There is something very strange about this image from the Hubble Space Telescope. If you look closely, you can see two nearly mirror-image orange galaxies that appear to be connected by a long filament.
Fascinatingly, these are not two galaxies at all, but one called SGAS J143845+145407. There appears to be only two, thanks to the way the gravity of a massive object (or objects, like a galaxy cluster) distorts the space through which distant light travels.
Imagine placing a heavy weight on a trampoline, with the weight representing the galaxy cluster and the trampoline mat representing spacetime. Now roll some marbles from one side of the trampoline to the other. Their normally “straight” paths appear to curve along different paths, much like rays of light through a distorted space.
This quirk of gravity, called gravitational lensing, can be used to magnify light from background galaxies that would otherwise be too distant to see in detail, as shown in the diagram below.
Gravitational lenses like these can therefore be an important tool in understanding the distant Universe.
Sometimes that light can get really smeared and distorted, as seen in the recent deep-field image from the James Webb Space Telescope. These strange, wobbly, worm-like objects are lensed galaxies. When the lens effect results in four images of a distant object centered around the central lens mass, it is called an Einstein Cross.
SGAS J143845+145407 appears in just the right place behind a small cluster of galaxies for gravitational lensing to produce two near-perfect images of the galaxy, with the added bonus of both appearing larger and more detailed.
The light from SGAS J143845+145407 traveled approximately 6.9 billion years to reach us. That’s about half the current age of the universe. The cluster’s light has traveled about 2.8 billion years.
SGAS J143845+145407 is of scientific interest because it is a glowing infrared galaxy that is relatively bright due to high star forming activity. Studying galaxies like this one can help scientists understand star formation and how it has changed throughout the history of the universe; For this type of work, gravitational lenses can be invaluable.
Using gravitational lensing, scientists were recently able to reconstruct the star formation distribution in SGAS J143845+145407 and study the details of the process. They found the galaxy to be fairly typical of its type, and this information helps contextualize and characterize other galaxies.
Webb is expected to reveal even more detail, but Hubble has revolutionized the study of lensed galaxies. His observations were the first to resolve details within lens galaxies, giving scientists an incredible new window into the early Universe.
The image was published on the Hubble website.