A section of the 3D map constructed by BOSS.
The rectangle on the far left shows a cutout of 1000 sq. degrees
in the sky containing nearly 120,000 galaxies,
or roughly 10% of the total survey.
By the 1990s, astronomers determined
that the rate at which it is expanding is actually speeding up,
which in turn led to the theory of "Dark Energy". Since that time,
astronomers and physicists have sought to determine the existence of
this force by measuring the influence it has on the cosmos.
Known as the Baryon Oscillation Spectroscopic Survey (BOSS), their measurements have placed new constraints on the properties of Dark Energy. The new measurements were presented by Harvard University astronomer Daniel Eisenstein at a recent meeting of the American Astronomical Society.
As the director of the SDSS-III, he and his team have spent the past ten years measuring the cosmos and the periodic fluctuations in the density of normal matter to see how galaxies are distributed throughout the Universe.
which are imprinted in the early universe
and can still be seen today in galaxy surveys like BOSS.
Credit: Chris Blake
and Sam Moorfield
And while other recent surveys have
looked further afield - up to distances of 9 and 13 billion light
years - the BOSS map is unique in that it boasts the highest
accuracy of any cosmological map.
Determining the nature of cosmic objects at great distances is no easy matter, due the effects of relativity.
As Dr. Eisenstein told Universe Today via email:
In the past, astronomers have made accurate measurements of objects within the local universe (i.e. planets, neighboring stars, star clusters) by relying on everything from radar to redshift - the degree to which the wavelength of light is shifted towards the red end of the spectrum.
However, the greater the distance of an object, the greater the degree of uncertainty.
The spheres show the current size of the "baryon acoustic oscillations" (BAOs)
from the early universe, which have helped to set the distribution of galaxies
that we see in the universe today.
Galaxies have a slight tendency to align along the edges of the spheres
- the alignment has been greatly exaggerated in this illustration.
BAOs can be used as a "standard ruler" (white line)
to measure the distances to all the galaxies in the universe.
Rostomian, Lawrence Berkeley National Laboratory
As the largest of the four projects that
make up the SDSS-III, what sets BOSS
apart is the fact that it relies primarily on the measurement of
what are called "baryon acoustic oscillations" (BAOs).
As Dr. Daniel Eisenstein explained:
With these new, highly-accurate distance measurements, BOSS astronomers will be able to study the influence of Dark Matter with far greater precision.
An international team of researchers
have produced the largest 3-D map of the universe to date,
which validates Einstein's theory of General Relativity.
In addition to measuring the distribution of normal matter to determine the influence of Dark Energy, the SDSS-III Collaboration is working to map the Milky Way and search for extrasolar planets.
The BOSS measurements are detailed in a series of articles that were submitted to journals by the BOSS collaboration last month, all of which are now available online.
And BOSS is not the only effort to understand the large-scale structure of our Universe, and how all its mysterious forces have shaped it.
Relying on data obtained by the CMB data obtained by the ESA's Planck satellite and information from the Dark Energy Survey, they also hope to measure the influence Dark Energy has had on the distribution of matter in our Universe.
In a few years time, we may very well come to understand how all the fundamental forces governing the Universe work together.