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UWGA / Engineering / ASTR 2313 / What is the sun's photosphere?

What is the sun's photosphere?

What is the sun's photosphere?


School: University of West Georgia
Department: Engineering
Course: Astronomy
Professor: Dr. team
Term: Fall 2017
Cost: 50
Name: ASTR Test 3
Description: flash card style notes for chapters 9-12 in astronomy, for test 3
Uploaded: 10/26/2017
15 Pages 63 Views 4 Unlocks

Lily Anna Head (Rating: )

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Concept/Question Definition/Answer 

What is the sun's photosphere?

What is the Sun's photosphere?

The innermost region of the suns atmosphere with a  

density of 0.01% of the air we breathe

Why can we only see one layer of the Suns atmosphere?

The upper two layers are nearly transparent to most  

wavelengths of visible light, so we see straight through them to  the photosphere

Where is the photosphere darkest?

At the limb, the edge

How do gases move in granules and why?

Hot gases move up in the center of each granule and  

cooler gases cascade down word around its edges; this is caused  by convection

Stefan-Boltzmann Law

Hotter regions emit more photons per square meter then  

do cooler regions; this is why the centers of the granules are  brighter than the edges

Why can we only see one layer of the sun's atmosphere?

What is the chromosphere?

A region of less dense stellar gas above the photosphere We also discuss several other topics like What are the three domains of symptoms of adhd?

What are spicules?

Jets of gas in the chromosphere


Outermost region of the suns atmosphere

Transition zone If you want to learn more check out What are the three reasons why ad slopes down?

Between the chromosphere and Corona in which the  

temperature skyrockets to about 1million K

What are the two mechanisms that heat the Corona?

First, energy is carried and released there by the suns  

magnetic fields. Second, jets of very hot gas are sent up from the chromosphere into the Corona

When can the chromosphere and corona be seen?

When there's an eclipse or with special telescopes

How do gases move in granules and why?

Concept/Question Definition/Answer 

What is solar wind?

Gas that is moving fast enough to escape the suns  


How long is the sunspot cycle?

11 years

Differential rotation

The equatorial regions rotate more rapidly than the polar  regions

Zeeman effect

The splitting of a single spectral line into two or more lines Plasma

A mixture of electrically charged ions and electrons


The study of the sun's interior by recording vibrations

What is the solar cycle and how long is it?

22 years and the time it takes solar magnetic fields to  If you want to learn more check out Define industrial city 1875-1920.

return to their original orientation

Magnetic dynamo model

The sun's magnetic field was created as a result of the  

sun’s rotation and the resulting motion of the ionized particles  found throughout it If you want to learn more check out What are the four key elements of diabolical witches?


Brighter, hotter areas of the chromosphere

Coronal holes

Darker, cooler; act as conduits for gases to flow out of the  sun

What happens when a coronal hole faces the earth?

The solar wind in our direction increases dramatically

What do solar flares do?

Concept/Question Definition/Answer 

Release vast quantities of high-energy particles, as well as  x-rays and ultraviolet radiation

Coronal Mass Ejections

Huge loop, canopy, or balloon shaped volumes of high  

energy gas being ejected from the Corona

Thermonuclear fusion

The process of using nuclei at such extreme temperatures Hydrogen fusion

The conversion of hydrogen to helium

What is solar luminosity and how is it produced?

The total energy output per second; to produce this  

luminosity the sun converts 600 million metric tons of hydrogen  into helium within its core each second

What does the solar model say?

Begins with the inward force due the suns gravity. This  

force increases the pressure and temperature in the suns core  causing hydrogen fusion. Because the sun is not shrinking there  must be an outward force that counters the inward force of  gravity If you want to learn more check out What is nicolaus copernicus known work?

Hydrostatic equilibrium

The balance between the inward force of gravity and the  

outward force from the motion of the hot gas

Where is the radiative zone?

Extends from the core to about 70% of the way out to the  photosphere

Cerenkov radiation

A flash of light emitted when an electron goes through  


Ch. 10

stellar parallaxWe also discuss several other topics like What are the two kinds of conventional terms?

Concept/Question Definition/Answer 

the apparent motion of nearby stars among the  

background of more distant stars due to Earth's orbit

apparent magnitude

brightness of stars as seen from Earth; denoted by m

negative versus positive apparent magnitude

negative apparent magnitude is brighter than a positive  


absolute magnitude

denoted by M; how bright a star actually is at 10 pc

inverse square law

the rule for how quickly the brightness of an object  

changes with distance

how we determine the peak of a star's blackbody spectra  


stellar spectroscopy

 of a star's spectrum; tells us its surface temperature

what are Balmer lines?

visible hydrogen lines

why were some of the A-P categories dropped?

because the Balmer lines can be weak whether it is hot or  cool

how are spectral types further broken up?

each spectral type is broken up into 10 temperature  

subranges and these are further indicated by 0 (hottest) through  9 (coolest)

giant stars

to the right of the main sequence; bright but cool

red giants

a little cooler than giants


Concept/Question Definition/Answer 

bigger and more luminous than giants

white dwarfs

hot, dim, tiny remnants of stars; the size of Earth

supergiant luminosity class

Ia and Ib

giant luminosity classes

II, III, and IV

main sequence luminosity class


what luminosity class is the sun?

G2 V

spectroscopic parallax

method of determining distances between stars

what is the common error amount in spectroscopic parallax 10%

optical doubles

binary stars that lie in the same direction, so they look like  a single star

visual binaries

both stars can be seen in the pair

the formula for the sum of the masses

the cube of the semi-major axis divided by the square of  

the period

center of mass

the common point that the binary stars orbit

which star is closer to the center of mass?

the more massive one

spectroscopic binaries

Concept/Question Definition/Answer 

binary stars that produce spectral lines that shift back and  forth

spectroscopic binaries' lines

most often only a single set of lines can be seen instead of  double

Ch. 11

interstellar medium

matter between stars

how much mass does the interstellar medium contain?

10% of the mass in our galaxy

what is the interstellar medium composed of?

gas containing atoms and molecules and tiny pieces of  


why does the interstellar medium glow?

scattered light from stars in the area

reflection nebula

bluish haze, starlight scattered from the interstellar gas  

and dust


dense region of interstellar gas and dust

larger bodies of gas and dust that nebulae are in bedded in molecular clouds

interstellar extinction

darkening of light by intervening gas and dust

interstellar reddening

an object appears redder than it actually is when we see it  through visible wavelengths through the interstellar medium

dark nebulae

are regions of interstellar gas and dust that are dense to  

prevent most visible light from getting to us

Concept/Question Definition/Answer 

emission nebulae

regions of interstellar gas and dust that glow from energy  

they get from nearby stars, exploding stars, and collisions  between nebulae

how have we been able to discover distant stars that are obscured by the  interstellar medium?

the objects also emit radio or infrared photons that are  

scattered relatively little on their way to us

supernova remnants

ashes of dead star; have a distinctly arched appearance

what causes supernova remnants to glow?

collides with preexisting matter exciting the electrons and  molecules

how does a star form from supernova remnants?

when the shell of the supernova rams into a giant  

molecular cloud with enough speed it compresses the cloud  causing it to become Jeans Unstable, causing the birth of a star

Bok globules

small regions of the giant molecular cloud become jeans  

unstable making them denser and darker, the dark regions are  called Bok globules

why can protostars not be seen in visible light?

they are enshrouded by their outer layer of gas and dust

brown dwarfs

pre-main-sequence stars that do not have enough  

gravitational force that heat their cores immensely, so they  contract to planetlike orbs of hydrogen and helium

T-Tauri stars

gas-ejecting stars in spectral classes G and cooler

Herbig Haro objects (HHO)

the jets from T-Tauri stars slam into interstellar gas causing  it to glow and creating HHO

Concept/Question Definition/Answer 

H II regions

nebulae that are predominantly ionized hydrogen

OB association

collection of hot, O and B stars that produce the ionizing  

ultraviolet radiation

when do stars appear on the main sequence?

it depends on their mass

zero-age main sequence (ZAMS)

set of locations on the H-R diagram where pre-main

sequence stars first become stable objects - neither shrinking nor expanding

main sequence stars and equilibrium

main sequence stars are the stars in hydrostatic  


will higher mass stars shine longer?

no; they burn more fuel more quickly than low mass stars

red dwarfs

lowest-mass main sequence stars; masses between 0.08M 0.4M; fully convective stars

hydrogen shell fusion

hydrogen rich gas outside of the core is compressed inward and heated enough to begin helium fusion

Pauli exclusion principle

nature does not allow two identical particles to exist at the  same time and at the same place

exclusion principle and helium fusion

as helium electrons are pushed together, the exclusion  

principle forces many of them to move faster so they do not  become identical

electron degeneracy pressure

cores of low mass giants are supported by this; electrons in the exclusion principle are called degenerate, and keeping the

Concept/Question Definition/Answer 

electrons apart provides pressure that keeps the core from  collapsing

what temperature does helium fusion begin?

100 million K

helium flash

when the core temperature and the fusion rate increase  


triple alpha process

dominant process for fusing helium in the core of giants; 3  helium atoms fuse to become carbon atom

what are the two steps of triple alpha process?

two helium nuclei fuse to create beryllium, which either  

carbon is formed or the beryllium turns back into helium; if  carbon fuses with helium, it produces oxygen

instability strip

the region between the main sequence and the right side  

where stars have begun helium fusion and expand

how can variable stars be identified?

their changes in brightness in a field of stars with constant  luminosity

RR Lyrae variables

stars that are post-helium flash that pass through the lower end of the instability strip as they move horizontally on the H-R  diagram

cepheid variable

brightens and fades because the star's outer layers expand and contract

type 1 cepheids

brighter, more massive, metal-rich stars

type 2 cepheids

dimmer, lower mass, metal-poor stars

Concept/Question Definition/Answer 

globular clusters

gravitationally bound groups of old stars from which few  

can escape

horizontal branch stars

hot stars less than 2M fusing helium in their cores

turnoff point

surviving portion of the main sequence that are just  

beginning to exhaust the hydrogen in their cores

population I stars

open clusters that formed from the debris of older metal

rich stars

population II stars

formed from older metal-poor stars

Roche lobs

the region surrounding binary stars; takes on a figure 8  


Roche lobs and mass

the more massive star is always in the larger lobe

detached binary

when two stars are so far apart they live life cycles as if  

they were isolated and single

semidetached binary

when two stars are close, and one overflows is Roche lobe contact binary

when both stars completely fill their Roche lobes, because  they touch and exchange gas; not as common

overcontact binary

more common than contact; they overflow their lobes  

giving rise to a common atmospheric envelope

Ch. 12

Concept/Question Definition/Answer 

asymptotic giant branch star (AGB)

once helium shell fusion begins and the energy pushes the  outer envelope of the star and it leaves the horizontal branch  and ascends

planetary nebula

the core is showing, the expanding gas and dust is  

considered to be a  

does a white dwarf have an atmosphere?

yes, a thin layer of hydrogen and helium

how does a nova occur?

occur in close binary systems that contains white dwarfs  

the star deposits energy into; once the temperature increases  enough hydrogen fusion ignites and blows it into space; the  explosion is the nova

Chandrasekhar limit

the limit of the amount of mass a white dwarf can have

type Ia supernova

semidetached white dwarfs that blow apart completely

what causes a supernova?

a companion star dumps gas onto a white dwarf causing it  to cross the Chandrasekhar line  


process of converting low-mass elements into higher-mass  elements

new shells in the star

each stage of fusion adds a new shell of matter onto the  

core which push the outer layers further out until the star is a  supergiant

silicon fusion in high-mass stars

the end product is iron, which then leads to the death of  

the star

Concept/Question Definition/Answer 


gamma-ray photons breaking apart the iron nuclei

type II supernova

happens in higher mass stars

 (primary) cosmic waves

high speed particles from supernovae aka photons

secondary cosmic waves

cosmic rays created from atoms in our atmosphere

neutron stars

cores stay intact as highly compressed clumps of neutrons neutron degeneracy pressure

when neutrons are pressed together they start to move  

rapidly and produce a pressure greater than the electron  

degeneracy pressure

how fast do pulsars rotate?

30 times every second

when do pulsars slow down?

when they get older


combining the two magnetic fields of the neutron star; also called soft gamma ray repeaters (SGR)

rotating radio transients

emission from neutron stars, it releases radio and other  



material in which electricity and heat flow without friction


material in which electricity and heat flow without the  

system of losing energy

Concept/Question Definition/Answer 


an isolated pulsar radiates energy causing it to slow down  so its solid surface changes shape, which then causes a jump in  the angular momentum - this causes a glitch in the rate at which  the pulsar is slowing down

x-ray burster

emits x-rays at a low level and all of the sudden an abrupt  increase occurs

why do x-ray bursters occur?

like novae, they occur because of their companion neutron  star

theory of special relativity

description of how motion affects our measurements of  

distance, time, energy, and mass

2 notions of theory of special relativity

1. your description of physical reality is the same  

regardless of the constant velocity at which you move; 2.  

regardless of your speed or direction you always measure the  speed of light to be the same

theory of general relativity

describes how spacetime changes shape in the presence of matter

spacetime and gravitational force

the curvature creates an attraction between all matter  

called gravity


in creating a black hole, matter compresses to infinite  

destiny, called  

superstring theory

best-known nascent theory for singularity

event horizon

the boundary between a black hole and the rest of the  


Concept/Question Definition/Answer 

schwarzchild radius

the distance from the center of the black hole to the event  horizon

gravitational radiation

when a stellar remnant collapses into a black hole it loses  all of its internal magnetic field, the field's energy is released as  this

gravitational waves

gravitational radiation travels as ripples in spacetime

what are the 3 properties matter keeps after entering a black hole? mass, angular momentum, and electric charges

2 types of black holes?

those that rotate (Kerr) and those that don't  



swirling region of space

when does a black hole have the most effect on you?

when you are very close to the event horizon


entering a black hole and coming out somewhere else

cosmic censorship

nothing can leave a region of space that contains a  


how do we know black holes exist?

their effects on the orbits of other stars and gas

where are most intermediate-mass black holes located?

in globular clusters

Wolf-Rayet stars

rotating stars with at least 20 M with strong magnetic fields and stellar winds

Concept/Question Definition/Answer 

virtual particle

process of black holes converting their mass into energy Hawing process

the energy from inside the black hole is transmitted  

outside the event horizon as gravitational radiation to replace  energy taken away from newly formed particles

result of Hawing process

the black hole losses its mass and evaporates

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