I have been photographing star trails for two hours. What are the rows of dots in the lower right corner? Why do some stars have no star trails? Does it feel like it's always there?

The dot in the lower right corner of your photo is often called the "star dot". These star points are the camera's response to a fixed light source and indicate the location of stars on the image. Star trails are caused by the movement of stars in the night sky. Due to the rotation and revolution of the earth, stars will show moving trajectories in the night sky.

During a long exposure, the camera will record the movement of stars in the night sky. This trajectory is called a star trail. Stars that don't have orbits may be because they are too close to the sun or too far away, or because their light is so faint that they do not move far enough during the exposure time to appear stationary on the image.

In addition, the camera lens and sensor will also affect the shape and brightness of the star point. For example, some cameras perform noise reduction on fixed light sources during long exposures, which can cause star points to take on strange shapes or become blurry.

In short, star trails and star points are common phenomena in night sky photography, and their appearance and shape are affected by many factors.