Webb and Hubble team up to capture galaxy cluster MACS0416

This cluster was the first of a series of extraordinary, ultra-deep universe views from an ambitious, collaborative Hubble project, the Frontier Fields, launched in 2014. Hubble led the way in searching for some of the faintest and oldest galaxies ever detected. Webb’s infrared view enhances this deep look by going further into the early universe with its infrared vision.

Rogier Windhorst, the principal investigator of the PEARLS program (Prime Extragalactic Areas for Reionization and Lensing Science) which conducted the Webb observations, stated that they are expanding on Hubble's legacy by exploring more distant and fainter objects.

To create the image, the shortest wavelengths of light were assigned blue, the longest wavelengths red, and the intermediate wavelengths green. The range of wavelengths, from 0.4 to 5 microns, produces a vivid panorama of galaxies.

Those colors indicate galaxy distances: The bluest galaxies are relatively close and often display intense star formation, as best detected by Hubble. In contrast, the redder galaxies tend to be more distant, as seen by Webb. Some galaxies also appear red because they have abundant amounts of cosmic dust that tends to block bluer colors of starlight.

Christmas Tree Galaxy Cluster

While the new Webb observations add to this aesthetic view, they were taken for a specific scientific purpose. The research team combined their three epochs of observations, each taken weeks apart, with a fourth epoch from the CANUCS (CAnadian NIRISS Unbiased Cluster Survey) research team. The aim was to search for objects varying in observed brightness over time, known as transients.

They identified 14 such transients across the field of view. Twelve of those transients were located in three galaxies highly magnified by gravitational lensing and are likely to be single stars or multiple-star systems that are briefly highly magnified. The remaining two transients are within more moderately magnified background galaxies and will likely be supernovae.

The team of researchers led by Haojing Yan from the University of Missouri in Columbia named MACS0416 as the Christmas Tree Galaxy Cluster due to its vibrant colors and the presence of twinkling lights within it. The team observed transients scattered throughout the cluster.

Finding so many transients with observations spanning a relatively short time frame suggests that astronomers could discover many more transients in this cluster and others like it through regular monitoring with Webb.

The team identified several transients, but one of them stood out from the rest. This star system is located in a galaxy that existed around 3 billion years after the Big Bang, and it appears magnified by at least 4,000 times. The researchers nicknamed this bright and highly magnified system "Mothra," about its monstrous nature. Another lensed star that the team discovered earlier was given the nickname "Godzilla."