Four retired telescope missions are helping astronomers uncover new insights into how dust behaves in galaxies.
Astronomers say the new survey of gas and dust surrounding four galaxies, all close to our own Milky Way, will provide new insights into star formation.
“These enhanced images … show us that 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 a new tab) Thursday (June 16).
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The observations were conducted by data collected from the European Space Agency’s (ESA) Herschel Space Observatory which operated from 2009 to 2013 and detected the dust’s heat signature in the far infrared.
The scientists also incorporated data from ESA’s Planck mission, which retired in 2013, and NASA’s Infrared Astronomical Satellite and Cosmic Background Explorer missions, which operated in the 1980s and 1990s.
Although all space telescopes eventually retire due to component failure or lack of fuel, their data may persist forever, as long as the information is properly preserved in an archive. And astronomers regularly revisit this old data to calculate long-term changes in galaxies, black holes, exoplanets and other celestial objects of interest and to 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 when 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 that dust greatly affects the work of astronomers, as it absorbs light from objects scientists want to study — nearly half of the starlight in the universe, the statement said.
But dust is not always an obstacle. Because it contains a range of heavier elements, like those that form planets, studying dust can help scientists understand the evolution of the cosmos.
Data from the Herschel Observatory was particularly helpful, providing details on the structure of dust in interstellar clouds, while other telescopes filled in the gaps. And the search comes even though the Herschel Telescope, the statement said, was not designed to observe light from diffuse clouds, nor into the outer regions of galaxies where there is less gas and dust.
With 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, far exceeding past estimates. The interaction of elements between galaxies is quite complex, paving the way for future studies to focus on various processes.
“In the densest dust clouds,” the statement said, “nearly all heavy elements can be encased in dust grains, increasing the dust-to-gas ratio. But in less dense regions, radiation destroyer from infant stars or shock waves from exploding stars will break up the dust grains and return some of those heavy elements locked up in the gas, again changing the ratio.”
The findings were presented at a press conference at the American Astronomical Society’s summer meeting, held June 12-16.