Astronomers have spotted a giant galaxy in the earliest stages of construction some 11 billion years ago, just three billion years after the Big Bang. This mighty galaxy—named GOODS-N-774 or “Sparky”—is chucking out newborn stars at a phenomenal rate, giving scientists a rare and exciting opportunity to study a process of galaxy formation that no longer occurs in our Universe today. The study has been published in Nature.
Galaxies are massive systems of stars, dust and gas bound together by gravity. There are 3 main types of galaxies: elliptical, spiral and irregular. Elliptical galaxies, such as Sparky, are shaped like an elongated sphere. Galaxies can range considerably in size, but giant elliptical galaxies are the largest.
It was theorized that these giant, gas-deficient galaxies develop from the inside out, starting off as a large, compact core. Until now, however, these elusive cores had never been spotted because they’re unique to the early Universe and probably heavily obscured from view. According to lead author of the study Erica Nelson, these dense cores were probably able to form early on because the Universe was generally much denser in the period shortly after the Big Bang.
Sparky was identified with the help of the Hubble Space Telescope, the Spitzer Space Telescope, the Herschel Space Observatory and the W.M. Keck Observatory. While Sparky may be small, it certainly packs a punch. A mere 6,000 light-years across, it already contains around twice as many stars as our home galaxy that is some 100,000 light-years across.
Using archival far-infrared images, the researchers were also able to determine the rate of star formation in its core. Impressively, Sparky is churning out around 300 stars per year; the Milky Way produces only around ten.
The researchers postulate that this intense rate of star formation is due to the fact that the core is forming within the heart of a gravitational well crammed with dark matter, an invisible material that acts as a scaffold for galaxy formation in the early Universe. They believe a torrent of gas is pouring into this well, sparking the birth of stars.
“They’re very extreme environments,” Nelson said in a news release. “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.”
The researchers suggest that this vast amount of dust and gas is likely the reason that star-forming cores such as these have evaded astronomers before. This material would heavily obscure the region, making it difficult to spot in optical and near-infrared surveys.
“We had been searching for this galaxy for years, and it’s very exciting that we finally found it,” said co-author Pieter van Dokkum. “The big challenge is to understand the physics driving the formation of such objects.” Hopefully, he says, the James Webb Space Telescope will help us find the answer.