4 dead telescopes' observations lead to stunning new galaxy portraits

A spiral galaxy
The Andromeda galaxy, or M31, is shown here in far-infrared and radio wavelengths of light. (Image credit: ESA, NASA, NASA-JPL, Caltech, Christopher Clark (STScI), R. Braun (SKA Observatory), C. Nieten (MPI Radioastronomie), Matt Smith (Cardiff University))

Four retired telescope missions are helping astronomers uncover new insights about how dust behaves in galaxies.

Astronomers say that the fresh survey of gas and dust surrounding four galaxies, all near our own Milky Way, will provide new information about star formation.

"These improved ... images show us that the dust 'ecosystems' in these galaxies are very dynamic," Christopher Clark, the imaging team lead and an astronomer at the Space Science Telescope Institute in Baltimore, said in a statement (opens in new tab) Thursday (June 16).

Related: The best Hubble Space Telescope images of all time!

The observations were led by data collected from the European Space Agency (ESA)'s Herschel Space Observatory that operated from 2009 to 2013 and detected the thermal signature of dust in far infrared light. 

The 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 '90s.

The Triangulum galaxy, or M33, is shown here in far-infrared and radio wavelengths of light.  (Image credit: ESA, NASA, NASA-JPL, Caltech, Christopher Clark (STScI), E. Koch (University of Alberta), C. Druard (University of Bordeaux))

Although all space telescopes retire eventually due to component failure or a lack of fuel, their data can persist essentially forever, as long as information is properly maintained in an archive. And astronomers regularly revisit that 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 as dying stars eject layers of gas, and its path can be altered by the pressure waves from exploding stars, ongoing winds from active stars and gravitational effects from other objects.

The Small Magellanic Cloud, which neighbors the Milky Way, as seen by the Herschel mission with help from three other retired space telescopes. (Image credit: ESA, NASA, NASA-JPL, Caltech, Christopher Clark (STScI), S. Stanimirovic (UW-Madison), N. Mizuno (Nagoya University))

All that dust greatly affects astronomers' work, since it absorbs light from the objects scientists want to study — nearly half of the universe's starlight, according to the statement.

But dust isn't always a hindrance. Because it contains a range of heavier elements, like those that form planets, studying dust can help scientists understand the evolution of the cosmos.

The Large Magellanic Cloud (LMC) in a far-infrared and radio wavelength view. (Image credit: ESA, NASA, NASA-JPL, Caltech, Christopher Clark (STScI), S. Kim (Sejong University), T. Wong (UIUC))

Data from the Herschel observatory was particularly helpful, providing details on how dust is structured within interstellar clouds, while other telescopes filled in gaps. And the research comes even though the Herschel telescope, the statement said, was not designed to look at light from diffuse clouds, nor in the outer regions of galaxies where there is less gas and dust present.

With data from the quartet of observatories combined, astronomers estimated that the dust-to-gas ratio in a single galaxy may vary by a factor of 20, which exceeds by far past estimates. The interplay of elements between galaxies is quite complex, pointing the way for future studies to zoom in on various processes.

"In the densest dust clouds," the statement said, "almost all the heavy elements can get locked up in dust grains, which increases the dust-to-gas ratio. But in less dense regions, the destructive radiation from newborn stars or shockwaves from exploding stars will smash the dust grains and return some of those locked-up heavy elements back into the gas, changing the ratio once again."

The results were featured in a press conference at the summer meeting of the American Astronomical Society, held between June 12 and 16.

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Elizabeth Howell
Staff Writer, Spaceflight

Elizabeth Howell, Ph.D., is a staff writer in the spaceflight channel since 2022. She was contributing writer for Space.com (opens in new tab) for 10 years before that, since 2012. Elizabeth's reporting includes an exclusive with Office of the Vice-President of the United States, speaking several times with the International Space Station, witnessing five human spaceflight launches on two continents, working inside a spacesuit, and participating in a simulated Mars mission. Her latest book, "Why Am I Taller?", is co-written with astronaut Dave Williams. Elizabeth holds a Ph.D. and M.Sc. in Space Studies from the University of North Dakota, a Bachelor of Journalism from Canada's Carleton University and (soon) a Bachelor of History from Athabasca University. Elizabeth is also a post-secondary instructor in communications and science since 2015. Elizabeth first got interested in space after watching the movie Apollo 13 in 1996, and still wants to be an astronaut someday. Mastodon: https://qoto.org/@howellspace