AST 2002 - Final Exam Questions with
Complete Answers.
What is the cosmological principle? - Answer - There is nothing special about our place in
the universe
- Matter and energy obey same physical laws everywhere
What is our full cosmic address? - Answer Earth, Solar System, Milky Way, Local Group, Virgo
Supercluster, Observable Universe
In the organizational diagram below, the term Earth would most appropriately fit in the area
labeled? - Answer Solar System; Our Earth best fits in the bubble of our Solar System
In the organizational diagram below, the term Big Dipper constellation would most
appropriately fit in the area labeled? - Answer Milky Way
In the organizational diagram below, the term Virgo supercluster would most appropriately fit in
the area labeled? - Answer Universe; The Virgo Supercluster belongs in the larger bubble of
the Universe.
What is light travel time (LTT)? - Answer Time it takes light to travel from one place to
another
LTT Moon from Earth? - Answer 1 1/3 sec
LTT Sun from Earth? - Answer 8.5 minutes
What is look back time (LBT)? - Answer How far back in time we see in years equals light
travelled in years
The Andromeda Galaxy is about 2,500,000 ly away. Thus, the light that we observe from
Andromeda was emitted? - Answer 2,500,000 years ago; Since it takes light (moving at the
speed of light) one year to travel 1 LY, then if Andromeda is 2,500,000 LY away it would take
2,500,000 years to arrive here on Earth.
The Crab Nebula is the remnant of an exploded star. The explosion was witnessed by Chinese
astronomers in the year 1054 AD. The Crab nebula is about 6500 ly away. This means that the
explosion occurred in the year? - Answer 5446 BC; Since the Crab Nebula is 6500 LY away,
,that means it would have taken 6500 years for the light to arrive on Earth. This means it would
have to have happened 6500 years prior to the Chinese Astronomers viewing it.
How far away is the nearest star? - Answer 4.4 light years
What is the distance across the Milky Way? - Answer 100,000 light years
What is the distance to the nearest galaxy? - Answer 2,500,000 light years
Imagine that you were observing a distant star that was located in a galaxy 100 million ly away
from you. By analysis of the starlight received, you are able to tell that the image we see is of a
10 million year old star. You are also able to predict that the star will have a lifetime of 50 million
years, at which point it will end in a catastrophic supernova.
How old does the star appear to us here on Earth (in million yrs) - Answer 10; The question
states specifically that we see the star as a 10 million year old star.
Imagine that you were observing a distant star that was located in a galaxy 100 million ly away
from you. By analysis of the starlight received, you are able to tell that the image we see is of a
10 million year old star. You are also able to predict that the star will have a lifetime of 50 million
years, at which point it will end in a catastrophic supernova.
How long will it be before we receive the light from the supernova event (in million yrs)? -
Answer 40; Since this star has a lifetime of 50 million years and we see it as 10 million years
old already, this means the star will die according to observers on Earth in 40 million years.
Imagine that you were observing a distant star that was located in a galaxy 100 million ly away
from you. By analysis of the starlight received, you are able to tell that the image we see is of a
10 million year old star. You are also able to predict that the star will have a lifetime of 50 million
years, at which point it will end in a catastrophic supernova.
Has the supernova already occurred? If so, when did it occur (in million yrs)? - Answer 60;
Yes, the star has already died. Since it took 100 million years for light to reach us, the star is
technically 110 million years old. However it only has a lifetime of 50 million years. This means
the star has already died, 60 million years ago.
What is the celestial sphere? - Answer Extension of the Earth's equator into the celestial
sphere
What is the North Celestial Sphere (NCP)? - Answer The point on the celestial sphere directly
above the Earth's North Pole
What is the South Celestial Pole (SCP)? - Answer The point on the celestial sphere directly
below the Earth's South pole
, The celestial sphere is a what? - Answer - Scientific model
- It's not the way things really are but it's a useful way to think about the position and motion of
the stars
Stars appear to lie in ________________ on the celestial sphere? - Answer Fixed positions
Outside, we only see _________________ of the celestial sphere; the part that is above our
horizon. We call this our? - Answer - Half
- Local sky
What is the horizon? - Answer Boundary between Earth and Sky, all around the observer
What is the Zenith? - Answer Point directly overhead the observer- changes with location
What is the Nadir? - Answer Point directly below the observer- also changes with location
What is the Meridian? - Answer Imaginary north-south line based on observer
What is the Altitude? - Answer - Distance (angular) between the horizon and an object in the
sky
- 0-90 degrees
What is the Azimuth? - Answer - Direction around the horizon from the North, measure
clockwise
- 0-360 degrees
Where on Earth would you stand to see Polaris at your zenith? - Answer North Pole; Polaris
is the North Star and if you want it to be at your zenith, directly above you, you need to stand at
the North Pole.
Topocentric Coordinates- The Local Sky are? - Answer - Based on your time and location
- A star's coordination change with time
Circumpolar stars are? - Answer Always visible
Rise and set stars are? - Answer Rise in the east and set in the west
Complete Answers.
What is the cosmological principle? - Answer - There is nothing special about our place in
the universe
- Matter and energy obey same physical laws everywhere
What is our full cosmic address? - Answer Earth, Solar System, Milky Way, Local Group, Virgo
Supercluster, Observable Universe
In the organizational diagram below, the term Earth would most appropriately fit in the area
labeled? - Answer Solar System; Our Earth best fits in the bubble of our Solar System
In the organizational diagram below, the term Big Dipper constellation would most
appropriately fit in the area labeled? - Answer Milky Way
In the organizational diagram below, the term Virgo supercluster would most appropriately fit in
the area labeled? - Answer Universe; The Virgo Supercluster belongs in the larger bubble of
the Universe.
What is light travel time (LTT)? - Answer Time it takes light to travel from one place to
another
LTT Moon from Earth? - Answer 1 1/3 sec
LTT Sun from Earth? - Answer 8.5 minutes
What is look back time (LBT)? - Answer How far back in time we see in years equals light
travelled in years
The Andromeda Galaxy is about 2,500,000 ly away. Thus, the light that we observe from
Andromeda was emitted? - Answer 2,500,000 years ago; Since it takes light (moving at the
speed of light) one year to travel 1 LY, then if Andromeda is 2,500,000 LY away it would take
2,500,000 years to arrive here on Earth.
The Crab Nebula is the remnant of an exploded star. The explosion was witnessed by Chinese
astronomers in the year 1054 AD. The Crab nebula is about 6500 ly away. This means that the
explosion occurred in the year? - Answer 5446 BC; Since the Crab Nebula is 6500 LY away,
,that means it would have taken 6500 years for the light to arrive on Earth. This means it would
have to have happened 6500 years prior to the Chinese Astronomers viewing it.
How far away is the nearest star? - Answer 4.4 light years
What is the distance across the Milky Way? - Answer 100,000 light years
What is the distance to the nearest galaxy? - Answer 2,500,000 light years
Imagine that you were observing a distant star that was located in a galaxy 100 million ly away
from you. By analysis of the starlight received, you are able to tell that the image we see is of a
10 million year old star. You are also able to predict that the star will have a lifetime of 50 million
years, at which point it will end in a catastrophic supernova.
How old does the star appear to us here on Earth (in million yrs) - Answer 10; The question
states specifically that we see the star as a 10 million year old star.
Imagine that you were observing a distant star that was located in a galaxy 100 million ly away
from you. By analysis of the starlight received, you are able to tell that the image we see is of a
10 million year old star. You are also able to predict that the star will have a lifetime of 50 million
years, at which point it will end in a catastrophic supernova.
How long will it be before we receive the light from the supernova event (in million yrs)? -
Answer 40; Since this star has a lifetime of 50 million years and we see it as 10 million years
old already, this means the star will die according to observers on Earth in 40 million years.
Imagine that you were observing a distant star that was located in a galaxy 100 million ly away
from you. By analysis of the starlight received, you are able to tell that the image we see is of a
10 million year old star. You are also able to predict that the star will have a lifetime of 50 million
years, at which point it will end in a catastrophic supernova.
Has the supernova already occurred? If so, when did it occur (in million yrs)? - Answer 60;
Yes, the star has already died. Since it took 100 million years for light to reach us, the star is
technically 110 million years old. However it only has a lifetime of 50 million years. This means
the star has already died, 60 million years ago.
What is the celestial sphere? - Answer Extension of the Earth's equator into the celestial
sphere
What is the North Celestial Sphere (NCP)? - Answer The point on the celestial sphere directly
above the Earth's North Pole
What is the South Celestial Pole (SCP)? - Answer The point on the celestial sphere directly
below the Earth's South pole
, The celestial sphere is a what? - Answer - Scientific model
- It's not the way things really are but it's a useful way to think about the position and motion of
the stars
Stars appear to lie in ________________ on the celestial sphere? - Answer Fixed positions
Outside, we only see _________________ of the celestial sphere; the part that is above our
horizon. We call this our? - Answer - Half
- Local sky
What is the horizon? - Answer Boundary between Earth and Sky, all around the observer
What is the Zenith? - Answer Point directly overhead the observer- changes with location
What is the Nadir? - Answer Point directly below the observer- also changes with location
What is the Meridian? - Answer Imaginary north-south line based on observer
What is the Altitude? - Answer - Distance (angular) between the horizon and an object in the
sky
- 0-90 degrees
What is the Azimuth? - Answer - Direction around the horizon from the North, measure
clockwise
- 0-360 degrees
Where on Earth would you stand to see Polaris at your zenith? - Answer North Pole; Polaris
is the North Star and if you want it to be at your zenith, directly above you, you need to stand at
the North Pole.
Topocentric Coordinates- The Local Sky are? - Answer - Based on your time and location
- A star's coordination change with time
Circumpolar stars are? - Answer Always visible
Rise and set stars are? - Answer Rise in the east and set in the west
