To find the total energy the sun generates in a year, we can multiply the energy generated per second by the number of seconds in a year:
\[ \text{Energy per year} = (\text{Energy per second}) \times (\text{Seconds per year}) \]
Given:
- Energy per second = \(4 \times 10^{26}\) joules
- Seconds per year = \(3.15 \times 10^{7}\) seconds
Now, let's calculate:
\[ \text{Energy per year} = (4 \times 10^{26}) \times (3.15 \times 10^{7}) \]
We can multiply the coefficients (4 and 3.15) and add the exponents of 10:
\[ 4 \times 3.15 = 12.6 \] \[ 10^{26} \times 10^{7} = 10^{26 + 7} = 10^{33} \]
Now, we combine these results:
\[ \text{Energy per year} = 12.6 \times 10^{33} \]
To express this in proper scientific notation, we need to convert \(12.6\) into \(1.26\) (since we keep only one non-zero digit to the left of the decimal) and increase the exponent of 10 by 1:
\[ 12.6 \times 10^{33} = 1.26 \times 10^{34} \]
Therefore, the total energy the sun generates in a year is:
\[ \boxed{1.26 \times 10^{34}} \text{ joules} \]