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sachinism
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http://blogs.nationalgeographic.com/blogs/news/breakingorbit/2010/11/new-dark-matter-map-hubble.html?source=link_tw20101112hubble"
i found this article interesting , so shared here
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One of the brilliant things about astrophysics is being able to take pictures of invisible stuff.
Infrared telescopes, for example, allow astronomers to see "dark" nebulas (picture), clouds of dust and gas that weakly reflect light from nearby stars, glowing mostly in thermal emissions.
Similarly, high-energy x-rays and gamma rays let scientists "see" black holes, objects that by definition are so dense not even light can escape their gravitational pull.
OK, to be fair, we don't see the black hole directly, but rather the radiation from infalling material. But still, what we do see is pretty good proof of objects that once existed only in theory.
Dark matter is another substance drawn from theory that astrophysics is starting to make visible—although the trick to finding dark matter is a bit more complicated.
For starters, dark matter doesn't absorb or emit light, and so far we have no proof of it interacting directly with normal matter.
We know dark matter is there based solely on gravity. Stars move within galaxies, and galaxies rotate on their axes, in ways that suggest there must be more matter present than what we can see.
In addition, clusters of galaxies bend light from objects behind them (an effect known as gravitational lensing) more than they should based on the visible matter present.
The galaxy cluster Abell 1689 is among the most powerful gravitational lensing clusters ever observed, according to NASA, making it a great place to map the distribution of dark matter.
Now, a new picture of this lens-filled cluster from the Hubble Space Telescope has allowed astronomers to create one of the sharpest and most detailed maps yet of dark matter.
Abell 1689 is among the most powerful gravitational lensing clusters ever observed. Coe's observations, combined with previous studies, yielded 135 multiple images of 42 background galaxies.
"The lensed images are like a big puzzle," Coe says. "Here we have figured out, for the first time, a way to arrange the mass of Abell 1689 such that it lenses all of these background galaxies to their observed positions." Coe used this information to produce a higher-resolution map of the cluster's dark matter distribution than was possible before.
The purpose of creating a new dark matter map is to gain a better understanding of the distribution and properties of dark matter in our galaxy. This can help us solve the puzzle of how galaxies and structures in the universe formed and evolved.
The new dark matter map was created using data from the European Space Agency's Gaia satellite, which measures the positions and velocities of stars in the Milky Way. Researchers also used computer simulations to model the distribution of dark matter in the galaxy.
The dark matter map provides information about the density and distribution of dark matter in the Milky Way. It also reveals the presence of substructures, such as dark matter halos, which were previously unknown.
By providing a more accurate and detailed map of dark matter in the Milky Way, scientists can use this information to test and refine theories about the formation and evolution of galaxies. It also helps us understand the role of dark matter in shaping the structure of the universe.
The new dark matter map has the potential to revolutionize our understanding of the universe and the role of dark matter in its formation. It could also lead to new discoveries and advancements in our understanding of fundamental physics and cosmology.