It can be surprisingly difficult to study the Milky Way galaxy while you’re inside it, but astronomers are always looking for similar spirals elsewhere in the universe. A team analyzing data from the James Webb Space Telescope (JWST) now says one of the observatory’s first images may have featured the Milky Way’s twin, a galaxy known as The Sparkler. Because it is so distant, studying The Sparkler could be like studying our own galaxy in its infancy.
The Sparkler was revealed in the JWST’s deep field image, which leveraged the telescope’s incredible resolution and a gravitational lens to peer further back in time than ever before. Right near the center of the image is a distorted, pinkish disk studded with glowing dots (see above). When the deep field was released in the summer of 2022, scientists speculated that these dots could be globular clusters. The origin of these spherical collections of densely packed stars is a scientific mystery. The team, led by Duncan Forbes of Swinburne University in Australia and Aaron Romanowsky of San Jose State University in California, decided to follow up.
In the newly published paper, the researchers analyzed the age and metal content of the now-confirmed globular clusters. They determined that the clusters resemble younger versions of the ones still present in the Milky Way. Most of the clusters were old and showed high metal content, but a few showed lower metal content with an intermediate age — all part of the globular cluster mystery. The study speculates that The Sparkler, as seen in the Webb image, is evolving along the same lines as our galaxy.
A young Milky Way absorbing smaller galaxies. Credit: James Josephides/Swinburne University
Today, The Sparkler might look like the Milky Way, but our view is somewhat delayed. This object in the deep field image has a redshift of 1.38, meaning it appears as did roughly 9.1 billion years ago when the universe itself was only 4 billion years old. So, The Sparkler could be a mirror image of a young Milky Way, which formed with the help of globular clusters before it grew to its current size. The Sparkler is currently small, just 3% of the Milky Way’s mass, but the team believes some of those anomalous globular clusters are associated with satellite galaxies that are being absorbed. That’s one of the ways the Milky Way grew to its current size. “We appear to be witnessing, first hand, the assembly of this galaxy as it builds up its mass—in the form of a dwarf galaxy and several globular clusters,” says Professor Forbes.
We can’t draw many conclusions about the Milky Way based on The Spakler. The researchers say more data on distant globular clusters is needed. Only then will we know if The Sparkler is representative of the way large galaxies like the Milky Way grow by merging with dwarf galaxies and globular clusters.
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