An Unprecedented Look at Galaxy Formation
These galaxies are so distant that the universe was in its infancy when their light was emitted.
The galaxy proto-cluster, named LBG-2377, is giving scientists an
unprecedented look at galaxy formation and how the universe has
evolved. Before this discovery, the farthest known event like this was
approximately 9 billion light years away.
"When you observe objects this far away, you are actually seeing the
universe as it was a very long time ago," said Jeff Cooke, a McCue
Postdoctoral Fellow in physics and astronomy at UCI and lead author of
this study. "It is as if a timeline is just sitting out there in front
of you. These galaxies represent what the universe looked like well
before the Earth existed."
Using the Keck Telescope in Hawaii, Cooke detected LBG-2377 while
looking for single galaxies. At first, it appeared to be a bright,
single object. But after analyzing the wavelengths of its light
(galaxies emit light with telltale colors) he discovered it was three
galaxies merging together, and likely two additional smaller galaxies.
Scientists use light to look back in time. Because light takes a
measurable amount of time to travel, detecting it on Earth today allows
scientists to view the source as it was billions of years ago. In the
case of LBG-2377, scientists believe the light has been traveling for
11.4 billion years, beginning just a few billion years after the Big
Bang when the universe was only 15 percent of its current age. By
comparison, the Earth was formed about 4.5 billion years ago.
The process of galaxy formation largely is a mystery. Current theory is
that large galaxies formed over time from the interaction and merging
of smaller galaxies. This process began more than 12 billion years ago,
shortly after the Big Bang. Scientists have observed galaxies merging
over a large range of distances and time, providing hard evidence to
reinforce the theory. However, using current technology, it is
difficult to detect this process at the most extreme distances, when
galaxy formation was in its infancy.
Scientists believe galaxy clusters form in a similar manner. As
galaxies congregate and interact in large, dense regions of space, the
cluster grows with time. Witnessing this process first-hand helps
scientists confirm their theory and deepen their understanding of the
universe. Galaxy clusters can be detected at extreme distances with
current technology because they are bright, but they are difficult to
Clusters closer to Earth contain upwards of 1,000 galaxies. Our Milky
Way galaxy belongs to a lesser grouping of galaxies called the Local
Group, which contains more than 35 galaxies, but only a few bright ones.
"We believe LBG-2377 is a seed that eventually will grow into a massive
galaxy cluster," said James Bullock, director of the Center for
Cosmology at UCI and a study co-author.
"Our finding suggests that this is a monster structure being born in a
very bright, catastrophic event with a lot of gas and matter collapsing
at once," Bullock said. "We are not just seeing one solitary galaxy. We
are seeing a bunch of bright galaxies coming together at the dawn of
structure formation in the universe."
Scientists Elizabeth Barton and Kyle Stewart of UCI, along with Arthur
Wolfe of the University of California, San Diego, worked on this study.
The research was funded by a Gary McCue Postdoctoral Fellowship and the
National Science Foundation.