The camera can shoot the starry sky. Why can't the mobile phone shoot the starry sky well?

It's not the pixels. At present, most mobile phones have13 million pixels, but there are several high-end full-frame cameras (note that it is the last two years, and those old cameras must have low pixels, so I won't talk about it), such as Nikon D4s, Nikon DF and Sony A7s.

The mobile phone can't shoot the starry sky, and the fundamental reason is this:

The phone can't focus manually, and the phone won't automatically aim the camera at the starry sky. When a mobile phone shoots something, it will be clear if it is in focus, but it will be blurred if it is not in focus. Can you understand? When you take a selfie with your mobile phone, if your face is clear, then the background a few meters behind you is blurred, right? The mobile phone can't focus on the starry sky (because it is too dark). So you can't "shoot the starry sky well."

Because shooting the starry sky requires a long exposure time to ensure sufficient exposure, the camera can set the exposure time longer, for example, shooting a starry sky in 20 seconds. But the mobile phone is fully automatic, just like it can't focus on the starry sky, nor can it be exposed for a long time.

Suppose that the mobile phone can be exposed for a long time. But cameras can be fixed with tripods, and mobile phones lack peripheral products such as tripods. . . .

In addition to these, there are problems such as sensor size, lens quality and high sensitivity signal-to-noise ratio, but these are not fundamental problems. The fundamental problem is the three points I mentioned above.