for National Geographic News
January 5, 2010
Compact, ultra-blue galaxies spied for the first time in the deep universe are the most distant—and therefore the earliest—galaxies anyone has ever seen, astronomers announced today.
These galaxies started forming just 500 million years after the big bang, which is thought to have occurred around 13.7 billion years ago. That pushes back the known start of galaxy formation by about 1.5 billion years.
The objects were spotted in pictures taken by the Hubble Space Telescope's Wide Field Camera 3, a new camera installed in 2009. (See some of the first pictures taken by the upgraded Hubble.)
The Hubble images, combined with data from the Spitzer Space Telescope, show that the newfound galaxies are relatively small, and they appear very blue, a color linked to lighter elements such as hydrogen and helium.
Hydrogen fusion inside active stars creates heavier elements such as iron and nickel, which get spread across the universe when massive stars explode.
These elements cause modern galaxies to glow in a rainbow of colors, so the extreme blueness of the newfound galaxies suggests that they formed before very many massive stars had lived and died.
"We are looking back 13 billion years and finding extraordinary objects," said Garth Illingworth, an astronomer at the University of California, Santa Cruz (UCSC), and leader of one of Hubble's survey teams.
"We are looking back through 95 percent of the life of the universe."
Tiny Galaxies Were Only the Beginning
The deep Hubble view also reveals that the newly illuminated region is extremely active, said Rogier Windhorst of Arizona State University, leader of one of the other teams that analyzed the new data.
"If you look hard enough, you can see galaxies of almost every shape."
The snapshots represent an epoch in the early universe when galaxies were believed to be tiny toddlers. Most were just 5 percent the size of the Milky Way with one percent of its mass, UCSC's Illingworth said.
These galaxies are likely the beginnings of the theorized process of galaxy growth in which small galaxies gradually assemble into bulkier objects. "These are the seeds of the great galaxies today," Illingworth said.