I often walk around my house at night with the lights turned off and one night I noticed that looking straight at an object with very little light available made the object disappear from sight but if I directed my visual else where I could clearly see the object in my peripheral
$\begingroup$ "Peripheral vision is more light-sensitive than the central vision" written by AliceD here gives a great answer to your question. $\endgroup$– SarinApr 30, 2015 at 15:47
Its down to the structure of your eyes. The eyes are made of rods and cones, which have differences in detecting light.
Now, compare the images below.
As you can see, the peripheral vision is predominately due to your rods, and your central vision is made of cones.
Measured density curves for the rods and cones on the retina show an enormous density of cones in the fovea centralis. To them is attributed both color vision and the highest visual acuity. Visual examination of small detail involves focusing light from that detail onto the fovea centralis. On the other hand, the rods are absent from the fovea. At a few degrees away from it their density rises to a high value and spreads over a large area of the retina. These rods are responsible for night vision, our most sensitive motion detection, and our peripheral vision.
(Taken from: http://hyperphysics.phy-astr.gsu.edu/hbase/vision/rodcone.html)
You can read about the photorecptors of the eyes here: http://webvision.med.utah.edu/book/part-ii-anatomy-and-physiology-of-the-retina/photoreceptors/
$\begingroup$ This is not the complete story; this answer is more complete under linked question $\endgroup$– AliceD ♦Apr 18 at 10:40
Because peripheral vision uses the peripheral retina,which has mostly rods as photoreceptor,while central vision uses the foveola,a central part of the retina which mostly has cones as photoreceptors. Rods are more sensitive to light. That is why they are more efficient in the dark.