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The relatively cold, empty spot observed (circled at bottom right) is 1.8 billion light years across. (ESA and the Planck Collaboration)
Around 3 billion light years away from Earth, there's a strange patch of the universe that baffles scientists.The mystery is a "cold spot," a gigantic void that has surprisingly few galaxies present. At 1.8 billion light years across, it's the largest structure we've ever discovered.
As reported by the Guardian, astronomers from the University of Hawaii and elsewhere just published a new survey of this area, which was first noticed in 2004. Previously, all scientists knew was that the cold spot was an area of space from which relatively little energy emanated.
The new study confirmed that roughly 10,000 fewer galaxies than expected are present across the vast area — which means it has about 20 percent less matter, in total, than other areas of the visible universe.
The mysterious cold spot has puzzled scientists for a decade
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The European Space Agency's Planck satellite, launched in 2009, confirmed the existence of the cold spot with new data in 2013. (ESA)
In 2004, the cold spot was detected in scientists' measurements of a form of energy called the cosmic microwave background (CMB).The CMB is heat energy that constantly careens throughout the entire universe and is left over from the Big Bang. The violent event generated high-energy waves of radiation — which were subsequently stretched out as the universe cooled and expanded over billions of years — and now persist as a low level of microwave energy everywhere we look.
But as scientists mapped the CMB, they saw a huge area in the direction of the constellation Eridanus with surprisingly little energy: it's about 2.7°K colder than average temperature of the universe. Elsewhere, areas that large only vary by about a degree or so.
This didn't fit with our models for how the universe formed, since they predict that it should be relatively homogenous everywhere. The most obvious explanation was that the cold spot was simply an unexpected void — an area with relatively few galaxies — but when scientists mapped extremely distant areas of the universe in the direction of the cold spot in 2009, they didn't find any voids. Some scientists suggested the cold spot was the result of errors made by analyzing the CMB data, and others even controversially claimed it might be evidence of a parallel universe.
A partial explanation for the cold spot: fewer galaxies
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In the new survey, scientists counted galaxies with data collected by the Pan-STARRS telescope (left box) and found a void in the same location where the Planck satellite (right box) had detected the cold spot. (ESA Planck Collaboration)
To figure things out, scientists led by IstvΓ‘n Szapudi of the University of Hawaii at Manoa used data collected by a pair of telescopes to create a 3D map of galaxies in the direction of the cold spot. Instead of mapping distant galaxies like before, though, they mapped relatively nearby ones — galaxies that are 3 billion light years away (which isn't much distance in terms of the scale of the visible universe).This survey found a gigantic void with about 10,000 fewer galaxies than you'd expect, based on the overall density of galaxies in the universe. Other voids exist, but this is by far the largest one we've spotted so far — and is also the largest structure we've seen in the universe to date.
Such a giant void could account for the cold spot because as light travels across it, it should lose energy, with its wavelength getting slightly stretched out due to the expansion of the universe over time. This would partly explain why we see a bit less energy coming from that area of the sky in the CMB data.
However, it leaves an even bigger mystery: why are there so few galaxies in this area to begin with?
Read the research paper: http://dx.doi.org/10.1038/nature13674
Read Nature's news story: http://www.nature.com/news/earth-s-ne...
A new study in Nature finds that the Milky Way is part of a broader supercluster of 100,000 galaxies known as Laniakea. Nature Video
We know that the Earth and the solar system are located in the Milky Way galaxy. But how, exactly, does the Milky Way fit in among the billions of other galaxies in the known universe?
In a fascinating 2014 study for Nature, a team of scientists mapped thousands of galaxies in our immediate vicinity, and discovered that the Milky Way is part of a jaw-droppingly massive "supercluster" of galaxies that they named Laniakea.
This structure is much, much, much bigger than astronomers had previously realized. Laniakea contains more than 100,000 galaxies, stretches 500 million light years across, and looks something like this (the Milky Way is just a speck located on one of its fringes on the right):
It's hard to wrap one's head around how enormous this is. Each of those points of light is an individual galaxy. Each galaxy contains millions, billlions, or even trillions of stars. Oh, and this all is just our little local corner of an even broader universe. There are many other galaxy superclusters out there.
So how did the researchers figure out this structure existed — and how did they distinguish it from other superclusters?
The team of scientists, led by R. Brent Tully of the University of Hawaii, first studied the motion of some 8,000 galaxies in our neighborhood. By doing so, they could map out certain patterns. The universe overall has been expanding ever since the Big Bang. But the team also found that gravity was pulling some galaxies toward each other.
That helped them build the graph below, where galaxies moving away from us are shown in red, and the galaxies moving toward us in blue.
The map below shows some of the pathways within our broader supercluster of galaxies. There's an especially dense region called "The Great Attractor" (in red) that's slowly pulling the Milky Way and many other galaxies toward it:
What's interesting is that this structure is much bigger than anyone had realized. Astronomers had long grouped the Milky Way, Andromeda, and other galaxies around us in the Virgo Supercluster, which contained some 100 galaxy groups.
But as Tully and his colleagues found, and as the map above shows, this Virgo Supercluster is just part of a much, much bigger supercluster — Laniakea. (The name, aptly enough, means "immeasurable heavens" in Hawaiian.)
So what happens when we zoom out? The paper notes that Laniakea borders another supercluster known as Perseus-Pisces. And the scientists defined the borders as where the galaxies are consistently diverging:
What happens if we zoom out even further? Even Laniakea and Perseus-Pisces are just one small pocket of the much broader universe. That universe consists of both voids and densely packed superclusters of galaxies. It looks something like this:
We still don't have detailed maps of every last galaxy supercluster out there. But we now have one for our own home supercluster — and that's certainly a start.
Further watching: There's an excellent video from Nature breaking down the team's findings. The stills above come from that video.
Further reading: Over at Slate, Phil Plait has a nice breakdown of the study, which was released in September 2014.
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In a fascinating 2014 study for Nature, a team of scientists mapped thousands of galaxies in our immediate vicinity, and discovered that the Milky Way is part of a jaw-droppingly massive "supercluster" of galaxies that they named Laniakea.
This structure is much, much, much bigger than astronomers had previously realized. Laniakea contains more than 100,000 galaxies, stretches 500 million light years across, and looks something like this (the Milky Way is just a speck located on one of its fringes on the right):
Say hello to Laniakea, our local supercluster
It's hard to wrap one's head around how enormous this is. Each of those points of light is an individual galaxy. Each galaxy contains millions, billlions, or even trillions of stars. Oh, and this all is just our little local corner of an even broader universe. There are many other galaxy superclusters out there.
So how did the researchers figure out this structure existed — and how did they distinguish it from other superclusters?
The team of scientists, led by R. Brent Tully of the University of Hawaii, first studied the motion of some 8,000 galaxies in our neighborhood. By doing so, they could map out certain patterns. The universe overall has been expanding ever since the Big Bang. But the team also found that gravity was pulling some galaxies toward each other.
That helped them build the graph below, where galaxies moving away from us are shown in red, and the galaxies moving toward us in blue.
The galaxies around us are moving in identifiable patterns
Galaxies moving away from us are in red, those moving toward us in blue (Nature Video, based on Tully et al 2014)
That, in turn, let them create a map of the pathways along which all the galaxies are moving and demarcate some boundaries.The map below shows some of the pathways within our broader supercluster of galaxies. There's an especially dense region called "The Great Attractor" (in red) that's slowly pulling the Milky Way and many other galaxies toward it:
Many galaxies in Laniakea are being pulled toward the "Great Attractor"
What's interesting is that this structure is much bigger than anyone had realized. Astronomers had long grouped the Milky Way, Andromeda, and other galaxies around us in the Virgo Supercluster, which contained some 100 galaxy groups.
But as Tully and his colleagues found, and as the map above shows, this Virgo Supercluster is just part of a much, much bigger supercluster — Laniakea. (The name, aptly enough, means "immeasurable heavens" in Hawaiian.)
So what happens when we zoom out? The paper notes that Laniakea borders another supercluster known as Perseus-Pisces. And the scientists defined the borders as where the galaxies are consistently diverging:
Laniakea borders another supercluster: Perseus-Pisces
What happens if we zoom out even further? Even Laniakea and Perseus-Pisces are just one small pocket of the much broader universe. That universe consists of both voids and densely packed superclusters of galaxies. It looks something like this:
And... zooming out to the broader universe
We still don't have detailed maps of every last galaxy supercluster out there. But we now have one for our own home supercluster — and that's certainly a start.
Further watching: There's an excellent video from Nature breaking down the team's findings. The stills above come from that video.
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