## Astronomy C

raxu
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### Re: Astronomy C

What is the accepted value of Hubble's Constant, H_0? The most recent measurements have fluctuated between 67 and 73...

Would you expect the grader to accept any correct calculations with a reasonable H_0?
Richard
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### Re: Astronomy C

What is the accepted value of Hubble's Constant, H_0? The most recent measurements have fluctuated between 67 and 73...

Would you expect the grader to accept any correct calculations with a reasonable H_0?
My notes have it as 73.8, based off of NASA. I'd expect the grader to accept it if it's reasonably close, but it's probably best to just keep up with the constant, since using a constant of 67 would yield a pretty different result than using 73.8 to the point where it may just appear completely wrong.
Lower Merion 2017
Subtitled: Revenge of the Non-Harriton

Placement Record:

Code: Islip | Conestoga | Tiger | Regionals | States
Out of: 61 | 42 | 36 | 37 | 36

Chemistry Lab: 9 | - | - | 4 | 4
Astronomy: 14 | - | 5 | 10 | 3
Material Science: 12 | 19 | 9 | 5 | 9
Optics: 14 | 7 | 3 | 4 | 2

Unome
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### Re: Astronomy C

What is the accepted value of Hubble's Constant, H_0? The most recent measurements have fluctuated between 67 and 73...

Would you expect the grader to accept any correct calculations with a reasonable H_0?
My notes have it as 73.8, based off of NASA. I'd expect the grader to accept it if it's reasonably close, but it's probably best to just keep up with the constant, since using a constant of 67 would yield a pretty different result than using 73.8 to the point where it may just appear completely wrong.
If they don't say anything, I tend to use 70 because that's mostly likely to hit all of the ranges somewhat closely (or as closely as one can get with ~5% variance...)
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antoine_ego
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### Re: Astronomy C

What is the accepted value of Hubble's Constant, H_0? The most recent measurements have fluctuated between 67 and 73...

Would you expect the grader to accept any correct calculations with a reasonable H_0?
Often times, the test will tell you what value they want you to use to reduce the possible range of answers. For example, at MIT, they told us to use the value of 65.
Rest in Peace Len Joeris
```[b]2016 Air Trajectory Nationals - 3rd
2018 Hovercraft Nationals - 6th
2018 Mousetrap Nationals - 6th
2018 Nationals - Team 9th Place!
2019 Astronomy Nationals - 3rd!
2019 Nationals - Team 9th Place!
[/b]```
Acton-Boxborough Regional High School Captain 17-19

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### Re: Astronomy C

A question for anyone who was at the Mira Loma invite: what did you think of that test? I took it recently and it was quite different from what I've usually seen, though apparently it's fine according to the rules.
Lower Merion 2017
Subtitled: Revenge of the Non-Harriton

Placement Record:

Code: Islip | Conestoga | Tiger | Regionals | States
Out of: 61 | 42 | 36 | 37 | 36

Chemistry Lab: 9 | - | - | 4 | 4
Astronomy: 14 | - | 5 | 10 | 3
Material Science: 12 | 19 | 9 | 5 | 9
Optics: 14 | 7 | 3 | 4 | 2

antoine_ego
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### Re: Astronomy C

A question for anyone who was at the Mira Loma invite: what did you think of that test? I took it recently and it was quite different from what I've usually seen, though apparently it's fine according to the rules.
My understanding is that typically the Mira Loma and Troy invitational tests are much more math heavy then other ones. Usually they stress the concepts really heavily, and don't bother with the standard regurgitation of Wikipedia articles. I like it.
Rest in Peace Len Joeris
```[b]2016 Air Trajectory Nationals - 3rd
2018 Hovercraft Nationals - 6th
2018 Mousetrap Nationals - 6th
2018 Nationals - Team 9th Place!
2019 Astronomy Nationals - 3rd!
2019 Nationals - Team 9th Place!
[/b]```
Acton-Boxborough Regional High School Captain 17-19

embokim
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### Re: Astronomy C

Hey, just wondering if any tests would when solving Hubble's law, whether they would give Doppler effect portion of it to find velocity? instead of straight up them giving the values? Has the Hubble's Law questions been straight forward? Thanks!
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antoine_ego
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### Re: Astronomy C

Hey, just wondering if any tests would when solving Hubble's law, whether they would give Doppler effect portion of it to find velocity? instead of straight up them giving the values? Has the Hubble's Law questions been straight forward? Thanks!
I assume by Doppler effect portion you are referring to redshift. If so, yes, they appear routinely on most tests. For the most part they are straightforward, if anything, the trickiest part is figuring out whether it's moving towards or away from you, but that's still quite easy.
Rest in Peace Len Joeris
```[b]2016 Air Trajectory Nationals - 3rd
2018 Hovercraft Nationals - 6th
2018 Mousetrap Nationals - 6th
2018 Nationals - Team 9th Place!
2019 Astronomy Nationals - 3rd!
2019 Nationals - Team 9th Place!
[/b]```
Acton-Boxborough Regional High School Captain 17-19

Ashernoel
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### Re: Astronomy C

Hey, just wondering if any tests would when solving Hubble's law, whether they would give Doppler effect portion of it to find velocity? instead of straight up them giving the values? Has the Hubble's Law questions been straight forward? Thanks!
I like combining this with distance modules for some good problems
NT '19
Harvard '23

embokim
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### Re: Astronomy C

Suppose that now after a series of observations astronomers have deduced some properties of this pair of
stars. The parallax angle of this system is 0.0555…”. The mean separation of these two stars appears to
be 1.11”.

What is the semimajor axis of this binary star system, in AU?

How would you solve this question?
Thank You so much!
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