How to Convert Cgs to SI Units for Flux and Energy Values?

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SUMMARY

The discussion focuses on converting values from cgs (centimeter-gram-second) to SI (International System of Units) for flux and energy measurements. A specific example involves converting 10.7 mJy (milliJanskys) to SI units, where the correct conversion factor is established as 1.07 × 10-2 W/m2-Hz. Additionally, the conversion of a flux value, kappa, from 2 cm2.g-1 to SI units is clarified, with the correct result being 2 × 10-7 m2/kg after addressing the negative exponent in the grams conversion.

PREREQUISITES
  • Understanding of unit conversion between cgs and SI units
  • Familiarity with the concept of flux in astrophysics
  • Knowledge of the Jansky (Jy) as a unit of measurement
  • Basic mathematical skills for exponent manipulation
NEXT STEPS
  • Research the definition and applications of the Jansky (Jy) in astrophysics
  • Learn about SI unit conversions for other common astrophysical measurements
  • Explore the implications of flux measurements in astronomical observations
  • Study the significance of negative exponents in scientific notation
USEFUL FOR

Astronomers, astrophysics students, researchers in physics, and anyone involved in converting and interpreting flux and energy values in scientific contexts.

SorenaJ
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Hi

I have a value that is 10.7 mJy, that I need to convert to SI units. I thought it would be 1.7*10^(-2)*10^(-26) but that might be wrong?

Then I have a flux value, kappa, of 2 cm^2.g^(-1) that needs to be converted to meters and kilogram. I thought it was 2*10^(-7) m2/kg, but that might be wrong as well. I would get the 10^(-4) from converting from cm2 to m2 and the 10^(-3) from converting from g to kg.

Can anyone help?
 
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In the second part, you have the grams conversion wrong because it has a negative exponent. You should be dividing by 10^(-3), not multiplying by it.

I have no idea what a mJy is, but the 10^(-26) is a truly large factor.
 
SorenaJ said:
Hi

I have a value that is 10.7 mJy, that I need to convert to SI units. I thought it would be 1.7*10^(-2)*10^(-26) but that might be wrong?

10.7 = 1.07 × 10

10.7 m = 10.7 × 10-3 = 1.07 × 10-2

Don't drop those zeroes!

BTW, this is the definition of the Jansky (Jy):

https://en.wikipedia.org/wiki/Jansky

1 Jy = 10-26 W / (m2-Hz)
 
Thank you!
 

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