To convert \( 2.7 \times 10^7 \) degrees Fahrenheit into decimal notation, we multiply 2.7 by \( 10^7 \):
\[ 2.7 \times 10^7 = 2.7 \times 10,000,000 = 27,000,000 \]
Thus, the temperature of the sun at its center in decimal notation is:
27,000,000 degrees Fahrenheit.