Surface brightness to luminosity

In summary, surface brightness is the amount of light per unit area coming from a celestial object, while luminosity is the total amount of energy emitted per unit time. These two are related through distance and size of the object. Surface brightness is typically measured in magnitudes per square arcsecond and can be used to determine an object's size by calculating its distance and angular size. The surface brightness to luminosity ratio can vary significantly among different types of celestial objects and is often used in the study of dark matter, as it can reveal the presence of this mysterious substance.
  • #1
Warimi
1
0
Can anyone offer insight into the derivation of the surface brightness to solar luminosity conversion

S(mag/arcsec^2) = Mabs + 21.572 - 2.5log S (Solar luminosities/pc^2)

More or less my concern is the constant term, is it empirically observed value or is there a derivation for it?

thanks
 
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  • #2
The definition of magnitude and parsec are arbitrary, and if you take the log of those (multiplicative) constants and add everything you should get 21.572 in some way.
 

1. What is surface brightness and how is it related to luminosity?

Surface brightness refers to the amount of light per unit area coming from a celestial object. Luminosity, on the other hand, is the total amount of energy emitted by an object per unit time. Surface brightness and luminosity are related through the object's distance and size.

2. How is surface brightness measured?

Surface brightness is typically measured in units of magnitudes per square arcsecond. This is done by taking a series of images of the object with different exposure times, and then using photometric techniques to determine the brightness of each pixel. These values are then averaged and converted to magnitudes per square arcsecond.

3. Can surface brightness be used to determine the size of an object?

Yes, surface brightness can be used to determine the size of an object. By measuring the surface brightness and knowing the luminosity, the object's distance can be calculated. With distance and angular size, the physical size of the object can be determined.

4. How does surface brightness to luminosity ratio vary among different types of celestial objects?

The surface brightness to luminosity ratio can vary significantly among different types of objects. For example, galaxies tend to have lower surface brightness to luminosity ratios compared to stars, as galaxies have a much larger size and emit light from a larger area. Additionally, the surface brightness to luminosity ratio can vary within a single type of object, such as among different types of galaxies.

5. How does the concept of surface brightness to luminosity ratio relate to the study of dark matter?

The surface brightness to luminosity ratio is often used in the study of dark matter. By comparing the observed surface brightness to the expected surface brightness based on the luminosity of an object, scientists can determine the amount of dark matter present. This is because dark matter does not emit light, so it does not contribute to the object's luminosity, but it does affect the object's gravitational pull, which can be observed through its impact on surface brightness.

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