Comet C / 1861 G1 Thatcher is a comet, a celestial body that travels in from the far reaches of the cosmos that when it gets closer to the sun begins to burn away and produce a long tail. It is composed mainly of ice and dust. It was discovered by A.E. Thatcher.Its orbit takes 415 years to travel round the Sun.
The closest the Comet came to its orbitting target was 1861-6-03 at which point it was 0.9207 A.U. distance away.The Semi-Major Axis of the orbit is 55.6, which is the furthest point from the centre to the edge of an elliptical point.