When an object made of antimatter interacts with normal matter, both particles annihilate each other, releasing a large amount of energy. The exact survival time of an antimatter object in Earth's atmosphere would depend on its composition, mass, and other factors. However, it is safe to say that an antimatter object would not survive for very long in our atmosphere due to these annihilation reactions.
Upon annihilation, the energy released typically takes the form of gamma rays, which are high-energy photons. Gamma rays are not visible to the human eye, as they have much higher energy and shorter wavelengths than visible light. Therefore, an object made of antimatter would not shine in visible light directly.
However, the annihilation process could produce secondary effects that might lead to the emission of visible light. For example, if the annihilation occurs near other particles, such as atoms in the atmosphere, it can ionize them, creating excited states. When these excited states return to their ground state, they can emit photons in various wavelengths, including visible light. This phenomenon is known as "secondary emission" or "cascade radiation."
The exact characteristics of any visible light emitted would depend on the specific conditions and materials involved. It's important to note that the energy released during matter-antimatter annihilation is extremely high, and the resulting interactions can be highly destructive. Therefore, controlling and harnessing antimatter safely is a significant technological challenge and the subject of ongoing research in physics.