http://www.newsweek.com/amazing-green-comet-21p-make-closest-approach-earth-70-years-watch-live-1099146

On September 10, the Comet 21P/Giacobini-Zinner will make its closest approach to the Sun and Earth in 72 years as it journeys into the inner Solar System.

Currently travelling through space at speeds of more than 51,000 miles per hour, the object will be around 36 million miles away at its closest point to our planet. This may seem like a huge distance but in space terms it is relatively paltry and near enough that it will be visible from Earth.