A new image produced by the James Webb Space Telescope reveals new details about Stephan’s Quintet, the very first compact group of galaxies ever discovered that was featured in the 1946 film ‘It’s a Wonderful Life’.
I’m sure most readers of the column are familiar with the holiday classic “It’s a Wonderful Life.” If you’re not, this is the story of a man named George Bailey (Jimmy Stewart) who wants to travel and do great things but ends up running a building and lending association in a small community, all by being married and locked in a constant struggle with the greedy old banker in town. And when it finally looks like the banker is about to drive him to ruin, George decides to kill himself, whereupon an angel, just in time, intercedes and shows him, fancifully, what the city would have been like without him. The vision is so distressing that George begs the angel to bring him back to his plight, and now with boundless joy is saved, also in no time, thanks to the financial help of his friends.
American film critic, Roger Ebert wrote (opens in a new tab) from ‘It’s a Wonderful Life’ in 1999: “The film’s most comedic scenes – those galaxies flashing as the heavens consult over George’s fate – work because they’re disarmingly simple. a more sophisticated approach might have seemed laborious.”
Related: Gallery: 1st photos of the James Webb Space Telescope
See! Stephan Quintet
Ebert’s “cheesy scenes” appear in the first two minutes of the film’s beginning, where viewers are informally introduced to a cluster of five galaxies, known to astronomers as Stephan’s Quintet – the very first cluster of galaxies compact never discovered. The group, visible in the constellation Pegasus the Flying Horse, was discovered by French astronomer Édouard Stephan in 1877 at the Marseille Observatory and is the most studied of all groups of compact galaxies.
But to call it a “quintet” galaxy is a bit of a misnomer, as the biggest and brightest of the five – cataloged as NGC 7320 – is just an innocent bystander. While the other four galaxies – NGC 7317, NGC 7318A, NGC 7318B and NGC 7319 – are located about 290 million light-years away and form a true group of galaxies, NGC 7320 is much closer to us (relatively speaking) “only” 39 million light years away.
In contrast, these four other galaxies are so close to each other that they have begun to interact with each other. They are bound by gravity and will eventually merge into one large elliptical galaxy in several million years. In fact, two of these galaxies – NGC 7318A and NGC 7318B – have already begun to consolidate. The ensuing collision dragged long tails of gas, dust and stars from each galaxy, in turn triggering massive star-forming outbursts.
Since 1929, when Edwin Hubble discovered that our universe is expanding, we have known that most other galaxies are moving away from us. The light from these galaxies is shifted to longer (and that means redder) wavelengths – in other words, it is “red-shifted”. The redshift of a distant galaxy is easily measured by comparing its spectrum with a reference laboratory spectrum. Atomic emission and absorption lines occur at well-known wavelengths. By measuring the location of these lines in astronomical spectra, astronomers can determine the redshift of receding sources.
Initially, however, the difference in distance between the assembly of four of the Quintet’s galaxies and the much closer fifth galaxy produced a puzzle among cosmologists and astrophysicists. These four galaxies grouped together show a large redshift, corresponding to a recession rate of 4,000 miles (6,400 km) per second. But galaxy NGC 7320 showed a redshift indicating a much slower speed of just 491 miles (790 km) per second. This indicated that the four galaxies were about seven times further apart in space than the fifth.
Astronomers wondered how it could be.
Indeed, visually, the images appeared to show that NGC 7320 was connected to the other four members by weak tidal currents. Moreover, the degree of photographic resolution of the best observatory photographs of the 20th century seemed to imply that the other four members are not as far apart as their redshift values would indicate.
So if the five galaxies were physically linked, using the redshift to determine stellar distances – which indicated that a galaxy in the Quintet is much closer compared to its other four companions – could be wrong. American astronomer Halton Arp (1927-2013) is among those who have long believed this to be the case.
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Hubble to the rescue!
The Hubble Space Telescope finally solved this problem in 2000. Its superior imaging compared to terrestrial telescopes was able to bring out individual stars in NGC 7320 while images of the other four galaxies remained starless.
So it all ended up being a happy coincidence: NGC 7320 appears the same size as its four companions because although it’s actually much smaller than the other four, it’s also much closer; it just happens to be aligned with the other four galaxies seen from our Earth perspective.
And the steamboats that emanate from it and apparently interact with the other four are also an optical illusion.
Together, the five galaxies of Stephan’s Quintet are also known today as Hickson Compact Group 92 (HCG 92). This, despite the fact that NGC 7320 has no physical connection to the other four.
If you want to try and see the Quintet for yourself, extend an imaginary line from the star Mu Pegasi to Eta Pegasi and continue about the same distance beyond. Warning: these galaxies are not really targets for the beginner, as they need at least a 10 inch (250 mm) telescope to be seen clearly.
Between James Webb
Now, once again, the five galaxies that were featured prominently in a popular movie three-quarters of a century ago are brought to light again thanks to the brand new space observatory: the James Webb Space Telescope. Stephan’s Quintet was among the very first objects the all-new 21-foot (6.5-meter) telescope was turned towards when it was commissioned on July 12.
This latest image from Stephan’s Quintet is a huge mosaic of almost a thousand images. It is Webb’s largest image to date and contains over 150 million pixels used by Webb’s near-infrared camera (NIRCam) and mid-infrared instrument (MIRI). NIRCam’s high-resolution imaging capability allowed Webb to see individual stars and the foreground galaxy’s bright core on the left side of the image. The galaxy at the top of the image is home to a supermassive black hole – or active galactic nucleus – about 24 million times the mass of the sun. The supermassive black hole attracts material and produces light energy equivalent to about 40 billion suns.
Stephan’s Quintet is an incredible “laboratory” for studying how the merging and interaction of galaxies affect galactic evolution. According to a Statement from NASA, “Scientists rarely see in such detail how interacting galaxies trigger star formation in each other and how the gas in these galaxies is disrupted. Stephan’s Quintet is a fantastic ‘laboratory’ for studying these fundamental processes. for all the galaxies.”
Something to ponder the next time you watch “It’s a Wonderful Life.”
Indeed, the James Webb Telescope reveals Stephan’s Quintet in a truly new light.
It’s a wonderful picture!
Joe Rao is an instructor and guest speaker at New York’s Hayden Planetarium (opens in a new tab). He writes on astronomy for natural history review (opens in a new tab)the Farmers Almanac (opens in a new tab) and other publications. Follow us on twitter @Spacedotcom (opens in a new tab) and on Facebook (opens in a new tab).