The proximity of four of the quintets of Stefan’s galaxies to each other (the fifth only seems close) allows astronomers a glimpse of galactic mergers and intergalactic reactions. And also how black holes affect the flow of matter between galaxies
Stefan’s quintet, a visual bunch of five galaxies, is best known for its notable appearance in the classic film “This is a Wonderful Life.” Today, NASA’s James Web Space Telescope reveals the Stephen Quintet in a new light. This huge mosaic is Web’s largest imagery to date, covering an angular area equivalent to about one – fifth of the moon’s diameter. The image contains over 150 million pixels and is composed of nearly 1,000 image files. Separate.Web information provides new insights into how galactic interactions might have driven the evolution of galaxies in the early universe.
Thanks to its powerful infrared vision and highest spatial resolution, Web shows details never seen before in this group of galaxies. Sparkling clusters of millions of young stars and fresh star birth zones glorify the image. Drifting tails of gas, dust and stars are attracted from some of the galaxies due to gravitational interactions. Most dramatically, Webb was able to photograph huge shock waves that are created when one of the galaxies, NGC 7318B, shatters through the cluster.
Together, the five galaxies of the Stephen Quintet are also known as the Hickson Compact 92 (HCG 92) group. Although they are called “quintet”, only four of the galaxies are really close to each other and get into a cosmic dance. The fifth and leftmost galaxy, called NGC 7320, is at the front compared to the other four. NGC 7320 is located 40 million light-years from Earth, while the other four galaxies (NGC 7317, NGC 7318A, NGC 7318B and NGC 7319) are approximately 290 million light-years away. It is still quite close in cosmic terms, compared to galaxies billions of light-years away. Exploring such relatively close galaxies, such as these, helps scientists better understand structures that are most often seen in a much more distant universe.
This proximity provides astronomers with a good vantage point to predict mergers and interactions between galaxies that are so vital to the entire evolution of galaxies. Rarely do scientists see in such detail how galaxies interact and cause stars to form, and how the gas in these galaxies is disturbed. The Stephen Quintet is a fantastic “laboratory” for studying these fundamental processes for all galaxies.
Such tight groups may have been more common in the early universe, when their heated material and mutual attraction may have ignited very energetic black holes called quasars. Even today, the group’s leading galaxy – NGC 7319 – contains an active galactic nucleus, a massive black hole 24 times the mass of the Sun. It actively attracts matter and emits energy equivalent to 40 billion suns.
The Web Telescope studied the active galactic nucleus in great detail using a near-infrared spectrograph (NIRSpec) and a medium-infrared (MIRI) device. The integral field units (IFUs) of these devices – which are a combination of camera and spectrograph – provided the web team with a “data cube” consisting of a collection of images of the spectral features of the galactic core.
Similar to medical magnetic resonance imaging (MRI) imaging, IFUs allow scientists to “slice and cut” the information into many images for detailed research. A web penetrates through the dust mantle surrounding the nucleus to expose hot gas near the active black hole and measure the velocity of the bright currents. The telescope saw these currents driven by the black hole at a level of detail never seen before.
In NGC 7320, the leftmost and closest galaxy in the visual cluster (i.e. not gravitationally related to others), Webb was able to identify individual stars and even the bright core of the galaxy.
As a bonus, Webb has uncovered a vast sea of thousands of distant background galaxies reminiscent of the deep fields of mourning.
Combined with the most detailed infrared image ever of Stefan MIRI’s quintet and the nearby infrared camera (NIRCam), Web’s data will provide a wealth of new and valuable information. For example, this photograph will help scientists understand the rate at which supermassive black holes feed and grow. Webb also sees star-forming regions in a much more direct way, and is able to examine dust emissions – a level of detail that has not been achieved so far.
The Stephen quintet, located in the constellation Pegasus, was discovered by the French astronomer Edouard Stefan in 1877.
Image credit: NASA, ESA, CSA and STScI
For an article on the NASA website
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