Scientists have used one of the most powerful telescopes on Earth to produce the largest high-resolution 3D map of the Universe ever created.
The project has mapped over 47 million galaxies and bright objects powered by supermassive black holes – known as quasars – to produce the biggest hi-res 3D cosmic map to date.
But it's not finished. The telescope behind the project, known as the Dark Energy Spectroscopic Instrument, or DESI, is set to continue observations into 2028 and make the 3D map even bigger.
A mission to map the Universe
Scientists say the Dark Energy Spectroscopic Instrument has now surveyed the whole of its planned map of the Universe.
DESI is mounted on the Nicholas U. Mayall 4-meter Telescope at NSF Kitt Peak National Observatory in Arizona, USA.
Following a 5-year survey of the sky, the DESI team say the telescope has finished ahead of schedule and with much more data than expected.
It has produced the largest high-resolution 3D map of the Universe ever made.
More on dark energy
Researchers will now use the map to explore dark energy, which is thought to make up about 70% of our Universe and to be causing the expansion of the Universe to accelerate, rather than slow down.
The survey involves over 900 researchers across more than 70 institutions.
DESI began collecting data in May 2021, with a plan to capture light from 34 million galaxies and quasars.
DESI ended up observing over 47 million galaxies and quasars, as well as 20 million stars.
Discovering dark energy's identity
Why is the expansion of the Universe apparently speeding up?
Until relatively recently, the prevailing theory was that the expansion of the Universe would slow down over time.
But in the late 1990s, scientists measured the distances of far-away galaxies by looking at types of stellar explosions known as Type Ia supernovae, which always shine with the same luminosity.
How bright they appear from Earth enables scientists to work out how far away they are.
Their calculations led scientists to conclude that distant galaxies were further away than expected, which could only be the case if the expansion of the Universe was accelerating.
The unknown force apparently accelerating the Universe's expansion has become known as 'dark energy'.
The DESI team say that, by looking at how galaxies clustered in the past and comparing that with their distribution today, they can trace the influence of dark energy's influence over 11 billion years.
One of the key results from DESI's first three years of data is that it suggests dark energy might be changing over time.
But once the full five years of data is studied, scientists say they'll have much more information to test the theory.
This could provide a key clue as to how the Universe is changing over time and, ultimately, how it could end.
What the scientists say
"Ultimately, we are doing this for all humanity, to better understand our Universe and its eventual fate," says Stephanie Juneau, associate astronomer and NSF NOIRLab representative for DESI.
"After finding hints that dark energy might deviate from a constant, potentially altering that fate, this moment feels like sitting on the edge of my seat as we analyse the new map to see whether those hints will be confirmed."
"The size and scope of the map, and how quickly we’ve been able to execute, is phenomenal," says Michael Levi, DESI director and a scientist at Berkeley Lab.
"We’re going to celebrate completion of the original survey and then get started on the work of churning through the data, because we’re all curious about what new surprises are waiting for us."
"This new three-dimensional map is enabling world-class legacy science," says Rita Tojeiro, Professor of Astronomy at the University of St Andrews in the UK, who has been involved in the project for over a decade.
"Each of the 47 million galaxies and quasars that DESI observed tells a unique story. We can collect these individual stories to reveal the overarching narratives of how galaxies form and evolve through cosmic time.
"Because DESI is revealing the three-dimensional cosmic web in which galaxies live with unprecedented detail, we can now study how galaxies respond to cosmic structures around them in ways that have not been possible before."
What's next
DESI scientists say the project has now measured data for six times as many galaxies and quasars as all previous measurements combined.
Now the team will start analysing the completed dataset, and the first dark energy results are expected in 2027.
DESI collaborators are still analysing the first three years of data from the study, using the information gathered to fine-tune what we know about dark energy and its effect on the Universe.
Scientists say observations will continue through 2028 and will grow the size of the map by about 20%.
It will eventually cover regions closer to the plane of the Milky Way, which are brighter and therefore make discerning distant objects more challenging.
And the survery will revisit what it's already covered to gather data on more distant, fainter 'luminous red galaxies.'
The survey will also look at dwarf galaxies and the chaotic aftermath of stars ripped from other galaxies by the Milky Way's gravity, known as 'stellar streams'.
