The quarians established a colony on the planet Haestrom in order to investigate and study the strange phenomenon occurring with the system's star. The star appeared to be maturing quicker than it should be, as evident by the large increase in size and the massive magnetic eruptions that scramble communications and make standing in the sunlight a death sentence.
In Mass Effect 2
, Commander Shepard
travels to Haestrom to recruit Tali
, a former squadmate of his in the first game. When the crew arrives, they discover that the geth have moved in and taken over the colony, which the quarians fighting to get back. While on the planet, Shepard cannot stay in the sunlight for long or his shields will overheat, after which he will begin to burn up. Thus, Shepard and the crew must stay in the shade by effectively utilizing cover throughout the mission.