Nasa’s James Webb Space Telescope and Hubble Space Telescope have published an image of an expansive galaxy cluster known as MACS0416.
Nasa has combined the power of two of its most powerful space telescopes to create one of the most comprehensive views of the universe ever taken.
The panchromatic image was made using a combination of visible and infrared light. It portrays MACS0416, a pair of colliding galaxy clusters that will eventually combine to form an even bigger cluster, located about 4.3 billion light years from Earth.
The image reveals a wealth of details never seen before, such as a bounty of galaxies outside the cluster and a sprinkling of sources that vary over time.
This cluster was the first of a set of unprecedented, super-deep views of the universe from an ambitious, collaborative Hubble program called Frontier Fields, inaugurated in 2014.
Hubble pioneered the search for some of the intrinsically faintest and youngest galaxies ever detected, while Webb’s infrared view significantly bolsters this deep look by going even farther into the early universe with its infrared vision.
“We are building on Hubble’s legacy by pushing to greater distances and fainter objects,” said Rogier Windhorst of Arizona State University, principal investigator of the PEARLS program (Prime Extragalactic Areas for Reionization and Lensing Science).
To make the image, the shortest wavelengths of light were colour-coded blue, the longest wavelengths red and the intermediate wavelengths green. The broad range of wavelengths, from 0.4 to 5 microns, yields a particularly vivid landscape of galaxies.
Those colours give clues to galaxy distances. While the bluest galaxies are relatively nearby and often show intense star formation, the redder galaxies tend to be more distant as detected by Webb.
Some galaxies also appear very red because they contain copious amounts of cosmic dust that tends to absorb bluer colours of starlight.
“The whole picture doesn’t become clear until you combine Webb data with Hubble data,” said Windhorst.
The Webb observations were taken for a specific scientific purpose. To obtain them, 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 goal was to search for objects varying in observed brightness over time, known as transients. The team identified 14. Twelve of them were located in three galaxies that are highly magnified by gravitational lensing. The remaining two transients are within more moderately magnified background galaxies and are likely to be supernovae.
“We’re calling MACS0416 the Christmas Tree Galaxy Cluster, both because it’s so colourful and because of these flickering lights we find within it. We can see transients everywhere,” said Haojing Yan of the University of Missouri in Columbia.
One of the transients the team identified stood out in particular. The team nicknamed the star system “Mothra” in a nod to its “monster nature”. It is located in a galaxy that existed about 3 billion years after the Big Bang and is magnified by a factor of at least 4,000.
The $10bn James Webb Telescope was finished years late at a cost far higher than planned, but was finally launched on Christmas Day 2021 with a minimum 10-year plan to study the cosmos.
Webb’s spectra have already confirmed the distances of some of the farthest galaxies ever observed, and discovered the earliest, most distant supermassive black holes. The telescope has also allowed scientists to take unprecedented images, such as those of Jupiter’s storms and what has been considered the “deepest view of the universe” to date.
Last summer, Nasa announced its plans to use both the Hubble and James Webb telescopes to remotely study Io, one of Jupiter’s moons and the most volcanically active body in the solar system.
The team’s discoveries have been published in the Astrophysical Journal and Astronomy & Astrophysics.
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