Astrophysicists Construct Most Complete 3D Map of the Universe, Fill Gaps in Cosmological History

An international consortium of scientists has analyzed, as part of a vast program of cosmological surveys, several million galaxies and quasars, thus retracing a more continuous history of the Universe and offering a better understanding of the mechanisms of its expansion. The latest 6-year-long survey called eBOSS was initiated, and led in part, by EPFL astrophysicist Jean-Paul Kneib.

It is the largest 3D map of the Universe produced to date. It is the fruit of a twenty-year collaboration of several hundred scientists from around thirty different institutions around the world, all united within the “Sloan Digital Sky Survey” (SDSS), with data collected from an optical telescope dedicated to the project located in New Mexico, in the United States.

Released today in the form of more than twenty scientific publications, this latest mapping of the night sky is an unprecedented and ambitious astronomical survey from 2014 until 2020. Resulting from the analysis of several millions of galaxies and quasars, this latest survey builds upon existing data as early as 1998 to fill certain gaps in cosmological history and to improve our understanding of the mechanisms underlying the expansion of the Universe.

EPFL (Ecole polytechnique fédérale de Lausanne) is directly involved in this important project. This latest cosmological survey of the SDSS, called “The extended Baryon Oscillation Spectroscopic Survey” (eBOSS), includes more than 100 astrophysicists, of which several are researchers from EPFL. Jean-Paul Kneib, who heads EPFL’s Astrophysics Laboratory (LASTRO), initiated the eBOSS survey and was its principal investigator (PI) for several years.

“In 2012, I launched the eBOSS project with the idea of ​​producing the most complete 3D map of the Universe throughout the lifetime of the Universe, implementing for the first time celestial objects that indicate the distribution of matter in the distant Universe, galaxies that actively form stars and quasars,” reports Jean-Paul Kneib. “It is a great pleasure to see the culmination of this work today. ”

Jean-Paul Kneib

Jean-Paul Kneib. Credit: EPFL

Thanks to the extensive theoretical models describing the Universe after the Big Bang, as well as observation of the Cosmic Microwave Backgound Radiation (CMBR), the infant Universe is relatively well known. Scientists have also explored its expansion history over the most recent few billion years from Supernovae distance measurements and galaxy maps, including those from previous phases of the SDSS. “We know both the ancient history of the Universe and its recent expansion history fairly well, but there’s a troublesome gap in the middle 11 billion years,” says cosmologist Kyle Dawson of the University of Utah, who leads the team announcing today’s results. “Thanks to five years of continuous observations, we have worked to fill in that gap, and we are using that information to provide some of the most substantial advances in cosmology in the last decade.”

“Taken together, detailed analyses of the eBOSS map and the earlier SDSS experiments, we have now provided the most accurate expansion history measurements over the widest-ever range of cosmic time,” says Will Percival of the University of Waterloo, eBOSS’s Survey Scientist. “These studies allow us to connect all these measurements into a complete story of the expansion of the Universe.”

SDSS Observable Universe Map

The SDSS map is shown as a rainbow of colors, located within the observable Universe (the outer sphere, showing fluctuations in the Cosmic Microwave Background).
We are located at the center of this map. The inset for each color-coded section of the map includes an image of a typical galaxy or quasar from that section, and also the signal of the pattern that the eBOSS team measures there. As we look out in distance, we look back in time. So, the location of these signals reveals the expansion rate of the Universe at different times in cosmic history.
Credit: Anand Raichoor (EPFL), Ashley Ross (Ohio State University), and the SDSS Collaboration

The finalized map shows filaments of matter and voids that more precisely define the structure of the Universe since its beginnings, when it was only 380,000 years old. From there, the researchers measured the recurring patterns in the distribution of galaxies, thus identifying several key cosmological parameters, including the density of hypothetical dark matter and energy in the Universe, with a high degree of precision.

To carry out this survey, the teams involved in the eBOSS project looked at different galactic tracers that reveal the mass distribution in the Universe. For the part of the map relating to the Universe six billion years ago, researchers observed the oldest and reddest galaxies. For more distant eras, they concentrated on the youngest galaxies, the blue ones. To go back further, that is to say up to eleven billion years, they used quasars, galaxies whose super-massive black hole is extremely luminous.

Slower expansion?

This map reveals the history of the Universe, and in particular, that the expansion of the Universe began to accelerate at some point and has since continued to do so. This seems to be due to the presence of dark energy, an invisible element that fits naturally into Einstein’s general theory of relativity but whose origin is not yet understood.

When eBOSS observations are compared with studies of the Universe’s early days, discrepancies appear in estimates of the Universe’s expansion rate. The currently accepted expansion rate, called the “Hubble constant,” is 10% slower than the value calculated from the distances between the galaxies closest to us. It is unlikely that this 10% difference is random due to the high precision and wide variety of data in the eBOSS database.

To date, there is no commonly accepted explanation for these disagreements between the different estimations of the speed of expansion, but the fact that a still unknown form of matter or energy from the early Universe could have left traces in our history is an interesting possibility.

For more on this research, including more videos and images, see Largest 3D Map of the Universe Ever Created.

7 Comments on "Astrophysicists Construct Most Complete 3D Map of the Universe, Fill Gaps in Cosmological History"

  1. John Campbell | July 26, 2020 at 8:25 am | Reply

    What a disgraceful presentation. Astronomers have taken a tiny slice observation of the sky and drawn premature conclusions upon it whilst ignoring that cosmological expansion is not uniform. This is a classic case of “let’s spin a narrative based on flimsy, incomplete evidence”.

    This is not science, it is pop media.

    • Torbjörn Larsson | July 26, 2020 at 3:20 pm | Reply

      What a disgraceful comment, to expound on your drivel. The result of 20 years hard work and 20+ papers is not to be thrown away by someone not even enough interested in the subject to care.

  2. Torbjörn Larsson | July 26, 2020 at 3:22 pm | Reply

    Congratulations to the interviewed to being part of a long hard work having such a high qualitative result [ arXiv:2007.08991v1] ! It is also a fascinating result shortly after the ACT telescope in Antarctica released consistent data from cosmic background radiation. It impressed me that it ruled out dark-energy-free models with such low uncertainty (given flat space).

    The overall uncertainty is impressive, reduced towards one percent. Previously most accurate compilation show that if you start with a low redshift (close objects), the estimate of the expansion parameter’s present value is above 72 km s ^ -1 Mpc ^ -1, which would mean that you see new physics if I eye-ball correctly, but that the tension disappears when you look further out [ Seshadri Nadathur, Will J. Percival, Florian Beutler, Hans A. Winther. Testing Low-Redshift Cosmic Acceleration with Large-Scale Structure. Physical Review Letters, 2020; 124 (22) DOI: 10.1103/PhysRevLett.124.221301].

    Another study shows that there can be large measurement errors, you can completely change the uncertainty in the present value of the expansion parameter to uncertainty in the present value temperature of the cosmic background radiation [Mikhail M. Ivanov, Yacine Ali-Haı̈moud, and Julien Lesgourges. H0 tension or T0 tension? arXiv:2005.10656.] This study does not go into this but joins other integrative works – no new physics is required. With increased precision in curvature follows a larger universe, now perhaps at least 100 million times larger volume than we can see.

    What fascinates me most, however, is that cosmologists have completely released the inhibitions against the selection bias (“anthropic universe”) that Weinberg discovered and later satisfactorily tested. “Nevertheless, the observed consistency with flat ΛCDM at the higher precision of this work points increasingly towards a pure cosmological constant solution, for example, as would be produced by a vacuum energy finetuned to have a small value. This fine-tuning represents a theoretical difficulty without any agreed-upon resolution and one that may not be resolvable through fundamental physics considerations alone (Weinberg 1989; Brax & Valageas 2019). This difficulty has been substantially sharpened by the observations presented here.”

    I note that it is the universe that renormalization theory proposes. It suggests a lack of a governing more fundamental theory in addition to quantum field theory. (And as the only such “fundamental theory” natural supersymmetric string theory has failed to produce dark matter in the LHC accelerator as well as the ACME electron sphericity experiment.) It is also the universe the Planck collaboration sees in its cosmology parameters paper 2018. They find the variant of inflation theory, a “slow roll” scalar field similar to the Higgs field, which naturally generates an infinite number of local hot big bang universes.

  3. We are not God, we are just an insignificant speck of dust in the universe which only came into existence just a second ago compare to the age of the universe yet we claim to be God see it all and know it all. We are really just a spoilt brat and need to growup

    • Torbjörn Larsson | July 27, 2020 at 12:18 pm | Reply

      Science spoiled us the last few centuries because it is the first time we see a process that lets us arrive at knowledge. And the universe spoiled us by being habitable (well, duh) and in so doing served up the observations that we have been able to use to “see it all and know it all” – cosmology and its study object the universe as a system, in coarse terms. It both enlightens and cheer people up.

      Nitpick: The new claim based on results such as this is that observations says there are no superstitious magic ‘gods’.

      If space is flat on vast distances, it is zero energy and – if inflation before the hot big bang isn’t infinite – it arose spontaneously. There are no signs of superstitious magic forces whether you talk of ‘stars forces’ as in astrology or ‘god actions’ as in other religions.

      • Torbjörn Larsson | July 27, 2020 at 12:24 pm | Reply

        I should add that the absence of observation where we expect presence according to the superstition means it has failed (i.e. there are observably no ‘gods’).

        Also, see my longer comment – Weinberg’s selection bias (“anthropic universe”) is currently most likely (simplest alternative) and it is explicit on that life and a habitable universe is just an utterly rare random coincidence.

  4. curious–what is the theoretical limit of human expansion, i.e. if a rocket left today at 99.99% speed of light, what is the most distant galaxy it could ever reach in all eternity, given our current understanding of the rate of expansion?

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