Science / Medicine : Oldest Galaxy Found; Challenges Theory

The oldest and most distant galaxy yet known has been discovered, pushing back by several billion years the time when the first stars of the universe were formed.

The newly found galaxy, about 10 times the size of the Milky Way, was discovered by Simon Lilly of the University of Hawaii’s Institute for Astronomy.

Lilly spotted the galaxy, called 0902+34, on two different telescopes based atop Hawaii’s dormant Mauna Kea volcano. His report has been accepted for publication in the Astrophysical Journal.

The discovery moves the start of the epoch of galaxy formation to within a billion or so years of the big bang--the explosion in which the universe was born--so close that it challenges a widely held theory about the nature of the universe. According to that theory, most of the universe’s mass consists of “cold dark matter,” so called because it cannot be detected. If the theory is true, astronomers believe, it would have been unlikely that galaxies would have formed as early as the one just discovered.

The question of cold dark matter is important because it bears on whether the universe has enough mass so that its collective gravitational pull will eventually reverse the current expansion. The known mass of the universe is not enough for this to occur, and unless astrophysicists can find the so-called missing mass, the universe should continue expanding.

Until now the oldest confirmed galaxies were ones that formed 10 billion to 11 billion years ago. The big bang began roughly 15 billion years ago. Until Lilly’s discovery, however, there was no solid evidence of galaxies so early in the history of the universe.