Macbook Pro 13" with i5 shows 4 processors in activity monitor

Just got our son a new Macbook Pro 13 inch with the i5 processor. On Apple's website, it shows that this computer comes with a dual-core. However, when I run the activity monitor, it shows 4 processors (4 black areas) under CPU usage when I click on the CPU tab. Also, the program menumeters also shows 4 processors in the menubar and they all are usually running at differenet percents which indicates to me that this has 4 processors.

Anybody know what's going on? It's supposed to be a dual core machine.