Test 2

Which of the following types of stars will spend the longest time (the greatest number of years) on the main sequence?

K

Which statement about the Sun's rotation is TRUE?

The Sun rotates at different rates at different latitudes on the Sun

Astronomers have concluded that the Sun's activity varies in an 11-year cycle. Which of the following statements about this cycle is TRUE:

The number of sunspots gets larger and smaller over the course of 11 years

Which of the following statements about the Sun's photosphere is NOT TRUE?

The photosphere is significantly hotter than all the layers of the Sun beneath it (further inward)

How can astronomers measure the age of a meteorite that fell from the skies?

They measure the amount still left of radioactive materials in the meteorite, and how much has turned into decay products

One of the best ways to learn more about a world is to have samples from its surface to analyze in our laboratories. From which of the following worlds do we NOT yet have a sample to analyze here on Earth?

Venus

Which of the following worlds does NOT have a ring (as far as we know)?

Venus

Neutron star

a compact object of extremely high density composed almost entirely of neutrons

Open cluster

a comparatively loose cluster of stars, containing from a few dozen to a few thousand members, located in the spiral arms or disk of our Galaxy; sometimes referred to as a galactic cluster

Solar wind

a flow of hot, charged particles leaving the Sun

A type of star cluster that contains mostly very old stars is

a globular star cluster

Plasma

a hot ionized gas

Prominence

a large, bright, gaseous feature that appears above the surface of the Sun and extends into the corona

Sunspot

a large, dark feature seen on the surface of the Sun caused by increased magnetic activity

Zero-age main sequence

a line denoting the main sequence on the H-R diagram for a system of stars that have completed their contraction from interstellar matter and are now deriving all their energy from nuclear reactions, but whose chemical composition has not yet been altered substantially by nuclear reactions

Main-sequence turnoff

a location in the H-R diagram where stars begin to leave the main sequence

Association

a loose group of young stars whose spectral types, motions, and positions in the sky indicate a common origin

Stony meteorite

a meteorite composed mostly of stony material, either primitive or differentiated

Iron meteorite

a meteorite composed primarily of iron and nickel

Helium flash

a nearly explosive ignition of helium in the triple-alpha process in the dense core of a red giant star

Triple-alpha process

a nuclear reaction by which three helium nuclei are built up (fused) into one carbon nucleus

Maunder minimum

a period during the eighteenth century when the number of sunspots seen throughout the solar cycle was unusually low

Exoplanet

a planet orbiting a star other than our Sun

Meteorite

a portion of a meteor that survives passage through the atmosphere and strikes the ground

Coronal hole

a region in the Sun's outer atmosphere that appears darker because there is less hot gas there

Planetary nebula

a shell of gas ejected by and expanding away from an extremely hot low-mass star that is nearing the end of its life (the nebulae glow because of the ultra-violet energy of the central star)

Meteor

a small piece of solid matter that enters Earth's atmosphere and burns up, popularly called a shooting star because it is seen as a small flash of light

Coronal Mass Ejection (CME)

a solar flare in which immense quantities of coronal material—mainly protons and electrons—is ejected at high speeds (500-1000 kilometers per second) into interplanetary space

Type 2 supernova

a stellar explosion produced at the end point of the evolution of stars whose mass exceeds roughly 10 times the mass of the Sun

Solar flare

a sudden and temporary outburst of electromagnetic radiation from an extended region of the Sun's surface

stony-iron meteorites

a type of differentiated meteorite that is a blend of nickel-iron and silicate materials

At the beginning of the solar system's history, a ready supply of proto-planets or mini-planets crashed into the developing planets and each other - something astronomers call the "era of giant impacts." How long do astronomers estimate this era lasted?

about 100 million years (0.1 billion)

Astronomers have found that the level of the Sun's activity varies over the centuries. How did they come to realize that this is so:

all of the above

Which of the following stages will our own Sun go through in the future:

all of the above

The event in the life of a star that begins its expansion into a giant is

almost all the hydrogen in its core that was hot enough for fusion has been turned into heli

Active region

an area on the Sun where magnetic fields are concentrated; sunspots, prominences, flares, and CMEs all tend to occur here

Which of the following statements about the violent events on the Sun called flares is FALSE?

astronomers think that flares are connected with sudden changes in the magnetic field of the Sun

Astronomers first detected the presence of a wind of particles coming from the Sun by

by noting the wind's effects on the tails of comets

Coronal Mass Ejections from the Sun have many serious effects on or near the Earth. Which of the following is NOT one of these effects?

causing huge cyclones around the equator of the Earth

Which part of the Sun's atmosphere has the lowest density (number of atoms per unit volume)?

corona

Which part of the Sun's atmosphere is the hottest?

corona

The ten million tons of particles that escape the Sun each year in the form of the solar wind get out mainly through regions called

coronal holes

One of the best proofs that our theory of how the solar system formed is correct is that astronomers now observe

disks around other stars which show evidence of gaps where planets may be forming

The Sun's chromosphere and corona were discovered

during total eclipses of the Sun

As a star becomes a giant, its outer layers are expanding. Where does the energy for expanding these layers come from?

from the fusion of hydrogen into helium in a shell around the core

Which of the following is not part of some active regions on the Sun?

granulation

If stars with masses like our Sun's cannot make elements heavier than oxygen, where are heavier elements like silicon produced in the universe?

heavier elements are made in the cores of significantly more massive stars than the Sun, which can get hotter in the middle

One of the most perplexing issues raised by the discovery of thousands of exoplanets is the existence of "hot Jupiters" - planets with the masses and compositions of Jupiter, but orbiting closer to their stars than Mercury does in our solar system. What is our best idea currently about how such "hot Jupiters" came to be?

hot Jupiters formed further out in their star system, and then migrated inward somehow

The most common element in the Sun is

hydrogen

A science fiction writer needs an environment for her latest story where stars are as crowded together as possible. Which of the following would be a good place to locate her story?

in a globular cluster

Some of the early planetesimals that formed the solar system still survive today. Where would you find such planetesimals?

in the asteroid and Kuiper belts

The most stable (tightly bound) atomic nucleus in the universe is:

iron

As astronomers have learned more about the structure of the Sun, they have found that it

is made entirely of hot gas

If you trace back the history of a carbon atom in your little finger through all of cosmic history, where did this atom most likely originate?

it was fused from 3 helium nuclei in the core of a red giant star long before the Sun existed

How long a main sequence star remains on the main sequence in the H-R diagram depends most strongly on

its mass

Aurora

light radiated by atoms and ions in the ionosphere excited by charged particles from the Sun, mostly seen in the magnetic polar regions

The first technique that allowed astronomers to find exoplanets involved:

measuring changes in the radial velocity (Doppler shift) of the star caused by the pull of orbiting planets

Three kinds of worlds are round in our solar system. Which of the following is NOT a type of world that is typically round?

minor planet (asteroid)

Astronomers have long realized that supernovae -- when they explode -- give off an enormous amount of light. But observations of Supernova 1987A (in the Large Magellanic Cloud) revealed that the supernova gives off even more energy in another form? That form is:

neutrinos

After it experiences a "helium flash" a star like the Sun will have a brief period of stability, fusing helium into carbon (and sometimes oxygen). During this brief stable stage, the star

none of the above

Meteor shower

occurs when many meteors appear to radiate from one point in the sky; produced when Earth passes through a cometary dust stream

Globular cluster

one of about 150 large, spherical star clusters (each with hundreds of thousands of stars) that form a system of clusters in the center of our Galaxy

You are out on the beach, enjoying the warm sunshine with friends. As you glance up at the Sun (only briefly we hope), the part of the Sun that you can see directly is called its:

photosphere

If most stars are low-mass stars, and low-mass stars typically eject a planetary nebula, why then do astronomers see relatively few planetary nebulae in the sky?

planetary nebulae expand rapidly and soon become too faint to be visible

The material inside the Sun is in the form of a

plasma

How do astronomers know that the age of the solar system is about 4.5 billion years old?

radioactive dating of the primitive meteorites indicates they have that age (since they are left-over building blocks of the solar system)

Which of the following is a way for astronomers to learn more about the interior of the Sun?

study the oscillations (pulsations) of the Sun's surface

Astronomers now believe that the differences in composition among the planets reflect what characteristic in the early solar system

temperature

Which of the following is not a characteristic that worlds in our solar system have in common:

that all the planets have solid surfaces on which we can see impact craters

One region on Earth that has become a rich source of new meteorites in recent decades (including the meteorite from Mars that got famous because some scientists claimed they had found evidence for the building blocks of life on Mars) is:

the Antarctic

As a cluster of stars begins to age, which type of star in the cluster will move off the main sequence of the H-R diagram first?

the O and B type stars

What mechanisms do astronomers believe is responsible for making the Sun's outer atmosphere so much hotter than its photosphere?

the Sun's magnetic field interacting with the charged particles that make up the atmosphere

Nucleosynthesis

the building up of heavy elements from lighter ones by nuclear fusion

Nova

the cataclysmic explosion produced in a binary system, temporarily increasing its luminosity by hundreds to thousands of times

The reason that worlds like the Earth are differentiated is that

the continuing impacts on a growing protoplanet eventually melted the entire body

Which part of the Sun has the greatest density?

the core

If we look back to the first generation of stars made when the Galaxy was first forming, how do they differ from stars being formed today?

the first generation stars contain little or no elements heavier than helium

What incident in a massive star's life sets off (begins) the very quick chain of events that leads to a supernova explosion?

the fusion of iron

Accretion

the gradual accumulation of mass, as by a planet forming from colliding particles in the solar nebula

For solid rocky worlds, a general rule is

the larger the world, the slower it cools off and the more it will keep its internal heat

How do astronomers know how strong the magnetic field of the Sun is?

the measure the Zeeman effect (the splitting of spectral lines)

The ages of stony meteorites have been measured to be roughly equal to:

the oldest ages we have measured for any bodies in the solar system

Corona

the outer (hot) atmosphere of the Sun

The Sun's photosphere is

the part of the Sun from which the light comes that we see when we look at the Sun with our eyes

Chromosphere

the part of the solar atmosphere that lies immediately above the photospheric layer

Differential rotation

the phenomenon that occurs when different parts of a rotating object rotate at different rates at different latitudes

Which of the following pieces of observational evidence does our modern "solar nebula" theory of the formation of the solar system NOT explain directly?

the plane of the orbit of Pluto

Transition region

the region in the Sun's atmosphere where the temperature rises very rapidly from the relatively low temperatures that characterize the chromosphere to the high temperatures of the corona

Photosphere

the region of the solar (or stellar) atmosphere from which continuous radiation escapes into space

Granulation

the rice-grain-like structure of the solar photosphere; produced by upwelling currents of gas that are slightly hotter, and therefore brighter, than the surrounding regions, which are flowing downward into the Sun

Sunspot cycle

the semiregular 11-year period with which the frequency of sunspots fluctuates

Astronomers call the vast, rotating cloud of vapor and dust from which the solar system formed:

the solar nebula

Helioseismology

the study of pulsations or oscillations of the Sun in order to determine the characteristics of the solar interior

When stars become giants, which of the following does NOT usually happen?

their mass grows significantly as they incorporate planets and interstellar matter near the star

Sunspots are darker than the regions of the Sun around them because

they are cooler than the material around them (although still very hot compared to Earth temperatures)

A key difference between the protoplanets that formed in the outer solar system and those that formed in the inner solar system was that

those in the outer solar system were in a place where ice, not just rock, condensed and thus could grow larger

Among solid worlds, which type of world is most likely to have significant geological activity?

those that are the largest (and retain heat the best)

In a planetary nebula, the shell of expelled material is glowing intensely. What is the main source of energy for this glow?

ultraviolet radiation from the collapsing hot star at the center

How do astronomers know what the outer layers of the Sun are made of?

we take an absorption line spectrum of the Sun, and the absorption lines tell us what elements are present in the outer layers

When a single star with a mass equal to the Sun dies, it will become a

white dwarf