## Astronomy C

Test your knowledge of various Science Olympiad events.
Magikarpmaster629
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### Re: Astronomy C

Unome wrote:
Magikarpmaster629 wrote:This QM is severely laking in math...

The system 'Beta Constellationi' contains two stars, A and B. It has a measured trigonomic parallax of 0.03 arcseconds and the angular size of the semi-major axis is 2.93 arcseconds. The system takes 465.5 years to fully orbit.

1. What is the distance to the system in parsecs?
2. What is the actual distance between stars A and B in AU?
3. What is the mass of the system? Give your answer in solar masses.
4. The distance from the center of mass of the system (also known as the barycenter) to star A is 60 AU. What is the distance to star B from the barycenter?
5. What are the individual masses of stars A and B?
```1. 33.33 parsecs
2. 97.66 AU?
3. uhhh... 1148120.12 solar masses? lol
4. 37.66 AU???
5. if 3 and 4 are correct, A = 507518.948 solar masses and A = 640601.172 solar masses (iirc stars don't actually get this big, right?)```
Stars don't get that big; you messed up on 3 and 5. 1, 2, and 4 are fine. You or someone else can try again.

EDIT: Actually there's a chance I messed up...the distance between the stars should be the same as the semi-major axis, but I could be wrong. Looking it up now.

EDIT 2: That does work...check Kepler's Third Law again.

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### Re: Astronomy C

```1. 33.33pc
2. 97.66 AU
3. 4.298 solar masses
4. I'm not 100% sure what you mean - is this just supposed to be 97.66-60 = 37.66 AU?
5. B is 2.641085 solar masses, A is 1.6575 solar masses (these may be a bit off due to rounding along the way)```
Unome, I think you might have forgot to cube or square something (but more likely the latter, since your answer is so large) while doing stuff with Kepler's Third Law. The most massive star, R136a1, is 265-375 solar masses, while a lot of theoretical estimates give a maximum mass of usually 70-300 solar masses.
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Magikarpmaster629
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### Re: Astronomy C

```1. 33.33pc
2. 97.66 AU
3. 4.298 solar masses
4. I'm not 100% sure what you mean - is this just supposed to be 97.66-60 = 37.66 AU?
5. B is 2.641085 solar masses, A is 1.6575 solar masses (these may be a bit off due to rounding along the way)```
Unome, I think you might have forgot to cube or square something (but more likely the latter, since your answer is so large) while doing stuff with Kepler's Third Law. The most massive star, R136a1, is 265-375 solar masses, while a lot of theoretical estimates give a maximum mass of usually 70-300 solar masses.
Yeah, that's right.

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### Re: Astronomy C

(sorry for the late post!)

Consider the graph below, which shows two quantities for a white dwarf, mass and density, plotted as a function of radius. X-values increase going to the right, and y-values increase going up.

(a) Which colored line shows the mass?
(b) Which colored line shows the density?
(c) What does this graph suggest about the relationship between mass and radius for this type of star?
(d) Is your answer to (c) also true for main-sequence stars?
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Magikarpmaster629
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### Re: Astronomy C

Adi1008 wrote:(sorry for the late post!)

Consider the graph below, which shows two quantities for a white dwarf, mass and density, plotted as a function of radius. X-values increase going to the right, and y-values increase going up.

(a) Which colored line shows the mass?
(b) Which colored line shows the density?
(c) What does this graph suggest about the relationship between mass and radius for this type of star?
(d) Is your answer to (c) also true for main-sequence stars?
a) Black
b) Red
c) There is an inverse relationship between mass and radius
d) No; they have a direct relationship

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### Re: Astronomy C

Magikarpmaster629 wrote:
Adi1008 wrote:(sorry for the late post!)

Consider the graph below, which shows two quantities for a white dwarf, mass and density, plotted as a function of radius. X-values increase going to the right, and y-values increase going up.

(a) Which colored line shows the mass?
(b) Which colored line shows the density?
(c) What does this graph suggest about the relationship between mass and radius for this type of star?
(d) Is your answer to (c) also true for main-sequence stars?
a) Black
b) Red
c) There is an inverse relationship between mass and radius
d) No; they have a direct relationship
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### Re: Astronomy C

DSO fun time!

This is an image of a system that consists of a red giant and a white dwarf.
a) What is the name of this DSO?
b) This DSO is a prototype of what type of variable star? This type is a subcategory of what class of periodic variables?
c) What type of binary system is this DSO in?

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### Re: Astronomy C

Magikarpmaster629 wrote:DSO fun time!

This is an image of a system that consists of a red giant and a white dwarf.
a) What is the name of this DSO?
b) This DSO is a prototype of what type of variable star? This type is a subcategory of what class of periodic variables?
c) What type of binary system is this DSO in?
```a. Omricon Ceti (Mira)
b. Mira Variable, Long period variable(?)
c. Semi-detached binary system(?)```
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### Re: Astronomy C

Magikarpmaster629 wrote:DSO fun time!

This is an image of a system that consists of a red giant and a white dwarf.
a) What is the name of this DSO?
b) This DSO is a prototype of what type of variable star? This type is a subcategory of what class of periodic variables?
c) What type of binary system is this DSO in?
```a. Omricon Ceti (Mira)
b. Mira Variable, Long period variable(?)
c. Semi-detached binary system(?)```
I guess I was kinda vague on b and c. I was looking for 'symbiotic binary' on b but semi-detached works too. Your turn.

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### Re: Astronomy C

Magikarpmaster629 wrote:
Magikarpmaster629 wrote:DSO fun time!

This is an image of a system that consists of a red giant and a white dwarf.
a) What is the name of this DSO?
b) This DSO is a prototype of what type of variable star? This type is a subcategory of what class of periodic variables?
c) What type of binary system is this DSO in?
```a. Omricon Ceti (Mira)
b. Mira Variable, Long period variable(?)
c. Semi-detached binary system(?)```
I guess I was kinda vague on b and c. I was looking for 'symbiotic binary' on b but semi-detached works too. Your turn.
Could you explain how "symbiotic binary" would be a possible answer choice for (b)? (or did you mean (c), in which case, what would you put for (b)?)

Anyways, here's my question: A team of astronomer catalogs a Star A as a subdwarf. 20 years later, after carefully analyzing this star's movement through the sky, another team of astronomers notices that the proper motion of this star is unusually high.

(a) What does this imply about the distance to Star A?
(b) Briefly describe explain how the new evidence about Star A's proper motion could be used as evidence that it is, in actuality, a white dwarf as opposed to a subgiant star

Everybody's really excited about this new discovery, which launches even more in depth observations of the system!! They soon discover that Star A is actually composed of two white dwarfs, X and Y, having the radial velocity chart below:

(c) Suppose that X is the more massive star. Which colored line shows it's radial velocity?
(d) Going from phase = 0.0 to phase = 2.0 represents how many orbits?
(e) Suppose that the period of these two stars decreases. What type of wave (which LIGO detected evidence for) is produced as a result of this?
(f) Before the astronomers discovered that the Star A was a binary system, they used parallax to estimate that its distance from Earth was d1. Using parallax once again, they estimate the distance to this system, taking into account that it's a binary star system, coming up with a new distance d2. Which of the two distances is bigger?
(f) The combined mass of these two stars is about 0.9 solar masses, which isn't massive enough to result in a Type Ia supernovae. Instead, when the two merge, what type of star will they form?
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