ASTRO 102 Mid-term ISU
Does the US chase Europe or the other way around?
US chases Europe
How often, or when, is the Moon in the sky at noon as seen from Ames?
Usually when it is crescent.
Two other special points are the NCP and the SCP. What is the declination for these two points?
+90 and -90; like Earth's north and south poles
One rotation on Earth's axis is equal to
... 24 hours
The zero point for latitude is the ...
... Equator
The starting point for longitude is the ...
... Prime Meridian
Mean solar time is equal to ...
... [(your mean solar time) - (Greenwich mean solar time)] x 15 degrees
When you cross the IDL going east you need to...
... set your clock back 24 hours or subtract a day
When you cross the IDL going west you need to ...
... set your clock forward 24 hours or add a day
The prime meridian is also known as ...
... the Greenwich Meridian.
Right ascension is described as ...
... the number of hours in front OR behind the sun on vernal equinox (March 21); time of day or night
One revolution around the sun is equal to
...365.25 days = one year
12 noon in solar times is
...when the sun is on the observer's local meridian
Consider these stars: Alpha, Beta, Gamma, Delta, Epsilon, and Omega; what is the sidereal time when the Vernal Equinox crosses the meridian
0 hours
What is the 24-hour clock time when it is 3 AM? 11 PM?
0300; 2300
If it is 7 PM in Los Angeles, what time is it in New York?
10 PM
Equation for determining time difference between 110.86 W and 25 E longitude.
110 + 25 = 135; 135/15 = 9; One hour of time difference per 15 degrees longitude = 9 hours of time
There is a location on Earth that has a mean solar time 8 hours different than Greenwich's mean solar time. What is this location's longitude?
120 E OR 120 W; the question is not specific
What time is it in Rome when it is 7 PM here?
2 AM the next day
Number of days per year zenith sun is experienced
2 days; one if you are at exactly 23.5 N or 23.5 S
If you observe that Polaris is 20 degrees above your horizon to the North, where are you?
20 degrees North latitude
An object that rises at azimuth 80 will set at azimuth _____________.
280
What is the altitude of the NCP for an observer who is at latitude 33 N?
33 degrees
Latitude of Ames, IA.
42 N
A star rises five degrees north of east. Where will it set?
5 degrees north of west
For an observer at 40 N: what is the altitude of the celestial equator (CE) on the meridian?
50 degrees
Consider these stars: Alpha, Beta, Gamma, Delta, Epsilon, and Omega; what is the sidereal time when Beta crosses the meridian?
6 hours
If the noon sun on March 21 is 30 degrees above your horizon to the South, where on Earth are you?
60 degrees North latitude (90 - latitude)
On a 24-hour clock, we might eat dinner at 1800. What time is that in terms of AM/PM.
6:00 PM
How many time zones separate Rome and Ames? How many degrees?
7 time zones; 105 degrees (Ames @ 90 W; Rome @ 15 E; (90 + 15)/15 = 105/15 = 7 time zones)
What is the time called int he zones centered at 75 W, 105 W, and 120 W?
75 = EST, 105 = CST, 120 = PST
Observer at 110.86 W and 31.68 N needs to contact chair person at 25 E. How big is the time difference between the observer and the chair person if neither are on daylight savings?
9 hours
Is Rome 7 hours ahead or behind Ames?
Ahead (it is east of Greenwich)
Which two states are not in these four time zones?
Alaska and Hawaii
Time of day a new moon is in the sky
All day and not at all during the night (for most observers)
Consider these stars: Alpha, Beta, Gamma, Delta, Epsilon, and Omega; which will cross the meridian first after the Vernal Equinox crosses the meridian?
Alpha (3 h, +17 degrees)
A bright star is shining in the southern sky about 10 degrees south of your zenith. You email your astronomer friends, "What is that bright object at altitude (fill in) and azimuth (fill in)?" You (do or do not) need to tell your friends what time you made this observation.
Altitude = 10 degrees from zenith = 80; Azimuth = 180 degrees South; You DO need to tell your friend the time of day you made the observation because as Earth turns the sky "moves" East to West.
You observe a very bright star due South and about 3 fists above the horizon. You send an email to your astronomer friend asking, "What is that object at altitude (X) and azimuth (Y) degrees?"
Altitude = 30; Azimuth = 180
The ______________ if the NCP is equal to the observer's ______________.
Altitude; Latitude
AM means
Ante Meridiem = before the sun crosses the meridian; before noon
Explanation for azimuth 80 setting at 280
Azimuth 80 is 80 degrees from the north point and 10 degrees north of where the CE crosses the horizon. When the object sets, it will still be 80 degrees from the North Point and 10 degrees North of where the CE crosses the horizon; this point is 360 - 80 = 280.
When you travel westward, you have to shift your watch ___________ each time you pass a time zone boundary. On the same trip, when you pass the international date line, you have to shift the date __________.
Back; Forward
Consider these stars: Alpha, Beta, Gamma, Delta, Epsilon, and Omega; which of these is farthest north?
Beta (6h, +89 degrees)
When the moon is full for an observer located in Ames, what is its phase for an observer located in Australia?
Both observers will see the same phase, although the Australian observer will see the moon when it is night there and day in Iowa.
It is 7 am daylight savings time on Monday in California. You are planning to call your cousin who is in Sydney, Australia. What time and what day is it in Sydney? California is in time zone 120 W and Sydney is 150 E.
Cali = Monday, 7 AM, PST Sydney = Tuesday, 12 AM, Syd 120 W - 180 (IDL) = 60 degrees/15 = 4 time zones 180 (IDL) - 150 E = 30 degrees/15 = 2 time zones 4 + 2 = 6 time zones 6 + 1 daylight savings hour = 7 hours difference West across IDL = add a day, subtract hours = Tuesday, 7 - 7 = 0 hours = 12 AM in Sydney
The NCP makes a 90 degree angle with the ____________________.
Celestial Equator
This is perpendicular to your meridian and 90 degrees from the North Celestial Pole.
Celestial Equator
Which direction does Earth spin?
Counterclockwise
This is one of two points where horizon and celestial equator intersect.
East Point
In order to cross a number of time zones you should travel
East to West or vise versa relative to Greenwich
Solar time is equal to sidereal time
False, four minutes different; Solar = 24 hours, Sidereal = 23 h 56 min
On the ocean on a calm day, your ___________ separates the sea from the sky.
Horizon
You observe several a faint object in the sky with the same angular size as the moon; from your observations, you can conclude that the object is
It is impossible to tell without also knowing how far away the faint object is.
A star rises five degrees north of east. What can you say about the altitude of this star when it transits the meridian?
It will transit the meridian less than 5 degrees north of the CE, but we don't know more than that because we don't know the latitude.
Latitudes that experience a zenith sun
Latitudes between 23.5 N and 23.5 S
The sidereal day is shorter than the solar day because the earth rotates and revolves in the same sense - counterclockwise. Venus rotates in the opposite direction to its revolution - is its sidereal day longer or shorter than its solar day?
Longer because it is revolving in the opposite direction it is rotating.
This runs from North to South over your head
Meridian
Lines of Longitude
Meridians
If the bright winter constellation Orion is directly overhead, then where on Earth might you be?
Near the equator
How often does the sun pass through your zenith when you are in Ames?
Never, as seen from Ames.
Why is it summer in New Zealand when it is winter in Iowa?
New Zealand is in south of the equator, so when the sun is in the southern part of the sky, we have winter and they have summer; when we have spring, they have fall
Can an observer who lives in Iowa see the Crux?
No, because the Cruz is only visible to inhabitants of the southern hemisphere.
Can an observer who lives in Australia see the North Star?
No, because the North Star is only visible to inhabitants of the northern hemisphere.
The sun rises and sets, as does the moon. As seen from a location on Earth that is arbitrary and in no way special, do all stars also rise and set, or do some stars stay in the sky all the time, or do all stars stay in the same place in the sky and neither rise nor set?
No, not all stars will "rise" and "set". From most places there are some stars (like Polaris from Ames) that stay in the sky all the time while other stars and constellations (like Orion) rise and set.
South Star
None
Which of the following will be circumpolar for an observer located at the Earth's equator? Orion, Taurus, Ursa Major, or Polaris.
None of these are circumpolar for an observer at the equator.
Meridian
Noon
Time of day half moons rises or sets
Noon
This is on your meridian but not on your horizon and not straight overhead.
North Celestial Pole
This is one of two points where horizon and meridian intersect.
North Point
Can see more circumpolar constellations and over the course of a year fewer stars in the sky
Observer closer to N or S pole than observer closer to equator
Can see more stars over the course of a year and fewer circumpolar constellations
Observer closer to the equator than observer closer to N or S pole
Can observe all stars in the sky over a year
Observer located at Earth's equator
All the constellations north of the celestial equator are circumpolar for ...
Observer located at the North Pole
All the constellations south of the celestial equator are circumpolar for ...
Observer located at the South Pole
Can not see any constellations north of the celestial equator
Observer located at the South Pole
Can not see Polaris
Observer located south of the Earth's equator
One fist is equal to approximately how many degrees
One fist = 10 degrees
Name the four time zones of the lower 48 states of the United States, starting with California.
Pacific Standard Time, Mountain Standard Time, Central Standard Time, Eastern Standard Time
An object's apparent daily motion across an observer's sky is _________________ to the CE. This means when the object rises north of east, it will set ___________________ of west. Similarly, if an object rises south of east, it will set _________________ of west.
Parallel; North; South
Why do observers in the North and South Hemisphere see the same moon?
Phase of the moon has to do with where the moon is in its roughly 4-week orbit around Earth; this is the same for all observers around the world (only half of them can see the moon at any given moment).
North Star
Polaris
PM means
Post Meridiem = after the sun crosses the meridian; after noon
If you have two observers, on opposite sides of the earth at the equator, can they see the same things at the same time? Can they see the same things but at different times?
Same things but at different times
Mercury's sidereal day and solar day are ...
Sidereal = 2/3 of a year Solar day = 2 years
A traditional sundial measures what type of time?
Solar
Type of time measured by a sundial
Solar time
City A is located at 30 E, 40 N and City B is located at 40 E, 30 N. To get from A to B, do you go north or south? East or west? Will your trip be shorter if you first go east or west, then go north or south; or shorter if you go north or south then east or west?
South; East; It will be shorter if you go East and then South because the Earth is a sphere and the closer you are to the equator (south) the longer the distance from east to west.
Circumpolar
Stars that stay in an observer's sky all night, do not rise or set
When it is winter in Iowa, what is the season in New Zealand?
Summer
Equator
Sun rises vertically
The observatory at which the prime meridian was named
The Greenwich Observatory
Correct cause for the phases of the Moon.
The moon is a sphere illuminated by the sun.
North Point
The point on your horizon closest to the North Celestial Pole
South Point
The point on your horizon closest to the South Celestial Pole
Zenith
The sky directly overhead; 90 degrees from horizon
If you have two observers, one at each pole, how much sky can they see?
They each see 1/2 the sky
Longitude zones
Time zones
Latitude zones
Tropics, Temperate zones, Arctic zones
A sundial uses the position of the sun in the sky to tell time.
True
Orion is visible from Ames (42 N) in our Southern sky at latitudes up to about 48 degrees.
True
South Pacific Islanders memorized which stars are "over" which islands and this allowed them to navigate without numbers.
True
Sundials do not keep time at a uniform rate.
True
The portion of sky above where two horizons intersect is visible by both observers at the same time.
True
Explanation for phases of the Moon.
When we see only the bright part of the moon, it appears full. When we see half the bright part and half the dark part, it is a half moon.
You observe a very bright star due South and about 3 fists above the horizon. You send an email to your astronomer friend asking what it is. Do you need to tell your friend what time of day you made the observation?
Yes, because as Earth turns the object in the sky will appear to move East to West.
You can measure longitude using what procedure?
You determine the time when the sun crosses the meridian and relate that to the time at your house.
If you dangle a weight on a rope, the line from the weight up the rope will point to this location in the sky
Zenith
A special line in the equatorial system is the celestial equator which has a declination of what?
Zero; like Earth's equator
A special point is the vernal equinox which has a right ascension of what?
Zero; like Earth's prime meridian
The expansion of the railroad from coast to coast brought about the development of _____________, where the same mean solar time is used for a range in longitude of 15 degrees wide.
Zone time OR Time zones OR Standard time
The point directly above an observer's head is called the...
the Zenith
The Norther Point, the South Point, and the Zenith all are on the observer's
the observer's Meridian
