While the scientific community marks the 100th anniversary of the publication of the theory of general relativity this month, NASA researchers have release images of galaxies that provide an in-depth example of one of the key tenants of Einstein’s theory of general relativity.
As the US space agency explained in a recent statement, one significant result of the century-old theory is that matter warps space-time—which in turn allows massive objects to cause a detectable bending of light from background objects. Also known as gravitational lensing, this phenomenon has been observed many times and been used by scientists to examine distant galaxies.
Now, in a paper currently available online and published in The Astrophysical Journal, experts at the University of Alabama, the National Observatory of Brazil, the Gemini Observatory, and the Harvard-Smithsonian Center for Astrophysics take an up-close look at one group of galaxies that demonstrates how gravitational lensing could lead to new discoveries.
Known as the “Cheshire Cat” group of galaxies because they have features resembling a smiling feline, the closest of these galaxies are located about 4.6 billion light years away, Space Alabama said. Some of those cat-like features are actually distant galaxies whose light has been stretched and bent by the large amounts of mass from dark matter (which can only be detected through the galaxies’ gravitational effect) present in the system.
The Cheshire Cat is slowly becoming a fossil group
This light-distorting mass is primarily located around the two giant “eye” galaxies and a “nose” galaxy. Lensing effects from four different galaxies located far behind the eye galaxies create the arcs of the circular “face,” and both these arcs and the individual galaxies in the system have been observed in optical light using the NASA Hubble Space Telescope.
The eye galaxies are the brightest members of their respective group of galaxies, and both groups are said to be on moving towards one another at speeds topping 300,000 mph. Evidence of this is present in data from the Chandra X-ray Observatory, which detected gas heated to a temperature of several million degrees and an active supermassive black hole at the center of the left eye.
NASA explained that astronomers believe that the Cheshire Cat group of galaxies will ultimately become a fossil group, or a gathering of galaxies which contain one giant elliptical galaxy along with a handful of other smaller, fainter ones. Fossil groups, they explained, could be a temporary stage of evolution experienced by all galaxy groups, and as a result, astronomers are anxious to learn more about them.
The Cheshire Cat group of galaxies could provide the first opportunity to observe this process as it happens. The study authors estimate that the two eye galaxies will eventually merge and leave behind one extremely large galaxy and dozens of smaller ones. The transformation will not happen quickly, however—NASA believes the merger could take about a billion years.
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Feature Image: NASA/CXC/UA/J.IRWIN ET AL; OPTICAL: NASA/STSCI
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