How to measure the distance of faraway galaxies?
Have you ever wondered how we can say that this galaxy is 55 million lights years away? don’t you ever wonder how we are able to measure these amazingly big distances?
I love space, and I am completely fascinated by the inner workings of mysterious complex structures like black holes and simple stars for that fact because even the simplest of them are amazing.
It’s fascinating to think that gravity, such a weak force, caused small particles to come together in such a way they became these huge bundles of pure energy only to fight their creator “gravity” and eventually explode or shed off their extra mass to become a supernova explosion or become a red dwarf or something else like a black hole or a kilonova.
The thing about stars that’s even more fascinating is how they and their eventual end is so useful to measure the far-away galaxies. You may ask how?
There are so many important mind-blowing, and amazing astronomical phenomena present. It’s very hard to choose the most interesting. But this one stands out a little bit for me. Type 1A supernovae. They are commonly used as standard candlesticks to measure the distances of galaxies. There are supernovas that are outshining entire galaxies.
They always shine with the same luminosity that astronomers understand very well; The interesting part of all this is why they always shine with the same brightness. Doesn’t the idea that the explosion of different stars always shines at the same magnitude appear to be ridiculous? But it is true.
These supernovas consist of stars that do not have enough mass for a supernova explosion, so they make a white dwarf when fuel ends. This is true for all small and medium stars, and they are available in abundance. So if enough mass is added to it, it goes supernova. The mass required is called critical mass, which is = 1.4*(mass of our sun) — — {Chandrasekhar limit}.
But they never reach that limit if they are left alone. But the thing is that they are not left alone — most of them are in a binary system. So if this companion star gets too close to the dwarf star, it starts eating it off until it reaches 1.4 times the mass of our sun, and then they go kaboom.
Astronomers use absolute and apparent magnitudes of this brightness to measure distance. Because the collapse always happens at the same mass, the luminosity of the explosion is always the same. making them standard candles. Such an elegant method and an interesting phenomenon.
