ASTR 1010K - Exam #1
First Law of Science
"For every observable effect, there is a physical cause."
Polaris
"Pole star"; located very close to the North Celestial Pole
The Moon revolves around the Earth in 27.3 days. What is the actual length of a month? Why?
*29.5 days *Due to the Earth revolving around the Sun
Right Ascension
*An east-west coordinate like longitude, but measured in time units (h, min) *Measured eastward along the celestial equator starting at the vernal equinox (00h00m)
SARA operates small telescopes. Where are these located at?
*Arizona *La Serena, Chile *La Palma, Africa
Declination
*Indicates how far north or south of the celestial equator a star is. (Like latitude) *Represented by Greek letter delta *Any point on the celestial equator is equal to 0 degrees *Objects north of the celestial equator have positive declinations (up to +90 degrees) *Objects south of the celestial equator have negative declinations (down to -90 degrees)
List the lunar phases in order.
*New *Waxing crescent *First quarter *Waxing gibbous *Full *Waning gibbous *Third quarter *Waning crescent *New
Match the moon phase to the angle.
*New: 180 degrees *Crescent: 90 degrees-180 degrees *Quarter (half): 90 degrees *Gibbous: 0 degrees-90 degrees *Full: 0 degrees
The Earth undergoes 3 fundamental motions. What are they?
*Rotates about its axis everyday (23 hrs, 56 min) *Revolves around the Sun (365.24 days) *Entire solar system revolves around the center of the Milky Way galaxy (One galactic year = 230 million years)
What three conditions must be simultaneously met for an annular solar eclipse to occur?
*The Moon must be at New phase. *The Sun and Moon must be at a node. *The Moon must be near apogee (the point in its orbit farthest from the Earth).
The Sun is a luminous body, but the Earth and Moon are not. What does this fact lead to?
*The Moon's exhibition of phases *Solar eclipse and Lunar eclipse occurrances
Why does the weather become warmer in the summer?
*The Sun spends more time above the horizon, warming the ground *Solar insolation
Label the variables: d = (Θ / 57.29) x D
*d: object's physical diameter *Θ: angular diameter *D: distance
How many institutional members does SARA have?
15 (VSU is one of these)
How many "eclipse seasons" are in each year?
2, each six months apart and lasting one month
How long is a sidereal day?
23 hours 56 minutes
How long is a solar day?
24 hours
In what magnitude are the faintest stars visible to our unaided eyes located?
6th Magnitude
Sun's composition
75% Hydrogen(H), 23% Helium(He), 2% everything else("metals")
How many constellations are there?
88 total
Annular solar eclipse
A bright ring of sunlight encircling the Moon
Equatorial System
A coordinate system, using right ascension and declination as coordinates. A system that is fixed relative to the celestial sphere and rotates with it.
Stellar Magnitude System
A numerical scale for ranking the apparent brightnesses of stars.
Azimuth
An angle measured along the horizon (0 degrees is due North, 90 degrees is due East, 180 degrees is due South, 270 degrees is due West)
Parallax
An apparent shift in the position of an object when viewed from different locations
Meridian
An imaginary half-circle which passes through both the zenith and north celestial pole. it divides the sky into eastern and western halves.
North Celestial Pole
An imaginary point in the northern sky
Celestial Sphere
An imaginary sphere of which the observer is the center and on which all celestial objects are considered to lie.
What make up the altazimuth coordinates?
An object's altitude and azimuth
How many stars are visible to the unaided eye?
Approximately 6000
What is solar insolation?
As the Sun becomes higher in our sky the solar energy becomes "more concentrated"
What did the discovery of the Sun's composition lead to?
Astrophysics
Why do sundials not keep perfect time?
Because the Earth's axis is tilted, and it's orbit is elliptical leading to a varying orbital speed.
Astronomy
Deals with apparent positions and motions of celestial objects. (One of the oldest sciences.)
When is the winter solstice?
December 21-23
When do lunar eclipses occur?
During a Full Moon, when the Moon can pass into Earth's shadow.
When do solar eclipses occur?
During a New Moon, when the Moon can pass directly in front of the sun as seen from Earth.
Diurnal motion
Everything in the sky appears to move in a circle about the north celestial pole.
Autumnal Equinox
First day of autumn. The Sun rises due east and sets due west on this day. Day and night are again each twelve hours long.
Winter Solstice
First day of winter. The Sun rises farthest south of due east and sets farthest south of due west. This is the shortest day of the year.
In what direction do planets move?
From west to east relative to the stars
Horizon
Imaginary circle where the sky appears to meet the ground
When is the summer solstice?
June 20-22
Thursday?
Jupiter
When is the vernal equinox?
March 20-22
Tuesday?
Mars
Wednesday?
Mercury
Name the five planets that can be seen with the unaided eye.
Mercury, Venus, Mars, Jupiter, and Saturn
The apparent paths of the Moon and Sun in our sky intersect at two imaginary points called __________, located on opposite sides of the sky.
Nodes
What causes phases of the moon and planets?
Only half of the Moon/planets are illuminated at any given time, and they move relative to the Earth and Sun. This allows us to see different fractions of the sunlit side.
What's planets have phase angles which are always below 90 degrees?
Outer planets like Mars and Jupiter (Meaning we only ever see them in full or gibbous phase)
Saturday?
Saturn
When is the autumnal equinox?
September 21-23
SARA
Southeastern Association for Research in Astronomy
Circumpolar stars
Stars located close to the north celestial pole that never appear to rise or set.
Seasonal stars
Stars that can only be seen at certain times of the year
Where do the days of the week come from?
The 7 classical planets
What causes the seasons?
The Earth's rotation axis is tilted at an angle of 23.5 degrees relative to a line perpendicular to Earth's orbit.
Who established the boundaries for each constellation?
The International Astronomical Union (IAU)
Monday?
The Moon
What classical planet corresponds to Sunday?
The Sun
What determines if a star is circumpolar for certain locations?
The angle between a circumpolar star and the north celestial pole must be less than the observer's latitude.
Phase angle
The angle between the directions to the Sun and to the observer as measured from the center of that body.
Altitude
The angular distance between the object and the point on the horizon directly beneath it (0 degrees = horizon; 90 degrees = Zenith)
Retrograde motion of planets
The apparent motion of the planets when they appear to move backwards.
Describe stars in the 1st magnitude.
The brightest stars in the sky. (i.e. Betelgeuse, Aldebaran)
Precession
The conical motion caused by the gravitational interaction between the Earth, Moon, and Sun. (Also, the fourth motion Earth undergoes.)
Light year
The distance light travels in one year's time (equivalent to roughly 6*10^12 miles)
Vernal Equinox
The first day of spring. On this day, the Sun rises due east and sets due west, and day and night last twelve hours each.
Summer Solstice
The first day of summer. On this day, the Sun rises farthest north of due east and sets farthest north of due west. It's the longest day (shortest night) of the year.
Celestial Equator
The imaginary circle 90 degrees away from the Celestial Pole
Zenith
The imaginary point directly above/90 degrees away from the horizon
What is a synodic month?
The length of the phase cycle, which is equivalent to 29.5 days
What is our month derived from?
The lunar phase cycle
Ecliptic
The path the sun appears to follow
Equation of time
The relationship between apparent solar time and mean solar time
Astrophysics
The science of physical natures of objects within our universe. (One of the youngest sciences.)
How do we compensate for variations in time?
Using the equation of time
Friday?
Venus
When do total lunar eclipses occur?
When the Moon is entirely within the umbra of the Earth's shadow
When do partial lunar eclipses occur?
When the Moon is only partly in the umbra of Earth's shadow
When does a total solar eclipse occur?
When the observer is in the umbra of the Moon's shadow
When does a person see a partial solar eclipse?
When they are located in the penumbra of the Moon's shadow
