UK astronomers share bounty of new information

The video above shows a flythrough of the Sloan Digital Sky Survey’s map of the large-scale structure of the Universe.

Scientists from Portsmouth today marked the end of a major era in a massive worldwide astronomical project which has so far mapped millions of stars and galaxies.

Fourteen cosmologists from the University of Portsmouth’s Institute of Cosmology and Gravitation have played a major role in the Sloan Digital Sky Survey (SDSS) throughout its 2,000 nights of skywatching.

The bright spiral galaxy M51 and its fainter companion - The Survey has transformed the field of systematic galaxy analysis with accurate measurements of hundreds of parameters for hundreds of thousands of galaxies

The bright spiral galaxy M51 and its fainter companion – The Survey has transformed the field of systematic galaxy analysis with accurate measurements of hundreds of parameters for hundreds of thousands of galaxies. CREDIT: SDSS

Today, the SDSS issued the final data from the third survey (SDSS-III). Weighing in at more than 100 Terabytes, ‘Data Release 12’ contains measurements of the properties of nearly half a billion stars and galaxies, making it one of the largest and richest databases in the history of astronomy.

Professor Bob Nichol, spokesperson for SDSS-III from 2008 to 2010, and Director of the Institute of Cosmology and Gravitation said: “The Sloan Survey has revolutionised astronomy in many ways but particularly in giving their data away in regular public releases. It has changed the way astronomers view their data and fuelled thousands of research studies across the world.”

Today’s ‘Data Release 12’ provides the largest three-dimensional map of cosmic structures, traced by galaxies and intergalactic hydrogen, from the Baryon Oscillation Spectroscopic Survey.

Professor Nichol said:  “With such maps we can stare into the first half-million years of the history of the Universe and determine the content of the Universe to one percent accurate. Unfortunately, what we find is hard to understand, but that provides further challenges for the next generation of astronomical experiments and scientists.”

His colleague Dr Karen Masters is a member of the SDSS-III and also project scientist for the Galaxy Zoo, a citizen science project which launched using SDSS data.

Professor Bob Nichol

Professor Bob Nichol

She said: “The recent phenomenon of crowd-sourcing data through sites like www.galaxyzoo.org was only possible because of such data releases from SDSS and others. We now have over a million members of the public interacting with real data via the citizen science projects including galaxy zoo hosted at www.zooniverse.org. Not only is this a great public engagement opportunity, but it provides us with unique information on these SDSS data that we can’t obtain any other way.”

After a decade of design and construction, the SDSS began mapping the cosmos in 1998, using the dedicated 2.5-metre Sloan Foundation Telescope at Apache Point Observatory in New Mexico. Each phase of the project has used this telescope, equipped with a succession of ever-more-powerful instruments, for astronomical surveys. SDSS-III started observations in July 2008 and completed its six-year, $US45m programme in June 2014. The SDSS-III collaboration includes 51 member institutions and 1,000 scientists from around the world. The University of Portsmouth is the only full UK institutional member of the SDSS-III.

Dr Karen Masters

Dr Karen Masters

SDSS-III has devoted most of its 2,000 nights of observing to measuring spectra: passing light from individual stars and galaxies through a fibre-optic spectrograph, which divides light into component wavelengths much like a prism separates light into the colours of the rainbow.

Professor Claudia Maraston, from the Institute of Cosmology and Gravitation, said: “For each object that we observe, we’re actually measuring several thousand light intensities at different wavelengths. We can then pick out the light produced by particular kinds of atoms and molecules, which lets us measure the motions and chemical compositions of stars and galaxies. For example, the Sloan Extension for Galactic Understanding and Exploration (SEGUE) survey, which begun in SDSS-II and completed in SDSS-III, measured visible-light spectra of a quarter-million Milky Way stars. With so many stars, SEGUE gives us a great map of structure in the outer Galaxy.”

Scientists at the University of Portsmouth continue to play a major role in the Sloan Survey, which is continuing with SDSS-IV, a six-year mission to study cosmology, galaxies and the Milky Way.

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