There is something very strange about this image from the Hubble Space Telescope. If you look closely, you can see two almost mirror-like orange galaxies, apparently connected by a long filament.
Interestingly, it is not two galaxies at all, but one galaxy called SGAS J143845+145407. Only two are visible due to the gravitational force of a massive object (or objects such as a galaxy cluster) distorting the space through which distant light travels.
Imagine placing a heavy load on a trampoline, where the weight represents the galaxy cluster and the trampoline mat represents space-time. Now roll some marbles from one side of the trampoline to the other. Their normally “straight” paths appear to bend along different paths, unlike light rays traveling through distorted space.
This gravitational force, called gravitational lensing, can be used to magnify the light of background galaxies that are otherwise too distant to see in great detail, as shown in the diagram below.
Description of gravitational lenses. (NASA, ESA and L. Causeway)
Gravitational lenses like this can therefore be an important tool for understanding the distant Universe.
Sometimes this light can be really tainted and distorted, as seen recently A deep field image from the James Webb Space Telescope. These strange, wobbly, worm-like objects are lenticular galaxies. When the lensing effect results in four images of a distant object arranged around the central lens mass, this is called the Einstein cross.
SGAS J143845+145407 appears at just the right point behind the small galaxy cluster for gravitational lensing to create two nearly perfect images of the galaxy, and in addition, makes both appear larger and more detailed.
The light from SGAS J143845+145407 traveled about 6.9 billion years to reach us. That’s about half the current age of the Universe. The cluster’s light traveled for about 2.8 billion years.
Mirror images of SGAS J143845+145407 around gravitational lensing. (ESA/Hubble & NASA, J. Rigby)
SGAS J143845+145407 is scientifically interesting because it is a bright infrared galaxy and is relatively bright due to its high star formation activity. Studying galaxies like these can help scientists understand star formation and how it has changed over the history of the Universe; for this type of work, gravity lenses can be invaluable.
Using gravitational lensing, scientists have recently been able to Reconstruct the star formation distribution in SGAS J143845+145407, and learn the details of the process. They found that the galaxy was quite typical of its type, information that could help contextualize and characterize other galaxies.
Webb is expected to reveal more details, but the Hubble lens revolutionized the study of galaxies. His observations were the first to resolve the details inside lensed galaxies, giving scientists an incredible new window into the early universe.
The photo is published on the website Hubble website.
