It gives an unprecedented look at the time when dark energy turned on. Some five to seven billion years ago,
the expansion of the universe stopped slowing due to gravity and started to accelerate due to dark energy.
Yet the nature of dark energy remains a puzzle that astronomers are seeking to solve.
"We see the influence of dark energy on cosmic structure, but we have no idea what it is.
The data gathered by this survey will help answer that question," said Daniel Eisenstein (Harvard-Smithsonian
Center for Astrophysics), the director of SDSS-III.
"There's been a lot of talk about using galaxy maps to find out what's causing accelerating expansion,"
said David Schlegel of the U.S. Department of Energy's Lawrence Berkeley National Laboratory, BOSS's principal investigator.
"We've been making a map and now we're using it - starting to push our knowledge out to the distances when dark energy turned on."
One of the most amazing discoveries of the last two decades in astronomy, recognized with the 2011 Nobel Prize
in Physics, was that not only is our universe expanding, but it is accelerating. Galaxies are becoming farther
apart from each other faster and faster with time.
The leading contender for the cause of the accelerating expansion is a postulated new property of space dubbed
"dark energy." Alternatively, the universe may be accelerating because gravity deviates from Einstein's General
Theory of Relativity and becomes repulsive at very large distances.
The record of baryon acoustic oscillations (white circles) in galaxy maps helps astronomers retrace the
history of the expanding universe. These schematic images show the universe at three different times.
The representative-color image on the right shows the "cosmic microwave background," a record of what
the very young universe looked like 13.7 billion years ago. The small density variations present then
have grown into the clusters, walls, and filaments of galaxies that we see today. These variations included
the signal of the original baryon acoustic oscillations (white circle, right). As the universe has expanded
(middle and left), evidence of the baryon oscillations has remained, visible in a "peak separation" between
galaxies (the larger white circles). The SDSS-III results announced today (middle) are for galaxies 5.5
billion light-years distant, at the time when dark energy turned on. Comparing them with previous results from
galaxies 3.8 billion light-years away (left) measures how the universe has expanded with time.
Credit: E.M. Huff, the SDSS-III team, and the South Pole Telescope team. Graphic by Zosia Rostomian
Whether the answer to the puzzle of the accelerating universe is dark energy or modified gravity, the first step
to finding that answer is to measure accurate distances to as many galaxies as possible. From those measurements,
astronomers can trace out the history of the universe's expansion.
BOSS is producing the most detailed map of the universe ever made by using a new custom-designed spectrograph of
the SDSS 2.5-meter telescope at Apache Point Observatory in New Mexico to observe more than a million galaxies
over six years.
Today's announcement is based on a map of more than 250,000 galaxies created from the first year and a half of
BOSS observations. Some of these galaxies are so distant that their light has traveled more than six billion
years to reach Earth - nearly half the age of the universe.
Maps of the universe like BOSS's show that galaxies and clusters of galaxies are clumped together into walls
and filaments, with giant voids between. These structures grew out of subtle variations in density in the early
universe, which bore the imprint of "baryon acoustic oscillations" - pressure-driven acoustic (sound) waves
that passed through the early universe.
Billions of years later, the record of these sound waves can still be read in our universe.
"Because of the regularity of the ancient sound waves, there's a slightly increased probability that any two galaxies
today will be separated by about 500 million light-years, rather than 400 million or 600 million," said Eisenstein.
In a graph of the number of galaxy pairs by separation distance, that magic number of 500 million light-years shows up as a peak,
so astronomers often speak of the "peak separation." The position of this peak depends on the amount of dark energy in the Universe.
But measuring the distance between galaxies depends critically on having the right distances to the galaxies in the first place.
That's where BOSS comes in. "We've detected the peak separation more clearly than ever before," said Nikhil Padmanabhan of
Yale University. "These measurements allow us to determine the contents of the Universe with unprecedented accuracy."
"The Most Profound Mystery In All Of Science" -
Little is known about this force and its its repulsive gravity, which is causing the expansion of the universe to accelerate.
The riddles of dark matter and cosmic inflation, along with dark energy, these are the three pillars of modern cosmological theory,"
and none of them can be explained with physics that we know," Michael Turner, director of the Kavli Institute for Cosmological Physics says.
Alien Species Living In The Inner Milky Way Could Be In Danger
Few people doubt there is intelligent alien life in the Milky Way galaxy, but where can we expect to find it?
Astronomers think that while the inner sector of the MIlky Way Galaxy may be the most likely to support habitable worlds.
Unfortunately some of these places are also most dangerous to all life-forms.
Black Holes With No 'Table Manners' Eat Two Courses At Once!
It is still unknown how the supermassive black holes (SMBH) in galaxy centres accrete gas and grow.
Researchers from the University of Leicester (UK) and Monash University in Australia have investigated how some black holes got so big so fast that they are billions of times heavier than the sun.
Mercury Surprises Scientists
On March 17, MESSENGER (MErcury Surface, Space Environment, GEochemistry, and Ranging) completed its one-year primary mission, orbiting Mercury, capturing nearly 100,000 images, and recording data
that reveals new information about the planet's core, topography, and the mysterious radar bright material in the permanently shadowed areas near the poles.
Living Earth Simulator - Supercomputer Predicting The Future
In Douglas Adams book the Hitchhikers Guide to the Galaxy we encounter a machine called Deep Thought. It is the most powerful computer ever built. Deep Thought is capable of answering questions
concerning life, the Universe, and simply everything. Now scientists are planning to create a similar machine. It is called the Living Earth Simulator (LES).
Warp-Speed Planets Are Some Of The Fastest Objects In The Milky Way
Warped planets are some of the fastest objects in the Milky Way and they zoom through space near the speed of light.
Some years ago astronomers were astonished when they they found the first runaway star flying out of our Galaxy at a speed of 1.5 million miles per hour.
The discovery intrigued theorists, who wondered: If a star can get tossed outward at such an extreme velocity, could the same thing happen to planets?
Though the universe is filled with billions upon billions of stars, the discovery of a single variable star in 1923 altered the
course of modern astronomy. And, at least one famous astronomer of the time lamented that the discovery had shattered his world view.
Astronomical Mystery - Tremendous Explosion And Appearance Of Odd Rings
Twenty five years ago, on 1987 February 23, the brightest supernova of modern times was observed in the Large Magellanic Cloud.
The collision occurred at speeds near 60 million kilometers per hour and shock-heats the ring material causing it to glow.
Over time, astronomers have watched and waited for the expanding debris from this tremendous stellar explosion to crash into previously expelled material...
The "Cloaked" Star Was Difficult To Find
An object obscured by dust, and buried in a two-star system enshrouded by dense gas, is not easy to find.
A "cloaked" star was discovered after it ate a little of its neighbor. The meal must have given the star a bit of indigestion, because it
"burped" with a blast of high-energy radiation, which gave it away.