A galaxy twinkling with the universe’s oldest stars has been discovered by astronomers. Named “The Sparkler,” it is nine billion light years away. We are seeing it only four-and-a-half billion years after the Big Bang.
The Sparkler galaxy was captured by the First Deep Field image of the James Webb Space Telescope (JWST). The high-resolution snapshot contains thousands of galaxies and dense groups of millions of stars.
“JWST was built to find the first stars and the first galaxies and to help us understand the origins of complexity in the universe, such as the chemical elements and the building blocks of life,” says co-lead author of the study, Lamiya Mowla, Dunlap Fellow at the Dunlap Institute for Astronomy & Astrophysics in the Faculty of Arts & Science at the University of Toronto, in a statement.
“This discovery in Webb’s First Deep Field is already providing a detailed look at the earliest phase of star formation, confirming the incredible power of JWST,” she adds.
The Sparkler got its name for the compact objects appearing as small yellow-red dots surrounding it, referred to by the researchers as “sparkles.” They could either be young clusters actively forming stars — born three billion years after the Big Bang at the peak of star formation — or old globular clusters.
These are ancient collections of stars from a galaxy’s infancy. They contain clues about its earliest phases of formation and growth. Analysis showed five are among the oldest ones known.
“Looking at the first images from JWST and discovering old globular clusters around distant galaxies was an incredible moment, one that wasn’t possible with previous Hubble Space Telescope imaging,” says co-lead author Dr. Kartheik Iyer, also a fellow at the institute. “Since we could observe the sparkles across a range of wavelengths, we could model them and better understand their physical properties, like how old they are and how many stars they contain. We hope the knowledge that globular clusters can be observed at from such great distances with JWST will spur further science and searches for similar objects.”
The Milky Way galaxy has about 150 globular clusters. The study sheds light on how and when these dense clumps of stars formed.
It is known they can be extremely old. But it is incredibly challenging to measure their ages. Using very distant globular clusters to age-date the first stars in distant galaxies has not been done before and is only possible with JWST.
“These newly identified clusters were formed close to the first time it was even possible to form stars,” says Mowla. “Because the Sparkler galaxy is much farther away than our own Milky Way, it is easier to determine the ages of its globular clusters. We are observing the Sparkler as it was nine billion years ago, when the universe was only four-and-a-half billion years old, looking at something that happened a long time ago.
“Think of it as guessing a person’s age based on their appearance,” she continues. “It’s easy to tell the difference between a 5- and 10-year-old, but hard to tell the difference between a 50- and 55-year-old.”
Astronomers could not see the surrounding compact objects of the Sparkler galaxy with Hubble. This changed with JWST’s increased resolution and sensitivity, unveiling the tiny dots surrounding the galaxy for the first time in the First Deep Field image.
The Sparkler galaxy is special because it is magnified by a factor of 100 due to an effect called gravitational lensing. A galaxy cluster in the foreground distorts what is behind it, much like a giant magnifying glass. The technique also produces three separate images of the Sparkler, allowing astronomers to examine it in greater detail.
“Our study of the Sparkler highlights the tremendous power in combining the unique capabilities of JWST with the natural magnification afforded by gravitational lensing,” explains Dr. Chris Willott, leader of the CAnadian NIRISS Unbiased Cluster Survey (CANUCS). “The team is excited about more discoveries to come when JWST turns its eye on the CANUCS galaxy clusters next month.”
The researchers combined new data from JWST’s Near-Infrared Camera (NIRCam) with Hubble archival data. NIRCam detects faint objects using longer and redder wavelengths to observe past what is visible to the human eye and even Hubble. Both magnifications due to the lensing by the galaxy cluster and the high resolution of JWST are what made observing compact objects possible.
The Canadian-made Near-Infrared Imager and Slitless Spectrograph (NIRISS) instrument on the JWST provided independent confirmation.
The objects are old globular clusters because the researchers did not observe oxygen emissions with measurable spectra given off by young clusters that are actively forming stars.
NIRISS also helped unravel the geometry of the triply lensed images of the Sparkler.
“JWST’s made-in-Canada NIRISS instrument was vital in helping us understand how the three images of the Sparkler and its globular clusters are connected,” says co-author Marcin Sawicki, a professor at Saint Mary’s University in Halifax, Nova Scotia. “Seeing several of the Sparkler’s globular clusters imaged three times made it clear they are orbiting around the Sparkler galaxy rather than being simply in front of it by chance.”
The study is published in The Astrophysical Journal Letters.
Report by Mark Waghorn, South West News Service