You are looking at the most detailed three-dimensional map of the Universe
known to humankind and it's called the Sloan Digital Sky Survey. Scientists from
around the world have just completed a 20-year long survey of the night sky
measuring the positions and distances of more than four million galaxies and
quasars. This detailed map will help scientists shed light on the remaining
mysteries of the Universe. Let's go on a journey from the local stars to the
largest scales of our universe. Beyond the local stars that draw familiar
constellations in the night sky, in the neighborhood of the Earth, in addition to
our own Milky Way, billions of galaxies are spread throughout the observable
Universe. Moving faster than light, we will take you through space in a journey
from our place in the Milky Way all the way out to the large scale structures of
the visible Universe and we'll tell you about how we're mapping it out. Since
1998, the scientific community has realized that the universe is not only
expanding, but its expansion is accelerating. This unexpected
acceleration constitutes one of the major conundrums in physics. From a
theoretical perspective, the acceleration may be accounted for by either assuming
that there exists some mysterious dark energy, or by modifying Einstein's theory
of gravity called General Relativity. In the same year, the Sloan Digital Sky
Survey was launched to tackle this enigma of the accelerating expansion of
the Universe. The Sloan Digital Sky Survey is a vast collection of the
angular positions of galaxies observed in the sky as well as their distances
from us determined by observing the systematic shift of galactic light
induced by the expansion of the Universe, the so-called redshift.
In this new map of our Universe, the large dark patches are mostly regions
obscured by the Milky Way that cannot be observed. During the last 20 years,
through four exploratory phases, the Sloan Digital Sky Survey has created the
most detailed three-dimensional maps of the Universe. To achieve this, it focused
on different classes of galaxies. Nearby galaxies red galaxies, more distant
star-forming galaxies, and super luminous distant active galaxies called quasars.
The fourth and latest Sloan survey took place from 2014 till 2020. During this
time the new project called "The Extended Baryon Oscillation Spectroscopic Survey"
or eBOSS for short, continued previous Sloan mapping of the extragalactic sky
and just recently finished measuring distances for 1 million galaxies and
quasars. These successive surveys allow scientists to trace the large-scale
structures of the Universe up to a fraction of its horizon represented by
the Cosmic Microwave Background emission, seen here as a colorful pattern
projected onto a sphere. The Cosmic Microwave Background is the thermal
relic of a universe which dates back to about 400 thousand years after the birth
of the Universe also known as the Big Bang. Adding the eBOSS data to the
previous Sloan exploratory phases 1 2 & 3, the Sloan Digital Sky Survey now has a
database of 4 million galaxies and quasars assembling the largest and most
complete 3D map of the Universe to date. This unprecedented achievement provides
scientists with new tools for shedding light on Dark Energy and also for
constraining the theory of General Relativity, leading to a better
understanding of the fundamental laws that rule
our Universe.