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Space

How big is the universe? The shape of space-time could tell us

We may never know what lies beyond the boundaries of the observable universe, but the fabric of the cosmos can tell us whether the universe is infinite or not

By Leah Crane

25 June 2024

https://www.esa.int/ESA_Multimedia/Images/2022/07/Stephan_s_Quintet_NIRCam_and_MIRI_imaging Stephan?s Quintet ? NIRCam and MIRI imaging An enormous mosaic of Stephan?s Quintet is the largest image to date from the NASA/ESA/CSA James Webb Space Telescope, covering about one-fifth of the Moon?s diameter. It contains over 150 million pixels and is constructed from almost 1,000 separate image files. The visual grouping of five galaxies was captured by Webb?s Near-Infrared Camera (NIRCam) and Mid-Infrared Instrument (MIRI). With its powerful, infrared vision and extremely high spatial resolution, Webb shows never-before-seen details in this galaxy group. Sparkling clusters of millions of young stars and starburst regions of fresh star birth grace the image. Sweeping tails of gas, dust and stars are being pulled from several of the galaxies due to gravitational interactions. Most dramatically, Webb?s MIRI instrument captures huge shock waves as one of the galaxies, NGC 7318B, smashes through the cluster. These regions surrounding the central pair of galaxies are shown in the colours red and gold. This composite NIRCam-MIRI image uses two of the three MIRI filters to best show and differentiate the hot dust and structure within the galaxy. MIRI sees a distinct difference in colour between the dust in the galaxies versus the shock waves between the interacting galaxies. The image processing specialists at the Space Telescope Science Institute in Baltimore opted to highlight that difference by giving MIRI data the distinct yellow and orange colours, in contrast to the blue and white colours assigned to stars at NIRCam?s wavelengths.

NASA, ESA, CSA, and STScI

This story is part of our Cosmic Perspective series, in which we confront the staggering vastness of the cosmos and our place in it. Read the rest of the series聽here.

In a sense, we are at the centre of the universe 鈥 but only because we can see the same distance in every direction, giving us the perfectly spherical observable universe. The speed limit of light combined with the inexorable expansion of the cosmos means that we can see about 46 billion light years in every direction. What lies beyond this horizon? That is a mystery we may never solve.

But there are clues. Two competing effects govern the overall size of the universe: gravity and dark energy. All matter has mass, which causes gravitational forces that pull everything towards everything else. To their surprise, however, cosmologists in the early 20th century found that distant galaxies seem to be hurtling away from us. The mysterious force causing this strange expansion of space was dubbed dark energy, and its nature remains elusive to this day.

“Up until the discovery of dark energy and the acceleration of expansion, the universe was simpler,” says cosmologist at the University of Chicago. Without dark energy, the universe would be much smaller and its size easier to predict.

Even with dark energy, the universe may only be slightly larger than what is observable. In March, , then at the Max Planck Institute for Gravitational Physics in Germany, and at the University of Waterloo in Canada …

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