A Solar orb is a Protoss device used to produce artificial sunlight.
Because of their new nomadic lifestyle, researchers are developing new ways to compensate for the loss of Aiur. As their race gains nourishment from sunlight, finding a ways to make new sources is a must. Some tribes are desperate enough to seek the Dark Templar for help.
For those too stubborn or distrustful to change that much, they use Solar orbs for nourishment. Through the use of Khaydarin crystals and fusion technology, the sphere creates the same amount of starlight as a miniature star (Justice League: Zero-point energy generator). Solar orbs also use medical technology to stimulate the natural healing abilities of all protoss repairing minor to moderate external wounds.