HIGHLIGHT for MY ANSWER
At the end after activating the partial halo, you jump to a portal on the ship with chief, cortanna and arbitor. if you notice arbitor heads to the front and cheif and cortanna stay to the back of the ship. the halo fires, destroying the arc and all the flood. it then cuts to the grave where they pressume MC is dead along with Cortanna. and Arbitor etches 117 (as in Spartan John 117, the MC) on the tombstone along with the other names and such. the war is over (the war is fought between UNSC and the remaining covanant on earth while the MC, Arbitor and company head off to the arc in chase of the Prophet of Truth) UNSC won and as the ship that jumped to warp when the halo fired enters earths atmosphere its only HALF the ship. The Halo pulse closed the warp hole before the whole ship could get through. Leaving the people on earth and the Arbitor to believe they were destroyed. But (this is the scene after the credits) it shows that MC and Cortana survived the break in the ship and are left adrift in the wake of the destroyed ark. At this point Cortana informs cheif that she sent out becons on their location and that it would be awhile before someone finds them. (years even, she said) so Cheif, looking tired.. gets in a cryo champer and basically tells Cortanna to wake him when she hears something. this leaving the opening for more story to be added later. so to sum up (because im really tired and havent slept.. [beat the campaign 4 hours after getting Halo 3]) Heres the cliff notes
- MC, Cort, Arb use a partially built Halo on the outskirts of the galaxy ( where the Arc is ) to destroy the flood and the Arc
- Before Halo fires they jump through a warp hole to get back to earth
- The power of Halo firing closes the portal too soon and the ship is split in two
- The half with Arb in it returns to earth
- The half with MC and Cort stays on the outskirts of the galaxy where the Ark was
- Arb informs Earth that MC and Cort where lost in the jump (dead to his knowledge)
- Cort sends out becons to inform earth they are still alive and there position
- Cort informs cheif it will take a while for someone to find them
- MC goes in cryo chamber untill they are found.
any other questions, feel free to ask, i fully understood, and enjoyed the ending. It was very well done.