Pitch Black

In the distant future, the transport ship Hunter-Gratzner passes a desert planet with its crew and passengers in cryostasis. The passengers consist of nomadic settlers who are relocating to other planets, a Muslim priest who goes by the title "Imam", accompanied by young pilgrims traveling to New Mecca, a boy named Jack, a pair of prospectors named Shazza and Zeke, a merchant named Paris, and a law enforcement officer, William J. Johns, who is transporting a notorious criminal, Richard B. Riddick. Riddick has surgically-modified eyes that allow him to see in the dark.
Debris ruptures the hull, killing several passengers including the captain. The surviving crew members, docking pilot Carolyn Fry and co-pilot Greg Owens, attempt to land the ship on the nearby planet. As the ship ruptures and falls apart, Fry is forced to jettison sections of the ship. Fry attempts to dump the passenger section of the ship to reduce their weight, but Owens prevents her. During the crash landing, several passenger compartments are destroyed and Owens sustains fatal injuries.
The group explore their surroundings. Riddick escapes and Johns warns everyone that he may kill them all. They notice that the three suns surrounding the planet keep it in perpetual daylight. Zeke goes missing and while searching for him, Fry escapes from photosensitive aggressive underground creatures. They find an abandoned geological research settlement, with a dropship with drained batteries. Inside the settlement, one of the young pilgrims is killed by the creatures. An orrery shows that an eclipse is imminent and that the creatures will be free to hunt above ground. Riddick rejoins the group and they return to the crash site to retrieve the power cells to power the dropship. Riddick reveals that Johns is not actually a law officer, but a bounty hunter who is attempting to collect the bounty on Riddick.
The group reaches the wreckage, but the eclipse begins before they can return to the settlement. The creatures pour out of the ground and kill Shazza and another of the children. The group decides to salvage any light source that they can and attempts to return to the dropship. Riddick agrees to lead them. En route Riddick reveals that Jack is actually a girl and the scent of her menstrual blood is attracting the creatures. Johns suggests to Riddick that he kill Jack and use her corpse as bait to keep the creatures off the rest of the group. Riddick instead wounds Johns, who is attacked by the creatures, providing a distraction.
Fry, Jack, Riddick and Imam make it to a cave near the ship after a rain puts out their flares. Riddick seals them in the cave and takes the power cells. Fry leaves the cave and finds Riddick powering up the ship to leave without them. She pleads with him to help her rescue Imam and Jack, but instead he offers to take her with him. Riddick has a change of heart and they retrieve Imam and Jack and take them to the ship, but Riddick is separated from the group and is wounded by the predators. Fry returns to help Riddick but she is killed after finding him. Riddick makes it to the ship and waits until the last moment before engaging the engines to incinerate as many creatures as possible. In orbit, Riddick tells Jack to tell anyone they meet that Riddick died on the planet below, and they depart for New Mecca.

Question: What is keeping the planet in perpetual daylight?
Answer: three suns