The brightness of a star is closely related to its temperature. With the naked eye we can tell the difference in brightness between stars, and ancient man divided starlight into six classes according to this difference in brightness. 1st class stars are the brightest, while 6th class stars are the dimmest. There is a 2.25-fold difference in brightness between each magnitude, and a 100-fold difference in actual brightness between a 1st magnitude star and a 6th magnitude star.
Have you ever seen a searchlight? It's as tall as a man, and its intense cylindrical beam can shine for kilometers, illuminating planes flying in the night sky so brightly that it's blindingly bright. You must have also seen the fireflies flying in the bushes at night, there is a small point of light on its tail, so weak that it can only illuminate itself, can be said to be very dim. Searchlights and fireflies, one bright, the other dim, the difference in luminosity emitted by the two is really great. In the stellar world, however, the difference in the luminosity of the different stars is much greater than they are. Can you believe it? Read on, and you'll draw your own conclusions.
After the invention of the telescope, many faint star crystals were seen through telescopes that were invisible to the naked eye, and the differences in their brightness could be distinguished in greater detail. So people invented instruments to measure the brightness of the stars, and expanded the class of brightness to a range of decimals and negative numbers. According to this classification, the brightness of the moon at full moon is -12.6 magnitude stars, and the sun on a clear day is -26.8 magnitude stars. Aside from the Sun, the brightest star in the sky is Sirius, which is -1.6 magnitude star. Comparing the Sun and Sirius, although there is only a 25.2 magnitude difference between them, they are actually 12 billion times brighter than each other. The faintest star an astronomer can see with a modern telescope is a 20th magnitude star, and a 23rd magnitude star can be seen if photographed.
The brightness and magnitude above are regardless of the distance of the star, which is the brightness we see when we look at stars on Earth, hence the name apparent magnitude. But in reality, some stars that seem very bright may not be very luminous, just because they are very close to me. Similarly, some stars that appear to be very faint may be very luminous, just because they are far away from us. This kind of reasoning is also common in our daily life. For example, at night, when we walk along the streets of a city, we can see street lights from near to far. It seems that the near lights are brighter than the far lights. Can we say that the near lights are really brighter than the far lights? Of course not. They are actually the same brightness, and the only reason they appear to be different is because of the difference in distance. Therefore, in order to compare the luminosity of the stars themselves, astronomers assume that all the stars are placed at an equal distance (3.26 light-years), so as to determine their own luminosity and absolute magnitude. According to the absolute magnitude, the sun is only a faint star just visible to the naked eye, it belongs to 4.8 absolute magnitude. Sirius, on the other hand, has an absolute magnitude of 1.3, so its own luminosity is 25 times greater than that of the Sun.
There are stars in the sky whose luminosity can be hundreds of thousands of times greater than that of the Sun. When you put the sun at the same distance as Samsara, the sun looks like a 5th-magnitude star, and Samsara, which doesn't look like much, is more than 50,000 times brighter than the sun. This is nothing; there are other stars in the sky that are 500,000 to 1,000,000 times more luminous than the Sun, such as S in the constellation Swordfish and Gl in Scorpius. On the other hand, the faintest star in the sky is only 5.5 million times as luminous as the Sun (at an absolute magnitude of 19.2), and if you put it in the position of the Sun, it's not much more than a full moon. What a difference there is between the brightest and faintest stars in the sky! It is quite apt to say that they are searchlights and fireflies.