Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

A Ruler to Measure the Universe

17.05.2006


"Lighthouses in the Sky" Yield Biggest-Ever 3-D Map of the Cosmos


A schematic view of the new SDSS three-dimensional map, which includes regular galaxies (black points) and luminous red galaxies (red points) and extends 5.6 billion light-years, 40 percent of the distance to the edge of the visible universe.


The SDSS 2.5 meter telescope at Apache Point, New Mexico was used to create the new map of the universe.



A team of astronomers led by Nikhil Padmanabhan and David Schlegel has published the largest three-dimensional map of the universe ever constructed, a wedge-shaped slice of the cosmos that spans a tenth of the northern sky, encompasses 600,000 uniquely luminous red galaxies, and extends 5.6 billion light-years deep into space, equivalent to 40 percent of the way back in time to the Big Bang.

Schlegel is a Divisional Fellow in the Physics Division of Lawrence Berkeley National Laboratory, and Padmanabhan will join the Lab’s Physics Division as a Chamberlain Fellow and Hubble Fellow in September; presently he is at Princeton University. They and their coauthors are members of the Sloan Digital Sky Survey (SDSS), and have previously produced smaller 3-D maps by using the SDSS telescope in New Mexico to painstakingly collect the spectra of individual galaxies and calculate their distances by measuring their redshifts.


"What’s new about this map is that it’s the largest ever," says Padmanabhan, "and it doesn’t depend on individual spectra."

The principal motive for creating large-scale 3-D maps is to understand how matter is distributed in the universe, says Padmanabhan. "The brightest galaxies are like lighthouses — where the light is, is where the matter is."

Schlegel says that "because this map covers much larger distances than previous maps, it allows us to measure structures as big as a billion light-years across."

A natural ruler in space

The variations in galactic distribution that constitute visible large-scale structures are directly descended from variations in the temperature of the cosmic microwave background, reflecting oscillations in the dense early universe that have been measured to great accuracy by balloon-borne experiments and the WMAP satellite.

The result is a natural "ruler" formed by the regular variations (sometimes called "baryon oscillations," with baryons as shorthand for ordinary matter), which repeat at intervals of some 450 million light-years.

"Unfortunately it’s an inconveniently sized ruler," says Schlegel. "We had to sample a huge volume of the universe just to fit the ruler inside."

Says Padmanabhan, "Although the universe is 13.7 billion years old, that really isn’t a whole lot of time when you’re measuring with a ruler that’s marked only every 450 million light-years."

The distribution of galaxies reveals many things, but one of the most important is a measure of the mysterious dark energy that accounts for some three-fourths of the universe’s density. (Dark matter accounts for roughly another 20 percent, while less than 5 percent is ordinary matter of the kind that makes visible galaxies.)

"Dark energy is just the term we use for our observation that the expansion of the universe is accelerating," Padmanabhan remarks. "By looking at where density variations were at the time of the cosmic microwave background" — only about 300,000 years after the Big Bang — "and seeing how they evolve into a map that covers the last 5.6 billion years, we can see if our estimates of dark energy are correct."

The new map shows that the large-scale structures are indeed distributed the way current ideas about the accelerating expansion of the universe would suggest. The map’s assumed distribution of dark matter, which although invisible is affected by gravity just like ordinary matter, also conforms to current understanding.

Dead, red galaxies

What made the big new 3-D map possible were the Sloan Digital Sky Survey’s wide-field telescope, which covers a three-degree field of view (the full moon is about half a degree), plus the choice of a particular kind of galactic "lighthouse," or distance marker: luminous red galaxies.

"These are dead, red galaxies, some of the oldest in the universe — in which all the fast-burning stars have long ago burned out and only old red stars are left," says Schlegel. "Not only are these the reddest galaxies, they’re also the brightest, visible at great distances."

The Sloan Digital Sky Survey astronomers worked with colleagues on the Australian Two-Degree Field team to average the color and redshift of a sample of 10,000 red luminous galaxies, relating galaxy color to distance. They then applied these measurements to 600,000 such galaxies to plot their map.

Padmanabhan concedes that "there’s statistical uncertainty in applying a brightness-distance relation derived from 10,000 red luminous galaxies to all 600,000 without measuring them individually. The game we play is, we have so many that the averages still give us very useful information about their distribution. And without having to measure their spectra, we can look much deeper into space."

Schlegel agrees that the researchers are far from achieving the precision they want. "But we have shown that such measurements are possible, and we have established the starting point for a standard ruler of the evolving universe."

He says "the next step is to design a precision experiment, perhaps based on modifications to the SDSS telescope. We are working with engineers here at Berkeley Lab to redesign the telescope to do what we want to do."

"The Clustering of Luminous Red Galaxies in the Sloan Digital Sky Survey Imaging Data," by Nikhil Padmanabhan, David J. Schlegel, Uroš Seljak, Alexey Makarov, Neta A. Bahcall, Michael R. Blanton, Jonathan Brinkmann, Daniel J. Eisenstein, Douglas P. Finkbeiner, James E. Gunn, David W. Hogg, Željko Iveziæ, Gillian R. Knapp, Jon Loveday, Robert H. Lupton, Robert C. Nichol, Donald P. Schneider, Michael A. Strauss, Max Tegmark, and Donald G. York, will appear in the Monthly Notices of the Royal Astronomical Society and is now available online at http://arxiv.org/archive/astro-ph.

SDSS is managed by the Astrophysical Research Consortium for the Participating Institutions, which are the American Museum of Natural History, Astrophysical Institute Potsdam, University of Basel, Cambridge University, Case Western Reserve University, University of Chicago, Drexel University, Fermilab, the Institute for Advanced Study, the Japan Participation Group, Johns Hopkins University, the Joint Institute for Nuclear Astrophysics, the Kavli Institute for Particle Astrophysics and Cosmology, the Korean Scientist Group, the Chinese Academy of Sciences (LAMOST), Los Alamos National Laboratory, the Max-Planck-Institute for Astronomy (MPIA), the Max-Planck-Institute for Astrophysics (MPA), New Mexico State University, Ohio State University, University of Pittsburgh, University of Portsmouth, Princeton University, the United States Naval Observatory, and the University of Washington.

SDSS funding is provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the U.S. Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Funding Council for England. Visit the SDSS web site at http://www.sdss.org/.

Berkeley Lab is a U.S. Department of Energy national laboratory located in Berkeley, California. It conducts unclassified scientific research and is managed by the University of California. Visit our website at http://www.lbl.gov.

Paul Preuss | EurekAlert!
Further information:
http://www.lbl.gov

More articles from Physics and Astronomy:

nachricht A 100-year-old physics problem has been solved at EPFL
23.06.2017 | Ecole Polytechnique Fédérale de Lausanne

nachricht Quantum thermometer or optical refrigerator?
23.06.2017 | National Institute of Standards and Technology (NIST)

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Quantum thermometer or optical refrigerator?

23.06.2017 | Physics and Astronomy

A 100-year-old physics problem has been solved at EPFL

23.06.2017 | Physics and Astronomy

Equipping form with function

23.06.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>