Four retired telescope missions are helping astronomers discover new insights into how dust in galaxies behaves.
Astronomers say the new survey of gas and dust surrounding four galaxies, all near our Milky Way, will provide new information about star formation.
“These enhanced images show us that the dust ecosystems in these galaxies are very dynamic,” Christopher Clark, lead imaging team and astronomer at the Space Telescope Science Institute in Baltimore, said in a statement. (Opens in a new tab) Thursday (16 June).
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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 dust’s thermal signature in far-infrared light.
The scientists also combined data from the European Space Agency’s Planck mission, which retired in 2013, as well as NASA’s Infrared Astronomy Satellite and Cosmic Background Explorer missions, which operated in the 1980s and 1990s.
Although all space telescopes eventually retire due to component failures or lack of fuel, their data can essentially last forever, as long as the information is properly kept in the archives. Astronomers regularly revisit those old data to calculate long-term changes in galaxies, black holes, exoplanets and other celestial bodies 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 varies between galaxies, as well as within a single galaxy. Dust forms when dying stars eject layers of gas, and its trajectory can be altered by pressure waves from exploding stars, running winds from energetic stars and gravitational influences from other objects.
All that dust greatly affects the work of astronomers, because it absorbs light from the things scientists want to study — nearly half of the starlight in the universe, according to the statement.
But dust isn’t always a hindrance. Because it contains a host of heavier elements, such as those that make up planets, studying dust can help scientists understand the evolution of the universe.
Data from the Herschel Observatory has been particularly useful, providing details of how dust forms within interstellar clouds, as other telescopes fill in the gaps. The research comes even though the Herschel telescope, the statement said, was not designed to look at light from scattered clouds, nor into the outer regions of galaxies where there is less gas and dust.
With data from the quartet of observatories combined, astronomers estimated that the ratio of dust to gas in a single galaxy could vary by a factor of 20, exceeding previous estimates. The interaction of elements between galaxies is very complex, which points the way for future studies to magnify the various processes.
“In denser dust clouds, nearly all of the heavy elements can be trapped in the dust grains, increasing the dust-to-gas ratio. But in less dense regions, destructive radiation from newborn stars or shock waves,” the statement said. From exploding stars it will crush grains of dust and return some of those trapped heavy elements back into the gas, changing the ratio again. “
The results were presented at a press conference at the summer meeting of the American Astronomical Society, which took place June 12-16.
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