Much of the paper is devoted to calculations regarding the formation of heavier elements and rocky planets. Surprisingly, the lifetime of the largest stars is o

Much of the paper is devoted to calculations regarding the formation of heavier elements and rocky planets. Surprisingly, the lifetime of the largest stars is only 3 million years: For massive stars that are dominated by radiation pressure and shine near their Eddington luminosity LE = 1.3 × 1040 erg s−1(M⋆/100M⊙), the lifetime is independent of stellar mass M⋆ and set by the 0.7% nuclear efficiency for converting rest mass to radiation, ∼ (0.007M⋆c2)/LE = 3 Myr (El Eid et al., 1983; Bromm et al., 2001). Then it's a matter of figuring out how long it takes for matter to clump together and form stars/planets. After some math and citations in section 2: The above calculation implies that rocky planets could have formed within our Hubble volume by (1+z) ∼ 78 but not by (1+z) ∼ 110 if the initial density perturbations were perfectly Gaussian. However, the host halos of the first planets are extremely rare, representing just ∼ 2 × 10−17 of the cos- mic matter inventory. Since they lie ∼ 8.5 standard deviations (σ) away on the exponential tail of the Gaussian probability distribution of initial density perturbations, P(δ), their abundance could have been significantly enhanced by primordial non-Gaussianity (LoVerde and Smith, 2011; Maio et al., 2012; Musso and Sheth, 2013) if the decline of P(δ) at high values of δ/σ is shal- lower than exponential. The needed level of deviation from Gaussianity is not ruled out by existing data sets (Ade et al., 2013b). Non-Gaussianity below the current limits is expected in generic models of cosmic inflation (Maldacena, 2003) that are commonly used to explain the initial density perturbations in the Universe. Using current best knowledge about the early universe, it looks like planets did form, but were extremely rare. With some plausible tweaks to how "clumpy" the initial universe was, one ends up with lots more planets. Side note: much of the paper measures time in z (red shift) instead of years. See http://en.wikipedia.org/wiki/File:Distance_compared_to_z.png http://en.wikipedia.org/wiki/File:Distance_compared_to_z.png to get an idea of the relationship between the two. The red dotted line is time in the past. The black solid line is comoving distance[1]. For comparison, some really old objects are mentioned at http://en.wikipedia.org/wiki/Redshift#Highest_redshifts http://en.wikipedia.org/wiki/Redshift#Highest_redshifts 1. Distance if you could freeze the universe at the present day and lay out a bunch of yard sticks.