The map shows the inner part of the Milky Way has two prominent, symmetric spiral arms, which extend into the outer galaxy where they branch into four spiral arms.
“For the first time these arms are mapped over the entire Milky Way,” said Pohl, an Iowa State associate professor of physics and astronomy. “The branching of two of the arms may explain why previous studies – using mainly the inner or mainly the outer galaxy – have found conflicting numbers of spiral arms.”
The new map was developed by Pohl, Peter Englmaier of the University of Zurich in Switzerland and Nicolai Bissantz of Ruhr-University in Bochum, Germany.
As the sun and other stars revolve around the center of the Milky Way, researchers cannot see the spiral arms directly, but have to rely on indirect evidence to find them. In the visible light, the Milky Way appears as an irregular, densely populated strip of stars. Dark clouds of dust obscure the galaxy’s central region so it cannot be observed in visible light.
The National Aeronautics and Space Administration’s Cosmic Background Explorer satellite was able to map the Milky Way in infrared light using an instrument called the Diffuse IR Background Experiment. The infrared light makes the dust clouds almost fully transparent.
Englmaier and Bissantz used the infrared data from the satellite to develop a kinematic model of gas flow in the inner galaxy. Pohl used the model to reconstruct the distribution of molecular gas in the galaxy. And that led to the researchers’ map of the galaxy’s spiral arms.
The Milky Way is the best studied galaxy in the universe because other galaxies are too far away for detailed observations. And so studies of the galaxy are an important reference point for the interpretation of other galaxies.
Astrophysicists know that the stars in the Milky Way are distributed as a disk with a central bulge dominated by a long bar-shaped arrangement of stars. Outside this central area, stars are located along spiral arms.
In addition to the two main spiral arms in the inner galaxy, two weaker arms exist. These arms end about 10,000 light-years from the galaxy’s center. (The sun is located about 25,000 light-years from the galactic center.) One of these arms has been known for a long time, but has always been a mystery because of its large deviation from circular motion. The new model explains the deviation as a result of alternations to its orbit caused by the bar’s gravitational pull. The other, symmetric arm on the far side of the galaxy was recently found in gas data.
The discovery of this second arm was a great relief for Englmaier: “Finally it is clear that our model assumption of symmetry was correct and the inner galaxy is indeed quite symmetric in structure.”
Other scientific groups are already interested in using the new map for their research. A group from France, for example, hopes to use it in their search for dark matter.
Mike Krapfl | Newswise Science News
From rocks in Colorado, evidence of a 'chaotic solar system'
23.02.2017 | University of Wisconsin-Madison
Prediction: More gas-giants will be found orbiting Sun-like stars
22.02.2017 | Carnegie Institution for Science
On January 15, 2009, Chesley B. Sullenberger was celebrated world-wide: after the two engines had failed due to bird strike, he and his flight crew succeeded after a glide flight with an Airbus A320 in ditching on the Hudson River. All 155 people on board were saved.
On January 15, 2009, Chesley B. Sullenberger was celebrated world-wide: after the two engines had failed due to bird strike, he and his flight crew succeeded...
Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...
The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.
The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...
Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...
13.02.2017 | Event News
10.02.2017 | Event News
09.02.2017 | Event News
27.02.2017 | Materials Sciences
27.02.2017 | Interdisciplinary Research
27.02.2017 | Life Sciences