What is the interstellar medium (ISM)?

The vacuum of empty space between galaxies The gas and dust that fills the space between stars The atmosphere surrounding a star Dark matter that holds galaxies together

What is the interstellar medium made of?

Mostly dark matter with some hydrogen Equal amounts of gas, dust, and plasma About 99% gas (mostly hydrogen and helium) and about 1% dust Mostly heavy elements like iron and carbon

What are Giant Molecular Clouds (GMCs)?

Hot glowing clouds of plasma around young stars Clouds of gas ejected by dying stars The coldest, densest regions of the interstellar medium where star formation takes place Clouds of dark matter surrounding galaxies

Approximately how cold are Giant Molecular Clouds?

About 1,000 to 5,000 Kelvin — similar to the surface of a cool star About 10 to 30 Kelvin (-263°C to -243°C) About 100 Kelvin — about as cold as dry ice About 1 million Kelvin — as hot as the Sun's corona

What can trigger a Giant Molecular Cloud to begin collapsing and forming stars?

The cloud heats up until it ignites on its own A shockwave from a nearby supernova explosion compressing part of the cloud Ultraviolet light from distant stars melts the cloud Dark matter flowing through the cloud pushes it together

What happens once a Giant Molecular Cloud starts to collapse?

The whole cloud collapses into a single massive star The cloud explodes outward in a large blast The cloud fragments into many smaller dense cores, each of which can become one or more stars The cloud disappears because all the gas becomes a black hole

What type of gas makes up most of the ISM by mass?

Carbon dioxide, the most common molecule in space Helium, because it is lighter than hydrogen Oxygen, because it is needed for combustion Hydrogen, in various forms including atomic, molecular, and ionized

What are the tiny solid particles in the ISM dust made of?

Pure hydrogen ice crystals Silicate minerals and carbon compounds Solidified plasma from stellar flares Frozen water and ammonia only

How much mass can a Giant Molecular Cloud contain?

About the same mass as a single star like our Sun Up to millions of times the mass of our Sun About as much mass as a single planet No more than a few thousand solar masses — they are rare and small

Why does the density of a Giant Molecular Cloud matter for star formation?

Low density is needed so the gas can spread out and cool down Density has no effect — only temperature matters High enough density allows gravity to overcome the outward pressure of the gas, triggering collapse High density causes the cloud to evaporate faster into individual atoms

Which feature of Giant Molecular Clouds allows complex molecules like water and carbon monoxide to form?

Hot temperatures inside GMCs speed up chemical reactions Their extreme cold and high density shield the interior from ultraviolet radiation that would otherwise destroy molecules Magnetic fields in GMCs force atoms to bond together Gravity compresses atoms until they bond into molecules