In Destiny, what is the giant white sphere that protects humanity called?

In Destiny, the giant white sphere that protects humanity is called the Traveler.

The Traveler is a massive spherical celestial entity whose arrival transformed human civilization. It enabled the Golden Age, a period of technological progress and expansion through the Solar System. Its influence is also tied to the Light, the power used by Guardians to defend humanity.

The Collapse ended the Golden Age and nearly destroyed human civilization. After confronting the Darkness, the damaged Traveler remained above the Last City on Earth. Its presence helped preserve humanity's last major refuge and became the foundation of Guardian culture and belief.

The Traveler is not the Dreadnaught, the Hive warship associated with Oryx; the Leviathan, a vast Cabal vessel associated with Calus; or the Almighty, a Cabal superweapon. Those are enormous space structures, but only the Traveler is the white sphere linked to the Light and humanity's survival.