Star Systems
What is a star system?
A group of stars that orbit each other.
What is a galaxy?
A massive system of stars, gas, dust, and dark matter held together by gravity.
The Milky Way & Universe
Where is our solar system located in the Milky Way?
What does the universe contain?
All space, time, matter, and energy.
What is a light year?
The distance light travels in one year (~9.5 trillion km).
What is a binary star system?
Two stars orbiting around a common center.
What shape is an elliptical galaxy?
Round or oval-shaped.
How many stars does the Milky Way contain (approx.)?
Hundreds of billions.
What is the approximate age of the universe since the Big Bang?
About 13.8 billion years.
What is an open cluster?
A loose group of young stars.
What is a multiple star system?
Three or more stars bound by gravity.
What kind of galaxy is the Milky Way?
A spiral galaxy.
About how wide is the Milky Way?
~100,000 light years across.
What evidence do we have that the universe is expanding?
Redshift of galaxies shows they are moving away from us.
What is a globular cluster?
A tightly packed, spherical group of older stars.
What is the main difference between open and globular clusters?
Open clusters are loose groups of younger stars; globular clusters are tightly packed groups of older stars.
How do spiral, elliptical, and irregular galaxies differ?
Spiral = disk with arms, Elliptical = oval with old stars, Irregular = no definite shape (often from collisions).
What unit do astronomers use to measure distances in space?
Light years.
Roughly how many galaxies exist in the universe?
Billions
What is dark matter’s role in galaxies?
It provides extra gravity to hold galaxies together
Open clusters are loose groups of younger stars; globular clusters are tightly packed groups of older stars.
Because many stars are found in pairs rather than being alone.
Why do astronomers believe irregular galaxies form?
They are often created when galaxies collide.
Why do astronomers use light years instead of kilometers?
Because distances are so vast that kilometers are impractical; 1 light year = ~9.5 trillion km.
Why is the expansion of the universe important in astronomy?
It supports the Big Bang theory and shows the universe is dynamic, not static.
What is the universe?
All of space, time, matter, and energy.