To express the radius of Neptune, which is approximately 15,300 miles, in scientific notation, you need to convert the number into a format of \( a \times 10^n \), where \( 1 \leq a < 10 \) and \( n \) is an integer.
For 15,300, you would move the decimal point 4 places to the left to get 1.53. Therefore, you can express it in scientific notation as:
\[ 1.53 \times 10^4 \]
So, the radius of Neptune in scientific notation is \( 1.53 \times 10^4 \) miles.