Milky Way's mystery matter mapped: Scientists produce interactive 'guide' to help unravel secrets of strange interstellar molecules
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They are some of the most mysterious objects in our galaxy and have baffled astronomers for years.
Now scientists have produced a new detailed map that they hope will help to unravel what is floating in the space between the stars and absorbing some of the light they produce.
It had long been assumed that there was little sitting in the vacuum that exists between the billions of stars in the Milky Way.
Scroll down for interactive graphic and video
The pattern of mysterious molecules in relation to the stars and dust of the Milky Way is shown in the graphic above. Red shows the greatest concentrations of these molecules in the dustiest areas of our galaxy while blue denotes the lowest concentrations on the fringes
However, astronomers began to notice that the light coming from some of the stars in the Milky Way was being interfered with to produce distinct lines.
These became known as 'Diffuse Interstellar Bands' and are thought to be caused by the absorption of light by molecules floating around in the space between the stars.
Some have speculated that this 'interstellar medium' was composed of unusual rings of complex hydrocarbons and other large carbon-based molecules, but it has never been proved.
Now two teams at the John Hopkins University, in Baltimore, Maryland, have created a map that shows where these enigmatic molecules can be found in relation to the stars.
'These results will guide researchers toward the best observations and laboratory experiments to pin down the properties and nature of these enigmatic molecules,' said Ting-Wen Lan, who led one of the teams that compiled the map.
The interactive map above was produced by the team at John Hopkins University and allows the location of diffuse interstellar bands to be shown alongside the stars in the Milky Way or other features such as interstellar dust by dragging the bar in the top right corner or using the up or down cursor on your keyboard
The researchers created the map using huge volumes of data obtained during extensive surveys of the night's sky, such as from the Sloan Digital Sky Survey.
One group focused on the densest parts of the Milky Way using infrared observations that can cut through the dust clouds that obscure many of the stars there.
The other group analysed the visible light from half a million stars, galaxies and quasars located on the fringes of our galaxy.
Here the diffuse interstellar bands are harder to detect, but the researchers were able to see patterns in the type of environments where they are more likely to come from.
The light from the Milky Way, shown above, is concentrated along a plane and this is where most diffuse interstellar bands are detected
The researchers also looked at the interstellar dust that exists to see if this could provide clues about what the mystery molecules are
While molecules that absorb light in one way tended to be found in the densest regions of gas and dust, others were found in lonelier spots far away from stars.
This suggests that rather than being a random jumble of different molecules, the molecules in interstellar space are more organised than previously thought.
The team also found mysterious features in front of around 60,000 stars and were able to measure the motion of some of these.
The resulting map allows the location of the diffuse interstellar band to be seen alongside the Milky Way's stars and also shows where concentrations of molecules such as hydrogen,
Gail Zasowski, who led the second team that helped compile the map, said: 'For the first time, we can see how these mysterious molecules are moving around the galaxy.
'This is extremely useful and brings in new connections between these molecules and the dynamics of the Milky Way.'
Diffuse interstellar bands were first detected in 1922 by astronomer Mary Lea Heger at the Lick Observatory, in California.
While analyzing the light from stars, she found unexpected lines that were created by something existing in the interstellar space between the stars and the Earth.
Professor Brice Ménard, who oversaw the project at the department of physics and astronomy at Johns Hopkins University, said that while the map gave the most complete view so far of where the molecules that cause diffuse interstellar bands can be found, it was far from complete.
He said: 'Seeing where these mysterious molecules are located is fascinating.'
'We do not have a full map yet, but we can already see a lot of interesting patterns.
'Almost a hundred years after their discovery, the exact nature of these molecules still remains a mystery, but we are getting one step closer to understanding what they are made of.'
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