ASTRO1500 Trivia - 3/14/2025

What is the interstellar medium (ISM)?

• Smaller than the interstellar large

• The gas and dust between stars

• The gas and dust inside of stars

• Planets stranded in between stars

Answer explanation

The interstellar medium is all the gas and dust that isn't in or near a star

What percent of the ISM is gas (not dust)?

• 15%

• 50%

• 85%

• 99%

Answer explanation

The ISM is mostly gas, with a sprinkling of dust, this dust is important though, as it is what makes up all the planets

Tags

CCSS.6.RP.A.3C

Rank the different types of ISM clouds in decreasing temperature.

• Molecular Clouds, Ultra Hot ISM, HII regions, HI clouds

• Ultra Hot ISM, HII regions, Molecular Clouds, HI clouds

• Ultra Hot ISM, HI clouds, HII regions, Molecular Clouds

• Ultra Hot ISM, HII regions, HI Clouds, Molecular Clouds

Answer explanation

UltraHot ISM has a temperature of 10^6 K, HII regions have a temperature of 10,000 K, HI clouds: ~1,000 K, Molecular clouds: 10 K

How is ultra hot ISM usually formed?

• Heating up cold ISM

• Gravitational Contraction

• Exploding Stars

• Conservation of Angular Momentum

Answer explanation

UltraHot ISM usually result from a large star exploding, leaving behind a lot of very hot material

Which of the following is true about HII regions and HI clouds

• HI clouds are smaller than HII regions

• HII regions are made of ionized hydrogen, HI Clouds are not

• HI clouds are much easier to detect

• HII regions can do the 'spin-flip' transition

Answer explanation

HII means ionized, HI is neutral. This is the only correct answer, all of the others are lies

The pillars of creation image is an example of a ...

• Giant Molecular Cloud

• HI Cloud

• HII region

• UltraHot ISM

Answer explanation

The pillars of creation is a molecular cloud, which is partially responsible for it's bright colors!

Which type of ISM would form the most stars?

• Giant Molecular Clouds

• HII regions

• HI Clouds

• UltraHot ISM

Answer explanation

Giant molecular clouds, they are very dense and the gas is cool enough to get relatively close together

The densest part of a molecular cloud is called a ...

• Clump

• Blob

• HDA (High Density Area)

• Core

Answer explanation

The densest regions are called "cores" and form a lot of stars

Why are sunrises/sunsets red?

• Because blue light is easier to scatter then red light

• Because red light is easier to scatter then blue light

• The atmosphere absorbs all the red light during the day and re-emits it

• The sun gets redder later in the day

Answer explanation

Later in the day, the light has to go through more of the atmosphere, meaning more of the blue light can be scattered away, letting us only see the red light!

True or False: In addition to scattering, dust grains in the ISM can also absorb light.

• True

• False

Answer explanation

Dust grains can both absorb and emit light in the ISM, otherwise we wouldn't see extinction