Largest 3D map of the cosmos created – New mapping captures position and redshift of 7.5 million galaxies –

Deeper view: Astronomers have released the largest and most detailed 3D map of galaxies in the cosmos to date. It shows the position and redshift of more than 7.5 million galaxies – more than ever before. But that’s just the beginning, because by 2026 the project should have mapped 35 million galaxies. The 3D map was created using the Dark Energy Spectroscopic Instrument (DESI), an instrument specially developed for this three-dimensional mapping.

How many stars are there in our galaxy? And how many galaxies are there in the cosmos? Sky surveys, in which telescopes use special instruments and search algorithms to map the sky, should provide answers to these questions. The results of such projects are the star catalogs of the Gaia space telescope, but also maps that show the distribution and distances of galaxies in the cosmos. Astronomers hope that the latter will provide them with information about the continuing expansion of the cosmos and its hypothetical driving force, dark energy.

The ten-ton Dark Energy Spectroscopic Instrument (DESI) on the four-meter telescope. © KPNO/NOIRLab/ NSF/AURA/ P. Marenfeld

5,000 spectra simultaneously

The largest and most detailed 3D map of the galaxies in the Universe to date has now been published as part of the DESI project. It includes around 7.5 million galaxies and thus represents a new record – it provides more information than all previous galaxy maps combined, as the astronomers explain. Around a million more galaxies are added to the 3D map every month.

This galaxy mapping is made possible by a specially developed instrument, the Dark Energy Spectroscopic Instrument (DESI). Mounted on the four-meter telescope at Kitt Peak National Observatory in Arizona, this spectrograph scans the sky in eight-square-degree sections, recording 5,000 simultaneous light spectra in the visible to near-infrared radiation range.

The data obtained by the DESI project provide information about the position and redshift of the galaxies – and thus also about their distance and the speed at which they are moving away from us.

Cosmic Structures and Galaxy Evolution

On the one hand, the 3D mapping provides information about the spatial distribution of the galaxies in the cosmos: “In the distribution of the galaxies we see enormous clusters, filaments and voids,” explains Julien Guy from the Berkeley National Laboratory. “They represent the largest structures in the universe.” At the same time, these large structures provide clues to their formation and the processes in the early days of the cosmos. “In these structures we find an imprint of the early Universe,” says Guy.

At the same time, the spectra of distant galaxies also reveal more about how such clusters of stars form and evolve – and the role played by supermassive and intermediate black holes. In addition, it is still unclear how the oldest galaxies and quasars could have become so massive so early. Here, too, the mapping could provide valuable information.

On the trail of dark energy

Above all, astronomers are hoping for new information about the expansion of the cosmos and its driving forces from this 3D mapping. Because measurements show that the universe is expanding and that this expansion has accelerated in the last billion years. But so far, there is just as little consensus on the extent of this expansion as on what is driving it. These questions are therefore one of the main motivations for the DESI survey.

Dark energy is considered the most likely candidate for the force that is driving the galaxies and the entire space-time structure further and further apart. According to current theory, it makes up a good 70 percent of the universe and will ultimately also determine its future fate. But what the dark energy consists of and how exactly it works is unclear. Increasingly accurate mapping of the expansion could, however, at least provide indications of its mode of action and intensity.

The virtual pan through some levels of the 3D map reveals spatial patterns.© NOIRLabh

The goal is 35 million galaxies

The galaxy map that has now been published represents only a first interim result of the sky survey that started in May 2021. The DESI instrument is expected to continue scanning the night sky until 2026, measuring the positions and distances of at least 35 million galaxies. The automated survey focuses on around a million more galaxies every month.

Quelle: NOIRLab, DOE/Lawrence Berkeley National Laboratory

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