Posted by 
The collaboration between NASA’s James Webb Space Telescope and Hubble Space Telescope has resulted in a panchromatic image of the galaxy cluster known as MACS0416. This image combines visible and infrared light, providing one of the most comprehensive views of the universe ever captured.
MACS0416 is located approximately 4.3 billion light-years from Earth and consists of a pair of colliding galaxy clusters that will eventually merge to form an even larger cluster. By combining the infrared observations from the James Webb Space Telescope with visible-light data from Hubble, a wavelength coverage from 0.4 to 5 microns is achieved, revealing a vibrant landscape of galaxies.
The colors in the image offer clues to the distances of the galaxies. The bluest galaxies are relatively nearby and often exhibit intense star formation, as observed by Hubble. On the other hand, the redder galaxies tend to be more distant or contain significant amounts of dust, as detected by the Webb telescope. The combination of these telescopes captures rich details that would otherwise be inaccessible.
The image includes not only the galaxy cluster but also a multitude of galaxies outside the cluster. Additionally, there are variations in sources over time, potentially due to gravitational lensing, which occurs when light from distant background sources is distorted and amplified.
MACS0416 was the first subject of the Frontier Fields program, an ambitious and collaborative Hubble initiative launched in 2014 to study super-deep views of the universe. Hubble has been instrumental in detecting some of the faintest and youngest galaxies ever observed. Webb’s infrared view augments this exploration by probing even deeper into the early universe.
Rogier Windhorst of Arizona State University, the principal investigator of the PEARLS program, which conducted the Webb observations, emphasizes that they are building upon Hubble’s legacy by pushing the boundaries, studying objects at greater distances and with lower levels of brightness.
In terms of the colors in the image, the shortest wavelengths of light have been represented in blue, the longest wavelengths in red, and the intermediate wavelengths in green. The wide range of wavelengths from 0.4 to 5 microns contributes to the vivid depiction of the galaxies.
The colors also provide valuable information about galaxy distances. Blue galaxies typically indicate nearby objects with active star formation, while redder galaxies tend to be more distant. The presence of cosmic dust in some galaxies can make them appear red as they absorb the bluer colors of starlight.
To gain a complete understanding of the image, it is necessary to synthesize the data from both Webb and Hubble telescopes, as each contributes unique perspectives and insights.
The galaxy cluster MACS0416 as seen by Hubble in optical light (left) and Webb in infrared light (right).
The side-by-side comparison of galaxy cluster MACS0416 by the Hubble Space Telescope (left) and the James Webb Space Telescope (right) reveals different details due to their different capabilities. The Webb image, taken in infrared light, highlights galaxies that are too distant or dusty for Hubble to detect. As light from distant galaxies is redshifted due to the expansion of the universe, Webb’s ability to detect infrared light allows it to capture these elusive galaxies.
The Webb image required a total exposure time of about 22 hours, while the Hubble image took 122 hours of exposure time. Despite the aesthetic appeal of the image, the Webb observations were part of a specific scientific investigation. The research team combined multiple epochs of observations, each taken weeks apart, to search for objects that vary in brightness over time, known as transients.
The team identified 14 transients across the field of view, with 12 of them located in galaxies highly magnified by gravitational lensing. These transients are likely individual stars or multiple-star systems that experience brief periods of significant magnification. The other two transients were found in moderately magnified background galaxies and are likely to be supernovae.
The abundance of transients found within the cluster suggests that regularly monitoring clusters like MACS0416 with the Webb telescope could yield even more discoveries.
Among the transients identified, one star system stood out. Located in a galaxy that existed about 3 billion years after the Big Bang, this star system is magnified by a factor of at least 4,000. The team gave it the nickname “Mothra” due to its extremely bright and highly magnified nature. This star system joins another lensed star previously identified by the researchers, which they nicknamed “Godzilla,” drawing inspiration from Japanese cinema’s giant monsters known as kaiju.
Notably, Mothra is visible in both the Webb and Hubble observations, taken nine years apart. This is unusual, as the alignment between the foreground galaxy cluster and the background star needed to achieve such significant magnification would typically be disrupted by the motion of the star and cluster over time.
Image of the galaxy cluster MACS0416 highlights a special gravitationally lensed background galaxy.
In the captivating image of galaxy cluster MACS0416, a particular gravitationally lensed background galaxy steals the spotlight, originating approximately 3 billion years after the big bang. Within this distant galaxy lies a transient phenomenon, aptly nicknamed “Mothra” by the science team, representing a star magnified by a staggering factor of at least 4,000 times.
The magnification of Mothra is attributed not only to the gravitational pull of galaxy cluster MACS0416 but also to the influence of a mysterious “milli-lens,” speculated to possess a weight comparable to that of a globular star cluster. This celestial interplay adds layers of complexity to our understanding of distant cosmic phenomena.
The puzzle deepens as the team explores the most plausible explanation for the additional magnification – an unidentified object within the foreground cluster. They have successfully constrained its mass to a range between 10,000 and 1 million times that of our Sun. Despite these advancements, the true identity of this enigmatic “milli-lens” remains shrouded in mystery. Jose Diego of the Instituto de Física de Cantabria in Spain, lead author of the paper unraveling this discovery, suggests that the most likely candidate is a faint globular star cluster, eluding direct
