What you are seeing is a sphere of plutonium-238. In general, plutonium is not red, it is the usual metallic color. However, the 238 isotope undergoes natural decay which releases enough thermal energy to make it glow and red in color.

Plutonium 238 decays with a half-life of approximately 88 years. It means that one kilo of this isotope, after having irradiated uninterruptedly for 88 years, will have transformed half of its mass into other elements, while the other half will continue its radiation work, reducing to 250 grams after another 88 years, and so Street.

The heat produced during the decay of plutonium-238 can be used in the propulsion or energy production systems of space systems. Contrary to what one might think, the radiation emitted is not dangerous for health.

The particles emitted are exclusively of the alpha type (effectively helium ions) which cannot penetrate human skin. If ingested or inhaled, however, it is lethal.