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ANSWER SHEETS- ASTRONOMY ISLIP: Dec 10th, 2016: Stellar Evolution and Type Ia Supernovae
Team Number: ________ School: _________________Students: ___________________, _________________
Short Response SECTION I (12 points):
1)
2)
3)
4)
5)
6)
7)
8)
9)
10)
11)
12)
Answer: Accept anything from 200 to 50,000 luminosity.
Answer: As temperature increases, luminosity also increases. (Or accept “Direct”).
Answer: As a star’s size increases, luminosity also increases. (Direct).
Answer: As the star’s initial mass increases, its lifespan decreases. (indirect or inverse)
Answer: Sirius is both more luminous and higher in surface temperature than our Sun.
Answer: White Dwarf.
Answer: Approximately 10-13 million Kelvin.
Answer: Mg, Si, S, P. (Magnesium, Silicon, Sulfur, and Potassium) – must have all 4
Answer: Approximately 4 Solar Masses.
Answer: Deuterium
Answer: Hydrogen AND Helium
Answer: 11,428 BC +- 100yrs and approx 13000 yrs later
Multiple Guess Questions Section II (5 Points)
1) B
2) C
3) D
4) C
5) B
Fact Correction Section III (20pts)
1) REPLACE: “hybridization” with “ionization”
2) REPLACE: “A” with “O”
3) Replace: “Red” with “Blue”
4) Replace: “C” with “Si”
5) Replace: “F” with “G”
6) Replace “Carbon” with “Helium”
7) Replace: “neutron” with “electron”
8) Replace: “10,000” with “One Million” (1,000,000 or 1 x 106)
9) Replace: “Ultraviolet” with “Infrared”
10) Replace: “Decreases” with “Increases”
11) Replace: “Rosenberg” with “Chandrasekhar”
12) Replace: “greater” with “Less”.
13) Replace: “abundance” with “lack”
14) Replace: “Neutrinos” with “Neutrons”.
15) Replace: “pulsars” with “masers”.
16) Replace: “54” with “72” (*accept anything from 66 to 75)
17) Replace: “abundance” with “lack” (or dearth, etc)
18) Replace: “highest” with “lowest”
19) Replace: “square” with “cube”
20) Replace: “Oxygen” with “Hydrogen”
Mathematics Section III: 16 Points *Each question in this section is worth up to 4 points. Partial credit may be awarded
for an incomplete or incorrect answer in some instances. PLEASE SHOW ALL WORK ON THE ANSWER SHEETS
1) Please estimate how close a 0.5 solar mass white dwarf must come to the center of a 2 solar mass subgiant
companion (which has a radius 10 times more than that of our sun) in order for the white dwarf’s tidal field to
strip matter from the companion’s surface. Answer in km to 3 significant digits.
Answer: *Partial credit MAY be awarded for ALL partial answers which are “close”.
Mass of White Dwarf = Mwd Mass of the subgiant star = Msg
Rsg is the Radius of the subgiant.
D = the separation of their centers. We are looking for a place where the gravitational forces on a
mass (ma) from both objects are equal.
Gravitational force from subgiant is = G Msg*ma/Rsg2 Force from the white dwarf = GMwd/(D-Rsg)2
G Msg*ma/Rsg2 = GMwd*ma/(D-Rsg)2
2/102 = 0.5/(D-10)2
(D-10)2 = 25 *One solar radii is equal to 6.957 X 105 km
D = 1.04 X 107 km (accept answer +/- 20%)
2) Use a “radius – luminosity – temperature” relation to calculate the radius of a 12,000 K and 0.0004 solar
luminosity white dwarf (answer in km to 3 significant digits).
*Partial credit MAY be awarded for ALL partial answers which are “close”.
Answer: (Rwd/Rsun)2 = (Lwd/Lsun) * (Tsun/Twd) 4 = (0.0004/1) (5780/12,000) 4 = 0.000021
0.000021 = (Rwd/Rsun) 2
Sun’s Radius is = 695,700 km
Answer: 3188.1 km (+/- 20% to 3 sig figs)
3) What is the escape speed (in km/s) and surface gravity (relative to Earth gravities) of Sirius B? (use the
following data for Sirius B; 1.1 solar mass, and 0.008 solar radii). Answer in “km/s” (for escape speed), and
“Earth gravities” to three significant digits please.
Answer: M= 1.1 solar masses = 2.2 X 1030 kg and R= 0.008 solar radii = 5.6 X 106 m
v = square root of (2GM/R)
G = 6.67408 × 10-11 m3 kg-1 s-2
v= 7,240,000 m/s or 7240 km/s (+/- 20% to 3 sig figs)
Formula for “acceleration due to surface gravity”;
a = GM/R2 = 4.68 X 106 m/s2 Earth’s acceleration is only; 9.8 m/s2
Therefore, the white dwarf has 477,000 earth gravities (+/- 20% to 3 sig figs).
4) If a type Ia Supernovae has an apparent magnitude of -13.5 (and is a “perfect theoretical model” at the
Chandrasekhar limit for an Ia supernova), what is its distance in parsecs? (to the nearest one tenth)
Answer: According to current theory, a type Ia supernova should have an absolute magnitude of about -19.3
to -19.6 (this is due the Chandrasekhar limit);
In order to complete this problem we use the distance modulus equation;
(using -19.3 as the accepted value for a Ia supernova); 10.8 = 5 Log10 (d) = 2.16 = Log10 (d) = 102.16 = d
d= 144.5 pc (accept any answer from) 143.0 pc to 163.0 pc
Part IV. Image Matching Section (2pt/ea): 31 points.
1) Object Name: Sirius A & B
Object Letter: M
2) Object Name: Henize 3-1357 (Sting Ray Nebula)
Object Letter: H
3) Object Name: NGC 2392
Object Letter: Q
8) Object Name: Omicron Ceti
Object Letter: A and F (either 1pt, both 2pts)
9) Object Name: SNR G1.9 +0.3
Object Letter: G
10) Object Name: NGC 2440
4) Object Name: SNR 0509-67.5
Object Letter: D
Object Letter: R
11) Object Name: Henize 2-248
5) Object Name: HM Cancri (RX J0806.3+1527)
Object Letter: J
6) Object Name: SN 2011fe
Object Letter: N
7) Object Name: J075141/J174140
Object Letter: L
Object Letter: K
12) Object Name: Tycho’s SNR (SN 1572)
Object Letter: E
13) Object Name: SS Cygni
Object Letter: P
14) Object Name: M15
Object Letter: C
15) Object Name: NGC 1846
Object Letter: I
ESSAY QUESTION SECTION V: up to 16 points may be awarded for this section, and this question used to break TIES!
*Answer on the answer sheets provided:
In this section you will write a 700 word (approx.) essay about the following topic:
“How have discoveries concerning Ia Supernovae changed our understanding of the universe?”
(*Remember to “dot” or “bullet” the 8 facts you wish to count for credit and include at least 3 DSOs)
For this competition you have learned about type Ia Supernovae, but and not all type Ia events are the same. For this
essay, compare and contrast the different theories for how a type Ia supernova could be generated. If possible, show an
“evolution” of theories from the past to the present. Be certain to present at least three of this year’s DSO objects in
your essay.
In your Essay you must:
1) Include at least THREE “DSO” objects from this year’s competition, each with facts that are both “substantial and
relevant”. Failure to use at least three DSO objects properly will cause a deduction in score. Using more than
three DSO objects correctly will “break ties” between examinations.
2) You MUST use facts that are both “Substantial” and “Relevant”. Up to 8 points may be awarded for each essay
with facts that meet this criteria (•Which are also BULLETED so that they stand out in the document)
3) You may use more than 8 facts in your essay, but you should choose the BEST EIGHT of those facts to be the
ones you wish to use for point scoring. Those specific facts must be marked with a “bullet”. They do not have to
be written “in a list” format and may be embedded within the paragraph so long as they are marked with a
“Bullet” or “Dot” ● to indicate the factual information you wish to present for scoring.
4) If more than 8 facts are “Bulleted”, only the first 8 facts will be counted and measured for overall quality.
Points for Style: Up to 8 points will be awarded for the “Style” of your essay. Do the facts ‘flow’ consistently?
Is your essay clear, logical, and easy to follow? Did you make it engaging, creative, and informative? Essays will
be split into 4 basic “tiers” for style. Each “tier” will be split into a “lessor or greater” section based on the
overall quality of the essay.
0pts: This “essay” is merely a collection of facts with no real format.
1-2pts: Essay is structured, but poorly structured, or is confusing/difficult to understand.
3-4pts: Essay is easy to follow, with acceptable structure but not particularly engaging or creative.
5-6pts: Essay is well structured, creative, as well as an interesting read, the author has strong ‘voice’ and
‘direction’.
7-8pts: This point category will be awarded to the very best essay we have seen for this exam session. It may
be given only to the very best essay, or to several (possibly 2 or 3) essays if all are similarly impressive.