The firehose of James Webb Space Telescope (JWST) data has opened, and astronomers have begun to drink from it. Just days after the observatory鈥檚 first full-resolution image was released on 11 July, two groups of researchers have already analysed the data to recreate the structure of the galaxy cluster in the image.
The cluster, called SMACS 0723, is so massive that it warps space-time, bending and magnifying the light from the galaxies behind it in a process called gravitational lensing. JWST鈥檚 image of it is the deepest picture of the cosmos ever created.
鈥淚鈥檝e been preparing for this since 2005, when I started working on JWST, and when the image came out, it鈥檚 like I had been going through life without any glasses on and I finally got my first pair of prescription glasses,鈥� says at the University of Arizona. The day the deep-field picture was released, she assembled a team across as many time zones as possible so they could analyse the data around the clock, and then got to听work.
Advertisement
A similar tale was unfolding in the UK, where at Durham University and his colleagues began to examine the same observations. 鈥淚 expected to see galaxies that we鈥檇 never seen, so I was ready for new discoveries, but what I was amazed by was how many there were,鈥� says Mahler. 鈥淎t first, it was a bit overwhelming, like: what do we do with all of this?鈥�
The teams began by searching for background galaxies that appeared to repeat, being cloned by the effects of gravitational lensing. This is a common effect of the phenomenon. Mahler鈥檚 team found 16 repeated galaxies and Frye鈥檚 team found 13; both used them to reconstruct SMACS 0723 and calculate where dark matter is lurking within the cluster.
鈥淲hat we鈥檙e seeing, which is so spectacular, is this rich tapestry with so many colours and textures, but what you see is the tip of the iceberg,鈥� says Frye. 鈥淓very single blob that you see is a galaxy with 10 billion stars, but most of the cluster鈥檚 mass we can鈥檛 see because it鈥檚 invisible dark matter, just like most of an iceberg is underwater.鈥�
The researchers found that the cluster is more elongated than we had realised from previous observations with other telescopes. This oblong shape is most likely due to mergers with other large galaxy clusters.
鈥淎ll of this faint, diffuse light emission from the cluster that we see, this is completely new and unexpected,鈥� says Mahler. 鈥淚t鈥檚 telling us something about the history of the cluster 鈥� all those stars come from destroyed galaxies.鈥� As SMACS 0723 devoured other galaxy clusters, it ripped them apart, leaving stars and other matter strewn in a bright streak across the cluster鈥檚 centre.
Frye鈥檚 team also spotted an unexpected gap in that faint light. If the cluster finished destroying all those other galaxies a long time ago, we would expect the light to be smoothly distributed, but this strange void indicates that a huge merger may still be going on, says Frye.
One next step among many is to take a closer look at the background galaxies themselves. JWST鈥檚 resolution is so high that researchers can not only tell which ones are repeated images, but they can also spot bursts of star formation 鈥� and maybe even individual stars 鈥� in galaxies halfway across the universe.
SMACS 0723 has been thoroughly studied for years using other telescopes. 鈥淔or the first release, they tried to find a boring cluster鈥� but JWST is so good that it turned this 鈥榖oring鈥� cluster with nothing to learn into this amazing treasure,鈥� says Mahler. 鈥淲e are really seeing galaxies and star formation at the dawn of the universe.鈥�
Frye also leads a group that will use JWST to look at seven more galaxy clusters and their gravitationally lensed background galaxies over the course of the next month. Hers is one of several programmes designed to take incredibly deep images of the cosmos, so the coming months are sure to provide a surge of new insights on the earliest stars and galaxies, and the dark matter that sits between them and us.
References: ,
Sign up to our free Launchpad newsletter for a voyage across the galaxy and beyond, every Friday
