The most detailed 3D map of the universe is currently under construction, with astrophysicists unveiling details of the first 7.5 million galaxies out of 35 million.
The Dark Energy Spectroscopic Instrument (DESI) has completed its first seven months of a survey that is expected to take a total of five years.
An international collaboration of scientists, led by the US Department of Energy’s Lawrence Berkeley National Laboratory in California, are using the survey to create a ‘phenomenally detailed 3D map’ that will help explain dark energy.
It has so far catalogued over 7.5 million galaxies, and is adding more at about a million a month, on its mission to have a map showing 35 million unique galaxies.
The aim of the project is to shed light on the mysterious dark energy, a force that makes up 68 per cent of the universe and is accelerating its expansion.
Having the map will allow astronomers to understand how the universe began, and where it is going next, including whether it will expand forever, collapse or rip apart.
DESI’s three-dimensional ‘CT scan’ of the Universe. The earth is in the lower left, looking out in the directions of the constellations Virgo, Serpens and Hercules to distances beyond 5 billion light years
The project involves 5,000 individual telescopes each working autonomously. Fibre optics split the light from each observation, to give a full spectrum of colours
DARK ENERGY SPECTROSCOPIC INSTRUMENT (DESI)
The Dark Energy Spectroscopic Instrument (DESI) is an international science collaboration project involving researchers from the US, China, Spain, UK, France and more.
It involves 5,000 individual telescopes each working autonomously.
Each telescope can survey a single galaxy for up to 20 minutes, breaking out the light into colour bands.
The colours hold clues to the chemical make up, distance and speed of the individual galaxies.
It aims to measure the redshifts of tens of millions of galaxies, and reveal the 3D matter distribution across the universe – revealing the nature and role of Dark Energy in the universe.
DESI was originally proposed over a decade ago. DESI started its construction in 2015.
The instrument saw its first light in late 2019, delayed by Covid-19, causing it to be shut down for a period.
In December 2020, DESI turned its eyes to the sky again after several months of shutting down, testing out its hardware and software.
By May 2021, it was ready to start its science survey.
The survey has cataloged over 7.5 million galaxies, smashing through all records of galaxy surveys.
The previous largest galaxy survey is the Sloan Digital Sky Survey (SDSS).
In November 2021 alone, DESI cataloged redshifts of 2.5 million galaxies. By the end of its run in 2026, DESI is expected to have over 35 million galaxies.
DESI has obtained a lot of data and now the collaboration is turning to its scientific analysis.
They hope to yield scientific outputs on galaxy formation and evolution, including exploring the rare objects of extremely metal-poor galaxies, dwarf galaxies, and green-pea galaxies.
These galaxies are of key importance to the galaxy formation in the early universe and cosmic reionisation.
Project scientist Dr Julien Guy, of the University of California, Berkeley, said the team was seeing patterns and structures throughout the universe through the new map.
‘In the distribution of the galaxies in the 3D map, there are huge clusters, filaments, and voids. They are the biggest structures in the universe.
‘But within them, you find an imprint of the very early universe, and the history of its expansion since then.’
Professor Carlos Frenk, of Durham University, which is also involved in the project, said that despite being in the early stages, scientists are already breaking new ground.
‘DESI is already breaking new ground in producing this map of the universe which is the most detailed we’ve ever seen,’ he explained.
‘This will help us to search for clues about the nature of dark energy, but we will also learn more about the dark matter and the role it plays in how galaxies like the Milky Way form and how the universe is evolving.
‘We look forward with huge anticipation to the treasure trove of data that DESI will collect over the next few years. They will help uncover some of the most intimate secrets of the cosmos.’
One of the questions the team hope to solve with the survey is a quandary over the fact the expansion of the universe appears to be increasing in speed, rather than stopping and contracting, as the Big Bang Theory suggests should happen.
Astronomers believe dark energy – which makes up about 68 per cent of the known universe – is counteracting the pull of gravity, and stopping the contraction.
To confirm this, and to understand the phenomenon of Dark Energy, the team created DESI, made up of 5,000 automated mini telescopes, each of which images a new galaxy every 20 minutes.
It is able to survey more galaxies in a single year than every other telescope on the Earth combined, thanks in part to a state of the art fibre optic system that splits light from objects in space – such as galaxies and stars – into narrow bands of colour.
These colours reveal the chemical make-up of the target object, as well as information about how far away they are and how fast they are travelling.
DESI’s data will go 11 billion years back in time – revealing clues about the evolution of not just galaxies, but quasars – the brightest objects in the universe.
Victoria Fawcett, a PhD student at Durham, said: ‘I like to think of quasars as lampposts, looking back in time into the history of the universe.
‘DESI is really great because it is picking up much fainter and redder objects than previously discovered.’
She added: ‘We’re finding quite a lot of exotic systems, including large samples of rare objects that we just haven’t been able to study in detail before.’
By breaking down the light from each galaxy into its spectrum of colours, DESI can determine how much the light has been redshifted.
That is how far it is stretched out toward the red end of the spectrum by the expansion of the universe during the billions of years it traveled before reaching Earth. It is those redshifts that let DESI see the depth of the sky.
A slide through 3-D map of galaxies from the completed SDSS survey (left) and from the first few months of the DESI survey (right). The earth is at the centre, with the furthest galaxies plotted at distances of 10 billion light years
Star trails over the Nicholas U. Mayall 4-meter Telescope on Kitt Peak National Observatory near Tucson, Arizona
Earth is at the centre of a 1,000-light-year-wide ‘Swiss cheese’ bubble
Rather than being out on its own, the Earth is at the centre of a giant, 1,000-light-year-wide bubble, created by at least 15 supernova explosions, a new study has found.
There are thousands of young stars at the edge of this bubble, according to astrophysicists from the Space Telescope Science Institute in Baltimore, Maryland.
Working with experts from Harvard and Smithsonian, the team reconstructed the evolutionary history of the galactic neighbourhood over 14 million years.
In the 1970s astronomers discovered Earth was in a cosmic void, after realising no stars had formed in 14 million years, with all stars inside this ‘bubble’ emerging either before it formed, or passing through on their orbit of the galactic centre.
The new study found that multiple supernova explosions 14 million years ago blasted materials needed for star formation to the edge of a huge area of space, creating a ‘superbubble’ that is surrounded by a frenzy of star bursts, but with none inside.
The team likened the discovery to a Milky Way that resembles a ‘hole-y Swiss cheese’, where the holes in the cheese are blasted out by supernova, allowing new starts to form in the cheese, around the holes.
The more redshifted a galaxy’s spectrum is, in general, the farther away it is, and having a 3D map helps physicists chart clusters and superclusters of galaxies.
Those structures carry echoes of their initial formation, when they were just ripples in the infant cosmos, the team explained, adding that teasing those early echoes can tell astrophysicists about the expansion of the early universe.
‘Our science goal is to measure the imprint of waves in the primordial plasma,’ said Guy. ‘It’s astounding that we can actually detect the effect of these waves billions of years later, and so soon in our survey.’
Today, about 68 per cent of the content of the universe is dark energy, a mysterious form of energy driving the expansion of the universe ever faster.
As the universe expands, more dark energy pops into existence, which speeds up the expansion more, in a cycle that is driving the fraction of dark energy in the universe ever upwards.
Understanding the fate of the universe, and the impact of dark energy on its expansion, will have to wait until DESI completes more of its survey.
In the meantime, DESI is already driving breakthroughs in our understanding of the distant past, more than 10 billion years ago when galaxies were still young.
‘It’s pretty amazing,’ said Ragadeepika Pucha, a graduate student in astronomy at the University of Arizona working on DESI.
‘DESI will tell us more about the physics of galaxy formation and evolution.’
They are using DESI to understand how intermediate black holes behave in small galaxies, like our own Milky Way – and whether they always contain a black hole in their core.
When gas, dust, and other material falling into the black hole heats up (to temperatures hotter than the core of a star) on its way in, an active galactic nucleus (AGN) is formed.
The DESI team have already used the observations to detect a new Quasar, one of the brightest types of galaxies visible from Earth
Amateur astronomer discovers new galaxy nearly 3 million light-years from Earth by ACCIDENT
A group of astronomers, including an amateur stargazer, have discovered a new galaxy in deep space.
Further research is needed, but it’s possible that Pisces VII/ Tri III is an isolated dwarf galaxy or a satellite of the Triangulum galaxy (M33).
This is a spiral galaxy 2.73 million light-years from Earth.
If it is indeed an isolated dwarf galaxy, it would be the faintest field galaxy ever spotted and if it’s a satellite, it gives additional insight that the theory behind galaxy formation is accurate.
They found the galaxy by looking at public images of the DESI Legacy Survey to find new galaxies.
‘I found Pisces VII through the visual inspection in public images of the DESI Legacy Survey, precisely in order to identify new satellites in the Andromeda system, outside the areas already investigated in the past,’ Donatiello said in a statement.
‘I knew the likelihood of finding something new was real and I was right. A new galaxy has not been found in the Andromeda subgroup since 2013.’
In large galaxies, AGNs are among the brightest objects in the known universe. But in smaller galaxies, AGNs can be much fainter, and harder to distinguish.
The spectra taken by DESI can help solve this problem – and its wide reach across the sky will yield more information about the cores of small galaxies.
DESI is installed at the Nicholas U Mayall four metre telescope at Kitt Peak National Observatory near Tucson, Arizona.
The instrument saw first light in late 2019, but the Covid-19 pandemic shut it down for several months, with work continuing in December 2020.
‘It’s constant work that goes on to make this instrument perform,’ said physicist Klaus Honscheid of Ohio State University, an Instrument Scientist on the project.
Honscheid and his team ensure the instrument runs smoothly and automatically, ideally without any input during a night’s observing.
‘The feedback I get from the night observers is that the shifts are boring, which I take as a compliment,’ he said.
But that monotonous productivity requires incredibly detailed control over each of the 5,000 cutting-edge robots that position optical fibers on the DESI instrument, ensuring their positions are accurate to within 10 microns.
‘Ten microns is tiny,’ said Honscheid. ‘It’s less than the thickness of a human hair. And you have to position each robot to collect the light from galaxies billions of light-years away.
‘Every time I think about this system, I wonder how could we possibly pull that off? The success of DESI as an instrument is something to be very proud of.’
In November 2021 alone, DESI cataloged redshifts from 2.5 million galaxies. By the end of its run in 2026, DESI is expected to have over 35 million galaxies in its catalogue, enabling an enormous variety of cosmology and astrophysics research.
‘All this data is just there, and it’s just waiting to be analysed,’ said Pucha. ‘And then we will find so much amazing stuff about galaxies. For me, that’s exciting.’
WHAT IS DARK ENERGY?
Dark energy is a phrase used by physicists to describe a mysterious ‘something’ that is causing unusual things to happen in the universe.
The universe is full of matter and the attractive force of gravity pulls all matter together.
Then came 1998 and the Hubble Space Telescope observations of very distant supernovae that showed that, a long time ago, the universe was actually expanding more slowly than it is today.
The universe is not only expanding, but it is expanding faster and faster as time goes by,’ Dr Kathy Romer, scientist at the Dark Energy Survey told MailOnline, as illustrated in this Nasa graphic
So the expansion of the universe has not been slowing due to gravity, as everyone thought, it has been accelerating.
No one expected this, no one knew how to explain it. But something was causing it.
‘The universe is not only expanding, but it is expanding faster and faster as time goes by,’ Dr Kathy Romer, scientist at the Dark Energy Survey told MailOnline.
‘What we’d expect is that the expansion would get slower and slower as time goes by, because it has been nearly 14 billion years since the Big Bang.’