Which of the following is not a general difference between a planet and a star?
All planets are made of rock and all stars are made of gas.
Our solar system consists of?
The sun and all objects that orbit it.
A typical galaxy is a _________.
collection of a few hundred million to a trillion or more stars, bound together by gravity
Which of the following best describes what we mean by "the universe"?
...
What do astronomers mean by the Big Bang?
the event that marked the beginning of the expansion of the universe
What do we mean when we say the universe is expanding?
Average distances are increasing between galaxies.
Based on observations of the universal expansion, the age of the universe is about _________.
14 billion years
A television advertisement claiming that a product is light-years ahead of its time does not make sense because _________.
it uses "light-years" to talk about time, but a light-year is a unit of distance
The term observable universe refers to _________.
that portion of the universe we can see in principle, given the current age of the universe
On a scale in which the distance from Earth to the Sun is about 15 meters, the distance from Earth to the Moon is _________.
small enough to fit within your hand
On a scale where the Sun is about the size of a grapefruit and the Earth is about 15 meters away, how far away are the nearest stars besides the Sun?
About the distance across the United States
The number of stars in the Milky Way Galaxy is approximately _________.
a few hundred billion
An astronomical unit (AU) is _________.
the average distance between Earth and the Sun
What is the ecliptic plane?
the plane of the Earth's orbit around the Sun
How long does it take the Earth to complete one orbit around the Sun?
One year
Rank the following items according to their size (diameter) from left to right, from largest to smallest.
the universe, local supercluster, local group, the milky way galaxy, our solar system, the sun, jupiter, earth
Rank the following items that describe distances from longest distance (left) to shortest distance (right). (If two distances are equal, drag the second item on top of the first item.)
(Longest)
The distance from the Milky Way Galaxy to the Andromeda Galaxy
The distance from the Sun to the center of the Milky Way Galaxy
The distance from Earth to Alpha Centauri
One light year
The distance across the solar system (to Neptune)
One astrono
The Andromeda Galaxy is faintly visible to the naked eye. When you look at the Andromeda Galaxy, the retina of your eye is absorbing light that has traveled through space for ______ to reach you.
about 2 � million years
Consider the indicated events in the history of the universe that have helped make human life possible. Rank the events based on when they occurred, from longest ago to most recent.
1. The Big Bang, the universe begins to expand
2. elements such as carbon and oxygen first exist
3. nuclear fusion begins in the sun
4. earliest life on earth
5. dinosaurs go extinct
6. earliest life on earth
According to current scientific estimates, when did the Big Bang occur?
13.7 billion years
On the cosmic calendar, which compresses the history of the universe into a single year, about when did Earth form?
in early September
On the cosmic calendar, which compresses the history of the universe into a single year, about when did life arise on Earth?
in September
On the cosmic calendar, which compresses the history of the universe into a single year, about when did early humans first walk on Earth?
Just a few hours before midnight on December 31
About how many stars are visible to the naked eye on a clear, dark night away from city lights?
A couple thousand
What do astronomers mean by a constellation?
A constellation is a region in the sky as seen from Earth.
What is the ecliptic?
The path the Sun appears to trace around the celestial sphere each year
What is the celestial sphere?
The celestial sphere is a representation of how the entire sky looks as seen from Earth.
What do we mean when we talk about the Milky Way in our sky?
The patchy band of light that outlines the plane of the Milky Way Galaxy as seen from Earth.
Stars that are visible in the local sky on any clear night of the year, at any time of the night, are called _________.
circumpolar
We describe a location on Earth's surface by stating its _________.
latitude and longitude
If you are located in the Northern Hemisphere, which of the following correctly describes a relationship between the sky and your location?
The altitude of the north celestial pole equals your latitude.
Which of the following best describes why we have seasons on Earth?
The tilt of Earth's axis causes different portions of the Earth to receive more or less direct sunlight at different times of year.
Each choice below describes how a few astronomical phenomena are related to time periods. Which list is entirely correct? (Careful: some lists are partially correct.)
Earth's rotation defines a day.
The cycle of the Moon's phases takes about a month.
Earth's orbit defines a year.
If we have a new moon today, when we will have the next full moon?
In about 2 weeks
We cannot see a new moon in our sky because _________.
a new moon is quite near the Sun in the sky
The Moon always shows nearly the same face to Earth because ________.
the Moon rotates once in the same amount of time that it takes the Moon to orbit Earth once
Lunar eclipses can occur only during a _________.
A full moon
What is the saros cycle?
The roughly 18-year cycle over which the pattern of eclipses repeats
Which of the following lies in the ecliptic plane?
Earth's orbital path around the Sun
In January, Earth's rotation axis points in the direction of the star Polaris. Where does it point in July?
Toward the star Polaris
You've now seen that Earth's varying distance cannot be the cause of our seasons. So what is the cause of the seasons?
The tilt of Earth's axis causes different portions of the Earth to receive more or less direct sunlight at different times of year.
Star
large glowing ball of glass. generates light & heat through nuclear fusion
planet
moderately large object that orbits a star. shines by reflecting light
moon
an object that orbits a planet
what elements were only formed in the Big Bang?
only hydrogen & helium
in what direction does earth rotate?
from west to east
what determines what you see in the sky?
your latitude & time of year
what moon phase can a solar eclipse ONLY occur in?
new moon