NASA’s Hubble and Spitzer telescopes have been used to examine a distant elliptical galaxy known as Sparky. The observations represent the first glimpse at the earliest stages of massive galaxy construction, shedding light on an area of frenzied star production in the early universe.
The distant galaxy is just 6,000 light-years across, making it a fraction of the size of our own Milky Way, which measures some 100,000 light-years across. However, despite the huge difference in size, Sparky contains twice as many stars as our home galaxy.
The object’s galactic core is so far away that the observed light was created some 11 billion years ago, just three billion years after the Big Bang. It’s thought that the galaxy began as a dense core, then developed from the inside out.
The team also studied archival infrared images from the two telescopes, determining that Sparky produces around 300 stars a year – significantly more than the 10 stars per year produced in the Milky Way. The team’s findings indicate that the galaxy has been producing stars for a billion years prior to observation.
Yale University’s Erica Nelson, lead author on the study, commented on the observations, stating that "We really hadn’t seen a formation process that could create things that are this dense … 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."
It’s thought that Sparky’s star-forming environment as seen though the telescopes was extremely turbulent and chaotic, springing to life when a torrent of gas flowed into its core while it was forming inside a gravitational well of dark matter – a substance that provides structure in the construction of galaxies.
While the observable light from Sparky shows a very high level of star formation, it’s thought that this will eventually slow down, and that billions of years down the road, smaller galaxies may even emerge from it. It will then become a huge, sedate elliptical galaxy.
Team member Pieter van Dokkum commented on the significance of the findings, stating that "Our discovery settles the question of whether this mode of building galaxies actually happened or not … The question now is, how often did this occur?".
The team believes that there are other, similar galaxies out there, but that the infrared tech on board the current crop of telescopes isn’t quite capable of detecting them. That said, we should get answers before too long, with future telescopes like the James Webb Space Telescope being up to the task.