Exam 1 Flashcards
The average distance between Earth and the Sun
Astronomical unit (AU)
The distance light travels in one Earth year
Light year (ly)
Light travels at an indefinite speed; and takes some time to reach our eyes.
False; true
The closest star to the sun
Alpha Centauri
The Galaxy is about ________ ly across.
100,000
How big is the Observable Universe?
28.6 billion ly
A way of expressing very large or small numbers in a compact form.
Scientific Notation
Singularity that gives birth to the universe
The Big Bang
The Universe expands faster than the speed of light
Inflation Period
How are stars formed?
Massive gas/plasma clouds are compressed until a single sphere is hot enough for nuclear fission.
Most massive star, creating the elements more massive than iron
Supernova
The solar system formed 4.5 billion years ago.
True
Earth’s orbit divided by Earth’s orbital period
Speed
How fast is Earth’s orbit?
107,000 mph
Brightest star in the sky
Sirius
How to describe the location of a star in the sky
Celestial sphere
Angle of 0o to 90o
Altitude
Measured from North (0 degrees) going clockwise around a complete circle (360 degrees)
Azimuth
The sun and the moon do not have the same angular size.
False
How do we measure angular distance?
1 degree is equal to 60 arcminutes.
1 arcminute is equal to 60 arcseconds.
Stars “rise and set” due to the spinning of the Earth.
True
A star whose daily circle causes it to be visible at all times
Circumpolar
Why are some stars circumpolar?
Their daily circle is entirely above the entire horizon.
Why should we be careful when using celestial coordinates?
The time of day, location, and day in the year will be different.
How are we tilted downward, toward the sun?
Hemisphere tilted down due to changing tilt.
March 21st
Equal day and night
All places on Earth
Spring Equinox
June 21st
Northern Hemisphere has longest period of light
Summer Solstice
September 22nd
Equal day and night
All places on Earth
Fall Equinox
December 21st
Southern Hemisphere has longest period of light
Winter Solstice
Earth is closer to the Sun during winter.
True
Why is the Arctic Circle called “the land of the midnight sun”?
The sun doesn’t fall below horizon for one week during the Summer Solstice.
Why are the seasonal changes more noticeable in the Northern Hemisphere?
Land mass
The gradual wobble of the Earth’s axis with the respect to the Sun. (It has a 26,000 year period.)
Precession
Lunar Phase: Moon not visible
New Moon
Lunar Phase: Right sliver of moon
New moon to Full moon
Waxing Cresent
Lunar Phase: RIGHT half of moon visible
First Quarter
Lunar Phase: Moon full other than sliver on left side
Waxing Gibbous
Lunar Phase: Whole moon visible
Full Moon
Lunar Phase: Almost all of moon visible except for sliver on right side
Waning Gibbous
Lunar Phase: LEFT half of moon visible
Third Quarter
Lunar Phase: Left sliver
Waning Cresent
“Exposing” phases of moon
Waxing
“Retreating” phases of moon
Waning
The moon does not create its own light. The moon reflects the sun’s light.
True
What does the “Moon’s Synchronous Rotation” mean?
The moon’s orbital period is the same as its rotational period.
Time required to complete one cycle
Period
The shadow the moon casts that reflects no sunlight
Umbra
The shadow the moon casts that reflects partial sunlight
Penumbra
Lunar Eclipse: moon passes through the umbra
Total Lunar Eclipse
Lunar Eclipse: moon partially on the umbra
Partial Lunar Eclipse
Lunar Eclipse: moon passes through penumbra
Penumbral Lunar Eclipse
A lunar eclipse can occur during any phase.
False. It can only occur during a full moon.
The eclipses’ 18 year 11.3 day cycle
Saros cycle
Solar Eclipse: the moon is in front of the Earth, completely blocking out the sun for a portion of the Earth
Total Solar Eclipse
Solar Eclipse: areas not experiencing total solar eclipse
Partial Solar Eclipse
Solar Eclipse: the moon’s umbral shadow does not reach Earth
Annular Solar Eclipse
Understood during eclipses, responsible for GPS
General relativity
What are the “wandering stars” in the sky and why are they called that?
They are planets. They are called that because they followed a different pattern than the rest of the stars.
Appearing to move backward as Earth catches up and passes during orbit of the sun
Retrograde Motion
Star appearing to change its position
Stellar Parallax
Originally used to tell time
Sun dial
Most widely used calendar
Gregorian Calendar
Occurs every four years except in years that end in 00 not divisible by 400
Leap year
Said that heavenly motion must be perfect circles
Plato
Argued for an Earth-centered universe (geocentric)
Aristotle
Introduced multiple circles to circles to explain retrograde motion
Apollonius
Finalized geocentric model
Ptolemy
Why is one model favored over another?
Which one sounds better seems to make more sense to people.