Download Astronomy 12: Introduction to Astronomy

Astronomy 12
Astronomer:_______KEY_____
Stellar Evolution Worksheet
I. MULTIPLE CHOICE: Please fill in the letter corresponding to the most appropriate answer
1.How does the H-R diagram help astronomers identify stars?
a. It plots a star’s mass and core temperature, which allows astronomers determine the colour
and region of where star is formed.
b. It plots a star’s luminosity and spectrum, which allows astronomers determine the size of the
star.
c. It plots a star’s luminosity and surface temperature, which allows astronomers determine the
type of star, size of star, and the star’s stage of evolution.
d. It plots a star’s size and surface temperature, which allows astronomers determine its region of
origin
2. What is the Main Sequence?
a. The evolutionary path, as seen on the H-R diagram, that a star follows throughout its life.
b. The region on the H-R diagram where, once they are formed. new stars rest for most of their
lives.
c. The sequence of events a star follows from its formation to supernova.
d. The region on the H-R diagram where protostars first appear.
3. Define hydrogen burning.
a. The formation of a hydrogen gas cloud, also known as a nebula.
b. The chemical combustion of hydrogen.
c. The separation of the hydrogen envelope to form a planetary nebula.
d. The formation of helium by fusing hydrogen together.
4. When a star’s gravitational force pulling inwards and its internal pressure pushing outward are
balanced, it is considered to be in what?
a. Hydrostatic equilibrium
b. Supernova
c. Structural Balance
d. Proton-proton fusion
5. What is a helium flash?
a. The rapid fusion of helium in a red giant’s core.
b. An explosion that creates a planetary nebula.
c. A type of solar flares that occurs on the surface of sun-type stars.
d. A flash of white light that occurs when a star collapses into a white dwarf.
6. What is a planetary nebula?
a. The destroyed remains of a planetary solar system when a sun-type star expands into a red
giant.
b. The ejected envelope of a red giant that was formed from a sun-type star.
c. The disk of material around a protostar that will eventually form planetary system.
d. The initial massive gas cloud that stars and planets are formed from.
7. A white dwarf found in a binary system suddenly brightens, settles back down in a few months,
and has the possibility to repeat. What is this called?
a. Brown dwarf
b. Carbon-detonation supernova (Type I)
c. Planetary nebula
d. Core collapsing supernova (Type II)
8. What does ZAMS stand for?
a. Zero Asymptotic Massive Star
b. Zero-Age Main Sequence
c. Zygote Amalgamated Missing Sun
d. Zeppelin Acoustics Make Sound
9. What is the significance of the ‘turn-off point’ on the H-R diagram for a star cluster?
a. It determines the total mass of the cluster.
b. It determines the total luminosity of the cluster.
c. It determines the total number of stars in the cluster.
d. It determines the age of the cluster.
10. What is a brown dwarf?
a. The type of star a white dwarf becomes after a long period of time.
b. A protostar that has low mass and insufficient core temperature and pressure to produce
nuclear fusion.
c. The stage before a star becomes a black hole.
d. A chocolate-covered elf.
a
b
c
d
a
b
c
d
a
b
c
d
a
b
c
d
a
b
c
d
a
b
c
d
a
b
c
d
a
b
c
d
a
b
c
d
a
b
c
d
II. DIAGRAMS: Label or explain diagrams as indicated
11. Complete tree diagram below: describe the two types of supernovas.
Supernova
Type I – Carbon
Detonation
-lack H lines in spectra
-can be formed from WD in binary
system or supergiants with H/He
removed
-found everywhere in Galaxy
-produced from old, low-mass stars
-fixed maximum brightness
Type II – Core
Collapsing
-have H lines in spectra
-formed from young, massive stars
-observed in arms of spiral galaxies
-end result: NS or BH
-stay brighter longer, with variable
maximum brightness  brightness
decreases rapidly
12. Complete table below: For each STAGE, write the letter of its STAGE DESCRIPTION in the corresponding blank. See #7
as an example.
H-R Diagram
Stage
(7 to 14)
Stage Description
7. ___F___
A.
B.
C.
D.
8. ___I___
9. ___C___
10. ___D___
11. ___L___
12. ___B___
13. ___M___
14. ___A___
E.
F.
G.
H.
I.
J.
K.
L.
M.
Black Dwarf
Planetary Nebula
Helium Flash
Carbon core expands and
star returns to a balance
state.
Supernova
New Star
Oxygen fusion
Carbon burning
Forms a helium core as it
leaves the main sequence
Protostar
Fragmentation
Carbon core contracts and
star climbs Giant branch
again.
White dwarf
SHORT ANSWER QUESTIONS
13. Explain the general formation of a sun-type star (i.e. Steps 1-6).
Stage 1: Fragmentation of Nebula  with sufficient mass, nebula fragments repeatedly under
gravity
Stage 2: Fragmentation Stops  lower-mass fragments form until internal gas pressure greater
than gravity and fragmentation stops; thin fragment with hot center
Stage 3: Formation of a Protostar  protostar and protoplanetary disk form; heat and light from
gravitational energy at the core produce YSO (no fusion)
Stage 4: Can be Seen on H-R diagram  no fusion but gravitational collapse produces sufficient
surface temperature and luminosity to be measured on H-R diagram
Stage 5: Violent Surface Activity  due to increasing core pressure from gravity, core traps heat
that is released from time to time, causing violent surface activity
Stage 6: Helium Core is Formed  core temperature sufficient to produce proton-proton fusion
and helium deposited in core
14. Complete the Venn diagram below to compare the history of high mass stars with low mass stars (Hint: think the
formation, evolution and death of the different stars).
15. Phi Orionis is a Main Sequence star in the constellation Orion. It has a mass 18 times that of our Sun. Predict what will
happen to Phi Orionis when it leaves the Main Sequence on the HR Diagram.
Phi Orionis will continue to burn heavier elements at the core, producing layers of heavier elements, up to iron.
Eventually, this star will go supernova (Type II SN). After SN, a neutron star is produced.