At 1600 times the distance between the Milky Way and our nearest galactic neighbor (the Andromeda Galaxy), the super cluster of quasars (quasi-stellar radio sources) spans 4 billion light years along its widest dimension (i.e., it would take light 4 billion years to traverse its widest dimension).
Such large quasar groups (LQGs) are the largest structures that can be seen dating from the early universe; in this case, light from the original quasars in this group commenced almost 9 billion years ago (or when the universe was just 5 billion years old).
LQGs are typically comprised of anywhere from 5 to 40 member quasars, with the largest (previously found) being 70 to 350 megaparsecs (Mpc)* in size.
But this newest, “most extreme” LQG — found amongst the millions of images in the DR7QSO Sloan Digital Sky Survey (SDSS) — measures some 500 Mpc in its shortest dimension and 1240 Mpcs in its widest dimension. It has 73 member quasars.
The structure has been dubbed U1.27 (where ‘U’ stands for the connected unit of quasars, and the number refers to the mean redshift; oldest quasars have a red shift value of ≥6).
In fact, U1.27 is so large that it would seem to violate Einstein’s cosmological principle which asserts that, at large scales (such as measured in this LQG discovery), the universe should look the same no matter the direction or locale from which one looks.
So, according to that principle, astronomers calculated that such large-scale structures should be no larger than 1.2 billion light years across. The newly discovered LQG is, on average, 1.63 billion light years across (note: the measurement variability in its dimensions is due to its irregular shape).
Sky distribution of the 73 quasars of the new, Huge-LQG (U1.27, z¯=1.27, circles), is shown, together with that of the 34 quasars of the CCLQG (z¯=1.28, crosses). The members of each LQG are connected at the linkage scale of 100 Mpc. The area shown is approximately 29 .∘5 × 24 .∘0. The DR7QSO quasars are limited to i ≤ 19.1. Superimposed on these distributions is a kernel-smoothed intensity map (isotropic Gaussian kernel, σ = 0 .∘5), plotted with four linear palette levels (≤0.8, 0.8–1.6, 1.6–2.4, ≥2.4 deg−2), for all of the quasars in the joint redshift range of Huge-LQG and CCLQG (z: 1.1742 → 1.4232). (credit: Clowes et al)
In 2010, astronomers Yadav, Bagla & Khandai devised a “scale of homogeneity” with which to compare/measure such structures in respects to the concordance cosmology (i.e., their concordance, or agreement, with the cosmological principle). Previous discoveries of LQGs were only “marginally compatible” with this scale.
According Clowes et al (quoting from the published paper abstract):
“This new, Huge-LQG appears to be the largest structure currently known in the early Universe. Its size suggests incompatibility with the Yadav et al. scale of homogeneity for the concordance cosmology, and thus challenges the assumption of the cosmological principle.”
It may likely be the first time that Einstein has been proven wrong.
* A parsec is a unit of length used in astronomy, equal to about 30.9 trillion kilometres (19.2 trillion miles). In astronomical terms, it is equal to 3.26 light-years, and in scientific terms it is equal to 3.09×1013 kilometres (1.92×1013 miles).
The findings were recently published in Monthly Notices of the Royal Astronomical Society under the title ‘A structure in the early Universe at z ∼ 1.3 that exceeds the homogeneity scale of the R-W concordance cosmology’
The researchers responsible for the discovery are: Roger G. Clowes,Kathryn A. Harris, Srinivasan Raghunathan, Luis E. Campusano, Ilona K. Söchting, and Matthew J. Graham
Some source material for this post came from the Science NOW article:ScienceShot: The Largest Structure in the Universe by Sid Perkins
Top Image: (note: image is NOT of the UI.27 LQG) Quasars Acting as Gravitational Lenses. To find these cases of galaxy–quasar combinations acting as lenses, astronomers selected 23.000 quasar spectra from the SDSS); credit: NASA, ESA/Hubble and F. Courbin (Ecole Polytechnique Federale de Lausanne, Switzerland; CC – By 3.0
Michael Ricciardi is a well-published writer of science/nature/technology articles and essays, poetry and short fiction. Michael has interviewed dozen of scientists from many scientific fields, including Brain Greene, Paul Steinhardt, and Nobel Laureate Ilya Progogine (deceased). Michael was trained as a naturalist and taught ecology and natural science on Cape Cod, Mass. from 1986-1991. His first arts grant was for production of the environmental (video) documentary 'The Jones River - A Natural History', 1987-88 (Kingston, Mass.). Michael is also an award winning, internationally screened video artist. Two of his more recent short videos; 'A Time of Water Bountiful' and 'My Name is HAM' (an "imagined memoir" about the first chimp in space), and several other short videos, can be viewed on his website (http://www.chaosmosis.net). Michael currently lives in Seattle, Washington.
