Using a clever technique that pushed two of the world's most powerful telescopes to their limits, a team of scientists has discovered a "baby galaxy" so small, faint and distant that it may be one of the long sought-after building blocks of modern galaxies.
To find their galactic infant, the astronomers used a phenomenon predicted by Albert Einstein in the general theory of relativity--employing a massive group of galaxies, themselves, as an extra lens.
Most astronomers believe today's massive spiral and elliptical galaxies emerged from much smaller building blocks made up of clusters of stars. But astronomers have had a hard time seeing the galactic birthing process: Even the oldest known galaxies look similar to modern, mature galaxies, such as our own Milky Way.
"It's like we were trying to peer into the delivery room of the hospital and all we saw were adults," said Bruce Margon, associate director for science at the Space Telescope Science Institute in Baltimore.
Not anymore. The so-called baby galaxy is a scant 500 light-years across--nothing compared to the 100,000-light-year girth of our Milky Way, an average-sized galaxy.
It is estimated to contain just a few million times as much mass as our star, the sun. That's a fraction of the mass in our galaxy, where billions of stars reside.
The newly detected object formed when the universe, estimated to be 14 billion years old, was not even a billion-year-old tyke. The object is 13.4 billion light-years from Earth, meaning that light from the object traveled for 13.4 billion years before reaching our telescopes.
The object is so faint it could not be detected using existing ground or space telescopes. Instead, scientists used a phenomenon called gravitational lensing to boost the power of those telescopes by more than 30 times.
When light passes by a massive object, the gravitational field of the object causes the light to bend. That phenomenon, first predicted by Einstein, turns a truly huge object, like a galactic cluster, into a natural lens that can bend and focus light coming from behind it.
The scientists used one of these "natural telescopes," a dense cluster of galaxies called Abell 2218 that is 2 billion light-years from Earth, to detect the faint galaxy.
"Our strategy has been to use this cosmic magnification to find feeble objects," said Richard Ellis, a cosmologist at Caltech and lead author of the study that will be published in the Astrophysical Journal.
