A second ultra-large structure found in the distant cosmos has further
upended some of the fundamental cosmological presumptions.
It is 9.2 billion light-years from Earth to the Big Ring in the Sky. Its
radius is approximately 4 billion light-years, while its diameter is around
1.3 billion light-years. The circumference of the Big Ring would require
around fifteen full moons to completely cover it, if we could go outside and
observe it.
Ph.D. candidate Alexia Lopez of the University of Central Lancashire
(UCLan) has found this second ultra-large structure; two years prior, she
had also found the
Giant Arc
in the Sky. Surprisingly, the 3.3 billion light-year-wide Giant Arc and the
Big Ring are located in the same cosmological neighborhood; they are
separated in the sky by only 12 degrees and may be observed at the same
distance and cosmic time.
"With our current understanding of the universe, neither of these two
ultra-large structures is easy to explain," Alexia said. Furthermore,
something significant must be being revealed to us by their extraordinarily
massive sizes, unique forms, and cosmic closeness. But what exactly?
One theory is that baryonic acoustic oscillations, or BAOs, are connected
to the Big Ring. BAOs originate from oscillations in the early cosmos and
should manifest as spherical shells in the galaxy arrangement today, at
least statistically. Detailed examination of the Big Ring, however, showed
that it is not truly consistent with the BAO theory since it is not
spherical and is far too big."
It may be necessary to provide additional explanations, ones that deviate
from what is usually accepted as the accepted knowledge of cosmology. An
alternative hypothesis, Conformal Cyclic Cosmology (CCC), put out by Nobel
laureate Sir Roger Penrose, might be one option. It is possible that rings
throughout the cosmos indicate CCC.
A further possibility is the impact of cosmic strings moving through.
Cosmic strings are large-scale filamentary "topological defects" that may
have originated in the early cosmos. Jim Peebles, another Nobel laureate,
has proposed that cosmic strings may play a part in the genesis of certain
additional oddities in the large-scale galaxy distribution.
In addition, the Big Ring contradicts the Cosmological Principle, just as
the Giant Arc did earlier. Furthermore, the argument against the
Cosmological Principle gains strength if the Big Ring and the Giant Arc
combine to produce an even bigger structure.
These massive formations, along with others discovered by other
cosmologists, put our conception of what constitutes a "average" region of
space to the test. They are potentially problematic for the Cosmological
Principle since they are larger than what is thought to be theoretically
feasible.
"The Cosmological Principle presumes that the portion of the universe that
is visible to us is considered to be a 'fair sample' of what we anticipate
the remainder of the universe to be like," Alexia said. When we look at the
cosmos from a big enough scale, we anticipate matter to be uniformly
dispersed throughout space, therefore anything larger than a certain size
shouldn't show any obvious abnormalities.
The Big Ring's circumference is equivalent to that of the Giant Arc, and
the Giant Arc itself is nearly three times larger than the theoretical size
limit of structures now estimated by cosmologists to be 1.2 billion
light-years.
According to accepted cosmological theories, structures of this size are
not thought to be feasible. In the entire observable cosmos, we may
anticipate seeing only one really massive structure. Nonetheless, it is
really remarkable that the Big Ring and the Giant Arc are two enormous
structures that are even cosmic neighbors."
The Big Ring is seen as an almost perfect ring in the sky, but upon closer
inspection, Alexia discovers that it is actually more of a corkscrew-shaped
coil that is directly aligned with Earth. In the distant cosmos, the Giant
Arc appears as a massive, fairly symmetrical crescent of galaxies. Its
radius is about 1/15th that of the visible universe. Its size is double that
of the remarkable Sloan Great Wall of galaxies and clusters observed in the
comparatively close cosmos.
"The Big Ring and Giant Arc are the same distance from us, near the
constellation of Boötes the Herdsman, meaning they existed at the same
cosmic time when the universe was only half of its present age" said Alexia.
"When looking up at the night sky, they are also in the same area of the
sky, separated by just 12 degrees.
"Identifying two extraordinary ultra-large structures in such close
configuration raises the possibility that together they form an even more
extraordinary cosmological system."This data comes from a time when the
universe was around 1.8 times smaller than it is now, and it has traveled so
far to reach us that it has taken half the life of the universe to do it. In
our quest to comprehend the universe and its evolution, the Big Ring and the
Giant Arc provide a significant cosmic puzzle, both alone and
collectively."
The novel structure was found by Alexia, collaborator Gerard Williger from
the University of Louisville, U.S., mentor Dr. Roger Clowes from the
Jeremiah Horrocks Institute at UCLan, and by examining absorption lines in
the spectra of quasars from the Sloan Digital Sky Survey (SDSS).
They discovered the intervening Magnesium-II (or MgII; the term refers to
the atom having lost an electron) absorption systems back-lit by quasars,
which are distant super-luminous galaxies, using the same technique that
resulted in the discovery of the Giant Arc. These quasars, which are
extremely far away and extremely brilliant, function like enormous lamps
that shine a spotlight through much fainter, farther-off intervening
galaxies that would not otherwise be visible.
Alexia has presented her findings on the Big Ring at the 243rd meeting of the American Astronomical Society (AAS) on 10 January.
Provided by University of Central Lancashire
