August 16, 2014
Stubborn Stardust Mystery Could Be Solved Thanks To New Pseudo-3D Maps
redOrbit Staff & Wire Reports - Your Universe Online
Newly-created maps of the material located between the stars in the Milky Way could help astronomers solve a nearly century-long mystery involving stardust, according to a new study published in the August 15 edition of the journal Science.Researchers from the University of Ljubljana in Slovenia and Johns Hopkins University in Baltimore, along with an international team of colleagues, claim their work demonstrates a new method of uncovering the location – and ultimately, the composition of the material found in the vast expanse between star systems in a galaxy.
This expanse is known as the interstellar medium, and the material located there includes dust and gas made up of atoms and molecules that remain following the death of a star. It also supplies the building blocks for new stars and planets, Johns Hopkins professor of physics and astronomy Rosemary Wyse explained.
“There's an old saying that 'We are all stardust,' since all chemical elements heavier than helium are produced in stars,” Wyse said. “But we still don't know why stars form where they do. This study is giving us new clues about the interstellar medium out of which the stars form.”
Wyse, along with lead investigators Janez Kos and Tomaz Zwitter of the University of Ljubljana and their fellow scientists, focused on a mysterious feature in the light emanated by stars known as diffuse interstellar bands (DIBs). DIBs were discovered in 1922 by a graduate student whose photographs yielded dark lines indicating that some of the starlight was apparently being absorbed by something in the interstellar medium between Earth and that star.
While astronomers have gone on to identify over 400 diffuse interstellar bands, the materials that cause them to appear and their exact location remains unknown, the researchers explained. There has been some speculation that the absorption of starlight responsible for creating these dark bands indicates the presence of unusually large and complex molecules in the interstellar medium, but evidence to support these claims has been difficult to find.
The study authors believe it is important to determine the nature of this puzzling material because it could provide important information about the physical nature and the chemical composition on these interstellar regions. Details such as these are essential components of theories pertaining to the formation of the stars and the galaxies.
“In a completely new approach to understanding DIBs, we combined information from nearly 500,000 stellar spectra obtained by the massive spectroscopic survey RAVE (Radial Velocity Experiment) to produce the first pseudo-three-dimensional map of the strength of the DIB at 8620 angstroms covering the nearest 3 kiloparsecs from the Sun,” the authors wrote. They found that the DIB 8620 carrier has “a significantly larger vertical scale height” than the dust.
[ Watch: RAVE survey animation ]
These new pseudo-3D maps could help solve the mystery. The maps were created by a team of 23 scientists who reviewed data on 500,000 stars collected by RAVE over a 10-year period. The project also required use of the UK Schmidt Telescope in Australia to collect spectroscopic information from the light of as many as 150 stars at once.
“The maps are described as ‘pseudo-3D’ because a specific mathematical form was assumed for the distribution in the vertical dimension that provides the distances from the plane of the Milky Way, with the maps presented in the remaining two dimensions,” the university said, adding that the sample size “enabled the mapmakers to determine the distances of the material that causes the DIBs and thus how the material is distributed” throughout the galaxy.
Future research could use the techniques utilized by Wyse and her colleagues to create other maps, which should provide more insight into the mysteries surrounding DIB locations and the materials responsible for causing them. “To figure out what something is, you first have to figure out where it is, and that's what this paper does," Wyse said. “Larger surveys will provide more details in the future. This paper has demonstrated how to do that.”