H3+ The original mothercloud was mostly H2 and He. It didn't have molecular species containing C, N, and O that are good at radiating away heat they pick up by jostling each other when the cloud contracts. So it was hard for the early clouds to contract by their own gravity, because they lacked effective means of shedding the surplus energy by radiating it away. This positive ion (three protons and two electrons) is believed to have played a key role. It is a good radiator. So naturally people want to LOOK FOR THE LIGHT it would have radiated in early universe clouds--appropriately redshifted during the intervening years of course. So this group Pavanello et al ran a computer model of H3+ and found its vibration modes and energy levels and what wavelengths of light to look for. http://theop11.chem.elte.hu/main_index_files/2012_Pavanello_PRL.108.023002_H3p.pdf They published their results in 13 January 2012 Physical Review Letters There is also this press release blurb from the U of Arizona--containing some confused or misleading stuff but still of value as a popularization. http://uanews.org/node/46088 http://www.astrobio.net/pressrelease/4695/the-molecule-that-made-the-universe Later after the first generation of stars had "cooked" heavier elements like C, N, and O and burped them forth, the way stars do by various means, the clouds had an easier time contracting. Because they had good radiator molecules in them to help get rid of surplus energy as they contracted. So the subsequent generations of stars had an easier time forming, and this triatomic hydrogen ion would no longer have played such a key role.