Ch 15 The Milky Way Galaxy vocab and questions.

What is a Halo?

• A star

• a disk or circle of light shown surrounding or above the head of a saint or holy person to represent their holiness.

• A spherical cloud of stars and star clusters that contains almost no gas and dust.

• A game

What is a Central bulge?

• A flattened cloud of billions of stars that is visible above and below the plane of the Milky Way and through gaps in obscuring interstellar dust.

• A shooting star.

• A white dwarf.

• A group of stars.

What are astronomers referring to when they use the term "spherical component of the Galaxy"?

• An astronaut and a spaceship together.

• The halo and the central bulge together.

• A star and a planet together.

• A spaceship and a star together.

What do astronomers do to fully describe the rotation of our Galaxy?

• Ask their friends.

• Guess.

• Take a lot of pictures.

• Graph orbital velocity versus radius to produce a rotation curve.

Why do astronomers call mass in the galactic corona "dark matter"?

• Because they were bored.

• Because most of the mass is invisible, neither emitting or absorbing light.

• Because it's dark in space.

• Because it was a cool name.

What are "spiral tracers"?

• Objects used to map spiral arms.

• Objects used to measure stuff that spin.

• Objects used to look at spinning stuff.

• Objects used to make stuff spin.

What is a "grand-design galaxy"?

• A big galaxy.

• A really cool designed galaxy.

• A galaxy.

• A two-armed spiral visibly highlights the two density waves.

What does the "spiral density wave theory" describe?

• It describes stuff.

• It describes spiral arms as regions of compression that orbit around the center of a galaxy within the disk.

• It describes the groups of stars in our Galaxy.

• It describes waves.

How are Galactic fountains produced?

• By astronauts.

• From the big bang.

• By expanding supernova remnants, may help spread metals throughout the disk.

• By doing stuff.

What does the top-down hypothesis suggest?

• That the Milky Way Galaxy formed from a single, roughly spherical protogalaxy cloud of gas that gradually flattened into a disk.

• That the Milky Way is cool.

• That the Milky Way is pretty.

• That the Milky Way is fake.