Astronomy Flashcards
What is a Planet?
an astronomical object that orbits a star & is massive enough for its own gravitational pull
What is a Solar System?
planets, moons, & non-stellar objects that orbit the sun or central star
What is a Moon?
a natural satellite of a planet
What is a Star?
a self-luminous gaseous sphere
What is an Orbit?
a path followed by a star, planet, or satellite around a more massive body
What is Rotation?
turning around an axis, or to turn in a circle
What is Revolution?
the orbiting of one body in space around another
What is an Eclipse?
the effect caused by one body casting a shadow on another
What is a Solar Eclipse?
when the moon passes between the sun & earth, casting a shadow on earth
What is a Lunar Eclipse?
when earth passes between the sun & moon, casting a shadow on the moon
What is an Umbra?
the dark, central zone created by an eclipse (region where all direct sunlight is blocked)
What is a Penumbra?
the outer & lighter part of the shadow created by an eclipse (region where only part of the sun’s rays are blocked)
What are Phases?
the different sizes of the illuminated portion of a planet or moon due to its changing position
What is a Wax?
an increase in the phase of a moon or planet
What is a Wane?
a decrease in the phase of a moon or planet
What are Gas Giants?
the largest planets in the solar system (our outer planets, like Jupiter & Saturn), made largely of dense gaseous atmosphere
What are Terrestrials?
the smallest planets in the solar system (our inner planets), made primarily of rock
What is an Asteroid?
a small, rocky body that orbits the sun (aka a planetoid)
What is a Comet?
a body of ice & dust in orbit about the sun that develops a tail of ions & dust as it approaches the sun
What is a Meteroid?
a very small, rocky body that orbits the sun. most probaby come from asteroids
What is a Meteor?
a streak of light caused when a meteroid burns up in the atmosphere before it reaches the ground
What is a Meteorite?
a meteroid that reaches the earth’s surface without burning up completely
What is the Universe?
it consists of all existance, including all matter
What is a Galaxy?
a gravationally bound system, containing stars, gas, & dust
What is a Solar System?
it consists of the Sun & its planetary systems (planets, moons, non-stellar objects [comets, meteors, etc.] )
What is a Planet?
an astronomical object, orbiting a star or stellar remnant, that is massive enough to be rounded by its own gravity
What is a Spiral Galaxy?
- disk shaped
* curving arms
What is a Barred Spiral Galaxy?
a spiral galaxy with a central bar-shaped structure composed of stars
What is an Elliptical Galaxy?
- approximately ellipsoidal shape
* smooth, nearly featureless bright profile
What is an Irregular Galaxy?
- no distinct shape
* could have been a spiral or elliptical galaxy that has been distorted
What did Ptolemy believe? (and what was his year?)
Earth is the center of the universe; the sun & planets revolve around the earth.
140 A.D.
What did Capernicus believe? (and what was his year?)
Sun is the center of the universe; planets revolve around the sun.
1543
What did Brahe believe?
Other planets revolve around the sun; sun & moon revolve around the earth.
What did Kepler believe? (and what was his year?)
All planets revolve around the sun in elliptical orbits; the sun isn’t the center of the orbits.
1609
What did Galilei do? (and what was his year?)
Used a telescope to discover: 1) Jupiter’s 4 moons, 2) craters & mountains on our moon, 3) sunspots on the sun, and 4) the phases of Venus.
1609
What did Newton do? (and what was his year?)
Explained that the force that holds us to earth is gravity; the same force keeps objects in orbit.
1687
What did Herschel do? (and what was his year?)
Discovered Uranus & saw small, fuzzy patches of stars.
1781
What did Hubble do? (and what was his year?)
Discovered: 1) other galaxies through photography, 2) that small patchy stars are galaxies, and 3) that the Milky Way isn’t the entire universe.
1923
The moon travels…
around the Earth
What makes the moon appear as if it is changing shape in the sky?
the revolution of the moon around the earth
What is the phase of the moon?
the changing shape of the bright part of the moon that we see
What causes the different phases of the moon?
the phases depend on the moon’s position in relation to the sun & earth
What causes part of the moon to be lit up?
it is illuminated because it reflects light from the sun
How many different phases of the moon are there?
8 phases
How many days does our moon take to completely cycle through all 8 phases?
29.5 days
When the bright part of the moon is getting bigger, the moon is…
waxing
When the bright part of the moon is getting smaller, the moon is…
waning
When the moon is more than half-lit, it is called a…
gibbous moon
When the moon is less than half-lit, it is called a…
crescent moon
Why are you able to see the moon at night & at times during the day?
the moon rises & sets just like the sun does
What is another name for a new moon?
a dark moon
When is the best time to see a waxing crescent moon?
the 2nd & 3rd days after new moon
What is another name for a first quarter moon?
half moon
The moon travels around the earth in an…
orbit
What is a lunar month?
the time it takes the moon to pass through a complete cycle of its phases
The planets travel in nearly circular paths called…
orbits
Everything is held together & all movement in the solar system os governed by the pull of the sun’s…
gravity
Gravity is a ___ that attracts objects to each other.
force
Earth’s gravity is strong enough to keep the ___ orbiting around us.
moon
Why do night & day occur?
because of earth’s rotation on its axis
The earth revolves around the sun in an ___ orbit.
elliptical
It takes earth ___ days to orbit the sun. This is called a ___.
365.25 days; year
The earth completes one full ___ on its ___ in 23 hours & 56 minutes. This is an earth ___.
rotation; axis; day
The earth rotates in a ___ direction.
counterclockwise
The sun always appears to rise in the ___ & set in the ___.
east; west
Where are most asteroids located?
between Mars & Jupiter, in a region called an asteroid belt
Earth’s orbit is its ___ around the sun.
revolution
The moon is Earth’s ___ moon, and is one of over ___ moons in our sola system.
only; 96
About how far is the moon from Earth?
about 240,000 miles from Earth
How big is the moon’s diameter, and what is its size and gravity strength compared to Earth?
2,155 miles in diameter; about 1/4 of Earth’s size; 1/6 of Earth’s gravity
What is the moon’s extreme daytime & nighttime temperatures?
Daytime = 265°F Nighttime = -310°F
How was the moon formed?
About 4.6 billion years ago, a large body collided with Earth. At the time, Earth was mainly molten lava. Debris from the collision collected & orbited around Earth. Eventually, the debris pulled together due to gravity & formed the moon. The moon cooled & formed cracks where lava would flow & form laza basins.
What are the Highlands on the moon?
mountains up to 25,000 ft tall; the bright areas of the moon b/c light rocks reflect the sunlight
What does Maria mean?
it is Latin for “seas”
What is the Maria on the moon?
the darker areas of the moon; depressions created by giant meteorites that filled with lava during periods of volcanic activity
Where did Apollo 11 land in when it got on the moon?
it landed in a maria
Why does the moon have no protection from meteorites?
it has no atmosphere
How big are some craters on the moon?
up to 1,553 miles across
How are the craters formed?
most are formed by meteorite impact on the moon; some are formed by volcanic action inside the moon
What are some craters surrounded by?
bright streaks called rays
What are rays made of?
crushed rock thrown out of the crater at the time of impact
Who first saw the far side of the moon & when?
first seen by Luna 3 Russian space probe in 1959
How are the surface features of the far side of the moon different from the near side?
- more craters
- very few maria
- thicker crust
The moon rises & sets ___ minutes later each day.
50 minutes
The moon rotates on its axis every ___ days.
27 days
Why does the same side of the moon always face Earth?
b/c moon rotates on axis the same amount of time it takes to orbit Earth ( ~ 27.3 Earth days) –> SYNCHRONOUS ROTATION
What is a blue moon?
the 2nd full moon in 1 month - it is very rare (hence the saying “once in a blue moon”)
What is a harvest moon?
the full moon closest to the autumnal equinox
8 Phases of the Moon in Order:
- New Moon (day 0)
- Waxing Crescent (day 4)
- First Quarter (day 7)
- Waxing Gibbous (day 10)
- Full Moon (day 14)
- Waning Gibbous (day 18)
- Third Quarter (day 22)
- Waning Crescent (day 26)
- New Moon (day 29)
What is the difference between a solar eclipse and a lunar eclipse?
A solar eclipse is when the moon is between the sun and the earth, and a lunar eclipse is when the earth is between the sun and the moon.
Which eclipse (solar or lunar) can you not look directly at? Why?
You can’t look at a solar eclipse directly because you will get eye damage and maybe even go blind.
If you are in the umbra during an eclipse, you will see a ___ eclipse.
total
If you are in the penumbra during an eclipse, you will see a ___ eclipse.
partial
Which eclipse’s shadow is bigger: the shadow that falls on the earth during a solar eclipse or the shadow that falls on the moon during a lunar eclipse?
The shadow that falls on the moon during a lunar eclipse is bigger because it is the earth’s shadow, which is bigger than the moon’s shadow, which would fall on the earth during a solar eclipse.
Are you able to see a solar eclipse everywhere on earth?
No, because only people in the umbra and penumbra can see the solar eclipse. Umbra - see total eclipse; Penumbra - see partial eclipse
Are you able to see a lunar eclipse everywhere on earth?
No, because only people on the half of the earth in which it is nighttime can see a lunar eclipse. This is because the lunar eclipse is caused by earth’s shadow, & where it is nighttime is where earth’s shadow is.
During which phase of the moon can you see a solar eclipse?
new moon - because the moon is in front of the sun
During which phase of the moon can you see a lunar eclipse?
full moon - because the moon is on the opposite side of the earth as the sun
What is the corona?
the outer atmosphere of the sun
How long do total and partial solar eclipses last?
Total eclipse lasts for a few minutes. Partial eclipse lasts up to 2 hours.
Why does the moon turn red when it is in the umbra during a lunar eclipse?
the color wavelengths from the sun are scattered in earth’s atmosphere, except for the red wavelengths, which end up reflected on the moon
How long do total and partial lunar eclipses last?
Total eclipse lasts for up to 1 and a half hours. Partial eclipse lasts up to 4 hours.
Why don’t we see eclipses ever month?
the moon’s orbit is tilted about 5 degrees, so the moon may pass above or below the shadow.
About how many times a year do solar and lunar eclipses occur?
Solar Eclipses are ~ 2-4 times/year.
Lunar Eclipses are ~ 2 times/year.
Can partial or total eclipses seen more often? Why?
Partial eclipses can be seen more often because an umbra shadow is a lot smaller than a penumbra shadow.
What are Tides?
tides are daily movements of ocean water that change the level of the ocean’s surface
What causes tides?
the moon’s gravity. the moon pulls water on earth, creating a bulge that moves as the moon orbits
How long is a lunar day? Why is it longer than a solar day?
24 hours and 50 minutes; because the earth takes an extra 50 minutes to catch up to the moon
How many tides are there in a lunar day?
2 high tides & 2 low tides
How often do tides change?
2 high & 2 low tides every 24 hrs 50 mins. time between high tides: 12 hrs 25 mins. time between low tides: 12 hrs 25 mins. time it takes to change from a high tide to low tide: 6 hrs 12.5 mins
What are the high tides? How are they caused? Therefore, what are the low tides?
2 bulges of water on earth - one facing the moon (due to moon’s gravity) & one on opposite side of moon (due to inertia & earth’s rotation pushes the water outward. Therefore, low tide is the water area between the bulges.
What is a Spring Tide?
especially strong tides. occur when earth, sun, & moon are alligned so both sun’s & moon’s gravity contribute to tides - high tides = higher, low tides = lower
What are the 2 moon phases in which a Spring Tide occurs?
new moon; full moon
What is a Neap Tide?
especially weak tides. occur when sun & moon are perpendicular to each other sun’s & moon’s gravity cancel each other out - high tides & low tides = more moderate
What are the 2 moon phases in which a Neap Tide occurs?
quarter moons: first quarter moon; last quarter moon
What are the 4 inner planets (in order from closest to sun to farthest from sun)?
Mercury, Venus, Earth, Mars
What are the 4 outer planets (in order from closest to sun to farthest from sun)?
Jupiter, Saturn, Uranus, Neptune
What is a comet?
a small body of ice, rock, & cosmic dust loosely packed together
What are comets sometimes called? Why?
“dirty snowballs” - due to their composition
What happens when comets pass close enough to the sun?
solar radiation heats the water ice & the comet gives off gas & dust that forms a long tail
What are the 2 tails comets can have?
an ion tail & a dust tail
What are asteroids?
small rocky or metallic objects, most of which orbit the sun
What is the range of sizes an asteroid can be?
from a few meters to more than 900 km in diameter
What can the shapes of asteroids be?
some asteroids have an irregular shape; larger ones can be shaped like a sphere
What are asteroids also called?
minor planets
Where do most asteroids orbit the sun?
in a wide region between the orbits of Mars & Jupiter
What does this Asteroid Belt do?
it separates the inner & outer planets
What is a meteoroid?
a small rocky body orbiting the sun, much smaller than asteroids
Where do most meteoroids come from?
asteroids
As a meteoroid falls through the atmosphere at high speeds, it…
burns up
What is a meteor?
a bright streak of light caused by a meteoroid or comet dust burning up in the atmosphere
From the ground, when we see a meteor, we see a streak of light, aka a…
“shooting star”
How can meteor showers occur? (2 reasons)
- when a large number of very small meteors fall
2. when the earth passes through the dusty debris left behind in the orbit of a comet
What is a meteorite?
when a meteoroid enters the earth’s atmosphere & strikes the ground
When does a meteoroid become a meteorite?
when it hits the ground
What do the Inner and Outer planets have in common?
they both:
- orbit the sun
- rotate on an axis
- are spherical
What are the differences between the Inner and Outer planets? (i = inner; o = outer)
- composition (i=rocky; o=gas giants)
- size (i=smaller; o=larger)
- temperature (i=warmer; o=colder)
- density (i=more dense; o=less dense)
- rings (i=no rings; o=do have rings)
- moons (i=less moons; o=more moons)
- orbits (i=smaller; o=larger)
^- year length (i=shorter; o=longer) - placement in relation to Asteroid Belt (i=before; o=after)
