Spectacular Cosmographic Maps Chart Galaxies and Superclusters in Local Universe
- 4:13 pm |
Take a trip through our local universe and see the positions and movements of galaxies and clusters with this incredible new video map.
Looking like tiny islands in a vast ocean, the roughly 30,000 galaxies in this detailed map extend out to around 350 million light-years from our own Milky Way. These cosmic objects don’t float alone but tend to group together in clusters of hundreds or superclusters of thousands of galaxies. Enormous voids containing relatively little material stretch between the dense threads of galactic gas and dust.“The complexity of what we are seeing is overwhelming,” says astronomer Helene Courtois of the University of Lyon in France, lead author of a paper that appeared on arXiv.org on June 1, as she narrates the 17-minute video above.
The research uses a visualization tool called SDvision to reveal the richness of our cosmic neighborhood. It is meant to help astronomers get more of a personal feel for the local universe, said the authors in a paper accompanying the video.
“Maps with names for features promote a familiarity and specificity that contributes to physical understanding,” the authors wrote.
The labels given to features in our cosmic neighborhood – the Fornax cluster, Perseus-Pisces, the Great Wall – sound like they came from some exotic sci-fi or fantasy novel map. (Lest you think the Zone of Avoidance is a celestial forbidden sector, it simply represents areas obscured to astronomers by the light from our Milky Way.)
By understanding the large-scale structure of the cosmos, scientists can get a better handle on dark matter and dark energy, which are the dominant forces affecting the shapes of galactic superclusters. A nice bonus is that those without a scientific background can enjoy the work and be amazed at the physical wonder of our universe.
Distances in the video are given in what might seem an odd unit of measure: kilometers per second, which is usually associated with speed. But as Edwin Hubble observed in the early 1900s, the farther a galaxy is away, the faster it is moving from us. Because defining absolute distances in the universe is a bit tricky, astronomers prefer to tell you how quickly a particular object is moving away from us.
Here, Wired presents some of the highlights from this galactic mapping project but, if you have time for it, the full 17-minute video is a fascinating watch.
The researchers used several databases to complete their map, including the V8k catalog of galactic distances and speeds, which was developed mostly for use in planetarium programs. This projection shows where the mapped galaxies appear on the night sky and is color-coded to indicate distance. Galaxies within about 350 million light years of the Milky Way can be found here.
The closest galaxies appear here in a 3-D projection. Though some structure can be seen – mostly dense spots and large voids – it’s difficult to understand much of the cosmic organization. The video below starts at our home galaxy, the Milky Way, and travels outward, revealing some of the biggest nearby features.
As the scene quickly pans out, you can spot the Milky Way’s two satellite galaxies, the Large and Small Magellanic Cloud, which orbit our galaxy in the same way the moon orbits the Earth. The local group of 54 galaxies and dwarf galaxies follows shortly thereafter.
Our galactic assemblage is merely an outlying part of the 1,000-plus-galaxy-strong Virgo cluster, which can next be seen in the video along with a few other nearby clusters. Finally, the movie zooms out to include gigantic supercluster structures such as Coma and Pavo-Indus as well as the 500-million-light-year-long Great Wall, one of the largest known constructs in the universe.
A map of the nearest galaxies to our own shows how they are clustered in the same plane, like the planets of our solar system. The galaxies could be distributed anywhere in three dimensional space but gravitational interactions among them cause them to have this structure, with a large void both above and below the supergalactic plane.
The speeds and locations of galaxies in this image, extending out to about 20 million light-years, are known with very good precision. Dust and gas obscures the light of galaxies farther out, making measurements harder.
A view of the cosmic neighborhood with many features named. The Pavo-Indus Supercluster, Perseus-Pisces Supercluster, Virgo Supercluster, and Hydra-Centaurus Supercluster each containing tens of thousands of galaxies. Large voids can be seen as well and two gigantic features: the Great Wall and Southern Wall, which each span hundreds of millions of light-years. They function as enormous gravitational attractors.
This maps shows places of greatest density in the local universe, revealing how our local galactic area is really just a tiny blip in the surrounding structure. The mass in this image is dominated by a gigantic filament known as the Great Wall, along with smaller configurations like the Pavo-Indus and Perseus-Pisces superclusters.
Edwin Hubble noticed that the farther away a galaxy is, the faster it is moving from us. Later scientists realized that this is because of the expansion of space-time, which is happening constantly. But gravitational attraction causes galaxies to orbit one another in ways that don’t always line up with Hubble’s Law.
This velocity map contains arrows showing the direction that different galaxies and structures move relative to the Milky Way. This large-scale flow moves toward the Centaurus Cluster in our local neighborhood, which is why it is labeled as a great attractor. Colors represent the density of arrows, showing how much of the flow converges at Centaurus. The animation below shows the movement more vividly.
All images and videos: “Cosmography of the Local Universe,” Courtois, Helene, et al, arXiv:1306.0091, accepted for publication in the Astronomical Journal, 2013