Over one-third of the ‘normal’ matter in the local Universe – the visible stuff making up stars, planets, galaxies, life – is missing. It hasn’t yet been seen, but it’s needed to make our models of the cosmos work properly.
Said models suggest that this elusive matter might exist in long strings of gas, or filaments, bridging the densest pockets of space. While we’ve spotted filaments before, it’s tricky to make out their properties; they’re typically faint, making it difficult to isolate their light from that of any galaxies, black holes, and other objects lying nearby.
New research is now one ofthe first to do just this, finding and accurately characterising a single filament of hot gas stretching between four clusters of galaxies in the nearby Universe. The astronomers used ESA’s XMM-Newton and JAXA’s Suzaku X-ray space telescope to make the discovery.
This image shows the new filament, which connects four galaxy clusters: two on one end, two on the other. These clusters are visible as bright spots at the bottom and top of the filament (four white dots encircled by colour). A mottled band of purple stretches between these bright dots, standing out brightly against the black surrounding sky; this is the filament of X-ray-emitting hot gas that had not been seen before, and contains a chunk of ‘missing’ matter.
The purple band comprises data from Suzaku. The astronomers were able to identify and remove any possible ‘contaminating’ sources of X-rays from the filament using XMM-Newton, leaving behind a pure thread of ‘missing’ matter. These sources can be seen here as bright dots studded through – and removed from – the filament’s emission.
Read the full story
Download the annotated version
[Image description: The image shows a cluster of bright, colourful spots against a black background. The spots are primarily purple with areas of intense brightness in the centre, transitioning from yellow to green and blue. These spots are connected by a faint purple structure, forming an irregular extended shape with hazy blobs at either end.]