"We really hadn't seen a formation process that could create things that are this dense," said Erica Nelson of Yale University, lead author of the study. "We suspect that this core-formation process is a phenomenon unique to the early universe because the early universe, as a whole, was more compact. Today, the universe is so diffuse that it cannot create such objects anymore."
In addition to determining the galaxy's size researchers was able to determine how fast the galaxy was creating stars. They found Sparky produced about 300 stars per year compared with the 10 created in our galaxy.
"They're very extreme environments," Nelson said. "It's like a medieval cauldron forging stars. There's a lot of turbulence, and it's bubbling. If you were in there, the night sky would be bright with young stars, and there would be a lot of dust, gas, and remnants of exploding stars. To actually see this happening is fascinating."
Astronomers believe the accelerated star birth was spurred by a gas flow into the galaxy's core where it formed a gravitational well of dark matter. The star creating frenzy will most likely slow to a stop at some point over the next 10 billion years, it could also merge with other small galaxies.
"I think our discovery settles the question of whether this mode of building galaxies actually happened or not," said team member Pieter van Dokkum of Yale University. "The question now is, how often did this occur? We suspect there are other galaxies like this that are even fainter in near-infrared wavelengths. We think they'll be brighter at longer wavelengths, and so it will really be up to future infrared telescopes such as NASA's James Webb Space Telescope to find more of these objects."