New evidence suggests that hundreds of unseen dwarf galaxies made of dark matter encircle our Milky Way and other large, visible galaxies. Scientists believe that 80 to 90 percent of the universe must be made of this as-yet-undetected matter to account for the observed structure of the universe. According to Einstein, such large concentrations of matter should warp the surrounding space and bend light in much the same way that glass lenses do. With that in mind, astrophysicists at the University of California at San Diego and the Harvard-Smithsonian Center for Astrophysics in Cambridge analyzed how light from distant galaxies was warped by intervening, lensing galaxies in order to indirectly search for dark matter galaxies.
Image: EMILIO FALCO ET AL. Harvard-Smithsonian Center for Astrophysics
This so-called gravitational lensing can split an image of a single galaxy into two or more images. Imagine a rock that partly dams a stream so that water runs around it in two rivulets--a galaxy that lies between a distant light source and Earth can deflect light beams emitted toward our planet into multiple streams in a similar way, yielding numerous images. (For example, the image above depicts the quasar MG 0414+534 showing multiple images due to gravitational lensing by an intervening galaxy.) The number and appearance of these multiple images depends on the distribution of mass inside the intervening galaxies. If the lensing galaxies are surrounded by many smaller galaxies, the brightness of one of these lensed images could be significantly enhanced if it lined up with a dark matter galaxy.
Researchers Neal Dalal and Christopher Kochanek looked at seven different lensing galaxies that each divided the light of a distant galaxy into four images of varying brightness. They determined that about 2 percent of the lensing galaxies masses must be in the form of a halo of invisible, dark matter dwarf galaxies to explain the brightness variations detected among the multiple images of the background galaxies. The scientists remain puzzled as to why these dark matter galaxies contain few or no stars, however, since 10 to 20 percent of their mass should exist as normal matter. "Its difficult to hide that much material," Dalal observes. The findings will appear in the June 10 issue of the Astrophysical Journal.
Charles Choi | Scientific American
UNH scientists help provide first-ever views of elusive energy explosion
16.11.2018 | University of New Hampshire
NASA keeps watch over space explosions
16.11.2018 | NASA/Goddard Space Flight Center
Researchers at the University of New Hampshire have captured a difficult-to-view singular event involving "magnetic reconnection"--the process by which sparse particles and energy around Earth collide producing a quick but mighty explosion--in the Earth's magnetotail, the magnetic environment that trails behind the planet.
Magnetic reconnection has remained a bit of a mystery to scientists. They know it exists and have documented the effects that the energy explosions can...
Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.
Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...
Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.
In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...
On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.
When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure
Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...
09.11.2018 | Event News
06.11.2018 | Event News
23.10.2018 | Event News
16.11.2018 | Health and Medicine
16.11.2018 | Life Sciences
16.11.2018 | Life Sciences