First pictures uncover concealed galaxies in the "cosmic web"

If you're not an astronomer, you may not be aware of them, but the biggest structures in the universe are not galaxies or the super-clusters they form. Instead, they are invisible webs of dark matter that separate the vast emptiness of space from the galactic clusters containing stars, planets, and the majority of astronomical phenomena we are familiar with.

Astronomers have observed a web of filaments that extends throughout the universe, with galaxies collecting at its intersections. These filaments can measure up to 500 million light-years in length, however they are difficult to detect with the naked eye. Along the main stretches of the filaments, dust is attracted.


A recent Astronomy and Astrophysics study has given us a glimpse of the cosmic web that binds the universe together, with its ability to uncover hidden galaxies. This is an exciting development for astronomy.




Are cosmic webs responsible for maintaining the integrity of the universe?



Studying space directly can be difficult, so astronomers have to rely on noticing its effects on things closer to Earth. In the 1980s the filament was first spotted and since then it has been observed through its influence on light--for example how it causes refraction of light from objects behind it and how it interacts with powerful quasars. While this has provided some insight, more is needed.





It was only a matter of time before someone could devise a way to gain a clearer view of the subject, and thankfully, science has advanced to make this possible.




Employing the aptly named Very Large Telescope located in Chile along with the Multi-Unit Spectroscopic Explorer, an international research team focused on the Hubble Ultra-Deep Field. Famously used as a source of some of the most illuminating images of the cosmos, the region was observed for 155 hours, with 140 of those providing useful data. After a year of analyzing, the team generated these images.




The hydrogen is shown gathering near the filament, as seen in the Hubble Ultra-Deep Field Image, credited to Roland Bacon, David Mary, ESO, and NAS.




The exposure period is extended, allowing for faint light from hydrogen to be gathered and formed into a picture.




The pictures displayed include numerous galaxies that had not previously been detected. Further assessment of the data revealed that the hydrogen detected by the spectroscopic explorer could be attributed to a large population of undiscovered dwarf galaxies. Although these galaxies are too faint to be seen one by one, further investigations will have a starting point to look for them.




Roland Bacon, the lead author, explained to CNN that




Due to their low brightness and the vast distances between us and them, we cannot observe these galaxies directly; they are 11 billion light-years away, and we are viewing them as they were 2 billion years after the Big Bang. Nevertheless, we can still make out their combined light.




This revelation, in and of itself captivating, will provide a basis for additional exploration of the filament and has the potential to bring about a fresh comprehension of how dwarf galaxies are created.

"The image shows the light emitted by hydrogen atoms in the cosmic web in a region roughly 15 million light years across. In addition to the very weak emission from intergalactic gas, a number of point sources can be seen: these are galaxies in the process of forming their first stars." © Jeremy Blaizot / projet SPHINX