What constellations have detected stars that are no greater than 3 billion years old?

Question

I know stars, galaxies and clusters have been detected that are older than 12 billion years. But are there any sectors of space where there are no old stars and/or realtively few stars at all?

Answer 1

Hot blue-white stars (stellar classifications O and B) are relatively short-lived, so any of them you see are probably well under a billion years old. The Pleiades cluster stars (all B stars) has been estimated at 70 to 150 million years old. Scorpius, Orion, and Perseus are among the constellations whose prominent stars are mostly young. The bright stars in the Orion Nebula (M42) are estimated to be around a million years old. Other star-forming nebulae also are populated by very young stars.

Answer 2

The oldest rocks that have been found on earth date to 3.8-3.9 billion, via several radiometric dating methods. This establishes a lower limit for the age of the earth, that is, we know for a fact that the earth is atleast 3.8 billion years old. The actual age of the earth is measured with a Pb/Pb isochron age, derived from samples of the Earth and meteorites, where three isotopes of uranium and lead are measured. The ratio of these are then calculated. If the solar system formed from a common pool of matter, which was uniformly distributed in terms of Pb isotope ratios, then the initial plots for all objects from that pool of matter would fall on a single point. This is exactly what the evidence has shown so far, which demonstrates that the Earth is 4.55+-1% billion years old. This is a question that should have been asked in the science section though.