The Baryon Oscillation Spectroscopic Survey (BOSS) pioneered the use of quasars to chart the universe’s expansion and investigate the properties of dark energy through studies of large-scale structure. New techniques of analysis led by Berkeley Lab scientists, combined with other new BOSS quasar measures of the young universe’s structure, have produced the most precise measurement of expansion since galaxies formed.
Until recently, scientists thought they knew why Type Ia supernovae – the best cosmological “standard candles” – are all so much alike. But their favorite scenario was wrong. White dwarfs don’t all reach the Chandrasekhar limit, 1.4 times the mass of our sun, before they detonate in a massive thermonuclear explosion. Most Type Ia progenitors are less massive, and a few are even more massive. New work by the Berkeley Lab-based Nearby Supernova Factory can identify which theories of the strange circumstances that lead to a Type Ia explosion actually work and which don’t.
The Baryon Oscillation Spectroscopic Survey (BOSS), the largest component of the third Sloan Digital Sky Survey, has measured the clustering of nearly 1.3 million galaxies spectroscopically to determine the “standard ruler” of the universe’s large-scale structure to within one percent, the most precise such measurement ever made.
The Baryon Oscillation Spectroscopic Survey (BOSS), the largest component of the third Sloan Digital Sky Survey, has measured the clustering of nearly 1.3 million galaxies spectroscopically to determine the “standard ruler” of the universe’s large-scale structure to within one percent. This is the most precise such measurement ever made and is likely to establish the standard for years to come.
Berkeley Lab researchers take the furthest look back through time yet – 100 years to 300,000 years after the Big Bang – and find tantalizing new hints of clues as to what might have happened.
Type Ia supernovae are indispensable milestones for measuring the expansion of the universe. With definitive measures of Supernova 2011fe, the same “Backyard Supernova” that thrilled amateur and professional astronomers alike in the summer of 2011, the Nearby Supernova Factory led by Lawrence Berkeley National Laboratory demonstrates that this unusually close-by Type Ia is such a perfect example of its kind that future Type Ia’s – and models meant to explain their physics – must be measured against it.
In 2004 the Supernova Cosmology Project used the Hubble Space Telescope to find a tantalizing supernova that appeared to be almost 10 billion light-years distant. But Berkeley Lab scientists had to wait until a new camera was installed on the Hubble years later before they could confirm the candidate’s identity and redshift as a Type Ia “standard candle.” The spectrum and light curve of supernova SCP-0401 are now known with clarity; it is the supernova furthest back in time that can be used for precise measurements of the expansion history of the universe.
Through UC Berkeley and the Berkeley Center for Cosmological Physics, the Gordon and Betty Moore Foundation has made a $2.1 million grant to Berkeley Lab’s BigBOSS project. The grant funds the development of key technologies for modifying the 4-meter Mayall Telescope on Kitt Peak and constructing a precision instrument to study dark energy by mapping tens of millions of galaxies and quasars over the entire Northern Hemisphere sky.
By collecting tens of thousands of quasar spectra, the Baryon Oscillation Spectroscopic Survey (BOSS) has measured the large-scale structure of the early universe for the first time. Like backlights in the fog, the quasars illuminate clouds of hydrogen gas along the line of sight. No other technique can reach back over 10 billion years to probe structure at a time when the expansion of the universe was still decelerating and dark energy was yet to turn on.
Even as the “supernova of a generation” came into view in backyards across the northern hemisphere last August, physicists and astronomers who had caught its earliest moments were developing a surprising and much clearer picture of what happens during a titanic Type Ia explosion. Now they have announced the closest, most detailed look ever at one of the universe’s brightest “standard candles,” the celestial mileposts that led to the discovery of dark energy.