This Hubble Space Telescope snapshot features three magnified images showing a distant galaxies embedded in a cluster. Gravitational lensing is a trick of nature that produces these images. Multiple images are created by the galaxy cluster's enormous gravity. It magnifies and distorts light from distant galaxies behind it. The galaxy cluster is 7 billion light years from Earth. It's also known as SDSS J223010.47081017.8. Hubble has seen many gravitationally lensed galaxies. The Hubble snapshot shows images that are not common. The two magnified images at the bottom right are identical copies of each other. These two bright ovals represent the cores of this galaxy. This rare phenomenon is caused by the background galaxy crossing a ripple in space's fabric. This is the area with the greatest magnification. It is caused by gravity from dense amounts dark matter, which is the invisible glue that makes up the majority of the universe's mass. Two mirror images and a third image are created as light from faraway galaxies passes through the cluster along the ripple. The pull-out at the top right shows a close-up of this third image. This image is closest to the distant galaxy, which lies more than 11 million light-years from Earth. The researchers reconstructed this image and found that the distant galaxy looks like an edge-on barred spiral with continuous, clumpy, star formation. Hamiltons Object is the name given to the mirror images by the astronomer who found them. Credit: LEAD AUTHOR: NASA, ESA, Richard E. Griffiths (UH Hilo), CO-AUTHOR: Jenny Wagner (ZAH), IMAGE PROCESSING: Joseph DePasquale (STScI)
Gazing into the universe can be like looking into a funhouse reflection. This is because gravity creates optical illusions by warping the fabric of space.
These optical illusions are often created when the light of a distant galaxy is magnified, stretched and brightened by passing through a large galaxy cluster or massive galaxy in front. Gravitational lensing is a phenomenon that produces multiple brightened, stretched and stretched images of the background galaxy.
This allows astronomers the ability to study distant galaxies that cannot be seen by other means than gravitational lensing. It is difficult to reconstruct distant galaxies using the lensing's odd shapes.
Astronomers using the Hubble Space Telescope discovered one of these odd shapes while studying quasars, which are the bright cores of active galaxies. Two bright, straight objects were spotted that looked like mirror images. A second odd object was also nearby.
Astronomers were so puzzled by the features that it took several years for them to solve the mystery. With the help of two gravitational-lensing experts, the researchers determined that the three objects were the distorted images of a faraway, undiscovered galaxy. The biggest surprise was the fact that the three linear objects were identical copies of each others, an uncommon occurrence due to the alignment of the background galaxy with the foreground lensing group.
There have been many strange things that astronomers have seen scattered throughout the vast universe, including colliding galaxies and exploding stars. You would think that astronomers would recognize strange celestial objects when they spot them.
NASA's Hubble Space Telescope discovered what appears to be identical objects. Astronomers spent many years trying to figure out what they were.
Timothy Hamilton, an astronomer at Shawnee State University in Portsmouth (Ohio), said that "we were really stumped".
These oddball objects include a pair galaxy bulges, which are the central star-filled hubs of galaxies, and at least three almost parallel split streaks. Hamilton saw them accidentally while using Hubble for Hubble's survey of quasars (the blazing cores active galaxies)
Hamilton and his growing team, which included Richard Griffiths of University of Hawaii Hilo, spent a lot of time searching for answers, asking for help, and doing a lot of head scratching.
These linear objects were the stretched images from a distant galaxy with a gravitationally lensed, more than 11 billion light years away. They appeared to be mirror images.
The gravity of an uncatalogued foreground cluster of galaxies warped space, magnified, brightened, and stretched the image of a distant galaxy, a phenomenon known as gravitational lensing. Although Hubble surveys have shown many of the funhouse-mirror distortions due to gravitational lensing in Hubble surveys, this object is unique.
This is because the exact alignment of a background galaxy with a cluster of foreground galaxies produces two magnified copies of the same image. This rare phenomenon is caused by the background galaxy crossing a ripple in space's fabric. This is the area with the greatest magnification. It is caused by gravity from dense amounts dark matter, which is the invisible glue that makes up the majority of the universe's mass. Two mirror images and a third image can be seen to the side as light from faraway galaxies passes through the cluster.
Griffiths says this effect is similar to the bright, wavy patterns found at the bottom of swimming pools. He explained that a pool's rippled surface on a sunny day would show patterns of bright sunlight on its bottom. Gravitational lensing is responsible for the bright patterns at the bottom. The surface ripples act as partial lenses, focusing sunlight onto bright, squiggly patterns at the bottom.
The ripple magnifies and distorts the light passing through the cluster from the distant galaxy. The ripple creates two copies by acting as an imperfect curvy mirror.
On April 25, 1990, the Hubble Space Telescope was launched from Discovery. Hubble is able to see beyond the atmospheric distortions and can peer at galaxies, stars, and planets more than 13.4 million light years away. Credit: NASA/Smithsonian Institution/Lockheed Corporation
The mystery solved
This rare phenomenon was not well-known until Hamilton discovered the bizarre linear features in 2013.
He was able to see the parallel streaks and mirrored images in the quasar images as he looked through them. Hamilton and the other members of his team had never seen anything similar before.
Hamilton stated that Hamilton's first thought was that they might be interfacing galaxies with tidally stretched arms. It didn't fit very well, but it was all I could think of.
Hamilton and his team set out to unravel the mystery behind these enticing straight lines. They were later called Hamilton's Object after its discoverer. The strange image was shown to colleagues at astronomy conferences. This elicited many responses, including cosmic strings and planetary nebulae.
Griffiths, who wasn't part of the original team, suggested the best explanation to Hamilton when he showed the image to him at a NASA meeting. The lensing phenomenon that amplifies images of distant galaxies, such as Hubble's Hubble images of massive clusters of galaxy clusters, caused the magnified and distorted effect. Griffiths confirmed Griffiths's idea when he discovered a similar linear object within one of Hubble’s deep-cluster surveys.
However, the researchers still had a problem. The cluster that was lensing them couldn't be identified. Astronomers who study clusters of galaxies usually first look at the foreground cluster that is causing the lensing and then search for magnified images from distant galaxies within it. The Sloan Digital Sky Survey images showed that there was a galaxy cluster in the same region as the magnified images. However, it didn't show up in any cataloged surveys. Griffiths was convinced that the cluster was producing the lensed photos because of the unusual images found in the center.
Next, the researchers needed to determine if the three lensed images were located at the same distance. If so, then all of the distortions were from the same distant galaxy. The researchers were able to confirm this by using spectroscopic measurements at the Gemini and W. M. Keck observatories on Hawaii.
Based on reconstructions of the third lensed picture, the remote galaxy appears to be an edge-on barred spiral with ongoing star formation.
A separate group of researchers from Chicago discovered the cluster around the same time that Griffiths and Hilo undergraduates made spectroscopic observations. They used Sloan data to measure its distance. The cluster is located more than 7 billion light years away.
Griffiths' team had very limited information about the cluster and was struggling to understand these unusual lensing shapes. Griffiths explained that this gravitational lens was very different from other lenses previously studied by Hubble, especially in the Hubble Frontier Fields Survey of Clusters. You don't need to look at clusters for very long to see many lenses. This is the only lens that we have for this object. We didn't know anything about the cluster."
The invisible is mapped
Griffiths then called Jenny Wagner, a German expert in gravitational lensing theory from the University of Heidelberg. Wagner had previously studied similar objects and, with Nicolas Tessore (now at the University of Manchester), developed software to interpret unique lenses such as this one. The software enabled the team to understand how each of three lensed images were created. The team concluded that the dark matter surrounding the stretched images needed to be evenly distributed in space at small scales.
Wagner stated, "It is amazing that we only require two mirror images to see the scale of how clumpy and not dark matter can exist at these positions." We don't use lens models here. We only look at the observables in multiple images, and how they can be combined. Our method allows them to be folded together. This gives us an indication of how smooth the dark matter must be in these positions.
Griffiths stated that this result is significant because nearly 100 years after it was discovered, astronomers still don’t know what dark matter actually is. We know that it is some kind of matter but don't know what the constituent particle. We don't know what it does. It has mass and is subjected to gravity. It is important that we have some clues about the particle's size by observing the limits of smoothness or clumping. The more massive the particles, the smaller the dark matter clumps.
Continue reading Image: Hubble sees a distant galaxy through a cosmic prism
More information: Richard E Griffiths and co, Hamilton's object a clumpy galaxie straddling the gravitational cuustic of a cluster of galaxy: constraints on dark matter. Monthly Notices of the Royal Astronomical Society (2021). Information from the Journal: Monthly Notices to the Royal Astronomical Society Richard E Griffiths and co, Hamilton's object a clumpy galaxie straddling the gravitational Caustic of a Galaxy Cluster: Constraints on dark matter clumping. (2021). DOI: 10.1093/mnras/stab1375
