Chapter 15

by supernovae and strong winds from luminous stars

"Weather" in the interstellar medium is produced:

it allows us to study neutral hydrogen in the interstellar medium

21-cm radiation is important because:

brown dwarf

A __________ is a failed star that shines primarily because of energy derived from its gravitational collapse rather than nuclear burning.

more luminous

A surprising fact about a 1 M protostar is that, even though nuclear reactions have not yet started in their cores, they are ___________ than the Sun.

10 K

A typical molecular cloud has a temperature of approximately:

all of the above

An H II region signals the presence of:

angular momentum

An accretion dis forms around a collapsing protostar because infalling material must conserve:

increase due to the kinetic energy of infalling material

As a protostar evolves, its temperature:

spin faster

Because angular momentum must be conserved, as a gas cloud contracts due to gravity it will also:

hydrogen fusion never begins in their cores

Brown dwarfs are considered failed stars because:

100 um

Dust that is heated to 30 K will emit a blackbody spectrum that peaks at:

expand

For an object in hydrostatic equilibrium, if the temperature inside the object were to increase, the object would:

high-mass stars

If you could watch stars forming out of a gas cloud, which stars would form first?

dust grains

If you wanted to observe heavy elements in the interstellar medium, where would be the best place to look?

all of the above

If you wanted to study regions where star formation is currently happening you could use:

all of the above

In the interstellar medium, molecules survive only in regions with:

regions where hydrogen tends to be denser than the surrounding gas

Interstellar clouds are:

inhibit gravitational collapse

Magnetic fields inside a molecular cloud act to:

all of the above

Molecular cloud cores are places where you might find:

radio

Molecular clouds, which have temperatures of around 10 K, are best observed at ______ wavelengths.

gravity

Of the following processes at work in molecular clouds, which is the one that inevitably dominates the clouds evolution?

an astronaut would feel cold standing in the 10^6 K intercloud gas

Sitting in a 100 degree F hot tub feels much hotter than standing outside on a 100 degree F day. This analogy illustrates why:

cannot successfully execute the proton-proton chain reactions

Stars with a mass from 0.01 M to 0.08 M are very different from the Sun because they:

1 atom/cubic centimeter

The average density of the interstellar medium is:

low-mass stars

The most common types of stars in our galaxy are:

gravitational potential energy

The source of energy for a contracting protostar comes from:

red

Warm ionized gas in the interstellar medium appears _______ when imaged in the optical region of the electromagnetic spectrum.

the spin of an electron flips and aligns with the spin of a proton in a hydrogen atom

We detect neutral gas in the interstellar medium by looking for radiation at 21 cm that arises when:

Nuclear fusion begins in the core

What critical event transforms a protostar into a normal main-sequence star?

all of the above are true

What happens as a protostar contracts?

gas

When looking at the space between stars, what might you see?

the object appears redder and dimmer

When radiation from an object passes through the interstellar medium:

all of the above

Where have astronomers observed the existence of planets?