The most romantic thing I can think of is looking up at the stars with you...

"The stars are twinkling, the moon is round. The Milky Way flows backward into the cups and plates." When did we start to look up and admire the vast starry sky? In ancient times, the candlelight was dim, and when we opened the door and looked up, we could see the brilliant Milky Way. People observed the stars to guide agricultural production and coordinate laws. Although electric lights are popular and technology is developed today, the romance and wisdom of stargazing are still worth exploring.

We might as well start with the most easily recognizable Big Dipper, "Daishu, Daxuan, Tianji, Tianquan, Yuheng, Kaiyang, Yaoguang", and the order starts from the mouth of the Big Dipper, and the end of the handle is Yaoguang, also known as Pojun Star. The direction of the Big Dipper changes with the seasons. From the northern hemisphere where we are, it rotates around the North Pole, with the mouth of the spoon facing down in spring and the opposite in autumn. With the help of the positioning of the Big Dipper, we can easily find the north, and we can also use it as a reference to locate other stars. If the night sky is clear and you are safe, you might as well try to look at the Big Dipper and use the starlight to find your way home.

Look at this picture, can you find the Yaoguang Star in it?

With the most basic positioning, let's take a look at how to observe celestial bodies correctly. First of all, let's start with some basic astronomical knowledge. We use magnitude to measure the brightness of celestial bodies. The larger the magnitude value, the lower the apparent brightness. So what is brightness? Luminosity refers to the total energy radiated by a celestial body per unit time. It is an inherent quantity of stars, while brightness refers to the amount of radiation received by a celestial body per unit area per unit time on Earth. In simple terms, it can be understood that luminosity is "emitted" and brightness is what we "receive". The size of the apparent brightness depends on the luminosity of the celestial body, the distance from the sun, and the absorption and scattering of radiation by interstellar matter. Generally speaking, under a clear night sky, the limit of what the human eye can observe is a sixth-magnitude star.

The brightness of celestial bodies with a magnitude difference of 5 differs by 100 times, that is, for every magnitude difference of 1, the brightness differs by about 2.512 times. The specific formula is:

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Where m1 and m2 are the magnitudes of the star, and F represents brightness. According to the measurement band, the apparent magnitude can be divided into visual magnitude, photographic magnitude, and photoelectric magnitude. The magnitude measured in the full band is called thermal magnitude, which is the sum of the integration of all bands.

Most of the stars we see with our naked eyes are bright white, but the colors of many stars are not like this. The color of a star reflects the surface temperature of the star. The higher (lower) the temperature, the bluer (redder) the color. Why is this? Because the color of a celestial body and the shape of its radiation spectrum depend on the surface temperature, here we introduce the concept of color index, which refers to the difference in magnitude of the same celestial body in different bands. Since the magnitude has a logarithmic relationship with brightness, it also reflects the ratio of brightness. The size of the color index reflects the temperature of the celestial body. The higher the temperature, the smaller the absolute value of the color index. As shown in the following painting describing the "Meeting at the Magpie Bridge", due to the low temperature of Vega, the North Pole is light pink and the equatorial part is blue-white, so it presents a dreamy scene. Isn't it a combination of science and art?

Now that we have the theoretical basis, how do we put our observations into practice?

Experts have proved through experiments that the human eye's response to stimulation is the logarithm of light intensity. In other words, the changes in perception by the eyes are not as drastic as the changes in light. This actually protects us from going blind when faced with drastic changes in light.

Let's choose a clear night and find a place away from light pollution. In order to achieve the best observation status, we need to close our eyes first. Why do we do this? Because rod cells are the most important photoreceptor cells for night vision. In order to make rod cells and cone cells reach the best state during night vision, they need to adapt to the dark for at least 45 minutes. But in fact, we only need to close our eyes or stay in a dim light environment for more than 10 minutes, and then we can open our eyes and look up at the stars.

"We are closely connected to those distant galaxies. No matter how far away they are from us, the light that has traveled billions of years to reach the earth will eventually connect us." Let's look up at the starry sky. It is so far away and deep. The infinite truth is worth our hard pursuit. Maybe the weather is good tonight, let's go to see the stars together!