astr test 2

Which star has the highest surface temperature?

Spectral type B is the hottest

globular cluster

a large compact spherical star cluster, typically of old stars in the outer regions of a galaxy. found in the halo

luminosity class

Stars are classified on the basis of their spectral type and luminosity class

main-sequence lifetime

The main-sequence lifetimeis greater for low-mass stars than it is for high-mass stars.

brown dwarf

an object not quite massive enough to be a star

Red giant or supergiant stars

very cool but very luminous, found in the upper right of the H-R diagram

When does a newly forming star have the greatest luminosity?

when it is a shrinking protostar with no internal fusion

Choose the correct description of processes, which cause a white dwarf supernova.

white dwarf supernova occurs when the white dwarf gains enough mass for the carbon interior of the star to begin carbon fusion. The fusion begins almost instantly throughout the star, so the entire star ignites and the white dwarf explodes completely.

Which kind of these objects do you think is most common in our galaxy? why

white dwarfs, low mass stars are more common than high mass stars

Prostar

A contracting cloud of gas and dust with enough mass to form a star

Space and Time

Absolutes of relativity As velocity approaches c, time slows, length contracts and mass increases. If you observe something moving near light speed: Its time slows down. Its length contracts in direction of motion. Its mass increases. Whether or not two events are simultaneous depends on your perspective.

What is a red supergiant

Spectral type M, luminosity class I

Which star is the brightest?

The one with the most negative apparent magnitude

What is a white dwarf?

White dwarfs with same mass as Sun are about same size as Earth. Higher-mass white dwarfs are smaller.

Describe the 2 life stages a high-mass star goes thru that a low-mass star does not. Include the 2 possible resulting objects.

(1)High-mass stars go thru more stages of core contraction & shell burning until the core is made of iron. (2) Iron cannot produce energy thru fusion, so the core collapses until degeneracy pressure is overcome by gravity. Electrons combine with protons forming neutrons and releasing energy resulting in a supernova explosion. The core is a neutron star or a black hole, if the mass is large enough.<br>

Accretion Disks

Mass falling toward a white dwarf from its close binary companion has some angular momentum. The matter therefore orbits the white dwarf in an accretion disk.

white dwarfs

White dwarfsare no longer generating energy through nuclear fusion.

Supernova:

complete explosion of white dwarf, nothing left behind

Which of these colors of light passes most easily through interstellar clouds?

red light

What is a black hole?

A black hole is a massive object whose radius is so small that the escape velocity exceeds the speed of light.

How does a star's mass determine its life story?

Mass determines how high a star's core temperature can rise and therefore determines how quickly a star uses its fuel and what kinds of elements it can make.

Choose the correct explanation, why can the lives of close binary stars differ from those of single stars.

Mass exchange between two stars in a close binary system causes some stars with companions to change their masses throughout their lives, altering the life tracks in ways that do not affect single stars.

: Spacetime and Gravity

Mass warps spacetime, causing gravity

What can happen to a neutron star in a close binary system?

Matter falling toward a neutron star forms an accretion disk, just as in a white dwarf binary. Accreting matter adds angular momentum to a neutron star, increasing its spin

What can happen to a white dwarf in a close binary system?

Matter from its close binary companion can fall onto the white dwarf through an accretion disk. Accretion of matter can lead to novae and white dwarf supernovae.

What is the key observation needed to determine whether the compact object in Part C is a neutron star or a black hole?

Measure Doppler shifts in the spectrum of the main-sequence star so that you can determine the mass of the compact object.

What 2 characteristics of molecular clouds make them ideal for star formation?

Molecular clouds are favorable locations for star formation for two reasons: low temperature and high density. Their low temperature keeps their pressures about the same as other interstellar clouds, despite the higher density. But the higher density means that gravity is stronger in molecular clouds, so it is able to overcome the pressure in molecular clouds. This increased gravitational attraction allows collapse, leading to star formation.

Which star has the greatest luminosity?

Most negative absolute magnitude

main sequence star

Most of the stars near the Sun are main-sequence stars.

Explain how mass determines the lifespan of a star.

Smaller stars have longer lifetimes than larger stars. This is because the larger stars are much more luminous than the smaller ones. While the larger stars have more fuel to use up, their luminosities are so great that they consume their fuel supply faster and end their main-sequence lives sooner. If stellar luminosities were simply proportional to stars' masses, all stars would have the same lifetimes. But massive stars are much more luminous compared to their mass than are low-mass stars.

Do black holes really exist?

Some X-ray binaries contain compact objects too massive to be neutron stars—they are almost certainly black holes.

What do we mean by a star's spectral type, and how is spectral type related to surface temperature and color.

Spectral types are a way of classifying stars according to their color or what spectral lines we see in their light. The spectral types run OBAFGKM, where O stars are the hottest and M are the coolest. Hotter stars look bluer to us, and cooler stars look redder.

If stars A and B are both main-sequence stars and star A has a greater fusion rate than star B, which of the following statements hold(s)?

Star A must be more luminous than star B.Star A must be more massive than star B.

Why is mass the primary influence on star's life? What are the 3 mass groups?

Star mass is important because it determines how fast fusion will occur in its core and, as a result, how long it will reside on the main sequence. We categorize stars by mass into three groups: low-mass stars (less than 2 solar masses), intermediate-mass stars (between 2 and 8 solar masses), and high-mass stars (above 8 solar masses).

visual binary

Stars can be distinguished using a telescope

Under what conditions would a single star form?

Stars can form indepentently, but the cloud must be very cold and dense.

Why do stars tend to form in clusters?

Stars tend to form in clusters because more massive clouds are better able to overcome pressure and collapse.

giants

Stars that are cooler than the Sun yet 100 to 1,000 times as luminous as the Sun are classified as giants.

How are the lives of stars with close companions different?

Stars with close companions can exchange mass, altering the usual life stories of stars.

What is stellar parallax? How is it used to find the luminosity of the star?

Stellar parallax is the tiny movement of stars in our sky due to Earth's motion around the Sun. Since more distant stars show smaller parallaxes than closer ones, we can measure the amount that stars move over 6 months (half of an Earth orbit) and find the distance to the stars. Once we know this, we can use the apparent brightness of the star along with the inverse square law for light to determine the star's luminosity.

Nova or Supernova?

Supernovae are MUCH MUCH more luminous (about 10 thousand times)!!!

Describe how helium is produced in the Sun's core. What is this 3-step process called?

The Sun's overall nuclear reaction is to combine four protons to form a single helium nucleus. The actual process, called the proton-proton chain, requires three steps. In the first, two protons collide to form an isotope of hydrogen called deuterium. (This is done twice for each reaction.) In the second step, a deuterium nucleus is struck by a proton to become helium-3. (This step also occurs twice per reaction.) Finally, when two helium-3 nuclei collide, the formed helium-4 and two protons are released.

Einstein based his theories of relativity on what two absolutes?

The absolutes in the universe, according to special relativity, are that the laws of nature are the same for everyone and that the speed of light is constant for everyone.

absolute magnitude

The actual brightness of a star

What happens when black hole merge?

They should produce gravitational waves that we may be able to detect in the near future.

Astronomers have been able to discover several black holes by looking for black circles in the sky.

This statement is not sensible because a black hole will appear the same as empty space. The only way to detect a black hole is by its interaction with another object or a background light source.

Neutrinos

a type of fundamental particle that has extremely low mass and responds only to the weak force

What would you be most likely to find if you returned to the solar system in 10.0 billion years?

a white dwarf

Compared to a low-luminosity main-sequence star, stars in the lower left of the H-R diagram are __________.

hotter and smaller in radius

Which kinds of stars are most common in a newly formed star cluster?

m stars

highest to lowest temp

main sequence star, prostar, contracting cloud, molecular cloud

brighter and hotter stars have

shorter lifetimes

Stellar Parralax

small annual shifts in a stars apparent position caused by Earths motion around the sun, more distant stars have smaller parralax angles. Parallax was the first technique astronomers developed for measuring distance to stars.

he more distant a star, the __________.

smaller its parallax angle

molecular clouds

solid grains of interstellar dust prevent visible light from passing through.

main-sequence phase

surface radiates energy at same rate that core generates energyenergy generated by nuclear fusionlasts about 10 billion years

Before we can use parallax to measure the distance to a nearby star, we first need to know __________

the Earth-Sun distance

Sunspot cycle

the average number of sunspots on the sun gradually rises and falls, at solar maximum sunspots are more numerous.

gravitational equilibrium

the balance between pressure and gravity.

proton-proton chain

the chain of reactions by which low-mass stars (including the Sun) fuse hydrogen into helium

Spacetime is

the combination of time and the three dimensions of space.

main-sequence lifetime

the length of time for which a star of a particular mass can shine by fusing hydrogen into helium in its core

event horizon

the location around a black hole where the escape velovity equals the speed of light; the boundary of a black hole

main sequence turnoff point

the point on the hr diagram at which a clusters stars diverge from the main sequence. The age of the cluster is equal to the lifetimes of stars at its main sequence turnoff point

during the late phases of star formation..

the prospers luminosity declines and its surface temp increases

Which of the following is not relative in the special theory of relativity?

the speed of light

what is the smallest mass a newborn star can have

0.08m sun because its temp won't be high enough to sustain fusion below this.

Describe what happens to the core and outer layers during each of the 4 stages after a low-mass star leaves the main sequence.

1) The core shrinks heating the outer layers to the point where hydrogen fuses in a shell causing the outer layers to expand. (2) Eventually, the core expands because it reaches the temperature necessary for helium to fuse into carbon, and the fusion in the shell slows and outer layers shrink. (3) When core helium is gone, core contracts again, but now 2 layers of shell burning form (hydrogen & helium) resulting in expansion. (4) Degeneracy stops the contraction of the core andthe outer layers are "blown" out resulting in a planetary nebula, with the core becoming a white dwarf.<br>

our sun has a lifetime of

10 billion years

what is the greatest mass a newborn star can have?

100 solar masses

What is a neutrino? By counting solar neutrinos, what were astronomers trying to test? Why did the first test fail?

A neutrino is a subatomic particle with an extremely small mass. By counting solar neutrinos astronomers coluld study fusion in the suns core and they were trying to test if solar neutrinos are responsible for the suns energy. The first test failed because the number that they expected to get was much higher than what they actually found, this was because old detectors could not detect all three types of neutrinos.

What 2 conditions need to be present in order for a nova to be possible? What causes the explosion and where does it occur?

A nova is only possible in close binary star systems where one of the stars is a white dwarf. The white dwarf steals material from its companion forming a on its surface. As the hydrogen builds up on the surface, the pressure and temperature rise, and eventually hydrogen fusion becomes possible, resulting in an explosion.

In your own words, describe the formation of a planetary nebula? After a planetary nebula fades away, what is left behind?

A planetary nebula is a glowing shell of gas that was once the outer layers of a star. The gas glows because the hot core's ultraviolet light ionizes the gas. The core, now exposed, will cool with time and become a white dwarf.

How is a protostar different from a star? During the protostar phase, is what is happening to the total amount of mass? What is happening in the core?

A protostar is not producing energy in its core by nuclear fusion only stars create energy thru nuclear fusion. During the protostar phase, its mass continues to increase, but more slowly than when it initially began forming. The core heats up and increases the pressure outward because the thermal energy (photons) has become trapped due to the high density of the core.

Pulsars

A pulsar is a neutron star that beams radiation along a magnetic axis that is not aligned with the rotation axis

white dwarf

A small, hot, dim star that is the leftover center of an old star

How does a star's mass affect nuclear fusion?

A star's mass determines its core pressure and temperature and therefore determines its fusion rate. Higher mass stars have hotter cores, faster fusion rates, greater luminosities, and shorter lifetimes

What is the approximate mass of a white dwarf and a neutron star?

A typical white dwarf is about 1 solar mass. A neutron star has a mass of about 1.5-3 solar masses.

pulsating variable star

A variable star that goes through periods of swelling and brightening, then shrinking and dimming and experiences a change in magnitude during that cycle.

What is the aprroximate diameter of a whtie dwarf and a neutron star?

A white dwarf has approximately the same diameter as the Earth. A neutron star has approximately the same diameter as an average city.

What is a white dwarf

A white dwarf is the inert core of a dead star. Electron degeneracy pressure balances the inward pull of gravity.

stars

Cepheids are examples of pulsating variable stars.

Among the main-sequence stars listed, which one has the longest lifetime?

Alpha Centauri A, with spectral type G2, is the coolest and therefore the longest-lived main-sequence star in the table.

Red Giants: Broken Thermostat

As the core contracts, H begins fusing to He in a shell around the core. Luminosity increases because the core thermostat is broken - the increasing fusion rate in the shell does not stop the core from contracting.

Why would you not survive your trip into the black hole?

As we got very close to a black hole, the tidal forces would stretch us out and eventually tear us apart, if the extreme radiation environment did not kill us first.

When you look at your watch, how will your time appear to be moving? (falling int a black hole)

At the same rate it was moving before I started my trip.

How were neutron stars discovered?

Beams of radiation from a rotating neutron star sweep through space like lighthouse beams, making them appear to pulse. Observations of these pulses were the first evidence for neutron stars.

What do apparent magnitude & absolute magnitude have in common? Which is directly related to apparent brightness? luminosity?

Both are a measure of how bright a star is, where dimmer stars have a higher, more positive magnitude and brighter stars have a lower, more negative magnitude. Apparent magnitude is related to apparent brightness as it is how bright the star appears from Earth. Absolute magnitude is related to luminosity as it is how bright the star would appear if it were 10 pc away, thus eliminating the effect of distance on brightness.

Gamma-Ray Bursts

Brief bursts of gamma rays coming from space were first detected in the 1960s. Observations show that at least some gamma-ray bursts are produced by supernova explosions. Others may come from collisions between neutron stars. Most gamma-ray bursts come from distant galaxies. They must be among the most powerful explosions in the universe, probably signifying the formation of black holes. At least some gamma-ray bursts come from supernova explosions.

The life tracks shown on the diagram for different mass protostars are based on computer models. Observationally, how can astronomers test whether these models are correct?

By observing and comparing protostars and stars of different masses within a single star cluster.

White dwarf supernova

Can only occur in a binary systemSpectra always lack strong hydrogen lines.Can occur in a very old star clusterStar explodes completely, leaving no compact object behind.Has a brighter peak luminosity

Massive star supernova

Can only occur in a galaxy with ongoing star formationBlack hole or neutron star left behind

Structure of the Sun

Core, radiative zone, convection zone, photosphere, chromosphere, transition zone and corona

Describe how degeneracy pressure prevents a brown dwarf from collapsing and becoming a star. Will this still work when it becomes very cold?

Degeneracy pressure is a quantum mechanical effect that halts the contraction of protostars with masses less than 0.08 solar mass. Unlike thermal pressure, degeneracy pressure depends only on the density and not on the temperature. Since the degeneracy pressure does not weaken as the core cools, it will continue to support a core even when the core becomes cold.

Why are white dwarfs and neutron stars dependent on degeneracy pressure? What particle supplies degeneracy pressure in white dwarfs? neutron stars?

Degeneracy pressure is important to neutron stars and white dwarfs because it is what allows them to resist the pull of gravity. In the case of white dwarfs, the degeneracy pressure is provided by electrons, so that version is called "electron degeneracy pressure." For neutron stars, it is the neutrons that provide the pressure and this version of degeneracy pressure is therefore called "neutron degeneracy pressure."

What is the cause of stellar parallax?

Earth's orbit around the sun

How does a low-mass star die?

Ejection of hydrogen and helium in a planetary nebula leaves behind an inert white dwarf.

We should wear sunscreen so that our skin is not damaged by solar neutrinos.

False,Neutrinos pass right through Earth and everything else without damaging any life, and would not be blocked by a sunscreen

Open clusters are:

Found in the disk of the galaxy, and contain young stars

What is the suns spectral type?

G2V

What made the suns core hot enough to sustain nuclear fusion

Gravitational contraction

Nova:

H to He fusion of a layer of accreted matter, white dwarf left intact The nova star system temporarily appears much brighter. The explosion drives accreted matter out into space.

HR diagram

Hertz sprung-Russell diagram, a graph that shows the relationship between magnitudes and temperature. stellar masses decrease downward along the main sequence

How do high-mass stars make the elements necessary for life?

Higher masses produce higher core temperatures that enable fusion of heavier elements.

What are the life stages of a low-mass star?

Hydrogen fusion in core (main sequence) Hydrogen fusion in shell around contracting core (red giant) Helium fusion in core (horizontal branch) Double shell burning (red giant)

What is a neutron star?

It is a ball of neutrons left over from a massive star supernova and supported by neutron degeneracy pressure.

How does a high-mass star die?

Its iron core collapses, leading to a supernova

Watch the red dot representing the protostar in the video. After it reaches its highest point on the diagram, how do the protostar's surface temperature and luminosity change as it approaches the main sequence?

Its surface temperature increases, but its luminosity decreases.

How do the properties of long-lived stars compare to those of short-lived stars?

Long-lived stars begin their lives with less mass and a smaller amount of hydrogen fuel.Long-lived stars are less luminous during their main-sequence lives.

Choose the correct statement explaining what do we mean by a star's luminosity class and how we classify stars by spectral type and luminosity class.

Luminosity classes of stars are designated by Roman numerals and tell us what region of the H-R diagram the star falls in. The spectral type tells us the stars temperature while the luminosity class tells us its radius.

spectral sequence

O B A F G K M, hottest to coolest. the larger the number the cooler the star

Life Track after Main Sequence

Observations of star clusters show that a star becomes larger, redder, and more luminous after its time on the main sequence is over

Explain what is meant by the "random walk" of a photon.

Photons take hundreds of thousands of years to get out of the Sun because their paths zigzag repeatedly. Because the plasma is so dense in the Sun's interior, photons can only travel a fraction of a millimeter before "colliding" with an electron and deflecting into a new direction. So photons bounce around at random and only slowly make their way

The White Dwarf Limit

Quantum mechanics says that electrons must move faster as they are squeezed into a very small space. As a white dwarf's mass approaches 1.4MSun, its electrons must move at nearly the speed of light. Because nothing can move faster than light, a white dwarf cannot be more massive than 1.4MSun, the white dwarf limit (or Chandrasekhar limit).

When a star has used up all of the hydrogen in its core, it contracts but the rest of the star expands. Why?

The core of a red giant contracts because there is no more hydrogen fusion to heat the core and raise thermal pressure to resist gravity. However, the shell of hydrogen outside the core heats up to very high temperatures (hotter than the core during the main-sequence phase), and hydrogen fusion is occurring quickly. The star as a whole expands because the energy transport cannot keep up with the shell's increasing energy generation rate, so the thermal energy is trapped in the star and builds up, pushing the surface outward.

What is the defining process of a main-sequence star? How does this determine the luminosity of high-mass stars vs. low-mass stars?

The defining process of a main-sequence star, all stars along aspecific line on the H-R diagram, are fusing hydrogen into helium in their cores, and so it follows a particular relationship between luminosity and surface temperature. This relationship occurs because the more luminous stars have larger masses and therefore have higher rates of fusion in their cores. Because of the particular relationship between luminosity and radius along the main sequence, the more massive stars must also be much hotter than the less massive ones in order to emit their energy from their surfaces. (Hotter surfaces emit more light per unit area.)

How are the event horizon and Schwarzschild radius related? What basic property of a black hole determines the Schwarzschild radius?

The event horizon is the boundary between the inside of the black hole and the outside universe. The radius of the event horizon is called the "Schwarzschild radius" determined by the black hole's mass.

The Chandra X-Ray Observatory has detected X rays from a star system that contains a main-sequence star of spectral type B6. The X-ray emission is strong and fairly steady, and no sudden bursts have been observed. Which of the following statements are reasonable conclusions about this system?

The main-sequence star orbits either a neutron star or a black hole.Gas from the main-sequence star makes an accretion disk around another object.

Stellar Mass and Fusion

The mass of a main-sequence star determines its core pressure and temperature. Stars of higher mass have higher core temperature and more rapid fusion, making those stars both more luminous and shorter-lived.

What is the least amount of mass a star can have? Why is this a lower limit for star mass?

The minimum mass for a star is 0.08 solar mass. Below this mass, degeneracy pressure halts the collapse of the core before it gets hot enough to start fusion.<br>A brown dwarf is an object in which the degeneracy pressure halted the collapse of the protostar before fusion began, making it a "failed star."

Why are the very first stars thought to have been much more massive than the Sun?

The temperatures of the clouds that made them were higher because they consisted entirely of hydrogen and helium.

spectral lines

The wavelengths where a specific element can absorb or emit light, can be a way to measure surface temp.

Why are neutron stars the only possible object that can be a pulsar? Are all neutron stars seen as pulsars? Explain.

We know that pulsars are neutron stars because we have found pulsars at the centers of supernova remnants, right where we expect to see neutron stars. We are also confident that pulsars are neutron stars because we know of no other objects that could spin as fast as pulsars must. Not all neutron stars can be seen as pulsars. Older neutron stars have lost so much of their magnetic fields and their spins have slowed so much that we would not see pulses. Even a young neutron star would not necessarily be a pulsar: If the beam of radio waves was not oriented to sweep over the Earth, we would not see a pulsar even though some other planet might.

What causes a supernova to occur? What happens during the explosion that causes a neutron star to form? Under what condition would a black hole form instead?

When high-mass stars reach the stage of iron cores, degeneracy pressure will briefly support the core against collapse. However, this situation cannot last as gravity pushes the electrons past the limits and degeneracy pressure fails. In a fraction of a second, the iron core shrinks from the size of the Earth to a ball a few kilometers across. The contraction is halted by neutron degeneracy pressure. The contraction releases an enormous amount of energy that blows the outer layers away from the star in a supernova explosion. After the supernova, the core is left exposed. If the neutron degeneracy pressure is strong enough to resist gravity, a neutron star is left over. However, if even the neutron degeneracy pressure is insufficient to resist gravity, the core collapses a the black hole.

Why does the sun shine

With energy generated by fusion of hydrogen into helium in the suns core

What would it be like to visit a black hole?

You can orbit a black hole like any other object of the same mass—black holes don't suck! Near the event horizon, time slows down and tidal forces are very strong.

you observe people moving by you at very high speed, you will say that their time runs slowly, their lengths are contracted in the direction of motion, and their masses are increased from their rest masses. What will they say about you?

Your time runs slowly, your length is contracted in the direction of motion, and your mass is increased from your rest mass.

What slows the contraction of a star-forming cloud?

a contracting cloud begins its transformation into a star when its core starts trapping the thermal energy released b gravitational contraction. as pressure begins to push back harder, the contaction slows down and the central part of the cloud becomes a prostar.

main sequence

a diagonal area on an H-R diagram that includes more than 90 percent of all stars, they are all fusing hydrogen into helium in their cores.

why do stars form

a star can form in a molecular cloud only when gravity is strong enough to overcome the outward push of thermal pressure.

eclipsing binary

a star system in which one star periodically blocks the light from another

What do we need to measure in order to determine a star's luminosity?

apparent brightness and distance

sunspot cycle

average number of spots varies with a period of 11 years

why do stars tend to form in clusters

because gravity can more easily overcome pressure in more massive molecular clouds.

Giants and Supergiants

bright, cool stars in the upper right corner of the h-r diagram, cooler and more luminous than the sun, larger in radius than the sun.

how do we measure a star clusters age

by plotting its stars on an hr diagram and determining the hydrogen fusion lifetime of the brightest and most massive stars still on the main sequence

Neutron star

can have a mass of 1.5 solar massesmay be in a binary system that undergoes X-ray burstsmay be surrounded by a supernova remnantmay repeatedly dim and brighten more than once per second

Among the main-sequence stars listed, which one is the most massive?

chernar is the most massive of the main-sequence stars listed because it has the hottest spectral type of the main-sequence stars; thus, it appears higher on the main sequence of an H-R diagram, where masses are larger.

life stages of a star with the same mass as the sun

contracting cloud of gas and dust, prostar, main sequence g star, red giant, planetary nebula, white dwarf

Compared to a high-luminosity main-sequence star, stars in the upper right of the H-R diagram are __________.

cooler and larger in radius

coronal mass ejection

coronal gas that is thrown into space from the sun, they are highly energetic charged particles from the corona, leads to auroras on earth.

What would happen to the Earth if the Sun suddenly shrunk in size and became a black hole?.

earth would remain in the same orbit

protostar phase

energy generated by gravitational contractionradius much larger than the Sunpressure and gravity are not precisely balancedluminosity much greater than the Sun

conservation of angular momentum

ensures that a young prostar spins rapidly, and much of the material falling inward toward a prostar ends up in a spinning prostellar disk.

Relativity is "only a theory," and we have no way to know whether any of its predictions would really occur at speeds close to the speed of light.

false because This statement is false. We have tested relativity at high speeds for subatomic particles in particle accelerators.

When a newly forming star is at its greatest luminosity, what is its energy source?

gravitational contraction

low mass stars

he Sun is an exampleend life as a planetary nebulahave longer lifetimesfinal corpse is a white dwarf

Main-sequence stars

he majority of stars in our galaxythe Sun, for examplethe hottest and most luminous stars

supergiants

he stars known as supergiantsare the very largest and brightest of all the stars.

For someone watching you fall into the black hole, how will they see your time moving?

he time will be moving slower than before I started my trip.

Provided following are various elements that can be produced during fusion in the core of a high mass main sequence star. Rank these elements based on when they are produced, from first to last.

helium, carbon, oxygen, iron

At the center of the Sun, fusion converts hydrogen into

helium, energy, and neutrinos.

As a clump of interstellar gas contracts to become a main-sequence star, its changing position on the H-R diagram tells us __________.

how its outward appearance is changing

spectroscopic binary

identified through observations of Doppler shifts in its spectral lines

high mass stars

late in life fuse carbon into heavier elementshave higher fusion rate during main sequence lifeend life as a supernova

degeneracy pressure

leaws of quantum mechanics prohibit two electrons from occupying the same state in the same place

Compared to a main-sequence star with a short lifetime, a main-sequence star with a long lifetime is __________.

less luminous, cooler, smaller, and less massive

what are the typical masses of newborn stars

low mass stars are far more numerous than high mass stars.

Listed following are events or phenomena that occur during either the part of the sunspot cycle known as solar minimum or the part known as solar maximum. Match these items to the correct part of the sunspot cyclem

max:uroras are most likely in Earth's skiessolar flares are most commonsunspots are most numerous on the Sunorbiting satellites are most at riskoccurs about 11 years after a solar maximum (on average) Min:occurs about 5 to 6 years after a solar maximum (on average)

White dwarf

may be surrounded by a planetary nebulaemits most strongly in visible and ultravioletmay be in a binary system that undergoes nova explosions

Rank these stages based on the order in which they occur, from first to last.

molecular cloud, contracting cloud trapping infrared light, prostar with jets, main sequence star

Where do stars form?

molecular clouds.

A main-sequence star twice as massive as the Sun would last __________.

much less than half as long as the Sun

On which one of these objects would time on its surface run most slowly?

n object with the same mass as the Sun but only half as large in radius

Considering the mass and size of each, which has a higher density? (white dwarf or neutron star)

neutron star

White dwarfs

not much larger in radius than Earthvery hot but very dim

how does nuclear fusion begin in a newborn star?

nuclear fusion becomes self sustaining when a prostars core temp rises above 10 million k.

Which of the following is a valid way of demonstrating parallax for yourself?

old up your hand in front of your face, and alternately close your left and right eyes.

radiative diffusion

photons bounce randomly among gas particles

what parts of the sun can be seen with a telescope

photosphere, chromosphere, corona

Which stars have finished burning hydrogen in their cores?

rcturus, Acrux, and Betelgeuse have luminosity classes other than V, which means that they have left the main sequence and are no longer burning hydrogen in their cores.

Why do sunspots appear darker than their surroundings?

they are cooler than their surroundings.

What slows down the contraction of a star-forming cloud when it makes a protostar?

trapping of thermal energy inside the protostar