Chapter 1 Flashcards
An astronomical unit:
Earth’s average distance from the Sun
The star Betelgeuse is about 600 light years away. If it explodes tonight…
We won’t know about it until 600 years from now
Could we see a galaxy that is 50 billion light years away?
No, because it would be beyond the bounds of our observable universe
Which of the following correctly lists our “cosmic address” from smallest to largest?
Earth, solar system, milky way galaxy, local group, local supercluster, universe
If we represent the solar system on a scale that allows us to walk from the sun to pluto in a few minutes then:
The planets would be all be marble size or smaller and the nearest stars would be thousands of miles away
The total number of stars in the observable universe is roughly equivalent to:
The number of grains of sand on all the beaches on Earth
Light travels at a speed of
3×10^5 km/s
If stars existed but galaxies did not
We would not exist because we are made of material that required recycling in galaxies
The age of our solar system is about
One third of the age of the universe
The fact that nearly all galaxies are moving away from us, with more distant ones moving faster, helped us to conclude that:
The universe is expanding
Dark matter can be detected only by
its gravity, that affects other objects we can see
Why can’t you see dark matter in a telescope?
Dark matter does not emit light
Where does dark matter reside in our galaxy?
Most dark matter resides in the halo of the galaxy
What makes dark matter and dark energy mysterious?
Because we do not know what they exactly are
What makes dark matter and dark energy important?
Dark matter and dark energy make up the majority of the total energy within the universe
The observable universe is the same size today as it was a few billion years ago.
False
Because nearly all galaxies are moving away from us, we must be located in the center of the universe
False
When we say the universe is expanding:
the average distance between galaxies is growing with time
A person located on the equator is orbiting the center of the Earth to the East at 1670 km/s. Relative to the center of the Earth, a person on the North Pole is
Stationary, except spinning in place, once per day
The moon orbits the sun
once a year
How do the speeds at which we are moving with Earth’s rotation and orbit compare to the speeds of more familiar objects?
Earth’s rotation carries most people around the axis faster than a commercial jet travels, and Earth’s orbit carries us around the Sun faster than the Space Shuttle orbits Earth.
What is the ecliptic plane?
The plane of Earth’s orbit around the Sun
How long doe it take the Earth to complete one orbit around the sun?
one year
How long does it take our solar system to complete one orbit around the Milky Way galaxy?
230 million years
