## Astronomy C

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### Re: Astronomy C

Mostly correct. For 3, you could tell by reading the source, but the easiest way is to notice that both phases have exactly identical data, MEs, etc. - it's one phase of data, doubled to make it easier to interpret. Your turn.
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### Re: Astronomy C

Starting this up again:

An expanding ring of material from a supernova appears to be shaped as an ellipse due to its inclination with Earth (assume that the ring, in reality, expanded uniformly so it is actually circular). Its major axis is twice as long as its minor axis. What is the inclination of the ring?
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### Re: Astronomy C

Starting this up again:

An expanding ring of material from a supernova appears to be shaped as an ellipse due to its inclination with Earth (assume that the ring, in reality, expanded uniformly so it is actually circular). Its major axis is twice as long as its minor axis. What is the inclination of the ring?
Aren't there two potential answers (30 degrees or 60 degrees)
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### Re: Astronomy C

Starting this up again:

An expanding ring of material from a supernova appears to be shaped as an ellipse due to its inclination with Earth (assume that the ring, in reality, expanded uniformly so it is actually circular). Its major axis is twice as long as its minor axis. What is the inclination of the ring?
Aren't there two potential answers (30 degrees or 60 degrees)

It depends on where the angle is being measured from, which I forgot to specify T_T
If the angle between the plane in which the ring lies is 30 degrees with the horizontal or 60 degrees with the vertical it'd be correct
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### Re: Astronomy C

Starting this up for next year's topic:

Suppose an astronomer discovers an elliptical galaxy whose major axis is 2 times longer than its minor axis.

a. What would the classification of this galaxy be?
b. What assumption do you make when classifying the galaxy about its orientation when viewed from Earth?
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### Re: Astronomy C

Starting this up for next year's topic:

Suppose an astronomer discovers an elliptical galaxy whose major axis is 2 times longer than its minor axis.

a. What would the classification of this galaxy be?
b. What assumption do you make when classifying the galaxy about its orientation when viewed from Earth?
a. The Hubble classification of elliptical galaxies is En where n = 10(1 - b/a). Using this formula, you get that the galaxy is classified as E5.
b.You would assume that the galaxy is perpendicular to your line of sight from Earth, essentially flat from your point of view.
R. I. P. 01/20/2019

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### Re: Astronomy C

Starting this up for next year's topic:

Suppose an astronomer discovers an elliptical galaxy whose major axis is 2 times longer than its minor axis.

a. What would the classification of this galaxy be?
b. What assumption do you make when classifying the galaxy about its orientation when viewed from Earth?
a. The Hubble classification of elliptical galaxies is En where n = 10(1 - b/a). Using this formula, you get that the galaxy is classified as E5.
b.You would assume that the galaxy is perpendicular to your line of sight from Earth, essentially flat from your point of view.
Good answer! A few quick comments on the second part: the assumption is indeed that the galactic plane is perpendicular to the line of sight from Earth. I think the part saying it appears "flat" could be a bit ambiguous though and a proctor/grader could interpret it as meaning edge-on, instead of face-on. When you're viewing a (circular/disc-like) object at an angle, you're seeing the projection of the circle as an ellipse. To classify the galaxy, we need to know if we're viewing the galaxy at an angle or if it's actually that shape. Your turn

edit: After doing more reading, I've actually found that the Hubble scheme classifies galaxies entirely by how they appear to us on the Earth. The galaxy could be spherical in reality, but if it appears very elliptical, it'd be given a classification that says it's very elliptical. Bad question on my part
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### Re: Astronomy C

Starting this up for next year's topic:

Suppose an astronomer discovers an elliptical galaxy whose major axis is 2 times longer than its minor axis.

a. What would the classification of this galaxy be?
b. What assumption do you make when classifying the galaxy about its orientation when viewed from Earth?
a. The Hubble classification of elliptical galaxies is En where n = 10(1 - b/a). Using this formula, you get that the galaxy is classified as E5.
b.You would assume that the galaxy is perpendicular to your line of sight from Earth, essentially flat from your point of view.
Good answer! A few quick comments on the second part: the assumption is indeed that the galactic plane is perpendicular to the line of sight from Earth. I think the part saying it appears "flat" could be a bit ambiguous though and a proctor/grader could interpret it as meaning edge-on, instead of face-on. When you're viewing a (circular/disc-like) object at an angle, you're seeing the projection of the circle as an ellipse. To classify the galaxy, we need to know if we're viewing the galaxy at an angle or if it's actually that shape. Your turn
Suppose that you observe a galaxy edge-on, and it appears to resemble a lens. You observe two slight outgrowths that seem to be bars.
a. What is the name of this type of galaxy, and which two types of galaxies does it serve as an intermediate between?
b. Which type of stars are most common in this type of galaxy?
c. Provide two theories regarding the origin of this type of galaxy.
R. I. P. 01/20/2019

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### Re: Astronomy C

a. The Hubble classification of elliptical galaxies is En where n = 10(1 - b/a). Using this formula, you get that the galaxy is classified as E5.
b.You would assume that the galaxy is perpendicular to your line of sight from Earth, essentially flat from your point of view.
Good answer! A few quick comments on the second part: the assumption is indeed that the galactic plane is perpendicular to the line of sight from Earth. I think the part saying it appears "flat" could be a bit ambiguous though and a proctor/grader could interpret it as meaning edge-on, instead of face-on. When you're viewing a (circular/disc-like) object at an angle, you're seeing the projection of the circle as an ellipse. To classify the galaxy, we need to know if we're viewing the galaxy at an angle or if it's actually that shape. Your turn
Suppose that you observe a galaxy edge-on, and it appears to resemble a lens. You observe two slight outgrowths that seem to be bars.
a. What is the name of this type of galaxy, and which two galaxies does it serve as an intermediate between?
b. Which type of stars are most common in this type of galaxy?
c. Provide two theories regarding the origin of this type of galaxy.
```a. Lenticular galaxy (classification: SB0, because of the appearance of bars). It serves as an intermediate between spiral/barred spiral galaxies and elliptical galaxies.
b. Lenticular galaxies are old and don't have a lot of star formation. They generally contain older stars (e.g. Population II stars).
c. The first theory is that lenticular galaxies are "faded" spiral galaxies. As the spiral galaxy gets older, it "uses up" gas and dust and eventually loses its spiral structure, resulting in the lenticular galaxy. The second theory is that lenticular galaxies are the result of galaxies merging together because many lenticular galaxies have higher surface brightnesses than spiral galaxies. The resulting, newly merged galaxy is more massive and loses its "arms" and ends up looking like a disk.```
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### Re: Astronomy C

Good answer! A few quick comments on the second part: the assumption is indeed that the galactic plane is perpendicular to the line of sight from Earth. I think the part saying it appears "flat" could be a bit ambiguous though and a proctor/grader could interpret it as meaning edge-on, instead of face-on. When you're viewing a (circular/disc-like) object at an angle, you're seeing the projection of the circle as an ellipse. To classify the galaxy, we need to know if we're viewing the galaxy at an angle or if it's actually that shape. Your turn
Suppose that you observe a galaxy edge-on, and it appears to resemble a lens. You observe two slight outgrowths that seem to be bars.
a. What is the name of this type of galaxy, and which two galaxies does it serve as an intermediate between?
b. Which type of stars are most common in this type of galaxy?
c. Provide two theories regarding the origin of this type of galaxy.
```a. Lenticular galaxy (classification: SB0, because of the appearance of bars). It serves as an intermediate between spiral/barred spiral galaxies and elliptical galaxies.
b. Lenticular galaxies are old and don't have a lot of star formation. They generally contain older stars (e.g. Population II stars).
c. The first theory is that lenticular galaxies are "faded" spiral galaxies. As the spiral galaxy gets older, it "uses up" gas and dust and eventually loses its spiral structure, resulting in the lenticular galaxy. The second theory is that lenticular galaxies are the result of galaxies merging together because many lenticular galaxies have higher surface brightnesses than spiral galaxies. The resulting, newly merged galaxy is more massive and loses its "arms" and ends up looking like a disk.```