Image of the Day: The Virgo Cluster --"Proof of the Cosmic Thread Connecting Us to the Vast Expanse of the Universe"
The image above shows unusually large halos for the brightest galaxies as well as unusual faint streams of stars connecting galaxies of the Virgo Cluster that previously appeared unrelated. The cluster is a mixture of some 1300 spiral and elliptical galaxies, with the spirals of the cluster distributed in an oblong filament, approximately 4 times as long as wide, stretching along the line of sight from the Milky Way, while the elliptical galaxies are more centrally concentrated.
“By examining the positions of ancient groupings of stars, called globular clusters, we found that the clusters form a narrow plane around the Milky Way rather than being scattered across the sky,” said Dr. Stephan Keller of the Research School of Astronomy and Astrophysics at ANU.
“Furthermore, the Milky Way’s entourage of small satellites are seen to inhabit the same plane. What we have discovered is evidence for the cosmic thread that connects us to the vast expanse of the Universe. The filament of star clusters and small galaxies around the Milky Way is like the umbilical cord that fed our Galaxy during its youth,” Keller observed.
There are two types of matter that made up the Universe – the dominant, enigmatic dark matter and ordinary matter in the form of galaxies, stars and planets. “A consequence of the Big Bang and the dominance of dark matter is that ordinary matter is driven, like foam on the crest of a wave, into vast interconnected sheets and filaments stretched over enormous cosmic voids – much like the structure of a kitchen sponge."
“Unlike a sponge, however," Keller added, "gravity draws the material over these interconnecting filaments towards the largest lumps of matter, and our findings show that the globular clusters and satellite galaxies of the Milky Way trace this cosmic filament. Globular clusters are systems of hundreds of thousands of ancient stars tightly packed in a ball. In our picture, most of these star clusters are the central cores of small galaxies that have been drawn along the filament by gravity.
“Once these small galaxies got too close the Milky Way the majority of stars were stripped away and added to our galaxy, leaving only their cores.
“It is thought that the Milky Way has grown to its current size by the consumption of hundreds of such smaller galaxies over cosmic time,” he concluded.
The Daily Galaxy via Australian National University