How can we find the distance to a star that is too distant to have a measurable parallax?
If m is visual magnitude of a star, M is the absolute magnitude and d its distance from us,
Brightness faints in proportion to square of the distance.
Brightness is measured from light from the star.
With the notations m for visual magnitude, M for absolute magnitude and d for the distance of the star from the observer,
the distance is
s = 1 + 0.2 (m - M).
This could be modified as
Comparison with other stars is also useful. The formula used is
For comparison with Sun,
Madras ( now Chennai) based Pogson/s research in 19th century is quite relevant..
I think that I have paved the way for further studies, by the interested readers. .