Astronomy C

User avatar
PM2017
Member
Member
Posts: 491
Joined: January 20th, 2017, 5:02 pm
Division: Grad
State: CA

Re: Astronomy C

Postby PM2017 » January 1st, 2019, 3:18 pm

As for images, yes, all the images (they're pretty too!). Hope this helps, please keep questions coming if that was confusing!
Just adding to this, you should also label each image (we include Telescope, Wavelength, Date if important, and for the non-obvious images, we include a description. By non-obvious I mean like the supernovae inside a DSO.)
West High '19
UC Berkeley '23

Go Bears!

GarethM
Member
Member
Posts: 2
Joined: January 2nd, 2019, 7:39 pm

Re: Astronomy C

Postby GarethM » January 2nd, 2019, 7:51 pm

What reference value should be used for apparent/absolute visual magnitude? I can find luminosities for all wavelengths, but not just visible wavelengths.

User avatar
Unome
Moderator
Moderator
Posts: 4105
Joined: January 26th, 2014, 12:48 pm
Division: Grad
State: GA
Location: somewhere in the sciolyverse

Re: Astronomy C

Postby Unome » January 3rd, 2019, 12:49 pm

What reference value should be used for apparent/absolute visual magnitude? I can find luminosities for all wavelengths, but not just visible wavelengths.
Your question is a little unclear. What sort of reference values are you looking for?
Userpage
Chattahoochee High School Class of 2018
Georgia Tech Class of 2022

Opinions expressed on this site are not official; the only place for official rules changes and FAQs is soinc.org.

GarethM
Member
Member
Posts: 2
Joined: January 2nd, 2019, 7:39 pm

Re: Astronomy C

Postby GarethM » January 3rd, 2019, 3:30 pm

I’ve seen questions that ask to convert absolute visual magnitude to visible luminosity measured in watts. I understand that a decrease in 5 magnitudes is a 100x increase in brightness, but I don’t understand what that increase is measured from, i.e. what value is defined as 0 on the magnitude scale. I was thinking I could measure relative to a star with a known absolute magnitude and visible luminosity, but I can’t find information on the visible luminosity of any stars. I’ve found info on bolometric magnitudes for all wavelengths, but nothing for just visible.

I’m basically wondering how to calculate visible luminosity in watts when given absolute visible magnitude.

User avatar
Unome
Moderator
Moderator
Posts: 4105
Joined: January 26th, 2014, 12:48 pm
Division: Grad
State: GA
Location: somewhere in the sciolyverse

Re: Astronomy C

Postby Unome » January 4th, 2019, 4:44 am

I’ve seen questions that ask to convert absolute visual magnitude to visible luminosity measured in watts. I understand that a decrease in 5 magnitudes is a 100x increase in brightness, but I don’t understand what that increase is measured from, i.e. what value is defined as 0 on the magnitude scale. I was thinking I could measure relative to a star with a known absolute magnitude and visible luminosity, but I can’t find information on the visible luminosity of any stars. I’ve found info on bolometric magnitudes for all wavelengths, but nothing for just visible.

I’m basically wondering how to calculate visible luminosity in watts when given absolute visible magnitude.
My typical method is to take the Sun's absolute magnitude of around 4.85 and use its known luminosity in watts to convert.
Userpage
Chattahoochee High School Class of 2018
Georgia Tech Class of 2022

Opinions expressed on this site are not official; the only place for official rules changes and FAQs is soinc.org.

User avatar
PM2017
Member
Member
Posts: 491
Joined: January 20th, 2017, 5:02 pm
Division: Grad
State: CA

Re: Astronomy C

Postby PM2017 » January 4th, 2019, 11:51 pm

I’ve seen questions that ask to convert absolute visual magnitude to visible luminosity measured in watts. I understand that a decrease in 5 magnitudes is a 100x increase in brightness, but I don’t understand what that increase is measured from, i.e. what value is defined as 0 on the magnitude scale. I was thinking I could measure relative to a star with a known absolute magnitude and visible luminosity, but I can’t find information on the visible luminosity of any stars. I’ve found info on bolometric magnitudes for all wavelengths, but nothing for just visible.

I’m basically wondering how to calculate visible luminosity in watts when given absolute visible magnitude.
My typical method is to take the Sun's absolute magnitude of around 4.85 and use its known luminosity in watts to convert.
I do this as well.
West High '19
UC Berkeley '23

Go Bears!

jz123sst
Member
Member
Posts: 7
Joined: January 11th, 2019, 1:50 pm

Re: Astronomy C

Postby jz123sst » January 11th, 2019, 1:55 pm

Does anyone know if Astronomy will still be an event 2019-2020 (next year)? If so, what topics will it cover?

pb5754[]
Member
Member
Posts: 383
Joined: March 5th, 2017, 7:49 pm
Division: C
State: NJ

Re: Astronomy C

Postby pb5754[] » January 11th, 2019, 3:53 pm

Does anyone know if Astronomy will still be an event 2019-2020 (next year)? If so, what topics will it cover?
It definitely will be an event next year, and I'm not sure but I think the topic will be variable stars or star/planet formation.

jz123sst
Member
Member
Posts: 7
Joined: January 11th, 2019, 1:50 pm

Re: Astronomy C

Postby jz123sst » January 11th, 2019, 4:38 pm

So stellar evolution is a topic every year?

pb5754[]
Member
Member
Posts: 383
Joined: March 5th, 2017, 7:49 pm
Division: C
State: NJ

Re: Astronomy C

Postby pb5754[] » January 11th, 2019, 4:45 pm

So stellar evolution is a topic every year?
Yes... like there is a 99.9% chance I would say.


Return to “2019 Study Events”

Who is online

Users browsing this forum: No registered users and 0 guests