Color images of the Sparkler and its environs made by combining F090W, F150W, and F200W images at native spatial resolution. Mowla et al., arXiv: 2208.02233.

James Webb Spots Some of the Most Ancient Globular Clusters

According to scientists, it could be one of the earliest observed objects to have quenched their star formation in the Universe.


James Webb Space Telescope observations have revealed ancient globular clusters around a marvelous galaxy thanks to being strongly gravitationally lensed by the galaxy cluster SMACS J0723.3-7327.

A globular cluster is a dense collection of stars gravitationally bound together into one structure. It can range in size from 100 to 200 light-years across.


The stars in them number in the hundreds of thousands or perhaps in the millions. During the formation of a cluster, the stars are drawn inward by the large mass in the rich stellar center.

It is thought that globular clusters are relics of the first stages of galaxy formation in the Universe, making them one of the oldest objects.

The population of globular clusters is thought to exist in every galaxy. We know of at least 150 of these objects in our Milky Way Galaxy, and it is likely that there are more hidden within its thick disk.

In spite of the fact that globular clusters have been the topic of intense research for decades, we are still unsure when or how they form, said Dr. Lamiya Mowla, a postdoctoral researcher at the Dunlap Institute for Astronomy and Astrophysics, along with colleagues from Canada, Denmark, Japan, Slovenia, and the United States.

“We do know that most globular clusters in the Milky Way, and those around nearby galaxies, are very old.”

It has been estimated that the oldest globular clusters, based on main sequence fitting and the ages of the oldest white dwarfs, are approximately 12.5 billion years old, corresponding to formation redshifts of z = 5.


In the view of astronomers, globular clusters are formed in two ways.

According to the first hypothesis, globular clusters form primarily at very high redshifts when galaxies first gather. The formation channel driving present-day star formation differs from that driving globular cluster formation in the early Universe.

In the second view, starbursting and merging galaxies are associated with globular clusters. This scenario suggests that globular cluster formation is a natural product of continuous galaxy evolution in systems with high gas fractions, which peaks at lower redshifts.

In their study, Dr. Mowla and co-authors examined point sources (sparkles) seen around a gravitationally lensed galaxy in the first deep field of Webb’s telescope using data from the Near Infrared Camera and Near Infrared Imager and Slitless Spectrograph.

SMACS J0723.3-7327, a massive cluster of galaxies located in the southern constellation of Volans, magnifies the distant galaxy, nicknamed Sparkler, by a factor of up to 100.

There is a z=1.378 redshift in the galaxy, which means that we are looking at it as it existed around 9 billion years ago.

A total of twelve ‘sparkles’ have been found in and around the Sparkler.

There are at least five unresolved and red sources among the twelve, and scientists believe that they are evolved globular clusters at z=1.378.

A model of these sources’ colors and spectra shows four (33%) are typical of stellar populations formed at z > 9, i.e., in the first 500 million years of cosmic history and 13 billion years ago.


“If confirmed with additional spectroscopy, these red, compact ‘sparkles’ represent the first evolved globular clusters found at high redshift, could be among the earliest observed objects to have quenched their star formation in the Universe, and may open a new window into understanding globular cluster formation,” the authors concluded in the study published in the Astrophysical Journal Letters.

James Webb has completely changed the way we explore the universe, allowing astronomers to make unprecedented discoveries while delivering mind-boggling photographs of regions of space that were previously out of reach.

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Written by Ivan Petricevic

I've been writing passionately about ancient civilizations, history, alien life, and various other subjects for more than eight years. You may have seen me appear on Discovery Channel's What On Earth series, History Channel's Ancient Aliens, and Gaia's Ancient Civilizations among others.

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