Astronomy Test Review
What is our comic address in order of increasing size?
Our solar system is located a little more than half way from the galactic center to the edge of the galactic disk. -
The solar System
Milky Way Galaxy
Where is the Sun in the Milky Way?
-The sun is located in one of the Milky Way's outer arms, about 25,000 light years from the galactic center. - Also in the Orion Arim, more than half way out of the galaxy
How many galaxies are in our local group?
There are about 40 galaxies in our local group.
Are all the galaxies in our local group travelling away from each other? -
Yes, all galaxies in our local group are moving away from each other. Which galaxy in our local group is the largest?
The Andromeda Galaxy is the largest galaxy in our local group. -
About how many stars are in our galaxy?
-There are more than 100 billion stars in our galaxy.
How are heavier elements (that is, elements heavier than Lithium) produced? - The early universe only contained hydrogen, lithium, and helium. - Elements such as carbon, nitrogen, oxygen, and iron were made by stars through nuclear fusion and nuclear reactions.
In what sense are we then made of “star stuff”? Following this line of thought, why do scientists think the Universe was lifeless for at least about 2 billion years? -
We are made of “star stuff” because both the earth and us are primarily made of elements such as carbon, nitrogen, oxygen, and iron. Also, our solar system was made from 98% hydrogen and helium and 2% other elements that came from stars in earlier generations. -
Scientist believe the universe was lifeless for at least 2 billion years because it took this long for stars to produce the elements we are made of
What do we mean by the “Observable Universe”?
- The “observable universe” is the portion of the entire universe that we can potentially observe. The distance is about 14 billion light years.
Can we see the actual edge of our universe and consequently know exactly how big it is? -
We can’t see the edge of the universe; therefore we don’t know how big it is.
About how old is the universe?
-Our universe is approximately 14 billion years old.
-Our solar system is about 4 and ½ billion years old.
Define galaxy and solar system.
Galaxy: A great island of stars in space, containing anywhere from a few hundred million to more than a trillion stars, all held together by gravity and orbiting a common center. -
Solar System: The sun and all material that orbits it, including planets, dwarf planets, and small solar system bodies.
If we scale the history of the universe into one year, when did the Milky Way form? Earth? When did the dinosaurs become extinct? When did human civilization occur? -January 1st: The Big Bang
-February: The Milky Way is formed
-September 3rd: Earth is formed
-September 22nd: Early life on earth
-December 17th: Cambrian explosion
-December 26th: Rise of the dinosaurs
-December- 30th: Dinosaurs become extinct
- December 31st at 9:00 pm: Modern humans evolve
Define light year, astronomical unit, and parsec. Which is largest? Smallest? -Light year: The distance in which light can travel in one year, which is 9.46 trillion km. -Astronomical Unit (AU): The average distance between earth and the sun, which is about 150 million kilometers. 1 AU is the length of the semi-major axis on earths orbit. -Parsec: The distance to an object with a parallax angle of 1 arc second. Approximately equal to 3.26 light-years. - AU is the largest
- Parsec is the smallest
What is the speed of light in free space (that is a vacuum) - The speed of light in a vacuum is 299,792,458 meters per second.
How long does it take light to travel a distance of one AU? (That is, how long does it take light to reach us from the time it left the sun?) - It takes light...
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