One of the most fun ways to track down objects in our galaxy is the ancient globular clusters. They swarm in a sphere around the disc of the Milky Way, and many are older than the bulk of the stars in our galaxy. As we’ve been able to look at more and more galaxies, we have only found a handful of youngish globular clusters. These few systems hint at violent origins within the shockwaves of merging systems.
It has been hoped that as we look farther and farther back in time by looking at more and more distant systems whose light takes time to reach us, we’ll be able to find younger clusters and perhaps even discover the time when globular cluster formation was common.
Hubble tried. Hubble looked back as far as it could directly look with the Hubble Deep Fields. Hubble peered at lensed systems made visible by the gravity of massive galaxy clusters, but all it saw were fuzzy smears. Hubble tried, but Hubble’s 2.5-meter mirror was just too small to do the job.
But now we have JWST, with its 6.6-meter mirror, and amazing new possibilities.
In JWST’s first deep-field image, an image of a galaxy cluster, distant lensed galaxies are seen with never-before realized clarity. This image alone will take years to fully analyze!
One of the first papers to come out from this image was led by Lamiya Mowla and appears in The Astronomical Journal. This nine-page analysis focuses on just one distant galaxy magnified by the cluster’s gravity, called the Sparkler. According to Chris Willott: Our study of the Sparkler highlights the tremendous power in combining the unique capabilities of JWST with the natural magnification afforded by gravitational lensing.
And the cluster’s gravity shows us three lensed versions of this one system. From these differently distorted images, researchers were able to determine the sparkler is nine billion light years away, and the Sparkler was already old, with no longer star-forming globular clusters just 4.5 billion years after our universe formed! According to team member Kartheik G. Iyer: 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.
And it was a moment in which we gained no insight into how globular clusters form. Like Athena emerging fully adult from Zeus’s head, globular clusters just keep emerging fully formed in our images.
I, for one, am hoping that future research on other lensed systems will reveal even more ancient galaxies and, just once, let us clearly see how globular clusters form.
“The Sparkler: Evolved High-redshift Globular Cluster Candidates Captured by JWST,” Lamiya Mowla et al., 2022 September 29, The Astrophysical Journal Letters