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Re: Astronomy C

Posted: February 24th, 2018, 2:43 pm
by sciolyPA
A star has three times the mass of the sun, what would its schwarzschild radius be? (Also how do you hide your answer behind an answer box and how do you upload math equations to show work?)

Re: Astronomy C

Posted: February 24th, 2018, 2:49 pm
by Unome

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Answer
Schwarzschild radius =
The Sun's mass is approximately , in SI units, and .
Therefore

Re: Astronomy C

Posted: February 24th, 2018, 2:51 pm
by sciolyPA
Unome wrote:

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[hide]visible text|hidden text[/hide]

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[math]LaTeX code[/math]


Answer
Schwarzschild radius =
The Sun's mass is approximately , in SI units, and .
Therefore



Looks good and thanks for the help!

Re: Astronomy C

Posted: February 24th, 2018, 4:57 pm
by Unome
Image
1. What DSO was this data gathered from?
2. Is this image a spectrum, light curve, or radial velocity graph? (meta question to anyone who can answer - what would be a good way to phrase this without listing options?)
3. What orbital phenomenon does this image show?
4. How many times brighter is the star at peak brightness than at minimum?

Re: Astronomy C

Posted: February 24th, 2018, 5:58 pm
by PM2017
Unome wrote:Image
1. What DSO was this data gathered from?
2. Is this image a spectrum, light curve, or radial velocity graph? (meta question to anyone who can answer - what would be a good way to phrase this without listing options?)
3. What orbital phenomenon does this image show?
4. How many times brighter is the star at peak brightness than at minimum?


an answer to your meta question: You could ask, "What type of chart is shown in this image?"

(also, the sad feel when you can answer all the questions except for the first, and probably easiest one... I'm actually clueless as to which DSO this is...)

Re: Astronomy C

Posted: February 24th, 2018, 6:59 pm
by sciolyPA
Unome wrote:Image
1. What DSO was this data gathered from?
2. Is this image a spectrum, light curve, or radial velocity graph? (meta question to anyone who can answer - what would be a good way to phrase this without listing options?)
3. What orbital phenomenon does this image show?
4. How many times brighter is the star at peak brightness than at minimum?


Answer
1. HR 5171 A
2.light curve
3.It shows two stars in a binary system eclipsing each other, which accounts for the changing magnitude.
4.Is it 1.2 times brighter?

Re: Astronomy C

Posted: February 24th, 2018, 7:18 pm
by PM2017
PM2017 wrote:I'm actually clueless as to which DSO this is...


sciolyPA wrote:
Unome wrote:Image
1. What DSO was this data gathered from?
2. Is this image a spectrum, light curve, or radial velocity graph? (meta question to anyone who can answer - what would be a good way to phrase this without listing options?)
3. What orbital phenomenon does this image show?
4. How many times brighter is the star at peak brightness than at minimum?


Answer
1. HR 5171 A
2.light curve
3.It shows two stars in a binary system eclipsing each other, which accounts for the changing magnitude.
4.Is it 1.2 times brighter?


I'm actually stupid... HR 5171 A is the only binary of the type that fits with the light curve given this year...
EDIT: Wait, but doesn't the magnitude not match?

Re: Astronomy C

Posted: February 24th, 2018, 7:25 pm
by sciolyPA
PM2017 wrote:
PM2017 wrote:I'm actually clueless as to which DSO this is...


sciolyPA wrote:
Unome wrote:Image
1. What DSO was this data gathered from?
2. Is this image a spectrum, light curve, or radial velocity graph? (meta question to anyone who can answer - what would be a good way to phrase this without listing options?)
3. What orbital phenomenon does this image show?
4. How many times brighter is the star at peak brightness than at minimum?


Answer
1. HR 5171 A
2.light curve
3.It shows two stars in a binary system eclipsing each other, which accounts for the changing magnitude.
4.Is it 1.2 times brighter?


I'm actually stupid... HR 5171 A is the only binary of the type that fits with the light curve given this year...
EDIT: Wait, but doesn't the magnitude not match?



At an invitational earlier this year I got the the same graph with the same scale for HR 5171 A, so I hope it's right.

Re: Astronomy C

Posted: February 26th, 2018, 1:43 pm
by c0c05w311y
Unome and everyone really, could you please use image hosting site imgbb instead of imgur or something else so that PM2017, Jonboyage, and I (probably others too) can access the images at school? No need to re-post, just for the future. Thanks

Re: Astronomy C

Posted: February 27th, 2018, 9:30 am
by sciolyPA
A pulsar has a mass of 2.5E30 kg and a radius of 3E4 m.
a) What is its rotational inertia?
b) If it's initial period is 1.6 s, what is it's rotational kinematic energy?
c) Given that it has a spin down rate of .0006 s/y, find the rate of kinematic loss of the pulsar.

Re: Astronomy C

Posted: February 27th, 2018, 4:09 pm
by Adi1008
sciolyPA wrote:A pulsar has a mass of 2.5E30 kg and a radius of 3E4 m.
a) What is its rotational inertia?
b) If it's initial period is 1.6 s, what is it's rotational kinematic energy?
c) Given that it has a spin down rate of .0006 s/y, find the rate of kinematic loss of the pulsar.

Answer
a)

b)

c)

Re: Astronomy C

Posted: February 28th, 2018, 5:51 pm
by sciolyPA
Adi1008 wrote:
sciolyPA wrote:A pulsar has a mass of 2.5E30 kg and a radius of 3E4 m.
a) What is its rotational inertia?
b) If it's initial period is 1.6 s, what is it's rotational kinematic energy?
c) Given that it has a spin down rate of .0006 s/y, find the rate of kinematic loss of the pulsar.

Answer
a)

b)

c)



Looks good, your turn

Re: Astronomy C

Posted: February 28th, 2018, 9:51 pm
by Adi1008
sciolyPA wrote:
Adi1008 wrote:
sciolyPA wrote:A pulsar has a mass of 2.5E30 kg and a radius of 3E4 m.
a) What is its rotational inertia?
b) If it's initial period is 1.6 s, what is it's rotational kinematic energy?
c) Given that it has a spin down rate of .0006 s/y, find the rate of kinematic loss of the pulsar.

Answer
a)

b)

c)



Looks good, your turn

Image

In the image above:

a) What does the green line represent?
b) What does the light blue line represent?
c) What does the dark blue line represent?
d) The red arrows show evolutionary paths for different pulsars that start at the same location but have different braking indices. Put each evolutionary path (top, middle, and bottom) in order of increasing braking index.
e) The x-axis is on a (linear/logarithmic) scale

Re: Astronomy C

Posted: March 1st, 2018, 6:22 am
by Unome
Adi1008 wrote:
sciolyPA wrote:
Adi1008 wrote:
Answer
a)

b)

c)



Looks good, your turn

Image

In the image above:

a) What does the green line represent?
b) What does the light blue line represent?
c) What does the dark blue line represent?
d) The red arrows show evolutionary paths for different pulsars that start at the same location but have different braking indices. Put each evolutionary path (top, middle, and bottom) in order of increasing braking index.
e) The x-axis is on a (linear/logarithmic) scale

Answers (possibly)
(a - c) Are definitely going to be lines of equal mass/etc., though I'm not certain what any of them actually are. If this were an actual test, I'd probably put mass for all of them. I think dark blue is most likely to be mass though,
(d) I'm not sure, but I would assume a larger braking index implies an increasing decrease in period - therefore: top, middle, bottom.
(e) logarithmic

Re: Astronomy C

Posted: March 1st, 2018, 12:54 pm
by c0c05w311y
there's no way I would know this if I hadn't read the paper that this graph came from a few months ago, but the blue lines are constant magnetic field strength since its basically proportional to sqrt(P*Pdot) , the green lines are constant characteristic age since thats P/(2*Pdot) , and the light blue lines are constant Edot since thats basically proportional to Pdot / P^3 (drawing the lines does use some assumptions)