heic2310 — Photo Release

Webb, Hubble Combine to Create Most

Colourful View of Universe

The result: a vivid landscape of galaxies along with more than
a dozen newly found time-varying objects
9 November 2023

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The NASA/ESA/CSA James Webb Space Telescope and the NASA/ESA Hubble Space Telescope have united to

study an expansive galaxy cluster known as MACS0416. The resulting panchromatic image combines visible

and infrared light to assemble one of the most comprehensive views of the Universe ever obtained.

Located about 4.3 billion light-years from Earth, MACS0416 is a pair of colliding galaxy clusters that will

eventually combine to form an even bigger cluster.

About the Release

Release No.: heic2310

Images

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PR Image

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Galaxy cluster MACS0416 (Hubble

and Webb composite image)

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PR Image

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Galaxy cluster MACS0416 with

Mothra pullout

The image reveals a wealth of details that are only possible by combining the power of both space telescopes.

It includes a bounty of galaxies outside the cluster and a sprinkling of sources that vary over time, likely due to

gravitational lensing — the distortion and ampli�cation of light from distant background sources.

This cluster was the �rst of a set of unprecedented, super-deep views of the Universe from an ambitious,

collaborative Hubble programme called the Frontier Fields, inaugurated in 2014. Hubble pioneered the search

for some of the intrinsically faintest and youngest galaxies ever detected. Webb’s infrared view signi�cantly

bolsters this deep look by going even farther into the early Universe with its infrared vision.

To make the image, in general the shortest wavelengths of light were colour-coded blue, the longest

wavelengths red, and 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: the bluest galaxies are relatively nearby and often show intense

star formation, as best detected by Hubble, while the redder galaxies tend to be more distant and are best

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.

While the new Webb observations contribute to this aesthetic view, they were taken for a speci�c scienti�c

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 goal was to

search for objects varying in observed brightness over time, known as transients.

They identi�ed 14 such transients across the �eld of view. Twelve of them were located in three galaxies that

are highly magni�ed by gravitational lensing, and they are likely to be individual stars or multiple-star systems

that are brie�y very highly magni�ed. The remaining two transients are within more moderately magni�ed

background galaxies and are likely to be supernovae.

The �nding of so many transients with observations spanning a relatively short timeframe suggests that

astronomers could �nd many more transients in this cluster and others like it through regular monitoring with

Webb.

Among the transients the team identi�ed, one stood out in particular. Located in a galaxy that existed about 3

billion years after the Big Bang, it is magni�ed by a factor of at least 4000. The team nicknamed the star system

Mothra in a nod to its ‘monster nature’, being both extremely bright and extremely magni�ed. It joins another

lensed star that the researchers previously identi�ed and that they nicknamed Godzilla. Both Godzilla and

Mothra are giant monsters known as kaiju in Japanese cinema.

Interestingly, Mothra is also visible in the Hubble observations that were taken nine years earlier. This is

unusual, because a very speci�c alignment between the foreground galaxy cluster and the background star is

needed to magnify a star so greatly. The mutual motions of the star and the cluster should have eventually

eliminated that alignment.

The most likely explanation is that there is an additional object within the foreground cluster that is adding

more magni�cation. The team was able to constrain its mass to be between 10 000 and 1 million times the

mass of our Sun. The exact nature of this ‘milli-lens’, however, remains unknown. It is possible that the object is

a globular star cluster that’s too faint for Webb to observe directly.

The Webb data shown here were obtained as part of PEARLS (Prime Extragalactic Areas for Reionization and

Lensing Science), GTO program 1176(https://www.stsci.edu/jwst/science-execution/program-information?

id=1176).

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PR Image

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Galaxy cluster MACS0416 (Hubble

and Webb composite image,

annotated)

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PR Image

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Galaxy cluster MACS1416 (Hubble

and Webb images)

Also see our

Press Releases on

esawebb.org(https://esawebb.org/news/)

More information
The James Webb Space Telescope is the largest, most powerful telescope ever launched into space. Under an

international collaboration agreement, ESA provided the telescope’s launch service, using the Ariane 5 launch

vehicle. Working with partners, ESA was responsible for the development and quali�cation of Ariane 5

adaptations for the Webb mission and for the procurement of the launch service by Arianespace. ESA also

provided the workhorse spectrograph NIRSpec and 50% of the mid-infrared instrument MIRI, which was

designed and built by a consortium of nationally funded European Institutes (The MIRI European Consortium)

in partnership with JPL and the University of Arizona. Webb is an international partnership between NASA, ESA

and the Canadian Space Agency (CSA).

The Hubble Space Telescope is a project of international cooperation between NASA and ESA. NASA’s Goddard

Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute

(STScI) in Baltimore, Maryland, conducts Hubble and Webb science operations. STScI is operated for NASA by

the Association of Universities for Research in Astronomy, in Washington, D.C.

Image Credit: NASA, ESA, CSA, STScI, J. Diego (Instituto de Física de Cantabria, Spain), J. D’Silva (U. Western

Australia), A. Koekemoer (STScI), J. Summers & R. Windhorst (ASU), and H. Yan (U. Missouri)

Links
ESA Webb Seeing Farther Interactive Brochure(https://www.esa.int/About_Us/ESA_Publications/ESA_BR-

348_Webb_Seeing_farther)

Release on ESA/Webb website(https://esawebb.org/news/weic2327/)

Release on STScI website (Webb release)(https://webbtelescope.org/contents/news-releases/2023/news-

2023-146)

Release on STScI website (Hubble release)(https://hubblesite.org/contents/news-releases/2023/news-

2023-146)

Release on NASA website(https://www.nasa.gov/missions/webb/nasas-webb-hubble-combine-to-create-

most-colorful-view-of-universe/)

Yan et al. paper (The Astrophysical Journal)(https://arxiv.org/abs/2307.07579)

Diego et al. paper (Astronomy & Astrophysics)(https://doi.org/10.1051/0004-6361/202347556)

Contacts
Bethany Downer

ESA/Webb Chief Science Communications O�cer

Email: [email protected](mailto:[email protected])

Ninja Menning

ESA Newsroom and Media Relations O�ce

Email: [email protected](mailto:[email protected])

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