The Klingon star is more massive than Sol. It began running out of hydrogen in its core millions of years ago. As a result, the star has been growing larger and redder during that time. Its total luminosity has been increasing slowly but will increase much faster during the next few million years as the star runs out of core hydrogen completely and turns from an orange sub-giant into a red giant. This will render Qo’noS completely uninhabitable, but it is not something most Klingons worry about because it will occur in the distant future and they have more immediate concerns.
Qo’noS used to have two moons: Corvix and Praxis. The Klingons obtained energy from the molten core of Praxis until 2293, when lax safety precautions led to a massive explosion that destroyed the moon. The explosion damaged the Qo’noS ozone layer and led to massive devastation as chunks of Praxis bombarded the planet. Klingon scientists predicted that Qo’noS would be uninhabitable within a few decades without outside assistance. Chancellor Gorkon reached out to the Federation for aid, and this eventually led to a formal alliance between the Klingon Empire and the United Federation of Planets.
Acknowledgements: STARFLEET International, STARFLEET Academy http://acad.sfi.org/ http://sto.gamepedia.com/First_City http://cs.memory-alpha.wikia.com/wiki/Qo%27noS Nibiru created by Andrea Dopaso