Is Webb monitoring the first and oldest stars in the universe?

If you’ve never looked at the first deep field image taken by the James Webb Space Telescope, you need to.

The James Webb Space Telescope's first deep field
Sparkling galaxy within JWST’s first deep field. Credit: Lamia Mawla with images from NASA, ESA, CSA and STScI; Moola, Eyre et al. 2022

Within the beautifully detailed image, you can see swarms of some of the first galaxies in the universe, sparkling like gems across the vast expanse of space and time.

Looking deeper into the image, a Canadian research team has discovered the most remotely identified globular cluster, which may contain the first and oldest stars in the universe. Finding this is a task that Webb is specifically designed for.

says Lamia Moola, Dunlap Fellow at the Dunlap Institute for Astronomy and Astrophysics at the University of Toronto and co-lead author of the study.

spherical block image
Globular clusters, such as NGC 6441, one of the largest and brightest globular clusters in the Milky Way, are compact and dense with stars. Credit: ESA/Hubble/NASA/JBUTTO

The researchers focused on the Sparkler Galaxy, known as the small yellow-red “glint” of star clusters surrounding it. Five of the 12 “sparkles” analyzed turned out to be globular clusters, which are commonly found in the bulge and halo around galaxies and contain many old and red stars. Because they are highly interconnected, these groups are very stable and last for billions of years.

This discovery was made by the aptly named CANUCS: the Canadian NIRISS Unbiased Cluster Survey.

Spherical clusters were identified by the CANUCS team due to the lack of oxygen lines in the NIRISS (near infrared imaging and slit spectroscopic) data.

The presence of oxygen is important. If it is discovered, it indicates that the clusters were much smaller and actively involved in star formation.

Read more: Remnants of the ancient universe

Diagram describing a gravitational lens
This illustration shows a phenomenon known as gravitational lensing, which astronomers use to study very distant and very faint galaxies. Credit: NASA/ESA/L.Calçada

The incredible accuracy and sensitivity of JWST (and lucky natural magnification due to gravitational lensing by a galaxy in the foreground) allowed these ‘sparkles’ to be observed for the first time – something that Hubble’s instruments (predecessor of Webb) were not able to do. By using multi-wavelength observations of the clusters, scientists can better model and understand their physical properties such as the age and number of stars within them.

For very distant and very old globular clusters, this presents an opportunity to peek into the dressing room of the very early universe.

“These newly identified clusters formed near the first time that stars could have been formed,” Mola says. “Because the Sparkler Galaxy is much farther away than our Milky Way, it is easier to determine the ages of its globular clusters. We are watching Sparkler as it was nine billion years ago, when the universe was only four and a half billion years old.”

As Webb delves deeper into space, we can all expect to understand more about the origins of our universe, and ultimately ourselves as well.

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