Webb Finds the Same Young Galaxies More Than Once
A new Webb image shows a galaxy cluster multiplying the appearance of distant galaxies. Gravity, not a cosmic photocopier, made the copies.
The Discovery
A galaxy cluster called MACS J0454.1-0300 is acting as a vast gravitational lens. In a Webb image released on 29 September, galaxies behind it are stretched into arcs and, in some cases, appear multiple times. Those orange background galaxies are not members of the foreground cluster.
ESA/Webb reports two examples of four-or-more-image configurations in this cluster, the first time more than one such configuration has been seen in a single cluster. The data came from Webb observing programmes 5058 and 6882.
What Makes It Strange
The foreground mass bends background light along different paths. Some lensed galaxies appear as they were 800 million or two billion years after the Big Bang. ESA/Webb also identifies small bright regions magnified by more than 300 times; the magnification is an analysis of the lens, not a zoom setting on Webb.
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The foreground cluster does the bending.
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The more distant galaxies supply the light.
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Different apparent images can come from the same source.
The Implications
A 2014 Hubble view of this field existed, but Webb reveals hundreds of galaxies absent from that older image. One observing programme aims to monitor a lensed galaxy for an unusually magnified individual star. That is a future search, not a star detection announced here.
Gravity gave one distant galaxy more than one route to our eyes.