Astronomy chapter 1 & 6
If the history of the entire universe was condensed into a single year, dinosaurs would have died from the impact of a large meteorite or asteroid about:
December 30
What do we think first caused tiny solid bits of material in the solar nebula to accrete and stick together?
Electrical forces ("static electricity")
True or False?: NASA soon plans to launch a spacecraft that will leave the Milky Way Galaxy to take a photograph of the galaxy from the outside.
False, even a spacecraft that moved close to the speed of light would take tens of thousands of years to get to a good vantage point.
When the first solid bits in the solar nebula became large enough to be called planetesimals, what began to increase their growth rate?
Gravity
What do we think condensed out of the solar nebula?
Hydrogen compounds (water, methane, ammonia) where the nebula was cold (<150 K), Rocky material where the nebula was 500- 1500 K (depending on the type of rock), Metal where the temperature was 1000-1500 K
Where do asteroids come from?
Leftover planetesimals from the inner solar system
Where do comets come from?
Leftover planetesimals from the outer solar system
Which planets have a rocky, dense composition?
Mercury, Venus, Earth, and Mars
Why do we think that the solar system formed from a rotating, collapsing gas cloud that ended up as a disk orbiting the Sun?
Most of the planets revolve and rotate in the same direction, in the same plane, Conservation of angular momentum means a collapsing cloud will spin faster and faster, We see clouds of gas and dust in space, We see disks around young stars
Because nearly all galaxies are moving away from us, we must be located at the center of the universe.
No, everything moves away from everything else in an expanding universe and there is no unique center.
Suppose that, at this very moment, students are studying astronomy on planets in Andromeda. Could they know that we exist here on Earth?
No, the light from the solar system that has reached Andromeda came from a time before Earth had formed.
Could a solar system like ours have formed with the first generation of stars after the Big Bang?
No, there would not have been enough metals and rock to form terrestrial planets.
True or False: The observable universe is the same size today as it was a few billion years ago.
No, we can see light from more distant parts of the universe today than we could have seen a few billion years ago.
Earth rotates on its axis:
Once a day
The Moon revolves around Earth:
Once a month
Earth revolves around the Sun:
Once a year
Earth revolves around the Milky Way galaxy:
Once every 250,000 years
Most of the solar system's planets:
Revolve (orbit) around the Sun in the same direction, Rotate in the same direction as they orbit the Sun
The dense, rocky, and metallic planets are found close to the Sun because
Rocks and metals condensed at the relatively high temperatures close to the Sun.
Which is farther, the distance from San Francisco to Los Angeles, or the distance from you to the space shuttle if the shuttle passes directly overhead?
San Francisco - LA is further
Put these objects in the correct order, from nearest to farthest from Earth: Mars, the Moon, the Sun, the nearest stars, Pluto
The Moon, Mars, the Sun, Pluto, the nearest stars
Put these objects in the correct order, from nearest to farthest from Earth: The Sun, Alpha Centauri, Pluto, the Andromeda galaxy, the Milky Way
The Sun, Pluto, Alpha Centauri, the Milky Way, the Andromeda galaxy
What patterns can been seen comparing the inner four planets (Mercury, Venus, Earth, Mars) to the "Jovian" planets (Jupiter, Saturn, Uranus, Neptune)?
The inner four are much more dense, The inner four are rocky, the outer four gaseous
Why do we think the inner (terrestrial) planets became more dense than the outer planets?
The inner nebula was so hot that only metals and rocks were able to condense
How do astronomers look for planets whose orbits might cause them to pass in front of a star outside our solar system?
The measure the star's brightness, and look for periodic dimming ("transits")
If the history of the entire universe was condensed into a single year, Earth would have formed about:
The month of September
Which of the following can be used as an argument against the existence of other civilizations in the universe?
The relatively short lifetime of intelligent life on Earth.
In a scale model solar system that used a grapefruit to represent the Sun, how large would the Earth be?
The size of the point of a ballpoint pen
One difference between the terms solar system and galaxy is that
The solar system contains only one star but the galaxy contains many billions.
What do we think happened to the solar nebula after the planets formed?
The solar wind helped blow the gas away
What appears to have happened to increase the mass of Jovian planets even further?
Their gravity became strong enough to attract hydrogen and helium gas from the solar nebula
Why do we not feel or sense the various motions of Earth in the universe?
They are nearly uniform, and you can not sense uniform velocity, only acceleration, which is a change of velocity or direction
Why could the Jovian planets grow to be much larger than the terrestrial planets?
They formed beyond the frost line where ices can condense so they included hydrogen compounds
Considering the size and scale of the universe makes me:
Think it is remarkable that all of this was created for us
How do the "stellar winds" of young solar-type stars compare to the solar wind we see from the Sun today?
Young stars have much stronger winds
If the history of the entire universe was condensed into a single year, the first civilization would have appeared about:
11:59:30 P.M. December 31 (30 seconds before year-end)
About how old is the universe?
14 billion years
In a scale model solar system that used a grapefruit to represent the Sun, how far away would Pluto-the edge of the solar system-be?
2,000 feet
In a scale model solar system that used a grapefruit to represent the Sun, how far away should you put another grapefruit to represent Alpha Centauri, the next nearest star?
2,000 miles
About how old is Earth?
5 billion years
In a scale model solar system that used a grapefruit to represent the Sun, how far away would the Earth be?
50 feet
If the history of the entire universe was condensed into a single year, the earliest humans (hominids) would have appeared about:
9 P.M. December 31 (3 hours before year-end)
The phrase, "The Red Sox haven't won the World Series in light-years" doesn't make sense because
A light-year is a unit of distance, not time.
How much of the solar nebula condenses in the inner regions where the temperature is greater than 1300 K and in the outer regions where the temperatures are less than 150 K ?
About 0.2% in the inner region and 2% in the outer region.
At the speed of light, how long would it take to reach the nearest star, Alpha Centauri?
About 4 years
At the speed of light, how long would it take to go from Earth to the Sun?
About 8 minutes
What do we think the composition of the solar nebula was?
About 98% hydrogen and helium, and 2% heavier elements
What is the composition of the gas clouds (nebulae) we see in space?
About 98% hydrogen and helium, and 2% heavier elements
How can the Doppler shift be used to search for planets around other stars?
Astronomers look for a periodic, red-then-blue shift in the spectrum of the star
What is the "solar wind?"
Atoms and parts of atoms ejected from the Sun at high speed
