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Webb and Hubble Unite Again

The Webb Space Telescope and the Hubble Space Telescope have joined forces to explore the details of the MACS0416 galaxy cluster. The outcome is a mesmerizing panchromatic image, fusing visible and infrared light, presenting one of the most comprehensive views of the Universe to date.

Situated approximately 4.3 billion light-years away from Earth, MACS0416 [that could have used a better name] is a dynamic duo of colliding galaxy clusters destined to merge into a colossal cluster in the future.

This extraordinary image not only captures the cluster's grandeur but also shows a myriad of galaxies beyond its borders, adorned with transient phenomena, possibly influenced by gravitational lensing.

MACS0416 holds special significance as the inaugural subject of the Frontier Fields program, a pioneering Hubble initiative launched in 2014 to ponder unprecedented super-deep views of the Universe. Hubble, with its keen eye for the faintest and youngest galaxies, laid the groundwork for this cosmic exploration. Webb's infrared perspective takes it a step further, pondering deeper into the early Universe and enhancing the depth of our cosmic understanding.

The resulting image, a range of colours, reflects the diverse range of wavelengths captured by the telescopes, from 0.4 to 5 microns. Each wavelength is colour-coded, with blue representing the shortest wavelengths, red the longest, and green. This vibrant palette not only adds an aesthetic dimension to the image but also serves as a key to understanding the distances of galaxies within the cluster.

The bluer hues often denote nearby galaxies, showcasing intense star formation, while the redder tones indicate more distant galaxies, best observed by Webb. Some galaxies appear intensely red due to cosmic dust, absorbing the bluer hues of starlight.

The Webb observations were conducted with a specific scientific objective—to identify transient objects, those varying in brightness over time. A total of 14 transients were discovered, with twelve located in highly magnified galaxies, likely individual or

multiple-star systems undergoing brief, intense magnification. The remaining two transients, found in moderately magnified background galaxies, are likely supernovae.

One standout discovery among these transients is a star system aptly nicknamed Mothra. Situated in a galaxy that existed about 3 billion years after the Big Bang, Mothra is magnified by a factor of at least 4000, showcasing its 'monster nature' of extreme brightness and magnification. This celestial giant joins the ranks of another lensed star, affectionately dubbed Godzilla, forming a cosmic kaiju duo.

Interestingly, Mothra is visible not only in the recent Webb observations but also in Hubble's images taken nine years earlier. This longevity challenges expectations, hinting at the presence of an additional object within the foreground cluster contributing to the magnification. The mysterious 'milli-lens,' with a mass ranging from 10,000 to 1 million times that of our Sun, remains an enigma, possibly a faint globular star cluster eluding direct observation by Webb.


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