There is a planet half the radius of the Earth with a surface made up of diamonds.

 

There is a planet half the radius of the Earth with a surface made up of diamonds.

                                                           

55 Cancri e has a mass eight times that of Earth’s despite having half the radius, and may very well have a surface made up of graphite and diamonds.

It is only 40 light-years away and visible to the naked eye under the constellation of Cancer.