Combining the power of the space agency's Hubble and Spitzer space telescopes they have created an image in which the farthest galaxy appears as a diminutive blob that is only a tiny fraction of the size of our Milky Way galaxy.
However, it offers a peek back into a time when the universe was only 3 percent of its present age of 13.7 billion years, NASA said.
The newly discovered galaxy, named MACS0647-JD, was observed as it appeared 420 million years after the big bang, and its light has spent 13.3 billion years traveling to reach Earth.
MACS0647-JD is so small -- just 600 light-years across -- it may be in the first steps of forming a larger galaxy, astronomers said.
"This object may be one of many building blocks of a galaxy," study lead author Dan Coe of the Space Telescope Science Institute said. "Over the next 13 billion years, it may have dozens, hundreds, or even thousands of merging events with other galaxies and galaxy fragments."
The researchers say they hope to use Hubble to search for more dwarf galaxies at these early epochs, which if numerous could have provided the energy to burn off the fog of hydrogen that blanketed the early universe, a process called re-ionization that ultimately made the universe transparent to light.