Image source [1]: Artist impression of a transiting planet temporarily diminishing the star's brightness, leading to its discovery.
Hello friends, today we are going to talk a little about stellar magnitudes.
Flux:
In transport phenomena (heat transfer, mass transfer and fluid dynamics), flux is defined as the rate of flow of a property per unit area, which has the dimensions [quantity]·[time]−1·
Strictly speaking, we should say radioactive power, because it is the power of light radiated by an object that the observer captures per unit area.
The units of the flow are:
The brightness (L) of a star is the amount of energy per second that the star emits (erg s ^ 1).
The brightness is related to the flow (F) by:
The magnitude is a parameter that is used in astronomy to quantify the brightness of a celestial object. The term of magnitude was introduced by Hipparchus in the second century BC, who constructed a scale of magnitudes based on objects visible to the naked eye; I assign to the brightest stars a magnitude 1 and to the weakest ones a magnitude 6.
The problem of the classification of Hipparchus is that the "brightness" did not have an expression based on physical parameters In 1856, Norman R. Pogson proposed a similar method in which instead of brightness the owl received by the observer is used. Pogson defined a scale on which F1 = 100 - F6, where F1 is the flux of a star of magnitude 1 and F6 is the flux of a star of magnitude 6. One of the units fundamentally used in magnitudes is the parsec (pc ).
As mentioned above, the scale appears to work 'in reverse', with objects with a negative magnitude being brighter than those with a positive magnitude. The 'larger' the negative value, the brighter.
Image source [2]: Objects appearing farther to the left on this line are brighter, while objects appearing farther to the right are dimmer. Thus zero appears in the middle, with the brightest objects on the far left, and the dimmest objects on the far right.
The apparent magnitude, m1, refers to the observed brightness of a celestial object, that is, the F1 flux that we receive from said object
The apparent magnitude is defined as:
Image source [3]: 30 Doradus image taken by ESO's VISTA. This nebula has an apparent magnitude of 8.
Absolute magnitude is a measure of the luminosity of a celestial object, on a logarithmic astronomical magnitude scale. An object's absolute magnitude is defined to be equal to the magnitude that the object would have if it were viewed from a distance of exactly 10 parsecs (32.6 light years), with no extinction (or dimming) of its light due to absorption by interstellar dust particles.
The absolute magnitude is what a star will have if it were located at a distance of 10 pc (parsecs), which is given by: