A new galaxy that may have helped awaken the universe
New evidence from Hubble unveils the most distant galaxy yet, one forming stars 13 billion light-years away.
In their hunt for "origins," astronomers have peered into stellar nurseries in the Milky Way, found fledgling solar systems, and surveyed star-forming regions in other galaxies. Now they appear to have added one of the universe's most distant, earliest galaxies to the cosmic family album.
A team of astronomers from the US, France, and Britain announced on Sunday that it had discovered what looks to be a small galaxy some 13 billion light-years away - the most distant galaxy yet detected. And it appears to have been forming massive first-generation stars at a furious pace.
This, researchers say, suggests that this object and others like it may have played a key role in awakening the universe from its "dark ages" - a period when the young universe was filled with primordial hydrogen but no stars. Even when new stars did ignite their fusion furnaces, the light was obscured by a dense fog of neutral atoms until enough stars and protogalaxies evolved to ionize atoms and let light pass.
The new galaxy is unusual compared with its more mature counterparts, including those experiencing intense star formation, says California Institute of Technology astronomy professor Richard Ellis, a member of the research team. The galaxy appears to display traits "that theorists have predicted for objects that formed for the very first time."
With an estimated diameter of some 3,900 light-years, the young galaxy would fit comfortably within the Milky Way, whose disk stretches some 120,000 light-years across. Yet it is forming stars from 10 to 50 times as quickly as the Milky Way, says Jean-Paul Kneib, a researcher at Caltech who led the effort.
The find joins a small but growing list of celestial objects detected at such great distances. Most of these other objects, however, have been quasars - brilliant beacons of radiation that shine from galaxies with active, supermassive black holes at their centers. Each of these black holes tips the cosmic scales at several billion times the mass of the sun.
So far, researchers have discovered 13 quasars that appear to have formed when the universe was about 6 percent of its current age, according to Xiaohui Fan, an astronomer with the University of Arizona's Stewart Observatory. Last summer, for example, researchers using powerful radiotelescopes found a quasar who emissions began to travel the universe when the cosmos was only 870 million years old.
But quasars, Dr. Ellis notes, represent one extreme in galactic evolution and remain relatively rare. The small galaxy his group found may be the earliest detected representative of a broader, more common class of objects that helped bring a renaissance of light to the universe after the dark hiatus following its fiery beginning in the Big Bang.
Spotting and studying objects at such extreme distances is stretching current technologies to their limits. The new galaxy has proved to be no exception. Even using the clarity and resolving power of the Hubble Space Telescope to first detect the galaxy, then the light-gathering power of the 10-meter Keck telescopes atop Hawaii's Mauna Kea to study it in more detail, neither could have done the job without help from Abell 2218. This is the designation given to a cluster of galaxies whose combined gravity acted as a lens to magnify the young galaxy's image and brighten it some 25 times.
Even then, Hubble had to stare at the same spot in space for 15 hours and the Keck scopes for two full nights before they could collect enough faint photons to register useful images and gather tantalizing spectra. Moreover, the galaxy's great distance means that it is speeding away from earthbound observers as the universe continues to expand. At 13 billion light-years distant, the speeds are so great than radiation emitted within the new galaxy as ultraviolet light is "stretched" to much longer infrared wavelengths by the time it reaches Earth.
The researchers acknowledge that while several lines of evidence point to an extremely young age for this galaxy, they don't have spectroscopic signatures that many would consider the "smoking gun."
Such unambiguous spectroscopic evidence is difficult to get at these distances and with current technology, acknowledges Massimo Stiavelli, an astronomer with the Space Telescope Science Institute in Baltimore who was not part of the team. Still, he adds, the group's evidence "is reasonably convincing."
Dr. Kneib notes that his team had to overcome skepticism that they could achieve their goal when they first applied for telescope time. But now that the results are out - and to be published in an upcoming edition of the Astrophysical Journal - the team hopes to get more time to study the object, as well as to search for counterparts elsewhere in the sky.