celestial objects, often Polaris, over the horizon.
|
|
|
The Southern Hemisphere and Northern Hemisphere receive roughly equal amounts of sunlight when?
|
Equinox
|
|
|
The path the sun traces across the sky
|
The ecliptic
|
|
|
On the winter solstice, where is the sun compared to the celestial equator?
|
At its lowest point from the celestial equator
|
|
|
Radio station frequencies are measured in...
|
MHz (Mega Hertz)
|
|
|
Which way does the Earth rotate?
|
Eastward
|
|
|
Which way do the stars appear to rotate?
|
Westward
|
|
|
Newtonian telescope
|
Type of telescope
(1) Light bounces off a primary mirror (2) Bounces off a secondary mirror (3) Shoots through an eyepiece on the side of the object |
|
|
Cassegrain
|
Type of telescope
(1) Light bounces off a primary mirror (2) Bounces off a secondary mirror (3) Shoots through a hole in the primary mirror and continues through the eyepiece |
|
|
Why do the seasons occur?
|
Because Earth's axis is tilted in respect to its elliptical plane.
|
|
|
vernal equinox
|
Sun passes celestial equator heading north
|
|
|
summer solstice
|
Sun is farthest north
|
|
|
autumnal equinox
|
Sun passes celestial equator heading south
|
|
|
winter solstice
|
Sun is farthest south
|
|
|
The moon revolves around the earth how frequently?
|
28 days
|
|
|
Why can’t we see the other side of the moon from the Earth?
|
Because as it revolves around the Earth, it also rotates such that only one side is visible.
|
|
|
New moon
|
don’t see moon at all
|
|
|
Moon phases, list
|
new, waxing crescent, first quarter, waxing gibbous, full, waning gibbous, third quarter, waning crescent
|
|
|
Each time it takes to go through each principal phases of the moon
|
1 week
|
|
|
If Chicago sees a first quarter moon phase, Vietnam sees a moon in what phase?
|
a first quarter moon
|
|
|
New moon, relationship to the sun
|
same as the sun; sets when the sun sets, rises when the sun rises.
|
|
|
Full moon, relationship to the sun
|
opposite to the sun; sets with the sun rises, rises when the sun sets.
|
|
|
When does a first quarter moon set?
|
at midnight.
|
|
|
Where would a first quarter moon be at sunset?
|
a first quarter moon is 90 degrees behind the sun and thus, would be at its highest point in the sky at sunset.
|
|
|
Where would a first quarter moon be at sunset?
|
Noon position
|
|
|
The faint glow that you see on the waxing crescent is from what?
|
Earthshine – light from the sun bounces off the Earth and hits the moon
|
|
|
Earthshine
|
When light from the sun bounces off the Earth and hits the moon
|
|
|
Occultation
|
When the moon passes in front of a background star and blocks its light
|
|
|
Angle the moon subtends on the sky
|
½ degree
|
|
|
Angle of the sun on the sky
|
½ degree
|
|
|
Eclipse, define
|
When the moon passes in front of the sun
|
|
|
Why don’t we get a solar eclipse every new moon?
|
because the orbital planes of the sun and the moon are not the same.
|
|
|
Relationship between the orbital plane of the moon and the orbital plane of the sun
|
moon is 5 degrees off.
|
|
|
Line of nodes
|
The point at which the orbital planes of the sun and moon intersect
|
|
|
We get a total of how many lunar and solar eclipses every year?
|
2 to 3
|
|
|
Umbra
|
the central dark part of an eclipse, where observers will see the moon completely cover the sun
|
|
|
Umbra, size
|
couple hundred kilometers
|
|
|
Umbra, duration
|
seven minutes
|
|
|
Penumbra
|
see just part of the sun eclipse – looks like somebody took a bite out of the sun
|
|
|
Corona
|
very faint, hot atmosphere of the sun
|
|
|
Why do eclipse sizes vary?
|
because the moon’s distance from the Earth varies; farther away, it subtends a lesser angle on the sky, thereby covering less of the sun during an eclipse
|
|
|
Annular eclipse
|
same as a total eclipse, except the moon is far enough away that you see a ring of the sun
|
|
|
Lunar eclipses, define
|
when the Earth passes in front of the sun, blocking sunlight on the moon—moon passes through Earth’s shadow.
|
|
|
Solar eclipses only happen in what moon phase?
|
new moon
|
|
|
Why is the moon still lit during a lunar eclipse?
|
because some light from Earth’s atmosphere leaks out
|
|
|
Lunar eclipse, totality’s duration
|
An hour and a half
|
|
|
The path the planets travel across sky
|
the ecliptic
|
|
|
Planets, etymology
|
Greek, “wanderer”
|
|
|
Do planets twinkle?
|
no.
|
|
|
Why don’t planets twinkle?
|
Planets are close enough, while stars are basically dimensionless points of light
|
|
|
Aristotle
|
350 B.C., Geocentric
|
|
|
Problem with Geocentric model
|
Retrograde motion
|
|
|
When a planet, in its path across the sky, appears to back up and continue again
|
retrograde motion
|
|
|
Aristarchus
|
350 B.C.
(1) Proposed the sun was the center of the universe (heliocentric). (2) Explained retrograde motion. (3) A lot of people rejected this idea, unable to believe that the planet was not the center of the universe. (4) Critics said you’d have to see a parallax, but they didn’t see a parallax because the stars are too far away |
|
|
Ptolemy
|
140 A.D., offered a theory to explain retrograde motion that people believed for 1400 years thereafter -- that planets orbit around their own epicycles
|
|
|
Parallax
|
when the position of stars change depending on what side of the sun Earth is on
|
|
|
Copernicus
|
1543 A.D. Began to revive the heliocentric picture.
|
|
|
Tycho Brahe
|
Spent 30 years of his life mapping out the positions of the stars and planets on the sky. He was trying to prove stellar parallaxes. But he could not find the parallaxes. He couldn’t come up with the hard proof for a heliocentric model.
|
|
|
Johannes Kepler
|
(1) Tried to make sense out of Tycho Brahe’s numbers.
(2) It was clear from the numbers that a geocentric universe was wrong. (3) Came up with three laws of planetary motion. |
|
|
Kepler’s Three Laws of Planetary Motion
|
(1) Planets move in elliptical orbits around the Sun with the Sun at one focus
(2) A line joining a planet and the Sun sweeps out equal areas of the planet’s orbit in equal time; planets orbit faster the closer they are to the Sun (3) The square of any planet’s period (P) of orbital revolution about the Sun is proportional to the cube of its average distance (r) from the sun. When P is in years and r is in AU: p^2 = r^3 |
|
|
Galileo
|
(1) First person to point a telescope at a sky
(2) Discovered “flaws” in the universe; spots on the sun, mountains on the Moon (3) Found the size of Venus changes – in a geocentric picture, that makes no sense, but it made sense in the heliocentric model. (4) Found Jupiter had moons that orbited it, following the same Kepler’s laws. (5) Recognized as the father of astronomy |
|
|
Galileo’s first telescope
|
refractive, 2-inch lens
|
|
|
Newton
|
makes senses out of all of the astronomical data gathered. With his three laws of motion and law of gravity, he could help us understand Kepler’s laws.
|
|
|
Mass
|
amount of matter an object has
|
|
|
Weight
|
amount of force that the Earth has for an object with mass
|
|
|
Speed
|
amount of distance an object covers in an amount of time
|
|
|
Velocity
|
speed and direction of an object
|
|
|
Acceleration
|
change in an object’s velocity over time
|
|
|
Newton’s three laws of motion
|
(1) A body remains at rest or moves in a straight line at a constant speed, unless acted upon by an outside force.
(2) The acceleration of an object is proportional to the force acting on the object (F=ma; Force = mass x acceleration). (3) For every force, there is an equal and opposite reaction force. |
|
|
The Jovian Planets
|
the four planets beyond the terrestrial planets
|
|
|
The most massive planet in the solar system
|
Jupiter
|
|
|
Jupiter, mass
|
more mass than all the planets combined
|
|
|
Least dense planet in solar system
|
Saturn
|
|
|
Newtons laws, astronomical influences
|
1) Used to predict Halley's Comet
2) Discovered Neptune |
|
|
Clyde Tonbaugh
|
Found Pluto
|
|
|
Core of Jupiter, masses in earth masses
|
10 earth masses worth of rock
|
|
|
Jupiter would have to have how much more mass to be a star?
|
75 times more mass
|
|
|
Saturn's ring, origin
|
a moon disintegrated
|
|
|
Total mass in asteroid belt
|
less than the moon
|
|
|
Number of asteroids in asteroid belt
|
hundreds of thousands, but only 6 are larger than 300 km in diameters
|
|
|
Why didn't asteroids form into a planet?
|
Jupiter's gravity
|
|
|
Kuiper Belt
|
(1) Beyond the orbit of Neptune (2) Contains tens of thousands of icy bodies; some are comets (3) Extremely elliptic orbits (4) Orbiting out of the ecliptic plane
|
|
|
Pluto, classification
|
Dwarf planet, part of the Kuiper Belt
|
|
|
Oort Cloud, distance from Sun
|
50,000 AU
|
|
|
Oort Cloud, composition
|
Ice, rock: comets
|
|
|
Brightness
|
(1) the measure of how bright an object appears
(2) the amount of energy carried by the light through a given area at our distance from the illuminating object in a given time. |
|
|
Luminosity
|
(1) is a measure of how bright an object really is, which is the total amount of energy radiated by the object in a given time
|
|
|
Relationship between brightness, luminosity, and distance
|
B = L/4pi(distance)^2
|
|
|
Chromosphere, temperature
|
7,000-15,000K
|
