Star Quiz

Hertzsprung-Russell diagram (H-R diagram)

-shows the relation between stellar brightness (absolute magnitude) and temperature -diagram is made by plotting (graphing) each star's luminosity (brightness) and temperature

light-year

-the distance that light travels in 1 year -one light-year is 9.5 trillion kilometers (5.8 trillion miles)

supergiants

-very large giants are called _________

gravity which is trying to squeeze it and gas pressure which is trying to expand it

A main-sequence star is balanced between what two things?

Apparent magnitude

A measure of the amount of light from a star that is received on Earth.

Bright Nebula

A nebula that glows if it is close to a very hot star

What is a planetary nebula?

A ring-shaped cloud of gas and dust formed by an expanding shell of gas around an aging star. It's created when a star blows off its outer layers after it has run out of fuel to burn. These outer layers of gas expand into space, forming a nebula.

Gravity and gas pressure

A stable main sequence star is balanced between which two forces?

gravity, thermal nuclear energy

A star is a ball of very hot gases, caught between the opposing forces of _______ trying to contract it and _______ trying to expand it.

Which stars are considered low-mass stars?

A star is considered to be a "low mass" star if the mass of the star is less then 8x (Eight times) the mass of the Sun. The "Low Mass" Stars are found in the lower right corner of the main sequence section of the H-R Diagram.

What is hydrostatic equilibrium?

A star is in hydrostatic equilibrium when the outward pressure is equal to the inward force of gravity at every point in the star

50%

About how many stars in our galaxy are estimated to occur in pairs or multiples?

red giant

Above and to the right of main sequence stars on H-R lies this group of very bright stars

What is the difference between absolute and apparent magnitude? How is it measured?

Absolute magnitude is the measure of the intrinsic brightness of a celestial object, generally a star. Apparent magnitude is a measure of the apparent brightness of a celestial object, generally a star.

Vertical right side of H-R diagram

Absolute magnitude on -5 to +15 scale

helium

Almost 10% of the Sun's surface atoms are _______

Main-sequence stars

Band through the center of the H-R diagram. "Average star". Our sun is a part of this

protostars

Bodies that are not yet stars because they can't engage in nuclear fusion.

Mass

Brightness is also related to a star's ?

What is the difference between brightness and luminosity?

Brightness is how bright a star appears. Luminosity is the amount of light/energy the star emits from its surface.

Apparent Magnitude

Brightness of a star as viewed from Earth. This is measured in numbers from -5 to +15 (lower the number the brighter the star)

Nebula

Cloud of dust and gases

Apparent magnitude is the brightness of a star as seen from earth Absolute magnitude is the actual brightness of a star

Compare and contrast apparent magnitude and absolute magnitude

Stellar Brightness

Controlled by size, temperature, and distance

stellar brightness

Controlled by three factors: size, temperature, distance

Vertical left side of H-R diagram

Luminosity on an exponential scale

Top of H-R diagram

Spectral class (O,B,A,F,G,K,M). Sun is a class G star. O - hottest and M coolest Blue, White, Yellow, Red

gravity

Stars exist because of _______.

Bottom of H-R diagram

Surface temperature in Kelvin

What quantity is the spectral class of a star related to? List the spectral classes of stars in the order of decreasing temperature (from hottest to coolest).

The spectral class of a star is related to its temperature. In order of decreasing temperature; OBAFGKM.

What happens to the luminosity and temperature of a low-mass star when it becomes a red giant? Why?

The temperature decreases and the luminosity increases because the bigger the bright it is and due to all layers the heat decreases.

Giants and supergiants

What types of stars have high absolute magnitude, but low temperature?

A less massive star will live longer because it consumes fuel at a slower rate than do more massive stars.

Why are less massive stars thought to age more slowly than more massive stars, even though less massive stars have much less "fuel"?

Large quantities of interstellar matter block much of the visible light

Why are radio telescopes instead of optical telescopes used to determine the structure of the Milky Way Galaxy?

As they expand, their surfaces cool, which explains the red appearance

Why do red giants have a reddish appearance?

Zone of hydrogen fusion continues to move outward, leaving a helium core. Without any hydrogen in the core for fusion (energy), the core does not have enough pressure to prevent gravity contraction. The gravity contraction creates heat energy, some of which is radiated outward increasing nuclear fusion in the star's outer shell. This energy heat and expands the star's outer layer resulting in a giant body 100s to 1000s of times its original size. During expansion the core continues to collapse and heat until it reaches 100 million K when it is hot enough to convert helium into carbon.

Why does the Red Giant Stage occur?

Hubble's Law

a law that states that the galaxies are retreating from the Milky Way at a speed proportional to their distance

black hole

a massive star that has collapsed to such a small volume that its gravity prevents the escape of everything, including light - scientists think that as matter is pulled into a blackhole, it should become very hot and emit a flood of xrays before being pulled in

pulsar

a source that radiates short bursts or pulses of radio energy in very regular periods - one found in Crab Nebula during the 1970s is undoubtedly the remains of the supernova of 1054

nova

a star that explosively increases in brightness

Big Bang Theory

at one time the entire universe was confined to a dense, hot, supermassive ball then about 13.7 billion years ago a violent explosion occurred hurling all the material in all directions

planetary nebulae

beautiful, gleaming spherical clouds

nebula

clouds of dust and gases in space - two kinds: emission and dark nebula - sun begins its life as a nebula

galaxy

group of stars, dust and gases held together by gravity

red giant stage of star

hydrogen burning migrates outward - the star's outer envelope expands - its surface cools and it becomes red - all the hydrogen in the core is consumed, core begins to contract, it grows hotter, energy heats and expands outer layer, as it expands the surface cools - a red giant consumes both helium and hydrogen to produce energy

parallax

it is the slight shifting in the apparent position of a nearby star due to the orbital motion of Earth - nearest stars have the largest parallax angles, while those of distant stars are too small to measure

What is the correct order of evolutionary stages for a solar mass star? Be able to identify them on a H-R diagram.

main sequence, red giant branch, helium flash, horizontal branch, asymptotic branch, planetary nebula, white dwarf

medium mass stars death

mass similar to sun, evolve the same way as low mass stars during collapse from red giants to white dwarfs they cast off their outer layer creating expanding round cloud of gas called planetary nebula

low mass stars death

stars less than half the mass of the sun, consume fuel at slow rate, may remain on the main sequence for up to 100 billion years, never evolve into red giants, consume hydrogen fuel until they collapse into a white dwarf

red stars

stars that are cooler - energy emitted as longer-wavelength red light

white dwarfs

they're not white, stars in the lower-central part of the H-R diagram that are much fainter than main sequence stars

absolute magnitude

-"true" or intrinsic brightness of a star -brightness at a standard distance of 32.6 light-years -most stars _____ are between -5 and +15

black holes

-More dense than a neutron star -Intense surface gravity lets no light escape -As matter is pulled into it the matter becomes very hot and emits X-rays -Likely candidate is Cygnus X-1, a strong X-ray source -Pairs of jets extend outward from these accretion disks and are thought to return some material back to space -Following supernova explosions, if the core of a remaining star exceeds the three solar mass limit to form a neutron star gravity prevails over pressure, and the stellar remnant collapses; thus forming a _____.

eruptive variables

-explosive event -sudden brightening -called a nova

factors that control the apparent brightness of a star as seen from Earth

1. how big a star is 2. how hot a star is 3. how far away a star is

the properties of stars

1. temperature 2. mass 3. color

Main-Sequence stage

90% of a star's life is in the main-sequence stage. Stars age at different rates (lifespan determined by mass - shorter lifespan, less mass - longer lifespan)

main sequence stage of a star

90% of a stars life is hydrogen-burning, when hydrogen fuel is depleted, it dies - hot blue stars radiate energy at enormous rates so they deplete hydrogen in a few million years - least massive stars remain stable for 100s of billions of years - sun remains a main sequence star for about 10 billion years

hydrogen

90% of the Sun's surface atoms are _________

main sequence stars

90%, fall along a band that runs from upper left corner to lower right corner of H-R diagram - hottest ones are the brightest and coolest are the dimmest - they run from hotter more massive blue to cooler less massive red

Dark Nebula

A nebula that is not close to any bright star and therefore appears to be dark. It contains the matter that forms stars and planets

pulsar

A neutron star in extremely rapid rotation that radiates radio waves in short pulses. The radio waves are generated by the rotating magnetic fields of neutron stars are concentrated into two narrow zones that align with the star's magnetic poles.

What does an absorption spectrum look like and how is it formed?

An absorption spectrum is a rainbow with black lines, the opposite of what an emission spectrum looks like. The way it is formed is an electron absorbs the energy of a photon to jump to a high energy level leaving behind a black absorption line.

When do atoms emit photons? Briefly describe the process.

An atom emits a photon when it goes from the excited state and loses its energy. An electron can gain energy in the ground state and move up energy levels, when it gets to the excited state its starts to lose energy and that losing of energy is emitting a photon or the process of emission.

What does an emission spectrum look like and how is it formed?

An emissions spectrum looks like a set of colorful lines within a black background. It is formed by electrons that are excited therefore having a higher state and as the state falls they create energy. This energy is photons, hot gas is where you are going to get the emission spectrum

When the core of a protostar has reached about 10 million K, pressure within it is so great that nuclear fusion of hydrogen begins, and a star is born

At what point is a star born?

10 million K

At what temperature does nuclear fusion begin?

Hottest during the planetary nebula stage Brightest during its giant stage

At which stage in its evolution is the star the hottest? The brightest?

Birth of a star

Dark, cool, interstellar clouds are contracted by gravity. The temperature begins to rise and long-wavelength light is emitted. This becomes a protostar

Small, compact objects composed of incomprehensibly dense materials and have extreme surface gravity

How are white dwarfs, neutron stars and black holes similar?

mostly hydrogen (92%) with some helium (7%), and a small amount of heavier elements (>1%)

In the Milky Way Galaxy, what are nebulae made of?

Why doesn't a core made of iron support a massive main-sequence star?

Iron fusion does not create energy; it consumes energy and is thus cannot sustain a star. A high mass star will only fuse elements up to iron, then the iron core will collapse.

binary stars

One of two stars revolving around a common center of mass under their mutual gravitation. Can be used to determine the property most difficult to determine - the mass of a star.

When does a Type II supernova occur?

Outer layers of a star blow off in tremendous explosions, the light emitted being equivalent to a billion Suns. A star must have 8-50 times more mass than the Sun to occur. *Also because Iron stops fusing*

What are pulsars?

Pulsars are rapidly rotating neutron stars that consist of a combination of strong magnetic fields and rapid rotation leading to a beam of radiation that sweeps around like a lighthouse beam.

neutron stars

Remnants of explosive supernova events; in them the electrons are forced to combine with protons in the nucleus to produce neutrons. They have high surface temperatures, but their small size greatly limits their luminosity. It is predicted that they have a very strong magnetic field and a high rate of rotation.

What two factors affect a star's luminosity and how do they affect it?

Size- as the size increases the luminosity increases because the stars surface area is much greater Temperature - a hotter and larger star is more luminous than a cooler star and smaller star

supermassive black holes

The largest black holes found in the center of galaxies.

magnitude

The measure of a star's brightness.

What is the next step in a star's life when it exhausts the hydrogen in its core? Is anything fusing in the core? In shells around the core?

The next step is the star leaves the main sequence and becomes a red giant. Nothing is fusing in the core because it is degenerate, but hydrogen starts fusing in the shells around the core.

nuclear fusion

The source of the Sun's energy.

convection

The up-and-down movement of gas, called ______, produces the grainy appearance of the photosphere and is responsible for the transfer of energy in the uppermost part of the Sun's interior.

binary star

Two stars that orbit each other, pulled together by gravity. More than 50% of stars in the universe occur in pairs or multiples. These are called ?

during a medium mass star's collapse from red giant to white dwarf, they cast off their boated outer layer, creating a expanding cloud of gas. The remaining hot, central white dwarf heats the gas cloud, causing to glow. These gleaming spherical clouds are called planetary nebula

What causes a planetary nebula?

A star runs out of fuel and collapses due to gravity

What causes a star to die?

The most massive type of main sequence stars are hot, blue stars. The least massive stars are cool, red stars

What color is the most massive type of main-sequence star? The least massive?

Hydrogen Red giants consume hydrogen in their outer shells and eventually helium in their cores

What element is the main fuel for main sequence stars? For red giants?

It illustrates the star's evolution through color and absolute magnitude at various stages of evolution

Why is the H-R diagram useful in understanding Stellar evolution?

Sun

_____ is a yellow main-sequence star with an absolute magnitude of about 5. Because the vast majority of main-sequence stars have magnitudes between -5 and +15, its midpoint position in this range results in its classification as an "average star." It is also a G class star.

protostar

a collapsing cloud of gas ad dust destined to become a star - a developing star not not yet hot enough to engage in nuclear fusion - when its core has reached about 10 million K, pressure within is so great that nuclear fusion of hydrogen begins and a star is born

Hertzsprung-Russell Diagram

a graph used to study stars - it shows the relationship between the absolute magnitude and temperature of stars

supernovae

a star of extremely high density composed entirely of neutrons - neutron stars are thought to be remnants of supernova events

neutron star

a star of extremely high density composed entirely of neutrons - thought to be remnants of supernova events

light year

a way to express stellar distance which is the distance light travels in one year - 9.5 trillion kilometers

apparent magnitude

actual brightness of a star "as it appears from Earth" - the larger the number is, the dimmer the star is

star death

all stars, regardless of size eventually run out of fuel and collapse due to gravity

red shifts

also called Doppler shift toward the red end of the spectrum, occurs because the light waves are stretched which shows that Earth and the source are moving away from each other - red shifts of distant galaxies indicate the universe is expanding

sun

began as a nebula, will spend much of its life as a main sequence star, and then will become a red giant, planetary nebula, white dwarf and finally a black dwarf

apparent magnitude

-brightness when a star is viewed from Earth -decreases with distance -numbers are used to designate magnitudes; dim stars have large numbers

White Dwarfs

-fainter than main-sequence stars -small (approximate the size of Earth) -lower-central area on the H-R diagram -not all are white in color -make up perhaps 10% of all stars *Very dense because its full of degenerate matter

protostar stage

-gravitational contraction of gaseous cloud continues -core reaches 10 million K -hydrogen nuclei fuse -become helium nuclei, process is called hydrogen burning -energy is released, the immense heat released by hydrogen fusion causes the gases inside stars to move with more strength which raises the internal gas pressure -outward pressure increases -outward force (pressure) balanced by gravity pulling in -star becomes a stable main-sequence star

main-sequence stage

-hydrogen is continually being converted into helium -stars age at different rates: massive stars use fuel faster and exist for only a few million years, small stars use fuel slowly and exist for perhaps hundreds of billions of years

Magnitude

Measure of a star's brightness

Black Hole

More dense than a neutron star. Intense surface gravity lets no light escape. Edge called the event horizon. As matter is pulled into it it becomes very hot and emits X-rays. Likely candidate is Cygnus X-1

pulsating variables

Variable stars that fluctuate regularly in brightness and expand and contract in size.

Giants (or Red Giants)

Very luminous and large. Upper-right on the H-R diagram.

how big it is how hot it is how far away it is

What 3 factors control the apparent brightness of a star as seen from Earth?

The remains of low-mass and medium-mass stars. Extremely small stars with extreme densities. Its electrons are pushed close to the nucleus

What are White Dwarfs?

it can become a neutron star or a black hole

What are two possible results of the death of a massive star?

Stars that fluctuate in brightness

What are variable stars?

star's temperature

What can astronomers learn by studying a star's color?

sizes, colors, and temperatures of stars

What can we learn from studying an H-R diagram?

the red shift of distant galaxies and cosmic background radiation support the big theory

What evidence supports the big bang theory?

it becomes a red giant

What happens to the star after it leaves the main sequence?

dying stars are able to produce chemical elements beyond helium on the periodic table - that process is nucleosynthesis. First hydrogen nuclei combine to form helium. Then helium nuclei begin to fuse into other elements. Only the most massive stars can produce elements heavier than iron

What is Nucleosynthesis and how does it occur?

Sudden brightening of a star

What is a Nova?

large groups of stars, dust, and gases held together by gravity

What is a galaxy?

clouds of dust and gases between stars

What is a nebulae?

A protostar is a developing star not yet hot enough to engage in nuclear fusion.

What is a protostar?

A star can delay its death by fusing heavier elements and becoming a giant

What is an exception to rapid death of a star once its fuel is depleted?

First official stage of developing star not yet hot enough to engage in nuclear fusion. Gravitational contraction continues causing the core of the protostar to heat more intensely than the outer layer. When the core reaches 10 million K, pressure within is so great that nuclear fusion of hydrogen begins and a star is born

What is the Protostar Stage of stars?

At one time, the entire universe was confined to a dense, hot, supermassive ball. Then, about 13.7 billion years ago the an explosion occurred hurling this material in all directions

What is the big bang theory?

during fission, atomic nuclei are split apart to make smaller nuclei. During fusion, atomic nuclei combine to make a larger molecule

What is the difference between nuclear fission and nuclear fusion?

The first stage is a nebula or cloud of dust and gases. The last stage is a black dwarf

What is the first stage in the formation of a star? What is the last stage?

Hertzprung-Russell diagram

What is this a diagram of?

nebula, protostar, main-sequence star

What stages do ALL stars go through?

hydrogen and helium

What two elements does a red giant consume for energy?

Massive stars

What type of stars end their lives as supernovae?

White dwarfs

What types of stars have low absolute magnitude and medium temperatures?

Light year

What unit of measurement is used to express stellar distance?

black dwarfs

When white dwarf stars cool down they become ____.

dark, cool interstellar clouds

Where are stars born?

After the white dwarf stage because it is cold and dark

Where would the black dwarf stage be on the drawing? Why?

temperature

Which property of a star can be determined by its color?

medium mass and massive stars; because of their mass their temperatures and pressures are able to increase to use helium as well as hydrogen; low-mass stars are not able to reach those temperatures / pressures

Which stars become red giants? Why?

low mass and medium mass stars

Which stars become white dwarfs?

degenerate matter

White Dwarf stars are very dense; densities of this magnitude are only possible when electrons are displaced inward from their regular orbits around an atom's nucleus. Material in this state are called ______. Its atoms have been squeezed together so tightly that the electrons are pushed very close to the nucleus; however, the electrical repulsion that occurs between the negatively charged electrons supports the star against complete gravitational collapse. White Dwarf stars also have very hot surfaces.

blue stars

stars that are very hot with surface temperature over 30,000 K - energy emitted as short wave-length light that appears blue

yellow stars

stars with temperatures between 5000 - 6000 K

Absolute Magnitude

"True" or intrinsic brightness of a star. Brightness from a standard distance of 3.26 light-years. Also measured on a scale of -5 to +15

absolute magnitude

(astronomy) the magnitude that a star would have if it were viewed from a distance of 10 parsecs (32.62 light years) from the earth

main-sequence stars

-90 percent of all stars -they make up the band through the center of the H-R diagram -our Sun is in the main-sequence The hottest of these stars are the brightest, and the coolest are the dimmest. The luminosity of these stars is also related to their mass; the hottest (blue) stars are about 50 times more massive than the Sun, while the coolest (red) stars are only 1/10 as massive. *It is a star in which the force of gravity, in an effort to squeeze the star into the smallest possible ball, is precisely balanced by gas pressure created by hydrogen fusion in the star's interior.

death of medium-mass stars

-Red giant collapses; sun-like stars fuse hydrogen and helium fuel at accelerated rates, once the fuel is exhausted the red giant collapses -Planetary nebula forms -Becomes a white dwarf

death of massive stars

-Short life span -Terminate in a brilliant explosion called a supernova -Interior condenses -May produce a hot, dense object; either a neutron star or a black hole

red giant stage

-Stage begins when the usable hydrogen in the star's interior is consumed, leaving the helium-rich core. -Without a source of energy, the core no longer has the gas pressure necessary to support itself against the inward force of gravity; as a result, the core begins to contract. -The collapse of a star's interior causes its temperature to rise rapidly as gravitational energy in converted into thermal energy. Hydrogen burning migrates outward -Star's outer envelope expands, surface cools, surface becomes red; the star's gravitational force will eventually stop this outward expansion and the two opposing forces (gravity and gas pressure) achieve balance w/ the star as a giant or a supergiant -The core heats up some more and the core is collapsing as helium is converted to carbon -Eventually all nuclear fuel is used -Gravity squeezes the star

nebula

-a cloud of dust (interstellar dust and interstellar matter) and gases

red giants

-also known as giants -they're very luminous -they're large -they're located in the upper-right on the H-R diagram -their size can be estimated by comparing them with stars of known size that have the same surface temperature -only a small percent of stars are giants/supergiants

the more massive originally, the smaller white dwarf it makes because its greater gravitational force allows it to squeeze itself into a smaller, more compact object

How does the size of a white dwarf correlate to its original mass?

The sun began as a nebulae, became a protostar, and then a main sequence star. It will become a red giant, planetary nebula, white dwarf, and finally a black dwarf

Describe the life cycle of the sun

Solar structure

Divided into 4 parts, solar interior, photosphere, chromosphere, and corona

90% of its life. Once the hydrogen fuel in the star's core is depleted, it evolves rapidly and dies.

How long does an average star as a hydrogen-burning main-sequence star?

White Dwarfs

Fainter than the main sequence stars. Small (approximately the size of Earth. Located in the lower-central part of the H-R diagram. About 10% of stars. Very dense, atoms take up less space. Electrons are displaced inwards (degenerate matter) Cools to become a black dwarf.

Burnout and Death

Final stages of a star depend on mass. Low-mass star (0.5 solar mass) - Variable star then becomes a white dwarf Medium-mass star (0.5 - 3 solar masses) - Variable star planetary nebula (remnant of nova where the outer layers of the star are blown off) forms and becomes a white dwarf Massive star - Variable star then terminated in a brilliant explosion called a supernova (the star can fuse larger and heavier elements). May produce a neutron star or a black hole

Why do astronomers consider the spectrum of a star so important?

Fingerprint for the star, elements, characteristics of said star.

Neutron Star

Formed from a more massive star (star has more gravity and squeezes itself into a smaller space). Remnant of a supernova. Electrons combine with protons to produce neutrons. Small size. It has a strong magnetic field.

Protostar

Gravitational contraction of the gaseous cloud continues. Core reaches 10 million K. Hydrogen nuclei begins to fuse and becomes helium nuclei in a process called hydrogen burning. Energy is released, outward pressure increases, outward pressure balanced by gravity pulling in. The star then becomes a main sequence star.

Describe the relationship between gravity and gas pressure when a star depletes the supply of hydrogen in its core. What happens to the size of the core?

Gravity and pressure have to stay balanced. If the one is too high the star can explode or collapse. When Hydrogen finally stops fusing the core gets smaller because temperature and pressure decreases.

Why will a neutron star form when the core of a massive star collapses?

Gravity has the upper hand and forced electrons into protons producing neutrons. The core contracts until neutrons are filled tightly as the rules of quantum mechanics allow; it is because of neutron-degenerate matter

As absolute magnitude increases, so does temperature

How are absolute magnitude and temperature related within the main sequence?

some nebula become dense enough to contract, squeezing particles in the nebula, pulling every particle towards the center. As the nebula shrinks, gravitational energy is converted into heat energy. The initial contraction takes approx. 1 million years. This process continues with gradually increasing temperatures until it is hot enough to radiate energy from its surface in the form of long wavelength red light (protostar)

How are stars born?

The mass of a body can be calculated if it is gravitationally attached to a partner which is the case for any binary star system. Binary stars orbit each other around a common point called the center of mass. For stars of equal mass, the center of mass lies exactly halfway between them. If one star is more massive than its partner, their common center will be closer to the more massive one.

How can a binary star system be used to determine a star's mass?

it becomes hotter but less bright

How do the characteristics of the star change as it changes from a red giant to a planetary nebula?

Heat from hydrogen fusion causes the gases to increase their motion. This causes an increase in outward gas pressure. When the outward pressure EXACTLY balances the inward force of gravity, the star becomes a main-sequence star.

How does a star go from protostar to Main-Sequence Stage?

Red-Giant stage

Hydrogen burning migrated outwards. Star's outer envelope begins to expand. Surface begins to cool and turns red. Core begins to collapse as helium is converted into carbon. Eventually all the nuclear fuel is used and gravity squeezes the star.

What factor is most important in determining a star's position on the main-sequence and its subsequent evolution? Why?

It depends on the stars mass. The higher the mass of the main-sequence star the shorter its life is because with it being so big, energy has to burn so much faster to keep the star stable. With it having a higher mass and shorter life it goes through cycles faster of supergiant then explode. Low-mass stars have a longer life so they take a lot longer for evolution.

What is a white dwarf?

Leftover core of star remains as white dwarf. Masses 0.6-1.4 Mo, size like Earth. Hot, but not very luminous due to small size (only has non-fusing carbon core). Cool off because no nuclear fusion is occurring.

Why do higher mass stars live shorter lives on the main sequence than lower mass stars?

Lower mass stars live longer lives because higher mass stars burn through their nuclear fuel faster.

Where does nuclear fusion occur in the Sun and why?

Nuclear fusion occurs in the core of the sun because it is hot and dense enough for fusion to occur

When does a Type Ia supernova occur?

Occurs when the stars are in a binary system, when two stars are orbiting each other, and one must be a white dwarf

decreasing

On the H-R diagram, the main-sequence stars appear in ____ order, from hotter, more massive blue stars to cooler, less massive red stars.

relative sizes

Scientists have discovered that objects having equal surface temperatures radiate the same amount of energy per unit of area. Any difference in the brightness of two stars having the same surface temperature can be attributed to their _______.

Following the nova flare-up, the star returns to its pre-nova state. If a great amount of mass had been lost, it would not be possible, nor would it be possible for the star to experience more than one nova eruption.

Scientists think that only a small amount of a star's mass is lost during a nova. What evidence is used to support this theory?

Hertzsprung-Russell Diagram

Shows the relation between stellar brightness (absolute magnitude) and temperature. Diagram is made by plotting each star's luminosity and temperature.

Variable stars

Stars the fluctuate in brightness

the brilliant explosion that marks the end of a massive star. It is thought to occur when a massive star consumes most of its nuclear fuel. It implodes bursting inward, generating a shock wave that moves out from the star's interior. The shock wave destroys the star and blasts the outer shell into space creating the supernova event. Supernova events are rare. None have been observed since the invention of the telescope

Supernova

average star

The Sun is a ______

event horizon

The edge of a black hole.

iron

The final element generated in stars.

What is the ground state of an atom? The excited state?

The ground state is the lowest possible energy state, excited states are any states above the ground state.

death of low-mass stars

The interiors of low-mass stars never attain high enough temperatures and pressures to fuse helium, their only energy source is hydrogen fusion. Thus, low-mass stars never become bloated red giants; rather, they remain stable main-sequence stars until they consume their usable hydrogen fuel and collapse into hot, dense white dwarfs.

Where are the largest stars located? The smallest stars? Where are the hottest main-sequence stars located? The coolest?

The largest stars -supergiants- are located in the top right corner of the diagram, while the smallest stars -white dwarfs- are at the bottom left corner. The hottest main-sequence stars are towards the top left of the diagram, and the coolest are towards the bottom right.

stellar birth

The mutual gravitational attraction of particles in a thin, gaseous nebula causes the cloud to collapse on itself. As the cloud is squeezed to unimaginable pressures, its temperature rises, igniting nuclear furnace, and a star is born. The interstellar clouds that give birth to stars are about 92% hydrogen, 7% helium, and less than 1% heavier elements. -in dark, cool, interstellar clouds -gravity contracts cloud and temperature rises -radiates long-wavelength (red) light *One of the mechanisms that triggers star formation is a shock wave from a supernova of a nearby star. Also the slow dissipation of thermal energy is thought to cause it. Once gravity starts causing the cloud to collapse, gravitational energy (potential energy) is converted into the energy of motion (thermal energy) which causes contracting gases to gradually increase in temperature. When the temperature of these gaseous bodies increases sufficiently, they begin to radiate long-wavelength red light. Because these stars aren't hot enough to engage in nuclear fusion they aren't yet stars.

What does the onion structure of a high mass refer to? How long does the fusion of each layer take?

The onion structure is all the elements smaller than iron that a high mass star burns through because the core is so hot and since the pressure and temperature are so high it lives a shorter life which means fusion rates are fast. As the star is fusing it is using heavier and heavier elements causing the onion-like structure.

first-generation stars

The stars that formed early in the history of the universe; they were very massive and consisted mostly of hydrogen with lesser amounts of helium, the primary elements formed during the big bang. *Massive stars have relatively short lifetimes followed by violent explosive deaths. These explosions create the heavier elements.

What two variables are plotted on the H-R diagram? What 3rd characteristic can you determine from a star's location on the H-R diagram?

The variable on the x-axis is surface temperature in kelvin, increasing from right to left. The variable on the y-axis is luminosity relative to the sun. The 3rd characteristic that can be determined is the star's radius relative to the sun, with the bottom left being the smallest and the top right being the biggest.

planetary nebulae

These nebulae originate from the remnants of dying sun-like stars. They consist of glowing clouds of dust and hot gases that have been expelled near the end of a star's life.

What are the characteristics of a neutron star?

They are pretty small about the size of a city (1.4 - 3x the mass of the sun)

Main sequence

To what group of stars does the sun belong?

white dwarf

a star that has exhausted most or all of its nuclear fuel and has collapsed to a very small size - believed to be near its final stage of evolution

Evidence to support Big Bang Theory

red shift of galaxies and radiation called cosmic background radiation produced during the big bang

massive stars death

mass three times the sun, have short life spans, end in a brilliant explosion called supernova, during supernova star becomes millions of times brighter than prenova stage, very rare - the star's interior condenses and may produce hot dense object that is either a neutron star of a black hole

nuclear synthesis

process that produces chemical elements inside the stars

absolute magnitude

the apparent brightness of a star if it were viewed from a distance of 32.6 light years - a large cool star of high luminosity

color and temperature

two characteristics of stars

supergiant

very large, very bright red giant star