Galaxies are fiery, brilliant congregations of a myriad of dazzling stars that jitter-bug around the Universe, and they most often inhabit groups or clusters--groups being considerably smaller than clusters.
Clusters and superclusters of galaxies are the most massive structures known to dwell in the Universe, and they frequently host hundreds to thousands of separate galactic constituents glued together by gravity, thus forming the densest component of the large-scale structure of the Universe.
In February 2014, an international team of astronomers used a novel way of combining data derived from the two European Space Agency (ESA) satellites, Planck and Herschel, to identify more distant galaxy clusters than had ever before been possible.
According to the team's paper appearing in the Monthly Notices of the Royal Astronomical Society, they were able to use their new technique to detect a quartet of previously unknown galaxy clusters hosting literally thousands of individual galaxies located 10 billion light-years from Earth.
Even though astronomers have succeeded in discovering a large number of nearby galaxy clusters, they need to go back further in time in order to understand how these structures first formed in the ancient Universe--and this means they must spot clusters at much greater distances from Earth.
In astronomy, long ago is the same as far away--the further away a celestial object is, the more ancient it is.
This is because the further away an object is, the longer it has taken for its light to travel the immense journey from where it originated to meet the peering eyes of observers on our own planet.
No signal in the Universe can travel faster than light in a vacuum--and the speed of light, therefore, is considered to be something of a "universal speed limit.
" The light emanating from the most remote of the four newly discovered ancient clusters, identified by the team, has taken over 10 billion years to travel that long and treacherous journey to our planet.
This means the astronomers are seeing what that ancient cluster looked like when the Universe was merely three billion years old.
The Universe was born in the inflationary Big Bang about 13.
8 billion years ago.
Lead researcher, Dr.
David Clements, from the Department of Physics at Imperial College London in the UK, explained in a February 12, 2014 Imperial College London Press Release that "Although we're able to see individual galaxies that go further back in time, up to now, the most distant clusters found by astronomers date back to when the Universe was 4.
5 billion years old.
This equates to around nine billion light years away.
Our new approach has already found a cluster in existence much earlier than that, and we believe it has the potential to go even further.
" Astronomers need to find significant numbers of these more distant clusters.
The study team speculates that their new technique could result in about 2,000 additional clusters being spotted.
Ancient Galaxies Form Long Ago-And Far Away! The star-blasted galaxies dancing around the Universe caught fire a very long time ago, and began to light up the primordial Cosmos less than a billion years after the Big Bang.
The currently most widely accepted theory of galaxy formation indicates that large galaxies were rare denizens of the ancient Universe, and that they only eventually managed to reach their more mature and majestic sizes when they merged with other small and amorphous protogalactic structures.
The most ancient galaxies are thought to have been only approximately one-tenth the size of our own large barred-spiral Galaxy, the Milky Way, but they were just as brilliant.
This is because they were furiously churning out an enormous number of sparkling, searing-hot, and brightly glowing baby stars.
These extraordinarily brilliant, albeit relatively small, ancient galactic structures served as the "seeds" of the more mature galaxies bobbing around in the Cosmos today.
In the very ancient Universe, opaque blobs of gas merged together along enormous, heavy filaments of the mysterious, transparent dark matter that forms the great Cosmic Web.
Although we do not know the identity of the weird particles that compose the dark matter, it is understood that these strange particles are not the stuff of atoms that make up the familiar matter that composes stars, galaxies, planets, moons, and people--that is, all of the familiar atomic elements listed in the Periodic Table.
In fact, "ordinary" atomic matter, or baryonic matter, constitutes a mere 5% of the mass-energy content of the Cosmos.
It is currently thought that the dark matter accounts for 25% of the Universe, while most of it--about 70% of it--is composed of the dark energy! The dark energy is a bizarre substance, a property of Space itself, that is causing our Universe to accelerate in its expansion.
Our own Milky Way Galaxy, that whirls around like a star-splattered pin-wheel in intergalactic Space, is a large denizen of the Local Group, which hosts more than 40 galaxies.
Our Local Group, in turn, is situated near the outer limits of the Virgo Cluster of galaxies, whose core is about 50 million light-years from Earth.
The star-fired galaxies of our Cosmos trace out for us the mysterious, enormous, transparent, and invisible filaments of the Cosmic Web, constructed of bizarre, exotic dark matter.
The brilliantly lit galaxies that congregate together in groups and clusters have set fire to this invisible Cosmic Web, tracing out for our Earth-evolved human eyes--with their wonderful, brilliant light--that which we cannot see.
It is thought that the first galaxies were dark and opaque clouds of gas pooling in the secretive hearts of haloes of dark matter, and that they pulled in the first generation of fiery baby stars with their strong gravitational lure.
The sparkling new stars and the glowing gas lit up what was a murky expanse, as light at last soared freely through the ancient Cosmos.
A Quartet Of Galaxy Clusters Shine Brightly In The Ancient Universe Galaxy clusters can be recognized by satellite surveys at great distances.
This is because they hold enormous quantities of gas and dust that are being used for star-birth.
The process of star formation emits enormous amounts of readily detectable light.
Alas, most galaxy clusters dancing around in the modern Universe are dominated by giant elliptical galaxies in which the dust and gas has long since been depleted--having already gone into the formation of baby stars.
"What we believe we are seeing in these distant clusters are giant elliptical galaxies in the process of being formed," Dr.
Clements noted in the February 12, 2014 Imperial College London Press Release.
Galaxies are basically divided into two major types--although, in reality, it is considerably more complicated than this.
The two main basic galactic types are: 1.
elliptical galaxies that host a large number of stars, but contain only small amounts of star-forming dust and gas.
2.
spiral galaxies like our own Milky Way, which contain a large quantity of star-forming dust and gas.
Observations of the quartet of long ago and far away clusters were recorded by the Spectral and Photometric Imaging Receiver (SPIRE) instrument as part of the Herschel Multi-tiered Extragalactic Survey (HerMES).
Dr.
Seb Oliver, head of the HerMES survey, said in the February 2014 Imperial College London Press Release that "The fantastic thing about Herschel SPIRE is that we are able to scan very large areas of the sky with sufficient sensitivity and image sharpness that we can find these rare and exotic things.
This result from Dr.
Clements is exactly the kind of thing we were hoping to find with the HerMES survey.
" The astronomers are among the first to combine information gathered from two satellites that completed their operations in 2013--the Planck satellite, which scanned the entire sky, and the Herschel satellite, which surveyed select regions in greater detail.
The astronomers used Planck data to spot sources of far-infrared emission in regions covered by the Herschel satellite.
They then cross-referenced with Herschel data to observe these distant sources more closely.
Of sixteen candidate sources identified by the astronomers, most were confirmed as solitary, nearby galaxies that had already been discovered.
However, four were revealed by Herschel to be composed of multiple, dimmer sources, suggesting previously undiscovered galaxy clusters.
The team of astronomers then used additional existing data and new observations to calculate the distances of these clusters from our planet and to estimate which of the galaxies within them were still giving birth to sparkling new baby stars.
The astronomers are now trying to identify more galaxy clusters, using this technique, with the goal of peering even further back in time to that very ancient era marking the earliest stage of cluster formation.