To write \( 8.459 \times 10^{-5} \) in decimal form, you move the decimal point 5 places to the left.
Starting with 8.459:
- Move the decimal point 1 place to the left: 0.8459
- Move it 2 places: 0.08459
- Move it 3 places: 0.008459
- Move it 4 places: 0.0008459
- Move it 5 places: 0.00008459
So, \( 8.459 \times 10^{-5} \) converts to 0.00008459.
Therefore, the correct response is: .00008459.