Archive for September, 2012

Distant, ancient galaxy that helped form universe discovered

Wednesday, September 19th, 2012

A hunt for galaxies that brought the toddler universe out of its dark ages has bagged what may be the most distant specimen yet discovered, a galaxy seen as it was more than 13 billion years ago when it was just 200 million years old.

The galaxy, which was found using data from the Hubble and Spitzer Space Telescopes, is seen when the universe was only 500 million years old.

A munchkin by today’s standards, the galaxy’s mass was 200 million times the mass of the sun, compared with 700 billion solar masses for the Milky Way or 10 billion solar masses for the Milky Way’s smaller companion, the Large Magellanic Cloud.

But the newly discovered galaxy’s age – and the preponderance of hot, massive stars it hosted – place it among a category of objects that researchers say helped convert a fog of neutral hydrogen gas permeating the ancient universe into the transparent cosmos we see today.

The process, known as re-ionization, is thought to have started around 400 million years after the Big Bang, a sudden release of an enormous amount of energy that cosmologists have tagged as the birth of the universe.

Over the next 600 million years, stars and galaxies formed and the universe continued to expand. Radiation from the first generations of stars – and particularly from emissions stemming from the actions of super-massive black holes at the hearts of the rising number of growing galaxies – ionized the intergalactic hydrogen, in effect lifting the fog.

Relics of this period, 13-billion-year-old stars, populate the halo of the Milky Way, notes Wei Zheng, an astronomer at the Johns Hopkins University in Baltimore and the lead author of a formal report of the discovery, which is being published in Thursday’s issue of the journal Nature. (more…)