Midterm 3C

Stars are mostly made of A) hydrogen and helium B) pure hydrogen C) carbon, hydrogen, oxygen and nitrogen D) an equal mixture of all elements

hydrogen and helium

When a low mass star like our Sun dies, it leaves behind a A) white dwarf B) brown dwarf C) neutron star D) black hole

white dwarf

What is the minimum possible mass for a star? A) 0.01 solar masses B) 0.008 solar masses C) 0.1 solar masses D) 0.08 solar masses

0.08 solar masses

The most distant stars we can currently measure stellar parallax for are approximately A) 5 parsecs away. B) 1,000 parsecs away. C) 10,000 parsecs away. D) halfway across the Milky Way Galaxy. E) in the Andromeda Galaxy.

1,000 parsecs away.

Which is closest to the temperature of the Sun's core? A) 10,000 K B) 100,000 K C) 1 million K D) 10 million K E) 100 million K

10 million K

You measure the parallax angle for a star to be 0.1 arcseconds. The distance to this star is A) 10 light-years. B) 10 parsecs. C) 0.1 light-year. D) 0.1 parsec. E) impossible to determine

10 parsecs.

In an extrasolar planetary system containing a single planet, the parent star is measured to move about its center of mass every 24 years. Given this, what is the orbital period of the planet? A) 48 years B) 12 years C) 24 years D) this cannot be determined from this observation

24 years

How much mass does the Sun lose through nuclear fusion per second? A) 4 tons B) 4 million tons C) 600 tons D) 600 million tons E) Nothing; mass-energy is conserved.

4 million tons

What percentage of a star's total lifetime is spent on the main sequence? A) 10% B) 20% C) 50% D) 90% E) 100%

90%

Which of the following statements about open clusters is true? A) All stars in the cluster are approximately the same color. B) All stars in the cluster are approximately the same age. C) All stars in the cluster have approximately the same mass. D) All stars in the cluster will evolve similarly. E) There is an approximately equal number of all types of stars in the cluster

All stars in the cluster are approximately the same age.

Suppose the star Betelgeuse (the upper left shoulder of Orion) were to become a supernova tomorrow (as seen here on Earth). What would it look like to the naked eye? A) Because the supernova event destroys the star, Betelgeuse would suddenly disappear from view. B) We'd see a cloud of gas expanding away from the position where Betelgeuse used to be. Over a period of a few weeks, this cloud would fill our entire sky. C) Betelgeuse would remain a dot of light but would suddenly become so bright that, for a few weeks, we'd be able to see this dot in the daytime. D) Betelgeuse would suddenly appear to grow larger in size, soon reaching the size of the full moon. It would also be about as bright as the full moon.

Betelgeuse would remain a dot of light but would suddenly become so bright that, for a few weeks, we'd be able to see this dot in the daytime

If the sun's surface cooled, how would its appearance change? A) It would appear more red. B) It would appear more blue. C) It would become bright white. D) It would stay the same

It would appear more red.

Which of the following statements about globular clusters is true? A) All stars in the cluster are approximately at the same stage in their evolution. B) Most of the stars in the cluster are younger than 10 billion years. C) Most stars in the cluster are yellow or reddish in color. D) All stars in the cluster have approximately the same mass. E) There is an approximately equal number of all types of stars in the cluster

Most stars in the cluster are yellow or reddish in color

The stellar spectral sequence, in order of decreasing temperature, is A) OFBAGKM. B) OBAGFKM. C) OBAFGKM. D) ABFGKMO. E) BAGFKMO

OBAFGKM

You see two main-sequence stars with the same spectral type. Star 1 is dimmer in apparent brightness than Star 2 by a factor of 100. What can you conclude, assuming there is no absorption of either star's light by interstellar gas or dust? A) Without first knowing the distances to these stars, you cannot draw any conclusions about how their true luminosities compare to each other. B) The luminosity of Star 1 is a factor of 100 less than the luminosity of Star 2. C) Star 1 is 100 times more distant than Star 2. D) Star 1 is 100 times nearer than Star 2. E) Star 1 is 10 times more distant than Star 2.

Star 1 is 10 times more distant than Star 2.

What observations characterize solar maximum? A) The Sun becomes much brighter. B) The Sun emits light of longer average wavelength. C) The Sun rotates faster at its poles. D) There are many sunspots visible on the surface of the Sun. E) all of the above

There are many sunspots visible on the surface of the Sun.

At the time the hypothesis was suggested, what major problem was identified with the idea that the Sun was powered by gravitational contraction? A) Contracting objects cool down rather than heat up. B) This process would power the Sun for only about 25 million years, but geologists already had evidence the Earth was much older than that. C) This process could not possibly lead to the observed power output of the Sun. D) 19th century astronomers should have been able to measure the required change in the Sun's size.

This process would power the Sun for only about 25 million years, but geologists already had evidence the Earth was much older than that.

Which of the following luminosity classes refers to stars on the main sequence? A) I B) II C) III D) IV E) V

V

What are the standard units for luminosity? A) Watts B) Joules C) Newtons D) kilograms E) Watts per second

Watts

Which of the following extrasolar planets would be easiest to detect using the Doppler shift method? A) a massive planet far from its parent star B) a low mass planet far from its parent star C) a low mass planet close to its parent star D) a massive planet close to its parent star

a massive planet close to its parent star

Which of the following extrasolar planets would be the most difficult to detect using the Doppler shift method? A) a low mass planet far from its parent star B) a massive planet close to its parent star C) a low mass planet close to its parent star D) a massive planet far from its parent star

a low mass planet far from its parent star

Compared to young stars, very old stars have A) exactly the same chemical composition B) a lower proportion of elements heavier than helium C) a higher proportion of elements heavier than helium D) no elements heavier than helium at all

a lower proportion of elements heavier than helium

When Mercury or Venus passes in front of the disk of the Sun, we call this A) an eclipse B) a shadow event C) a transit D) an occultation

a transit

What is the CNO cycle? A) the process by which helium is fused into carbon, nitrogen, and oxygen B) the process by which carbon is fused into nitrogen and oxygen C) a type of hydrogen fusion that uses carbon, nitrogen, and oxygen atoms as catalysts D) the period of a massive star's life when carbon, nitrogen, and oxygen are fusing in different shells outside the core E) the period of a low-mass star's life when it can no longer fuse carbon, nitrogen, and oxygen in its core

a type of hydrogen fusion that uses carbon, nitrogen, and oxygen atoms as catalysts

Which of the following statements about spectral types of stars is true? A) The spectral type of a star can be used to determine its surface temperature. B) The spectral type of a star can be used to determine its color. C) A star with spectral type A is cooler than a star with spectral type B. D) A star with spectral type F2 is hotter than a star with spectral type F3. E) All of the above are true

all of the above are true

Which of the following is the most numerous type of main-sequence star? A) an O star B) an A star C) an F star D) a G star E) an M star

an M star

The wavelengths of radiation from a star that is moving away from us A) can be longer or shorter depending on the distance to the star B) are shorter than if the star were not moving C) are the same as if the star were not moving D) are longer than if the star were not moving

are longer than if the star were not moving

The wavelengths of radiation from a star that is moving toward us A) can be longer or shorter depending on the distance to the star B) are shorter than if the star were not moving C) are longer than if the star were not moving D) are the same as if the star were not moving

are shorter than if the star were not moving

The wavelengths of radiation from a star that is moving perpendicular to us A) can be longer or shorter depending on the distance to the star B) are shorter than if the star were not moving C) are longer than if the star were not moving D) are the same as if the star were not moving

are the same as if the star were not moving

Why does the Doppler shift method of detecting extrasolar planets only give us the minimum mass of a planet? A) because we don't necessarily know the density of the planet B) because we don't necessarily know the angle the planet's orbit makes with our line of sight C) because we don't necessarily know the diameter (size) of the planet D) because we don't necessarily know the mass of the parent star very

because we don't necessarily know the angle the planet's orbit makes with our line of sight

On the main sequence, stars obtain their energy A) from chemical reactions. B) from gravitational contraction. C) by converting hydrogen to helium. D) by converting helium to carbon, nitrogen, and oxygen. E) from nuclear fission.

by converting hydrogen to helium.

The center of mass of the solar system is A) midway between the Sun and Jupiter B) exactly at the center of the Sun C) just outside the orbit of Mercury D) close to but not exactly at the center of the Sun

close to but not exactly at the center of the Sun

In most extrasolar planetary systems the center of mass is likely to be located A) midway between the star and its most massive planet B) close to the center of the parent star C) exactly at the center of the parent star D) close to the center of the most massive planet

close to the center of the parent star

Compared to the star it evolved from, a red giant is A) hotter and brighter. B) hotter and dimmer. C) cooler and brighter. D) cooler and dimmer. E) the same temperature and brightness

cooler and brighter.

Which of the following methods has been the MOST successful in detecting extrasolar planets around other star systems? A) regular changes in the positions of the parent stars with respect to more distant stars as they move across the sky B) detection of brightness changes in a star as a planet passes in front of it C) detection of Doppler shifts in the spectra of the parent stars D) detection of reflected starlight

detection of brightness changes in a star as a planet passes in front of it

The age of stars in a cluster can be determined by A) fitting the position of the main sequence to the Sun. B) determining the main sequence turnoff point. C) finding pulsating variable stars in the cluster. D) finding spectroscopic binaries in the cluster. E) counting the number of stars in each spectral class

determining the main sequence turnoff point.

Solar-type stars in our galaxy are A) very common, making up about 50% of the total B) very rare (less than 1%) C) fairly common (several percent) D) the most common type of stars in our galaxy (75% or more)

fairly common (several percent)

Stars spend most of their lives A) fusing hydrogen into helium in their cores B) slowly dimming as they die with no fusion occurring in their cores C) as slowly brightening protostars D) fusing helium into carbon in their cores

fusing hydrogen into helium in their cores

At the center of the Sun, nuclear fusion converts hydrogen into A) hydrogen compounds such as methane. B) molecular hydrogen. C) radiation and elements such as carbon and nitrogen. D) radioactive elements such as uranium and plutonium. E) helium, gamma rays, and neutrinos.

helium, gamma rays, and neutrinos.

Which element has the lowest mass per nuclear particle and therefore cannot release energy by either fusion or fission? A) hydrogen B) oxygen C) silicon D) iron

iron

When a star finally runs out of hydrogen to fuse in its central core A) it grows smaller and dimmer, becoming a brown dwarf B) it grows larger and brighter, becoming a giant or supergiant star C) it grows smaller and dimmer becoming a white dwarf D) it remains the same size but grows brighter

it grows larger and brighter, becoming a giant or supergiant star

On a Hertzsprung-Russell diagram, where would you find white dwarfs? A) upper right B) lower right C) upper left D) lower left

lower left

On a Hertzsprung-Russell diagram, where would you find stars that are cool and dim? A) upper right B) lower right C) upper left D) lower left

lower right

If a star has an extrasolar planet, the amplitude of its radial velocity curve is related to the planet's A) mass B) orbital shape C) orbital period D) radius

mass

The core of the Sun is A) at the same temperature and density as its surface. B) at the same temperature but much denser than its surface. C) much hotter and much denser than its surface. D) constantly rising to the surface through convection. E) composed of iron.

much hotter and much denser than its surface.

When high-mass stars dies, they explode as supernovae, leaving behind a A) white dwarf B) neutron star or black hole C) brown dwarf D) red dwarf

neutron star or black hole

Brown dwarfs have A) very narrow habitable zones B) no habitable zones C) very wide habitable zones D) habitable zones similar to the Sun

no habitable zones

By what process does the Sun generate energy? A) nuclear fission B) nuclear fusion C) chemical reactions D) gravitational contraction E) gradual expansion

nuclear fusion

Brown dwarfs are A) stars in the process of forming B) very cool, low mass stars of spectral type M C) the burnt out cores of dead stars D) objects with insufficient mass to sustain nuclear fusion in their cores

objects with insufficient mass to sustain nuclear fusion in their cores

For the transit of an extrasolar planet to be observed, the A) orbital plane of the planet has to be aligned along our line of sight B) planet has to be very large C) orbital plane has to be perpendicular to our line of sight D) parent star has to be very small

orbital plane of the planet has to be aligned along our line of sight

What keeps the Sun's outer layers from continuing to fall inward in a gravitational collapse? A) outward pressure due to super-heated gas B) the strong force between protons C) electromagnetic repulsion between protons D) neutrinos produced by nuclear fusion drag gas outward

outward pressure due to super-heated gas

Which of the following is the phase of matter in the Sun? A) gas B) plasma C) liquid D) solid E) a mixture of all of the above

plasma

Which of the following sequences correctly describes the stages of life for a low-mass star? A) red giant, protostar, main-sequence, white dwarf B) white dwarf, main-sequence, red giant, protostar C) protostar, red giant, main-sequence, white dwarf D) protostar, main-sequence, white dwarf, red giant E) protostar, main-sequence, red giant, white dwarf

protostar, main-sequence, red giant, white dwarf

Which of the following methods has been the LEAST successful in detecting extrasolar planets around other star systems? A) regular changes in the positions of the parent stars with respect to more distant stars as they move across the sky B) detection of Doppler shifts in the spectra of the parent stars C) detection of brightness changes in a star as a planet passes in front of it D) detection of reflected starlight

regular changes in the positions of the parent stars with respect to more distant stars as they move across the sky

If the distance between us and a star is doubled, with everything else remaining the same, its luminosity A) is decreased by a factor of four, and its apparent brightness is decreased by a factor of four. B) is decreased by a factor of two, and its apparent brightness is decreased by a factor of two. C) remains the same, but its apparent brightness is decreased by a factor of two. D) remains the same, but its apparent brightness is decreased by a factor of four. E) is decreased by a factor of four, but its apparent brightness remains the same.

remains the same, but its apparent brightness is decreased by a factor of four.

What types of stars end their lives with supernovae? A) all stars that are red in color B) all stars that are yellow in color C) stars that are at least several times the mass of the Sun D) stars that are similar in mass to the Sun E) stars that have reached an age of 10 billion years

stars that are at least several times the mass of the Sun

Sunspots are cooler than the surrounding gas in the photosphere because A) they are regions where convection carries cooler material downward. B) strong magnetic fields slow convection and prevent hot plasma from entering the region. C) magnetic fields trap ionized gases that absorb light. D) there is less fusion occurring there. E) magnetic fields lift material from the sunspot and quickly cool the material.

strong magnetic fields slow convection and prevent hot plasma from entering the region

The color of a star is a measure of its A) surface temperature B) chemical composition C) mass D) size

surface temperature

The spectral sequence sorts stars according to A) mass. B) surface temperature. C) luminosity. D) core temperature. E) radius.

surface temperature

Which of the following best describes the axes of a Hertzsprung-Russell (H-R) diagram? A) surface temperature on the horizontal axis and luminosity on the vertical axis B) mass on the horizontal axis and luminosity on the vertical axis C) surface temperature on the horizontal axis and radius on the vertical axis D) mass on the horizontal axis and stellar age on the vertical axis E) interior temperature on the horizontal axis and mass on the vertical axis

surface temperature on the horizontal axis and luminosity on the vertical axis

What did Carl Sagan mean when he said that we are all "star stuff"? A) that life would be impossible without energy from the Sun B) that the Earth formed at the same time as the Sun C) that the carbon, oxygen, and other elements essential to life were created by nucleosynthesis in stellar cores D) that the Sun formed from the interstellar medium: the "stuff" between the stars E) that the universe contains billions of stars

that the carbon, oxygen, and other elements essential to life were created by nucleosynthesis in stellar cores

How can we explain the presence of extrasolar planetary systems with Jovian-sized planets at distances at which we normally find terrestrial planets? A) they are brown dwarfs that were captured by their parent stars B) these are massive terrestrial planets that formed close to their parent stars C) they are Jovian planets that were spun out from their rapidly spinning parent stars D) the Jovian planets formed farther out and then migrated inward

the Jovian planets formed farther out and then migrated inward

One of the fundamental principles of stellar evolution is that the more massive a star is A) the more heavy elements it contains B) the more planets it has around it C) the faster it evolves D) the slower it evolves

the faster it evolves

The presence of elements heavier than helium in stars is very important because A) they provide the raw materials for the formation of planets and life B) without them they could not form C) they help stabilize their interiors D) they are responsible for the fusion reactions at their centers

they provide the raw materials for the formation of planets and life

A star's luminosity is the A) apparent brightness of the star in our sky. B) surface temperature of the star. C) lifetime of the star. D) total amount of energy that the star will radiate over its entire lifetime. E) total amount of energy that the star radiates each second.

total amount of energy that the star radiates each second.

Stars only exhibit a Doppler shift if they are moving A) away from us along the line of sight B) perpendicular to our line of sight C) in a circular motion about us D) toward or away from us along the line of sight

toward or away from us along the line of sight

Which method of extrasolar planet detection is able to measure the compositions of extrasolar planet atmospheres? A) gravitational lensing B) Doppler technique C) transit technique D) astrometric technique

transit technique

High mass stars are much less common than low mass stars because they A) are born in much smaller numbers B) have much shorter lifetimes C) have much longer lifetimes D) two of these

two of these

On a Hertzsprung-Russell diagram, where on the main sequence would you find stars that have the greatest mass? A) upper right B) lower right C) upper left D) lower left

upper left

26) On a Hertzsprung-Russell diagram, where would you find stars that have the largest radii? A) upper right B) lower right C) upper left D) lower left

upper right

On a Hertzsprung-Russell diagram, where would you find red giant stars? A) upper right B) lower right C) upper left D) lower left

upper right

On a Hertzsprung-Russell diagram, where would you find stars that are cool and luminous? A) upper right B) lower right C) upper left D) lower left

upper right

Based on its surface temperature of 6,000 K, most photons that leave the Sun's surface lie in which region of the electromagnetic spectrum? A) microwave B) infrared C) visible D) ultraviolet E) X-ray

visible

Which of the following terms is given to a pair of stars that appear to change position in the sky, indicating that they are orbiting one another? A) visual binary B) eclipsing binary C) spectroscopic binary D) double star E) none of the above

visual binary

A star less massive than our Sun A) will have a longer lifetime B) will have a shorter lifetime C) will have the same lifetime as the Sun D) could have either a longer lifetime or a shorter lifetime depending on its chemical composition

will have a longer lifetime

A star more massive than our Sun A) will have a longer lifetime B) will have a shorter lifetime C) will have the same lifetime as the Sun D) could have either a longer lifetime or a shorter lifetime depending on its chemical composition

will have a shorter lifetime