The Largest Star

Largest Star by Massive : pistol star

-200 times of solar mass
-25000 light years far away


Largest Star by Luminosity : LBV 1806-20

-38 million solar luminosity
-30000-40000 light years far away






Largest Star by Radius : VY Canis Majoris

-1800 radii


-5000 light years far away


How could they know?

Massive-Star birth
Giant molecular cloud, GMC collapse because of the instability gravitational of the molecules.
And it became a protostar. Which some of them have larger mass than the sun but some don’t.

Luminousity
apparent magnitude
Δm = mf − mb
2.512Δm = ΔL
mf-magnitude number of a brighter star
mb- magnitude number of a fainter star
ΔL- variation in brightness
Radius
Angular size

It means if it far the angular size is small so we have to use the things to help.


Angular size(arc second) = size(km) / distances(parsec)




Things help to find angular size.


1.Inferometer


2. Telescope