Four retired telescope missions are helping astronomers discover new insights into how dust behaves in galaxies.
Astronomers say the new survey of gas and dust around four galaxies, all close to our Milky Way, will provide new insights into star formation.
“These enhanced images show us that the dust ‘ecosystems’ in these galaxies are very dynamic,” Christopher Clark, imaging team leader and astronomer at the Space Science Telescope Institute in Baltimore, said in a statement. (opens in new tab) Thursday (June 16th).
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The observations were led by data collected from the European Space Agency’s (ESA) Herschel Space Observatory, which operated from 2009 to 2013 and detected the thermal signature of dust in far-infrared light.
Scientists also incorporated data from ESA’s Planck mission, which retired in 2013, as well as NASA’s Infrared Astronomical Satellite and Cosmic Background Explorer missions, which operated in the 1980s and 1990s.
While all space telescopes eventually retire due to component failures or a lack of fuel, their data can essentially persist forever as long as the information is properly maintained in a file. And astronomers regularly revisit this old data to calculate long-term changes in galaxies, black holes, exoplanets and other celestial objects of interest and apply new analysis techniques.
The newly produced images focus on interstellar dust and gas to learn more about how the density of dust clouds can vary between galaxies as well as within a single galaxy. Dust forms as dying stars eject layers of gas, and its path can be altered by pressure waves from exploding stars, continuous winds from active stars, and gravitational effects from other objects.
All this dust greatly affects the work of astronomers, as it absorbs light from the objects that scientists want to study — nearly half of the starlight in the universe, according to the statement.
But dust is not always an obstacle. Because it contains a number of heavier elements, such as those that form planets, studying dust can help scientists understand the evolution of the cosmos.
The data from the Herschel observatory was particularly useful, providing details on how dust is structured in interstellar clouds, while other telescopes filled in the gaps. And the research takes place even though the Herschel telescope, according to the statement, was not designed to observe light from diffuse clouds, nor in the outer regions of galaxies, where there is less gas and dust present.
With the data from the quartet of observatories combined, astronomers have estimated that the dust-to-gas ratio in a single galaxy can vary by a factor of 20, which far exceeds previous estimates. The interaction of elements between galaxies is quite complex, pointing the way for future studies to amplify several processes.
“In denser dust clouds,” the statement said, “almost all heavy elements can become trapped in dust grains, which increases the dust-to-gas ratio. But in less dense regions, destructive radiation from newly formed stars -born or shock waves from exploding stars will crush the dust grains and return some of those trapped heavy elements back into the gas, changing the ratio yet again.”
The results were presented at a press conference at the American Astronomical Society’s summer meeting, held June 12-16.