Astronomy Today: Stars and Galaxies: Chapter 20

Cooler

Compared to other stars on the HR diagram, red giant stars are so named because they are

White dwarf

A high mass star will evolve off the main sequence to become a

triple-alpha process

3 He -> C + energy

contact binary

A binary star system in which both members fill their Roche lobes. The binary system now consists of two nuclear burning stellar car surrounded by a continuous common envelope.

white dwarf

A set of the dwarf star with a surface temperature that is hot, so that the object glows white. White dwarfs are typically about the size of the earth with a mass comparable to the sun.

After the helium flash

A star is located on the asymptotic giant branch of the H-R diagram when

white dwarf

A star like the sun will end up as a

Most of the hydrogen in its core

A star will evolve off the main sequence when it uses up

Useful is studying he evolution of stars, a table of numerical values, useful in studying the interiors of stars

A stellar model is

Protons

A white work and supported by the pressure of tape packed

Hotter

After the core of the sun like star starts to fuse helium on the horizontal branch, the core becomes

helium flash

And explosive event in the post-main-sequence evolution of a low-mass star. When helium fusion begins in a dense stellar core, the burning is explosive in nature. He continues until the energy released is enough to expand the car, at which point the star achieve stable equilibrium again.

Cooler and brighter

As a star exhaust the hydrogen in its core and the core contracts, the star becomes

Begins to fade and drop down to become a white dwarf

As the fusion process dies out, the star begins to do what on the H - R diagram?

When the central temperature reaches the nearly 100,000,000 K necessary.

At what temperature does a helium flash occur?

CNO cycle

Chain of reaction is that converts hydrogen into helium using carbon, nitrogen, and oxygen as catalysts.

Denser

Compared to the sun, stars planted near the bottom left of the H - R diagram are much

hydrostatic equilibrium

Condition in a star or other fluid body in which gravity is in word Paul is exactly balance by internal forces due to pressure

No the universe is not yet old enough to form black dwarfs

Do mini black dwarfs if exist in our galaxy?

CNO cycle

For more massive stars with higher central temperatures what is the dominant process is?

hydrogen shell burning

Fusion of hydrogen in a shell that is driven by contraction and heating of the helium core. Once hydrogen is depleted in the core of a star, hydrogen burning stops and the core contracts due to gravity, causing the temperature to rise, heating the surrounding layers of hydrogen in the star, and increasing the burning right there.

Helium burning shell

Shell of burning heilium gas surrounding a nonburning stellar core of carbon ash.

Very slow

Since a white dwarf star is very dense the continued calling is

By determining which of the stars have already left the main sequence

How can astronomers Measure the age of a star cluster?

For a few hours

How long can a star like the sun keep burning hydrogen in its core?

Two

How many reactions are there and the proton - proton cycle?

Greater than

In the hydrogen fusion process what occurs in normal stars, the total mass of the material that goes into the reaction is____the mass of what comes out

False

Main sequence stars like the sun swell into giant stars when the rate of hydrogen fusion increases dramatically in their cores

More rapidly than the sun

On the main sequence, massive stars burn their hydrogen fuel

Increases

Over the stars life span as a main sequence star the luminosity of the star slowly

asymptotic giant branch

Path on the H-R diagram corresponding to the changes that a star undergoes after helium burning ceases in the core. At this stage, the carbon core shrinks and drives the expansion of the envelope, and the star becomes a swollen red giant for a second time.

About 100 times its current size. This is the equivalent to about 70,000,000 km or almost half an AU

Roughly how big will the Sunday come when it enters the red giant phase?

blue straggler

Star found on the main sequence of the H - R diagram, but which should already have evolved off the main sequence, given its location on the diagram; thought to have form from mergers of lower mass stars.

red-giant branch

That section of the evolutionary track of a star that corresponds to continued healing from rapid hydrogen shell burning, which drives a steady expansion and calling of the outer envelope of the star. As the star gets larger in radius and its surface temperature cools, it becomes a red giant.

White Dwarf Region

The bottom left-hand corner of the H - R diagram, where the white dwarf stars are plotted

False

The central star of the planetary nebula is a white dwarf

planetary nebula

The ejected envelope of a giant red star, spread over a volume roughly the size of our solar system.

Black Dwarf

The end-point of the evolution of an isolated, low-mass star. After the white dwarf stage, the star cools to the point where it is a dark "clinker" in interstellar space.

core hydrogen burning

The energy burning stage for main sequence stars, in which they helium is produced by hydrogen fusion in the central region of the star. A typical star spends up to 90% of its lifetime in Hydrostatic equilibrium brought about by the balance between gravity and the energy generated by core hydrogen burning.

Proton-proton cycle

The energy for the thermal pressure in a star like the sun, that counteract the forces of gravity, is supplied by a hydrogen fusion reaction called the

Up and to the left

The evolutionary track of a massive star's starting point (stage seven) would be

mass transfer

The flow of gases from one star in a binary system to the other.

zero age main sequence (ZAMS)

The location of a star on the main sequence when it first becomes stable

electron degeneracy pressure

The pressure produced by the resistance of electrons to compression once they are squeeze to the point of contact.

Hydrogen

The primary constitute of most stars is

Neutrinos

The products of nuclear fusion reactions that most easily escape the interior of a star are

Subgiant branch

The section of the evolutionary track of a star that corresponds to changes that occur just after hydrogen is depleted in the core, and the core hydrogen burning Caesars. Shell hydrogen burning weeds the outer layers of the star, which causes a general expansion of the stellar and below.

Proton-proton cycle and CNO cycle

The two primary processes that provider energy for main sequence stars are?

Red Giant Region

The upper right-hand corner of the H - R diagram, we are red giant stars are plotted

Roche Lobe

The volume of space a star controls gravitationally within a binary system.

Supergiant

What is the lowest density star

Proton-proton cycle

What process is where one hydrogen nucleus fuses with another hydrogen nucleus?

Proton-proton cycle

When does central temperature of a main sequence star is less than 16,000,000 K the dominant process is?

CNO cycle

When protons collide with too much energy to permit fusion causing other atoms to serve a catalytic roll to permit what process?

Triple-alpha process

When temperatures in the helium which core of a star exceeded 100 million Kay, the healing begins to fuse in what process?

90% hydrogen and 10% helium

When the star first become stable, the core of the story is about

Mercury

When the sun becomes a red giant, it's photosphere may reach the orbit of

The upper right of the HR diagram

When the sun is on the red giant branch, it will be found at

Red giant

When the sun leaves the main sequence it's next stage in evolution is to become a

Brighter

When the sun leaves the main sequence, it will become

To the extreme left as a bright O star

Where does the central star of the planetary nebula plot on the H - R diagram?

Lower edge of the main sequence

Where is the zero age main sequence on the H-R diagram?

True

Whitehorse do not produce new energy they just radiate away excess energy as they cool

They are very small and therefore faint and hard to observe

Why are white dwarfs hard to observe?

It signifies the star jumping from stage 9 to stage 10

Why is the depletion of hydrogen in the core of a star such an important event?

red giant

a large, reddish star late in its life cycle that fuses helium into carbon or oxygen

horizontal branch

a region on the H-R diagram defined by stars burning helium to carbon in a stable core

Subgiant

helium core but no fusion occurring, grows in size. Star on the sub giant branch of the H - R diagram.

main-sequence turnoff

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