Astronomy C

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Re: Astronomy C

Postby bhavjain » November 21st, 2016, 6:16 pm

What is the typical density of a white dwarf?

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Re: Astronomy C

Postby jonboyage » December 13th, 2016, 8:36 am

Why is carbon monoxide an indicator of molecular hydrogen in interstellar dust clouds?

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Re: Astronomy C

Postby Magikarpmaster629 » December 27th, 2016, 5:52 pm

Why is carbon monoxide an indicator of molecular hydrogen in interstellar dust clouds?
This doesn't really pertain to the rules this year, but I suspect because carbon monoxide and molecular hydrogen only form in relatively cool environments. Image
This image of a system 490 parsecs distant depicts HM Cancri. This system has an orbital period of 5.4 minutes and an angular separation of 1.02*10^-6 arcseconds. What is the total mass of the system?
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Re: Astronomy C

Postby Adi1008 » December 27th, 2016, 6:46 pm

Why is carbon monoxide an indicator of molecular hydrogen in interstellar dust clouds?
This doesn't really pertain to the rules this year, but I suspect because carbon monoxide and molecular hydrogen only form in relatively cool environments. Image
This image of a system 490 parsecs distant depicts HM Cancri. This system has an orbital period of 5.4 minutes and an angular separation of 1.02*10^-6 arcseconds. What is the total mass of the system?
answer
1.18 solar masses
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Re: Astronomy C

Postby Magikarpmaster629 » December 28th, 2016, 6:43 am

Why is carbon monoxide an indicator of molecular hydrogen in interstellar dust clouds?
This doesn't really pertain to the rules this year, but I suspect because carbon monoxide and molecular hydrogen only form in relatively cool environments. Image
This image of a system 490 parsecs distant depicts HM Cancri. This system has an orbital period of 5.4 minutes and an angular separation of 1.02*10^-6 arcseconds. What is the total mass of the system?
answer
1.18 solar masses
yep
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Re: Astronomy C

Postby Adi1008 » December 28th, 2016, 12:27 pm

This doesn't really pertain to the rules this year, but I suspect because carbon monoxide and molecular hydrogen only form in relatively cool environments. Image
This image of a system 490 parsecs distant depicts HM Cancri. This system has an orbital period of 5.4 minutes and an angular separation of 1.02*10^-6 arcseconds. What is the total mass of the system?
answer
1.18 solar masses
yep
Image
This figure shows maximum-light type Ia supernovae plotted with distance modulus on the x-axis and absolute B magnitude on the y-axis. Filled symbols are maximum–light SNe (174) and open symbols are limit SNe (395).

(a) What best explains the distribution falling off sharply at the brighter end?
(b) What do the slanted lines represent?
(c) There is a lack of dimmer supernovae found at farther distances. What would best explain this?
(d) What does the figure tell you about the frequency of superluminous (that is, unusually bright) type Ia supernovae? Essentially, in reality, are they more common, less common, or as common as one would expect from this figure?
(e) What is the name of the bias in (d)?
Last edited by Adi1008 on December 29th, 2016, 11:14 pm, edited 1 time in total.
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Re: Astronomy C

Postby Unome » December 29th, 2016, 12:17 pm

My attempt
a) The Chandrasekhar limit. Type Ia supernovae brighter than roughly -19 magnitude are much more uncommon because they can't arise from mass accretion; they have to develop spontaneously or they will explode before they can get large enough to be over that magnitude. b) Lines of equal temperature? (or something else like that, idk) c) They are more difficult to detect because their apparent magnitude is much lower (probably a combination of being really dim and a lot of extinction). d) No idea what this is even asking e) Extinction bias? (maybe this is a real thing?)
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Re: Astronomy C

Postby Adi1008 » December 29th, 2016, 4:07 pm

My attempt
a) The Chandrasekhar limit. Type Ia supernovae brighter than roughly -19 magnitude are much more uncommon because they can't arise from mass accretion; they have to develop spontaneously or they will explode before they can get large enough to be over that magnitude. b) Lines of equal temperature? (or something else like that, idk) c) They are more difficult to detect because their apparent magnitude is much lower (probably a combination of being really dim and a lot of extinction). d) No idea what this is even asking e) Extinction bias? (maybe this is a real thing?)
You're on the right track!
a) I think this is pretty much it. Since the mass is limited by the Chandrasekhar limit, there's a hard physical limit to the amount of Nickel-56 that can be ejected during the supernova. Nickel-56 (and daughter Cobalt-56) is what powers the light curves of the supernova, so this serves as a hard limit for the maximum luminosity that the supernova can attain. b) Good guess, but it's actually lines of consistent apparent magnitude! A harder followup question to this would be to calculate the specific apparent magnitude each line represents c) That's pretty much it :) d) Essentially, brighter objects are easier to discover, for obvious reasons. As a result, when you do surveys like this, you'll likely get most, if not all of the bright stuff, but you'll miss a lot of the dim stuff. As a result, the bright stuff will be overrepresented. In reality, superluminous supernovae are less common than one would initially predict from this plot. Since they already make up such a small fraction of the data, in real life, they are quite rare. e) Malmquist bias!
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Re: Astronomy C

Postby jonboyage » February 2nd, 2017, 8:33 am

Lets revive this

Do the light curves of type Ia supernovae drop faster when they have brighter or dimmer peak absolute magnitudes (example: -19.2 vs -18.7)?
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Re: Astronomy C

Postby Unome » February 2nd, 2017, 8:41 am

Hopefully I remember this correctly
dimmer drops faster?
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Re: Astronomy C

Postby Avogadro » February 2nd, 2017, 8:43 am

I'll try
Dimmer
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Re: Astronomy C

Postby jonboyage » February 2nd, 2017, 9:06 am

Hopefully I remember this correctly
dimmer drops faster?
I messed up, you were correct, this is called the luminosity decline rate relation.
Last edited by jonboyage on February 2nd, 2017, 9:09 am, edited 2 times in total.
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Re: Astronomy C

Postby Unome » February 2nd, 2017, 9:08 am

Hopefully I remember this correctly
dimmer drops faster?
I don't think so :/
I have read in the past that the brighter ones drop faster
I looked it up just now and this is what I found
[quote="Wikipedia - Phillips relationship"]They found that the faster the supernova faded from maximum light, the fainter its peak magnitude was[/quote]
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Re: Astronomy C

Postby jonboyage » February 2nd, 2017, 9:12 am

Yeah you were right sorry, I checked online right after I posted just to make sure and I found that the dimmer ones drop faster.
Do you want to ask the next one?
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Re: Astronomy C

Postby Unome » February 2nd, 2017, 9:38 am

Yeah you were right sorry, I checked online right after I posted just to make sure and I found that the dimmer ones drop faster.
Do you want to ask the next one?
Sure. Here's a tie-in math question.
A type Ia supernova is discovered in a distant galaxy. Its maximum apparent magnitude is measured at 18.4. After monitoring the supernova for 15 days, the B band magnitude drops by 1.2. 1. What is the theoretical absolute luminosity of a type Ia supernova originating from a single progenitor? 2. Calculate the distance to the supernova based on this theoretical absolute magnitude. 3. Determine the speed at which the galaxy containing the supernova is receding. Use a Hubble constant of 70 km^-1*Mpc^-1 4. Based on the luminosity decline, determine the actual absolute magnitude of the supernova. 5. Recalculate the distance and recessional velocity based on the actual absolute magnitude.
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