Week 1 - How the elements are formed

Question 1

• When we use the term _____ we are discussing the
totality of all matter, energy, and space.

Answer 1

Universe

Question 2

___ and ____ emit the full spectrum of
electromagnetic radiation.

Answer 2

Stars and galaxies

Question 3

• Unfortunately for the astronomers, the Earth‟s protective
atmosphere also absorbed much of the incoming
radiation from the non-visible wavelengths.
• Scientists were soon devising ways to minimize or
eliminate the Earth‟s atmospheric filtering.
• Observatories were located on high mountains where the
atmosphere is thin .
• Balloons, aircraft, satellites, and spacecraft were utilized
to transport instruments to ever greater heights.

Answer 3

Studying the universe

Question 4

• While the galaxies are all moving away from each other at
the present time, they must have been closer together in
the past.
• The universe must have been much more compressed.
• In fact most astronomers think that the universe began as
a small, hot, extremely dense entity that rapidly expanded
(exploded) about 14 billion years ago – ______

Answer 4

The big bang

Question 5

• With our present knowledge of subatomic particles and
the structure of the universe we can extrapolate back to
about _____ second of the Big Bang.

Answer 5

10-43 sec

Question 6

• Experimental evidence supports the Big Bang in three
major areas:
• ________– galaxies today have a redshift in
their spectrum lines
• ________– microwave radiation
that fills all space and is thought to represent the
redshifted glow from Big Bang
• There is a H to He mass ratio of 3 to 1 in the stars and
interstellar material, as predicted by the Big Bang model.

Answer 6

Cosmological redshift – galaxies today have a redshift in
their spectrum lines
• Cosmic microwave background – microwave radiation
that fills all space and is thought to represent the
redshifted glow from Big Bang
• There is a H to He mass ratio of 3 to 1 in the stars and
interstellar material, as predicted by the Big Bang model.

Question 7

• With a doubt, our current knowledge of the formation of
the universe is incomplete.
• In 1980 the standard model was modified.
• This proposes that the universe
consists of a large number of separate regions – formed
at about 10-35 second.
• We can only detect information from one of these regions
– our “universe.”

Answer 7

Big Bang - Standard
& Inflationary Models

Question 8

• Much greater expansion took place between 10-35 second
and 10-30 second than in the standard model.

Answer 8

Inflationary Model of the Big
Bang

Question 9

• If the _______ is correct the entire universe is
gigantic and the portion that we can observe is only a tiny
fraction of the whole.
• At the present time the _______ is the best
theory to explain the origin of the universe.

Answer 9

Inflationary Model

Question 10

• this is a self-luminous sphere of hot gases, energized
by nuclear reaction and held together by the force of
gravity.
• the nearest star to Earth.
• enormous in size relative to the size of Earth.
• _______ diameter is approximately 100 times the diameter of
the Earth.

Answer 10

The Sun: Our Closest Star

Question 11

The Sun can divided into four concentric layers:

Answer 11

• The innermost core
• The “surface” is called the photosphere.
• The chromosphere is a layer of very hot gases above the
photosphere.
• The corona is the Sun‟s outer solar atmosphere.

Question 12

The this is the bright and visible “surface” of the
Sun.
• Temperature of 6000K
• Composition of 75% H, 25% He, and 1% C, O, N, Ne, and
others
• When viewed close-up, the photosphere surface appears
to have a „granular‟ texture.
• Each granule is a hot spot caused by an individual
convection cell bringing thermal energy to the surface.
• Each granule is about the width of Texas.

Answer 12

Photosphere

Question 13

• are huge patches of cooler, and therefore
darker material on the surface of the Sun.
• They are a distinctive feature of the photosphere.

Answer 13

Sunspots

Question 14

• The abundance of sunspots vary through an ____
sunspot cycle.
• Each sunspot cycle begins with the appearance of a few
sunspots near the 30o
“N & S” latitudes.
• The number of sunspots slowly increase, with a maximum
number in the middle of the cycle at around the 15o
region.
• The number of sunspots then slowly taper off during the
last half of the 11-year cycle.

Answer 14

Sunspot Cycle

11 year

Question 15

Interestingly, this also have magnetic polarity.
• Each 11-year cycle is similar except that the polarities are
reversed.
• Therefore the 11-year sunspot cycle is actually a
manifestation of a more fundamental 22-year magnetic
cycle.

Answer 15

Sunspot Cycle

Question 16

• ________‟s temperature is approximately 1 million K.
• Prominences occur within the corona region of the Sun.

Answer 16

Corona

Question 17

• In the extreme high-temperatures of the corona protons,
electrons, and ions are furnished with enough energy to
escape the Sun‟s atmosphere.
• These particles are accelerated enough to escape the Sun‟s
tremendous gravitational pull.
• The solar wind extends out from the Sun at least 50 AU.

Answer 17

Solarwind

Question 18

• The Sun‟s ______ is so hot that individual atoms cannot
exist.
• Continuous high-speed collisions result in the separation of
nuclei and electrons.

Answer 18

Interior of the Sun

Question 19

• Moving outward from the core of the Sun, both the
temperature and the density decrease.
• It is the nuclear fusion of ______ within the core that is
the source of the Sun‟s energy.
• In the Sun and other similar stars the nuclear fusion takes
place as a three step process called the

Answer 19

Interior of the Sun

H into He

Proton proton chain

Question 20

In the net reaction of the PP Chain, four protons form a
He nucleus, two positrons, two neutrinos, and two gamma
rays.
• The amount of energy released by the conversion of
mass conforms with Einstein‟s equation, E = mc2

Answer 20

Proton-Proton Chain

Question 21

• Approximately 6.00 X 1011 kg of H is converted into 5.96
X 1011 kg of He every second
• With a total mass of 1030 kg of H, scientists expect the
Sun to continue to radiate energy from H fusion for
another

Answer 21

5 billion years

Question 22

The Earth only receives a very small percent of the Sun‟s
radiated energy.
• Every second the Earth receives approximately 1.4 x 103
W/m2
, a value known as ______
• Even a very small variation (+/- 0.5%) in the solar
constant would have disastrous effects on our planet‟s
biota.

Answer 22

Solar Constant

Question 23

Recall that stars are composed dominantly of ____, with
some ____, and far lesser amounts of other elements.
• They exist as huge plasma spheres in which nuclear
fusion of H to He produces enormous amounts of energy
that is emitted.
• Although star masses can vary considerably, most have a
mass between 0.08 – 100 solar masses.
• One solar mass = mass of our Sun

Answer 23

H and He

Question 24

• Most stars are part of a ______ system, unlike our
Sun that is a single star.

Answer 24

Multiple star system

Question 25

• This Diagram results from plotting the stars‟ absolute magnitudes versus the temperatures of their photospheres.

Answer 25

The H-R (Hertzsprung-Russell) Diagram

Question 26

• Several types of star do not fall on the main sequence. • these are very large stars that are cool, yet still very bright • The very brightest are called • these are stars that are very hot, yet are dim due to their small size

Answer 26

Stars off the H-R Main Sequence • Several types of star do not fall on the main sequence. • Red giants – very large stars that are cool, yet still very bright • The very brightest are called red supergiants. • White dwarfs – stars that are very hot, yet are dim due to their small size

Question 27

__________ of stars shows that even the most distant stars contain the same elements we find in our solar system. • However, there are variations in the spectra depending on the temperature of the individual star‟s photosphere. • Therefore, the patterns of the absorption lines in the spectra can be used to determine both the composition and the surface temperature.

Answer 27

Spectral Analysis of the Stars

Question 28

• In the _____, stars have been placed in seven spectral classes -- O,B,A,F,G,K,M. • Note the horizontal top axis of the diagram.

Answer 28

H-R Diagram

Question 29

• Our ____ falls close to the middle of the main sequence and is a class G star. • this is the closest star to Earth (besides our Sun) and is a red dwarf or class M star.

Answer 29

• Our Sun falls close to the middle of the main sequence and is a class G star. • Sirius is quite a bit hotter than our Sun and is a class A star. • Astronomers have found that the majority of stars are small, cool, class M stars, also called red dwarfs. • Proxima Centauri is the closest star to Earth (besides our Sun) and is a red dwarf or class M star.

Question 30

• – gases and dust that is distributed amongst the stars • The gases consists of about 75% H, 25% He, and a trace of heavier elements by mass. • The dust (only about 1% of the interstellar medium) consists primarily of C, Fe, O, & Si. • About the size of particles in smoke

Answer 30

Interstellar Medium

Question 31

• The gases and dust do not appear to be distributed uniformly throughout space. •________ – concentrations of cool, dense clouds of gases and dust • Two major types of ____exist: bright and dark

Answer 31

Nebulae

Question 32

• Bright nebulae can, in turn, be divided into:

Answer 32

• Emission nebulae – energy from nearby stars ionize the hydrogen gas resulting in fluorescence • Reflection nebulae – dust within the nebulae reflect and scatter starlight, giving off a characteristic blue color

Question 33

• The most famous of the _____66 is located in the constellation Orion. • It appears like the head of a horse, back-lit by a bright emission nebula.

Answer 33

Dark nebulae

Question 34

• Stars begin to form as interstellar material (mostly H) gathers together. (accretion) • The accretion of the interstellar material may be due to several factors: • Gravitational attraction of the material • Radiation pressure from nearby stars • Shockwaves from exploding stars • A protostar forms as the interstellar material condenses and the temperature rises.

Answer 34

General Evolution of a Low-Mass Star

Question 35

• As the _____ continues to condense, the temperature continue to rise. • As the temperature continue to rise, the thermonuclear reaction begins in which H is converted to He. (fusion) • Recall the reaction below:

Answer 35

Protostar

Question 36

• When ______ begins, this is the time a star is actually born. • It moves onto the H-R main sequence, in a position determined by its temperature and brightness. • Ultimately both temperature and brightness are dependent upon the star‟s mass.

Answer 36

Star is born thermonuclear fusion

Question 37

• As the star continues to fuse H into He, it remains on the H-R main sequence. • The period of time that a star remains on the main sequence can vary widely. • A ____ star, such as our Sun, will remain on the main sequence for 10 billion years. • A _____ star may stay on the main sequence for trillions of years.

Answer 37

Low mass star

Question 38

• As H in the core continues to convert to He, the core begins to contract and heat up even more. • This extra heat eventually causes the H in the surrounding shell to proceed more rapidly, which in turn destabilizes the star‟s hydrostatic equilibrium, resulting in expansion. • At this point, when the star expands, it enters the red￾giant phase, and moves off the main sequence.

Answer 38

Stellar evolution

Question 39

When our Sun moves into its ______ phase (several billion years from now) it will swell and engulf Mercury and possibly Venus. • The core of a red-giant eventually becomes so hot that He will fuse into C and perhaps will create elements up through Ne. • this is the creation of elemental nuclei inside stars. • In high-mass red supergiants nucleosynthesis may continue all the way up to Fe.

Answer 39

Red giant phase

Question 40

This occur in the star‟s temperature and brightness during the red-giant phase. • For a short time it becomes a variable star, as its position on the H-R diagram moves left.

Answer 40

Variation

Question 41

• During and after the ______ stage the star becomes very unstable, resulting in the outer layers being blown off forming a planetary nebula. • Planetary nebula have nothing to do with planets. • Early and fuzzy photographs of planetary nebula reminded astronomers of an evolving solar system. • The expelled material diffuses into space, providing material for future generations of stars.

Answer 41

Variable star

Question 42

• Following the formation of a planetary nebula the remaining core is called a ____ • Thermonuclear fusion no longer occurs in a ____ and it slowly cools by radiating its residual energy into space. •______are not very bright and fall low on the H-R diagram. • A single teaspoon a matter in a ____ may weigh 5 tons!

Answer 42

White dwarf

Question 43

This is a class-A main sequence star. • _____ is a white dwarf at about 5 o‟clock.

Answer 43

Sirius A and B

Question 44

• During stellar evolution, what if a protostar cannot sustain thermonuclear fusion due to its small mass? • In this situation the protostar would not progress to the star phase and would result in a • Obviously _____ are very dim. • The first ____ was not discovered until 1996. – Gleise 229B • About 100 _____ have now be found.

Answer 44

Brown Dwarfs

Question 45

• _____ stars and low-mass stars form initially in similar manners. • _____ stars are hotter and brighter than low-mass stars. • _____ star move onto the main sequence at higher points. • ______ stars do not stay on the main sequence as long as low-mass stars, due to their higher rate of thermonuclear fusion.

Answer 45

High-Mass Star

Question 46

When high-mass stars moves off the main sequence they become red supergiants and eventually explode as _____. Much of the material is scattered into space leaving behind a neutron star or black hole.

Answer 46

Type II Supernovae

Question 47

As we have learned in sections 18.4 & 18.5, the initial mass that a celestial object acquires during its formation is very important in determining its eventual fate. • But the final mass left over after any stellar material is ejected turns out to be the conclusive determinant

Answer 47

Mass and Stellar Evolution

Question 48

Thses are giant assemblages of stars.

Answer 48

Galaxies

Question 49

These deals with the structure and evolution of the universe.

Answer 49

Cosmology

Question 50

• • For many years we were only able to gather information from one type of emitted electromagnetic radiation –_______

Answer 50

Visible light

Question 51

• In 1931 _____ became operational, giving scientists the ability to start gathering information from other wavelengths

Answer 51

Radio telescopes

Question 52

• Initially the universe was filled with ___ •

Answer 52

Protons

Question 53

• Within the first 4 seconds ___,___ and ___ formed.

Answer 53

protons, neutrons, and electrons

Question 54

D and He nuclei formed in the first ____ minutes.

Answer 54

3 mins

Question 55

After about ½ million years gravity began forming ____ and ____

Answer 55

Galaxies and stars

Question 56

A fourth phase of matter, called a ______ is created where nuclei and electrons exist as a high-temperature gas.

Answer 56

Plasma

Question 57

• The temperature at the central core of the Sun is

Answer 57

15 million K and the density is 150 g/cm3

Question 58

The innermost 25% of the Sun, the ____, is where H is consumed to form He

Answer 58

Core

Question 59

This is the volume or “bubble” of space formed by the solar wind.

Answer 59

Heiliosphere

Question 60

Virtually all the material in the heliosphere emanates from the

Answer 60

Sun

Question 61

are bright explosive events that occur on the Sun‟s surface.

Answer 61

Flares

Question 62

are enormous filaments of solar gases that arch out and over the Sun‟s surface. • may extend hundreds of thousands of km outward.

Answer 62

Prominences

Question 63

• The late 1600‟s were an unusually cold period on Earth, marked by an anomalously fewer number of sunspots. • In Europe this time was known as the ______ • Apparently, there is a strong connection between solar activity, as displayed by sunspots, and global climates on Earth

Answer 63

Little ice age

Question 64

The this is the pearly white halo or crown extending far beyond the solar disk • Visible during total eclipses of the Sun. • This can be interpreted to be the Sun‟s “outer atmosphere.”

Answer 64

Corona

Question 65

stars that consist of two close stars each orbiting about their shared center of mass

Answer 65

Binary star

Question 66

• Most stars are part of a _____ system.

Answer 66

Binary system

Question 67

• There are also _____ systems with three or more closely spaced stars but these are far less frequent.

Answer 67

Star system

Question 68

• Most stars become brighter as they

Answer 68

Hotter

Question 69

• These stars plot as a narrow diagonal band in the diagram.

Answer 69

H-R DIAGRAM

Question 70

• The hottest (and generally brightest) stars are _____. The coolest (and generally least bright) stars are _____

Answer 70

• The hottest (and generally brightest) stars are blue. The coolest (and generally least bright) stars are red.

Question 71

This is quite a bit hotter than our Sun and is a class A star.

Answer 71

Sirius

Question 72

Astronomers have found that the majority of star are small, cool, class M stars, also called

Answer 72

Red dwarfs

Question 73

energy from nearby stars ionize the hydrogen gas resulting in fluorescence

Answer 73

Emission nebulae

Question 74

dust within the nebulae reflect and scatter starlight, giving off a characteristic blue color

Answer 74

Reflection nebulae

Question 75

• – produced by the obstruction of a relatively dense cloud of interstellar dust • are visible as relatively dark areas as they are framed against some type of light-emitting region behind them.

Answer 75

Dark nebulae

Question 76

_____ stars fuse fuel fast, and only remain on the main sequence a few million years.

Answer 76

High mass star