A pair of just-released statistical studies of the universe suggest numerous habitable planets exist in our Galaxy, with one study suggesting a life-friendly planet within 20 light years of our Solar System. From my Nature article, Small stars host droves of life-friendly worlds, that broke news of this latter study, which used data from NASA’s Kepler telescope
For more than a century, the star HD 140283 has been studied, but only now has its age been estimated: within hundreds of millions of years of the age of the Universe. Delivering a scoop, my Nature article, Nearby star is almost as old as the Universe, details this important new conclusion:
The team then exploited the fact that HD 140283 is in a phase of its life cycle in which it is exhausting the hydrogen at its core. In this phase, the star’s slowly dimming luminosity is a highly sensitive indicator of its age, says Bond. His team calculates that the star is 13.9 billion years old, give or take 700 million years. Taking into account that experimental error, the age does not conflict with the age of the Universe, 13.77 billion years.
The very first generation of stars coalesced from primordial gas, which did not contain appreciable amounts of elements heavier than helium, he notes. That means that as old as HD 140283 is, its chemical composition — which includes a low but non-zero abundance of heavy elements — shows that the star must have formed after the first stellar generation.
Conditions for making the second generation of stars, then, “must have been in place very early”, says Bromm. The very first stars are usually thought to have coalesced a few hundred million years after the Big Bang, he notes. Massive and short lived, they died after only a few million years — exploding in supernovae that heated surrounding gas and seeded it with heavier elements.
The Nature article contains more information about the research and characteristics of early stars.