The relationship between constellations and galaxies ~ ~ ~

Constellation is just an artificially divided area from the perspective. Galaxies are real celestial structures.

For example, everything is clear. Think of your room as the earth. You sit in a room, and the window of that room is the whole sky. So your town (assuming the house is in a small town) is the Milky Way, so you might as well call it Yinhe Town.

If the glass of this window is divided into four squares, and you name it Fairy, Sagittarius, Bear and Orion according to the owner's strength, then the sky you see is divided into four constellations, namely Andromeda, Sagittarius, Bear and Orion. The scenery seen through each pane of glass is definitely uncertain, so the image of each constellation is different. Assuming that a sleeping cat, a stool and an ancient tower can be clearly seen in the distance through the first pane of glass, we can say that Andromeda contains three main stars: the cat star, the stool star and the tower star, and other landscape details seen through this pane also belong to this constellation, such as another barely visible town. You may not know the name of the town next door (just moved to Yinhe Town _), but since you see it through the glass, it's called Fairy Town (our fairy galaxy is out! )。

When you are in Yinhe Town, you can only see the local scenery of the town (such as sleeping cats, stools and ancient pagodas), but you can't see the whole town from the window, so Yinhe is not a constellation, but a galaxy (town).

The 88 constellations in the actual sky can be understood as dividing the window into 88 grids, so each constellation contains both celestial bodies in the Milky Way and other galaxies outside the river (most galaxies outside the river can only be seen with astronomical telescopes), which is equivalent to seeing the scenery of the town and other nearby towns through the pane.

Finally, you ask which is bigger, constellation, nebula or galaxy? First of all, because constellations represent the general name of what is seen from the pane, nebulae and galaxies are concrete landscapes. So it is meaningless to compare the size of constellations with nebulae and galaxies.

Nebulae are interstellar dust masses, large and small, which can be regarded as open spaces, pools and streets in towns, so they must be smaller than the whole town, which means nebulae are smaller than galaxies.

Barely speaking, each constellation must contain countless galaxies (most of which can only be seen with extremely powerful telescopes). For example, you can see countless towns from every window glass (you can see other towns far below the horizon with an extremely powerful perspective telescope in your hand). From this point of view, it can also be said that the concept of constellation is bigger than that of galaxy.