It is part of unicode.
If you open charmap and use the font Arial Unicode MS
![enter image description here](https://cdn.statically.io/img/i.sstatic.net/K5rpk.png)
So you see 0270
is the hex for superscript 0.
Funnily enough 1,2,3 are missing from that range. And If you click 4, you'll see 0274 is he hex for superscript 4.
The 1,2,3 are here
Some people type them easily 'cos they are on android phones and if you long press a digit then it goes superscript.
The rest are here 0,4,5,6,7,8,9 in superscript and subscript, and after the 9, it has superscript and subscript +,-,=,(,).
![enter image description here](https://cdn.statically.io/img/i.sstatic.net/tV5uz.png)
![enter image description here](https://cdn.statically.io/img/i.sstatic.net/VvW39.png)
Babelmap shows clearly the unicode for each , in a tabular format that aligns the glyph with the equivalent hex.
![enter image description here](https://cdn.statically.io/img/i.sstatic.net/Rvbmw.png)
Related- Finding all fonts that contain a specific character
Babelmap shows that there's a number of fonts that support them
![enter image description here](https://cdn.statically.io/img/i.sstatic.net/7YdBN.png)
Also, if you see somebody type one of those superscripts, you can paste it into MS word and do ALT-X and see the unicode.