Galaxy

High school (ages 12+)
Space & Astronomy

Name:

Date:

Step 1 · Read the article

Open the article and read it at the level above. Then answer the questions below in your own words.

https://smallwhale.org/articles/galaxy

Write what each word means, using the article.

Do not copy the article. Write two things you learned, the way you would explain them to a friend.

Answers below are taken from the article’s stored facts, so they match what the student read.

1. How heavy is the Galaxy?Dark matter, comprising over 90% of a typical galaxy's mass
2. What is the scientific classification?Gravitationally bound system of stars, gas, dust, stellar remnants, and dark matter
3. What is the estimated number of galaxies in observable universe?200 billion to 2 trillion
4. Why does most of a galaxy's mass come from dark matter?Dark matter is invisible but pulls on everything with gravity. In a galaxy, it makes up more than 90% of the total mass, helping keep the stars and gas in place.
5. How do scientists know there are so many galaxies in the universe?By looking at the sky with powerful telescopes, scientists count the bright islands of stars and estimate there are between 200 billion and 2 trillion galaxies.

Dark Matter: A hypothetical form of matter that does not emit, absorb, or reflect light, interacting only through gravity.
Supermassive Black Hole: A black hole with a mass millions to billions of times that of the Sun, found at the center of most large galaxies.
Intergalactic Medium (IGM): The extremely diffuse plasma that fills the space between galaxies.
Light-year: The distance that light travels in a vacuum in one Julian year (approximately 9.46 trillion kilometers or 5.88 trillion miles).