Astronomy CH 13-15

Main sequence stars range in mass from approximately:

0.08 to 150 M

The habitable zone for the Sun covers the area that is between _____ from the Sun.

0.9 to 1.4 AU

The average density of the interstellar medium is:

1 atom/cm3

A typical molecular cloud has a temperature of approximately:

10 K

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

100 um

Approximately how long does it take the photos released in nuclear reactions in the core of the sun to exit the photosphere?

100,000 years

The suns magnetic field reversed direction every

11 years

The fraction of the Sun's mass that is made of heavy elements is:

2 percent

How many arcseonds are there in 1 degree?

3,600

Light from the photosphere reaches Earth approximately __________ times faster than photons released in fusion in the core.

6 billion

To measure the parallax of the most distant stars measurable, we would make two measurements of the star's position on the sky separated by:

6 months

Roughly what percentage of stars in our galaxy are main-sequence stars?

90 percent

When astronomers refer to "heavy elements," which elements are they talking about?

All elements more massive than helium

What happens as a protostar contracts?

All of the above are true

What is the difference between brightness and luminosity?

Brightness is how much light we see from a star; luminosity is how much light it emits.

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

Cannot successfully execute the proton-proton chain reactions

Which of the following methods is not used to transport energy from the core to the surface of the sun?

Conduction

Eclipsing binary system's:

Contain stars that pass in front of one another during their orbit

In the interstellar medium, molecules survive only in regions with: A. Low temperatures B. High densities C. Lots of dust D. All of the above

D. All of the above

Which if the following are manifestations of solar magnetic activity? A. Sunspots B. Prominences C. Flares D. All of the above

D. All of the above

Parallax is used to measure a star's:

Distance

How is the distance to a star related to its parallax?

Distance is inversely proportional to parallax.

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

Dust grains

An H II region signals the presence of: A. Newly formed stars B. Young stars C. Ionized hydrogen gas D. O- and B- type stats E. All of the above

E. All of the above

Molecular cloud cores are places where you might find: A. Protostars B. Herbig-Haro objects C. Molecular hydrogen D. Carbon monoxide E. All of the above

E. All of the above

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

Expand

What spectral class is the Sun?

G2

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

Gravity

Stars are made mostly of:

Hydrogen

Magnetic fields inside a molecular cloud act to:

Inhibit gravitational collapse

Which of the following properties would not be plotted on the horizontal axis of an H-R diagram?

Luminosity would not be plotted

What type of star is most common in the solar neighborhood?

Main-sequence

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.

More luminous

Which sequence correctly lists the spectral classes of stars in order from hottest to coolest?

O B A F G K M

If neutrinos oscillated between five different types of neutrino during their transit from the Sun to Earth, then how many neutrinos would we have detected compared to what was emitted by the Sun?

One-fifth as many

The majority that fuels the Sun is generated where?

Only in its core

Molecular cloud, which have temperatures of around 10 K, are best observed at _______ wavelengths.

Radio

If we know the temperature and luminosity of a star, we can also calculate its

Radius

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

Red

Star A and Star B both have the same temperature but different sizes and distances. As a result, star A is more luminous than star B, but star B is brighter than star A. Which of these statements shout the absolute and apparent magnitudes I'd the two stars is correct?

Star A has a larger apparent magnitude, while Star B has a larger absolute magnitude

Stars A and B appear equally bright, but star A is twice as far away from us as star B. Which of the following is true?

Star A is four times as luminous as star B

Star A is a red star. Star B is a blue star. Which is hotter?

Star B is hotter

Two main-sequence stars have the same temperature. If star A is four times brighter than star B, then:

Star B is two times farther away than star A

Star E is the same temperature as star F, but star E is four times as luminous as star F. How do the radii of the stars compare?

Star E has twice the radius of star F

Which stars are the most common?

Stars with a smaller mass and a smaller radius than the Sun's

What advantage do you gain by having two eyes that are separated on your face, rather than being very close together?

Stereoscopic vision

The Hayashi track of a low-mass protostar in the H-R diagram is a path of approximately constant:

Temperature

The interior zones of the Sun are distinguished by:

Their modes of energy transport

In which region of an H-R diagram would you find the main-sequence stars with the widest habitable zones?

Upper left

On a typical H-R diagram, where are the stars with the largest radio located?

Upper right corner

Star A is a red star. Star B is a blue star. You are able to determine that both stars are the same size. Which star is brighter?

We also need to know the distance of the stars to determine their brightness.

The solar spectrum is an example of a(n) _________ spectrum.

absorption

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

all of the above

Where have astronomers observed the existence of planets?

all of the above

What type of spectrum do most stars produce?

an absorption spectrum on top of a blackbody spectrum

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

an astronaut would feel cold standing in the 10⁶ K intercloud gas

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

angular momentum

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

brown dwarf

Balance of energy in the solar interior means that:

energy production rate in the core equals the rate of radiation escaping the Sun's surface

In the proton-proton chain, the net reaction is that 4 hydrogen nuclei are converted to 1 helium nucleus and _____ are released.

gamma ray photons, positrons, and neutrinos

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

gas

The source of energy for a contracting protostar comes from:

gravitational potential energy

We can determine how the density changes with radius in the Sun using:

helioseismology

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

high mass stars

Brown dwarfs are considered failed stars because:

hydrogen fusion never begins in their cores

As a protostar evolves, its temperature:

increases due to the kinetic energy of infalling material

By studying how the surface of the Sun vibrates like a struck bell we can determine its:

interior density

21-cm radiation is important because:

it allows us to study neutral hydrogen in the interstellar medium

The most common types of stars in our galaxy are:

low mass stars

The Hertzsprung-Russell diagram is a graph of ____ for stars.

luminosity versus temperature

When two atomic nuclei come together to form a new species of atom, it is called:

nuclear fusion

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

nuclear fusion begins in the core

The solar neutrino problem was solved by:

postulating that neutrinos had mass and oscillated between three different types

Hydrostatic equilibrium is a balance between:

pressure and gravity

Our Sun is unique compared to the other stars in our galaxy because of its:

proximity

Interstellar clouds are:

regions where hydrogen tends to be denser than the surrounding gas

Two stars with similar temperatures but different sizes will have:

similar spectral types but different luminosities

Astronomers can measure the speed of the stars in a binary system by measuring the _______ of the stars.

spectra

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

spin faster

The stars that have the largest radii are classified as:

supergiants

The spectral class of a star is related to its:

temperature

Detection of solar neutrinos confirms that:

the core is powered by proton-proton fusion

The faster-moving star in a binary is:

the less massive star

When radiation from an object passes through the interstellar medium:

the object appears redder and dimmer

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

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

Sunspots appear dark because:

they have lower temperatures

The brightest stars in the sky also tend to be:

very luminous

For which type of binary system are astronomers able to resolve each of the two stars individually?

visual binary