As we have learned more about the surrounding universe over the past many decades and centuries, that universe, and the various things within it, just keeps getting bigger and bigger.

We've come a long way from that small, Earth-centered view of the universe that our ancestors held many centuries ago. Even the realization during the 16th and 17th centuries that our Earth was just one of several planets orbiting around the sun served to enlarge our view of that universe.

Then, of course, came the realization that all the stars we see in the nighttime sky are, in actuality, distant suns more or less like our own. As soon as the distances to some of the stars were determined in the mid-19th century -- which showed that even the nearest stars are so far away that their light takes years to make the journey to us -- the universe became much bigger.

Up through the first two decades of the 20th century, the common belief was that all the stars, together with everything else we see in the nightime sky, are all a part of one large "galaxy" -- informally dubbed the "Milky Way," after the hazy band of light we see stretching across the sky at night.

In actuality, the combined light of thousands of distant stars was considered to be several tens of thousands of light-years across. We now know that the Milky Way's size is in the neighborhood of 100,000 light-years.

In the 1920s, American astronomer Edwin Hubble showed that many of the hazy patches of light in the nighttime sky are, in fact, separate galaxies in their own right; even the nearest large galaxy, the bright spiral-shaped one in the constellation Andromeda (now high in the western sky during the evening hours) is so far away that its light takes 2 1/2 million years to get to us.


As time went on, we continued to discover more distant galaxies -- first tens of millions, then hundreds of millions and eventually billions -- of light-years away from us.

The most distant known galaxy at this writing is known as UDFj-39546284. It located in the constellation Fornax, southwest of Orion, and in our southern skies on these cold January nights. It is so far away that the light we see from it left on its journey to us more than 13.3 billion years ago.

Most of the galaxies we see in the nighttime sky are not single, isolated objects; the vast majority of them are contained in gatherings we call "clusters."

The Milky Way, the large galaxy in Andromeda, together with various "companion" galaxies, as well as some very tiny galaxies that have recently been discovered, constitute one such cluster that has been dubbed the "Local Group."

As galaxy clusters go, the Local Group is quite small. A large cluster in the constellation Virgo (now in our eastern sky in the morning) contains several hundred relatively large galaxies. Another, more distant, cluster in the adjacent constellation of Coma Berenices contains several thousand galaxies.

While galaxy clusters can be several tens of millions of light-years across, even these aren't the largest structures in the universe. The clusters themselves congregate into what are called "superclusters;" the cluster of galaxies in Virgo, for example, is the nucleus of what is called the "Virgo supercluster," which contains the Local Group. The cluster of galaxies in Coma Berenices is the nucleus of another such supercluster.

And it doesn't stop there. Detailed survey maps of the distant universe conducted in the late 1980s revealed the clusters and superclusters of galaxies in the universe are contained within large filament-like structures. The largest known at the time, which contains the Coma Berenices supercluster and is dubbed the "Great Wall," is hundreds of millions of light-years long. A handful of other "Great Walls" have been detected since then, the largest being dubbed the "Sloan Great Wall" (so called because it was discovered in data taken with the Sloan Digital Sky Survey based in southern New Mexico).

The Sloan Great Wall, announced in 2003, is located in the same basic part of the sky as the first Great Wall, but is much more distant, being about one billion light-years away and 1.4 billion light-years long.

The Sloan Great Wall has been considered the largest known structure in the observable universe -- until now. Just last week, a team of astronomers led by Roger Crowes at the University of Central Lancashire in England announced their discovery in data taken by the Sloan survey. It is a large collection of quasars (which can be considered young and active galaxies) that is about four billion light-years long. This structure, which is formally known as U1.27, but informally dubbed the "Huge-LQG" (for "large quasar group"), can be found in the constellation Leo (now nearly overhead during the late morning. It is located about eight billion light-years away.

The Huge-LQG is so large that it might actually present difficulties for what is called the "cosmological principle." This principle, which is one of the bedrock assumptions we have about the universe as a whole, states that, over very large distance scales, the universe looks basically the same in all directions.

Since the Huge-LQG is a few percent of the size of the entire observable universe, it would seem to throw a bit of a wrinkle into that whole idea.

The news is still pretty early, so it's fair to say the verdict is still out. But it's also fair to say that discoveries like that of the Huge-LQG remind us that we still have much to learn about the universe in which we live.
