Glowing green orb over Wheeling, Illinois

On October 22, 2016, a witness was hiking in Wheeling (Illinois, USA). He has taken some photos. On two of them, he noticed a mysterious bright green orb like UFO. What is it?

Witness report:

I hiked on a trail near our home with my husband yesterday late afternoon. I took some pictures while hiking. Later on, while reviewing the pictures I took, we found there is some weird green lights in the middle of two pictures. Not sure if this related to any anomalies thing.