120 terms

astronomy chapter 2

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Terms in this set (...)

Constellation
-One of the stelar patterns identified by name, usually of mythological gods, people animals or objects
-The region of the sky containing that star pattern
-group of star resembles
-not a group of star but rather a section of sky, all stars in this section belongs to the constellation
-stars could be moving in opposite direction and could be very far apart but are named because thats how they appear to us
Asterium
-named grouping of stars that is not recognized as a constellations, due to boundaries crossing into starts
-The Big Dipper is an asterism. The Great Square of Pegasus is also an asterism.
bigger dipper
an asterium and part of ursa major
The Stars
The great square of pegasus is the boundary between andromeda and pegasus constellation boundaries, black square is the boundaries of the star
have coordinated for stars and numbers to find them
star names
most are dervied from arabic,
greek letters
star brightness
α- the brightest letters
β - the second brightest star
γ - The third brightest star
orton is the exception
brightness of the stars
-can measure brightness using magnitude scale, based on astronomical scale,
magnitude scale of stars
the larger the magnitude the fainter the stars, -3 is brighter than 3, we see projection of stars from close to earth and projected onto night skies, cant determine distance of stars due to projection
-ANYTHING abouve +5 you cant see to the unaided eye
The Greek Astronomers:
Hipparchus from rhodes (190-120 BCE) - the first to catalogue stars by their brightness
Ptolemy (140 CE) used the magnitude system.
star brightness
nothing to do with angular size rather related to intensity of light
Apparent Visual Magnitude (mv):
a measure of the brightness of a star as seen by human eyes on Earth.
Flux:
a measure of the flow of the energy out of a surface., flaux is the amount of energy crossing a unit area in a unit time, unit area perpendicular to direction of photons, flaux is how much luminous an area in a unit time (F = L/4πr^2)
-measure of light from a star that hits one square meter in one second
celestial sphere
an imaginary sphere of a very large radius surronding earth which celestial object seems to be attached to, planets, star and moon attached, model of sky
limitation to magnitude scales
-only studies visible light not ultraviolent
-only studies magnitude seen from earth not actual brightness since distance isnt accounted for
apperance of sky depends on
on observers location on earth
_________ motion of sky is due to ________ movement of earth
westward (W<----E), eastward (E---->W)
astronomical distance are measured in _______
degrees
Scientific Model:
a concept that helps one think about some aspect of nature but is not necessarily true
NCP
always appears at the latitudes of 0 latitude of observer, from where you are you can find north celestial depending distance of where you are, they are equal, distance= north celestial
zenith
the in the sky directly above the observer
Nadir
the point on celestial sphere directly below the observer; opposite of zenith, has 90 degrees from plane
celestial equation
rotation of the earth
circumpolar stars
those tat never rise or set, located on the poll in line, 34km latitude = 34km above
rotation of stars: looking north
rotation of stars for south, east, west
look at pictures
rotation
Motion around an axis passing through a rotating body.
Ex. rotation of Earth (day and night)
revolution
Revolution: Orbital motion about a point located outside the orbiting body.
Ex: Revolution of Earth around the sun (yearly cycle)
procession
-slow change in the orientation of earth axis of rotation of gravity induced
-Precession cycle 26000 years discovered by Hipparchus.
Is a phenomena.
The Pole Star (Polaris) will shift after about 8,000 years
The current northpole star is Polaris, In about 8,000 years it will be the bright star Deneb, and in about 12,000 years, Vega
-axis remains constant but processes around a path such as a top slowing, points to different constellation
-one cycle= 26 000 years
-earth doesnt spin perfectly upright
what are the two motions of earth
-daily spinning motion and procession
earth axis tilt
23.4 degrees
eclipitic
eastword motion of sun, the projection of earths orbit on celestial sphere
earths bulge
bulge in the middle, gravity of sun and moon both pull on bulge causing earths axis to twist upright relative to its orbit which causes earth procession and celestial poles and equator
cycle of the sun
go around the continuum of a point, will point to a different constellation, if you draw a line from earth through the sun and out then the plane will move, If you draw a line from the earth through the sun it will point to a different constellation, on the first of the month
the seasons
seasons are not caused by variation in the distance between earth and sun
rather seasons are caused by amount of solar energy, that earth north/ south falls at times of year, sun that earth receive will change due to tilt of axis
Ecliptic: the apparent path of the sun around the sky 1TW = 10^12 W
rotation of sun
sun appears to move west to east on celestial sphere, but from east to west is the movement
celestial equator
Imaginary line around the sky directly about the earth equator, located at two points, projection of earth equator on sky
what are the two point on the celestial equator
Vernal Equinox (March 20 Spring Begins)
Autumnal Equinox (September 22 Fall Begins)
North and South Celestial Pole:
the points on the celestial sphere directly above Earth's north and south poles
what are the four points on the ecliptic rotation of the sun
Summer Solstice (highest point)
Winter Solstice
Vernal Equinox
Autumnal Equinox
sunlight angle on earth
When the light from the sun hits the earth at an angle the sun's area of contact to the earth is more meaning less energy directed on the Earth
cycles of sun
-if light is straight down, you can see all of the light
-when on an angle will spread out and lacks energy, this causes colder temperature
-the angle the sun effects the temperature and determines flacks of energy
-in summer sun always passes high
-in winter at low points of orbit
-arc is bigger in the summer = longer days
-now our northen hemisphere is tilted away causing winter
-higher latitude= always have sun
Two Reasons For Cold Winters In the Northern Hemisphere
Winter sunlight is more spread out as the noon winter sun is lower in the sky than in the summer
The summer sun rises in the northeast and sets in the north west spending more than 12 hours in the sky whereas the winter sun rises in the southeast and sets in the southwest spending less than 12 hours in the sky
the cycles of the moon
1. The moon always keeps the same side facing the Earth.
2 .The changing shape of the moon as it passes through it's cycle of phases is produced by sunlight illuminating different parts of the side of the moon as seen by an observer, due to different position of the sun and moon, results in different faces on earth, all depends on long and lat of observer
3. The orbital period of the moon around Earth is not the same as the length of a moon phase cycle
how long is the cycle of the moon
Moon orbits eastwards around earth in 27.32 days
Complete cycle of lunar phases takes 29.53 days.
how much does the earth move every night
0.5 degrees
how much does the moon move each night
13 degrees
how far is the moon from earth
46 000km
how does the moon move across sky
always appear in the west, the more it changes, the more light we see from the moon, rises when the sun goes down, First half as moon grows from new to full (1-14), moon is said to wax, second half as moon shrinks from full to new, it's said to wane. (14-28)
-moves from west to east in sky
orbits eastward around earth
when new moon starts....
sun and new moon are at the same point, continue seperate and meet back, no moon is seen
eclipses
sun and moon have nearly equal apparent diameter
dark side of moon
There is no 'dark side' of the moon, all parts of the moon experience day and night in a month long cycle.
solar eclipses
sun is eclipsed (hidden) and the moon is blocking (angular sizes are the same), lasts less that 5 minutes due moon moving faster
umbra
the region of a shadow is totally shadowed
penumbra
portion of a shadow that is only partially shaded
annular
moon crosses in front of sun but too small to fully cover, small ring still seen, not dark, if moon is in farther part of its orbit during totality, diameter will be less than diameter of sun
what is the amount of eclipse seen related to
relates to your coordinates on earth
Lunar Eclipse:
The Darkening of the moon when it moves through the Earth's shadows.
The moons darkens and turns copper-red because of sunlight refracted through Earth's atmosphere.
Lunar Eclipses always occur at full moon but not at every full moon
saros cycles
an 18 year, 111/3 day period, after which the pattern of lunar and solar eclipses repeats.
stellar coordinates
The celestial sphere uses a coordinate grid similar to the longitude and latitude system used on earth, Declination δ (degrees) and Right Ascension α
Declination δ
- (degrees) the angular north-south distance measures from the celestial equator., latitude, above equator is positive, measured from celestial equator, positive is north, negative is south, capella is half way
Right Ascension α
(hours, minutes, seconds) - The angular east-west distance measured from the vernal equinox., longitude, from 0-24 hours, capella is 17 minutes
day corresponds to
lunar phase period
year corresponds to
sun rotation, one year= one full rotation
month correspo
...
Solar Day:
The average time between successive crossings of the sun on the local meridian (24 hours)
Sidereal Day:
The time between succesive crossings of any star on the local meridian (23 hours, 56 minutes, and 4.09 seconds)
Synodic Month
The time for a complete lunar phase (about 29.5 days)
Sidereal Month:
The time for the moon to orbit Earth once relative to any star (about 27.3 days)
Tropical (Solar) Year
Time between successive spring (autumnal) equinoxes
Sidereal Year-
The time for Earth to complete one full orbit around the sun relative to any star.
Apparent Solar Time:
Time measured by the location of the sun in the local sky such that
noon occurs when the Sun crosses the meridian
-sun position relative to our local meridian
-meridian = noon
how much does earth move every day
1 degree
Tropical Year
→ 365.25 Days minus 11 minutes (due to the precession of equinoxes)
The Egyptian Concept
365 days/year
ante meridian =
A.M
post meridian =
P.M
Which of the following definitions best describes a constellation?

Question options:

a region of the sky containing a certain star pattern


the dividing line between the north and south celestial hemispheres


a group of very faint stars


a group of very bright stars
a region of the sky containing a certain star pattern
Which of the following best describes the Big Dipper?

Question options:

an asterism


a constellation


a faint star near Polaris


the North Star
an asterism
What do stars in the same constellation have in common?

Question options:

They must be part of the same cluster of stars in space


They must have been discovered at about the same time


They are in the same part of the sky as seen from the Earth


They probably formed at the same time
They are in the same part of the sky as seen from the Earth
What languages do the standard constellation names come from?

Question options:

Greek and Latin


Greek and Arabic


Arabic and Sanskrit


Latin and Arabic
Greek and Arabic
Which star would appear brightest to an observer on Earth?

Question options:

δ Dra 3.07


α Cet 2.53


Nim 8.07


α CMa -1.46
α CMa -1.46
What causes the precession of the Earth's rotation axis?

Question options:

the force of gravity from the Sun and Moon on the Earth's equatorial bulge


the magnetic field of the Earth


the impacts of asteroids


the force of gravity from the Sun and Jupiter on the Earth-Moon system
the force of gravity from the Sun and Moon on the Earth's equatorial bulge
The Earth revolves in a counter clockwise direction around the sun at about 1 deg/day (360 deg and 365 days). Then this motion makes the sun to appear moving

Question options:

not at all-the sun does not appear to move


1 deg per day westward


1 deg per day eastward


15 deg per day eastward


15 deg per day westward
1 deg per day eastward
A person in Nashville , TN observes Venus in the western part of the horizon. Six hours later Venus will be

Question options:

high in the south


low in the south


not visible


nearly overhead
not visible
A person in Denver Colorado observes Jupiter in the eastern horizon right after the sunset. Where would the planet be after six hours?

Question options:

low in the west


nearly overhead


not visible


high in the south


low in the south
low in the south
here is an observer's nadir?

Question options:

the point directly opposite the observer's zenith


the north point on the observer's horizon


the point directly opposite the north celestial pole


the east point on the observer's horizon
the point directly opposite the observer's zenith
If the apparent visual magnitude of a star is 7.3, what does this tell us about the brightness of the star?

Question options:

It is not visible with the unaided eye


It appears faint because of its great distance from the Earth


It is one of the brighter stars in the sky


It is bright enough that it would be visible even during the day
It is not visible with the unaided eye
The star Vega has an apparent visual magnitude of 0.03 and the star HR 4374 has an apparent visual magnitude of 4.87. It has been determined that both stars are at the same distance from the Earth. What does this information tell us about the two stars?

Question options:

Vega must produce more energy per second than HR 4374


Together the two stars would have a magnitude of 4.9


Vega will appear fainter to us than HR 4374


Vega must produce less energy per second than HR 4374
Vega must produce more energy per second than HR 4374
Which of the following is equivalent to one-3,600th of a degree?

Question options:

minute of arc


precession


second of arc


angular diameter
second of arc
What is the term for the point on the celestial sphere directly above an observer, no matter where on the Earth the observer is located?

Question options:

north celestial pole


zenith


nadir


south celestial pole
zenith
Where is the zenith for an observer standing at a point on the Earth's equator?

Question options:

near the horizon and towards the south


directly overhead


near the horizon and towards the west


the position depends on the time of day
directly overhead
If the Earth had an orbital tilt of 0 degrees ( obliquity) then

Question options:

There would not be no seasons


Day and night would be 12 long every day everywhere on the Earth


An observer at the equator would see the sun pass at zenith every day


The direct rays of the sun would shine on the equator


All of the above
All of the above
On an imaginary planet that has an orbital tilt of 32 degrees, its corresponding Tropic of Cancer can be found at the latitude of

Question options:

66.5o N


32o N


23.5° N


58o N
32o N
Which of the following locations are closer to the South Celestial Pole ?

Question options:

(RA= 14h Declination=+88o)


(RA= 23h Declination=2o)


(RA= 18h Declination=-66o)


(RA= 14h Declination=-88o)
(RA= 14h Declination=-88o)
Based on your computer clock lets say that today is August 31, 2015 the sun is

Question options:

North on the Celestial equator moving North


South on the Celestial equator moving South


South on the Celestial equator moving North


North on the Celestial Equator moving South
North on the Celestial Equator moving South
How often is the sun at zenith for an observer at the equator?

Question options:

12 times per year


Never


Twice per year


Every day
Twice per year
An observer in the northern hemisphere watches the sky for several hours. Due to the motion of the Earth, this observer notices that the stars near the north celestial pole appear to move. What pattern does this apparent movement follow?

Question options:

from left to right


counter-clockwise around the celestial pole


clockwise around the celestial pole


from right to left
counter-clockwise around the celestial pole
If an observer travels north, toward higher latitudes, how does the number of circumpolar stars that he or she sees in the sky change?

Question options:

also depends on the longitude of the observer


increases


remains constant


decreases
increases
If you were standing at the Earth's North Pole, which of the following would be located at the zenith?

Question options:

the celestial equator


the nadir


the star Vega


the north celestial pole
the north celestial pole
How much of the night sky lies north of the celestial equator?

Question options:

Exactly half


All of the night sky


Less than half, because of the tilt of the equator to the ecliptic plane.


More than half, because of the precession of the poles
Exactly half
Seen from Winnipeg (latitude 50 degrees North), where is the star Polaris in the sky?

Question options:

50 degrees above the horizon


the position depends on the time of day


40 degrees above the horizon


directly overhead
50 degrees above the horizon
For an observer in Pond Inlet, Nunavut, at a latitude of 73° North, what is the angle between the northern horizon and the north celestial pole?

Question options:

17°


73°


23.5°


27°
73°
For an observer in Oberon Bay, Australia, at a latitude of 39° South, what is the angle between the southern horizon and the south celestial pole?

Question options:

45°


23.5°


39°


51°
39°
If the north celestial pole appears on your horizon, what is your latitude?

Question options:




45° N


90° N


90° S
Where in the sky would an observer at the Earth's equator see the celestial equator?

Question options:

The celestial equator would coincide with the horizon


The celestial equator would be directly overhead


The celestial equator would be at 45 degrees above the northern horizon


The celestial equator would be at 45 degrees above the southern horizon
The celestial equator would be directly overhead
Which of the following best defines the ecliptic?

Question options:

the plane that is perpendicular to the Earth's axis of rotation


the projection of the Earth's equator onto the sky


the path traced out by the Sun in our sky over one year against the background stars


the path traced out by the Moon in our sky in one month against the background stars
the path traced out by the Sun in our sky over one year against the background stars
Which of the following describes a concept very similar to latitude?

Question options:

declination


magnitude


meridian


right ascension
declination
Which of the following best describes Ursa Major (the Great Bear)?


another name for the Seven Sisters


another name for the Big Dipper


a constellation


an asterism
a constellation
Which of the following statements correctly describes the relationship between stars and constellations?


Only those stars that were visible to the ancient Greeks are located in constellations.


Every star is located in a constellation.


Only stars close to the ecliptic (the Earth's orbital plane) are located in constellations.


Only the brighter stars are in constellations.
Every star is located in a constellation.
Which of the following describes the magnitude scale?


It is no longer used today.


It was used to determine the rate of precession.


It originated just after the telescope was invented.


It can be used to indicate the apparent intensity of a celestial object.
It can be used to indicate the apparent intensity of a celestial object.
If the apparent visual magnitude of star A is 3.1, and the apparent visual magnitude of star B is 0.5, how do star A and star B compare in terms of apparent brightness as seen from Earth?


Star A is only slightly brighter than star B.


Star A is about the same brightness as star B.


Star A is fainter than star B.


Star A is much brighter than star B.
Star A is fainter than star B.
What aspect of an object depends on both the size of the object and the distance to the object?


proper motion


apparent magnitude


apparent brightness


angular diameter
angular diameter
What is the term for the point on the celestial sphere directly above an observer, no matter where on the Earth the observer is located?


south celestial pole


nadir


zenith


north celestial pole
zenith
Where is the zenith for an observer standing at a point on the Earth's equator?


near the horizon and towards the west


the position depends on the time of day


near the horizon and towards the south


directly overhead
directly overhead
An observer in the northern hemisphere watches the sky for several hours. Due to the motion of the Earth, this observer notices that the stars near the north celestial pole appear to move. What pattern does this apparent movement follow?

counter-clockwise around the celestial pole


from left to right


clockwise around the celestial pole


from right to left
counter-clockwise around the celestial pole
The Moon has an angular diameter of 0.5°. What is the Moon's angular diameter in minutes of arc?


50


1800


30


0.5
50
You point your finger toward the zenith right now, and then point there again six hours later. At both times, your finger was pointing in the same direction relative to one of the options below. Which one?


your horizon


the Sun


the ecliptic


the north celestial pole
Correct Response
your horizon
For an observer in Valdivia, Chile, at a latitude of 39° South, what is the angle between the southern horizon and the south celestial pole?


45°

39°


23.5°


51°
39°
For an observer in Waterloo, at a latitude of 43° North, what is the angle between the northern horizon and the north celestial pole?


43°


23.5°


74°


36°
43°
do questions that have diagrams
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