Nearby Dwarf Galaxy Contain Surprisingly Complex Organic Molecules
Astronomers have discovered chemical indicators of methanol, dimethyl ether, and methyl formate in the Large Magellanic Cloud. These findings are the largest organic molecules ever conclusively detected outside the Milky Way.
At 158,200 light years away from Earth, the Large Magellanic Cloud (LMC) is a chemically younger place compared to the Milky Way. Thes semi-spiral collection of a few tens-of-billions of stars lacks our galaxy’s abundance of heavy elements, like carbon, oxygen, and nitrogen.
With a lack of heavy elements, astronomers predict that the LMC should contain a comparatively tiny amount of complex carbon-based molecules. Previous observations of the interstellar cloud seem to support that view.
But now, observations with the Atacama Large Millimeter/submillimeter Array (ALMA), have brought to light a discovery of clear chemical “fingerprints” of the complex organic molecules methanol, dimethyl ether, and methyl formate. Though previous observations found hints of methanol in the LMC, the latter two are unprecedented findings and stand as the most complex molecules ever conclusively detected outside of our galaxy.
The work has been published online in the journal Astrophysical Journal Letters.
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Complex organic molecules, those with six or more atoms including carbon, are some of the basic building blocks of molecules that are essential to life on Earth and in all likihood elsewhere in the universe.If these complex molecules can readily form around protostars, it’s likely that they would endure and become part of the protoplanetary disks of young star systems. Such molecules were likely delivered to the primitive Earth by comets and meteorites, helping to jumpstart the development of life on our planet.
Astronomers found the molecules’ minute millimeter-wavelength signature emanating from two dense star-forming embryos in the LMC, regions known as “hot cores.” These observations may provide insights into the formation of similarly complex organic molecules early in the history of the universe.
“Even though the Large Magellanic Cloud is one of our nearest galactic companions, we expect it should share some uncanny chemical similarity with distant, young galaxies from the early universe,” said Marta Sewiło, an astronomer with NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and lead author of the paper.
Astronomers refer to this lack of heavy elements as “low metallicity.” It takes several generations of star birth and star death to liberally seed a galaxy with heavy elements, which then get taken up in the next generation of stars and become the building blocks of new planets.
Source - ALMA Observatory
"Due to its low metallicity, the LMC offers a window into these early, adolescent galaxies."
“Due to its low metallicity, the LMC offers a window into these early, adolescent galaxies,” noted Remy Indebetouw, an astronomer at the National Radio Astronomy Observatory in Charlottesville, Virginia, and coauthor on the study. “Star-formation studies of this galaxy provide a stepping stone to understand star formation in the early universe.”The astronomers focused their study on the N113 Star Formation Region in the LMC, which is one of the galaxy’s most massive and gas-rich regions. Earlier observations of this area with NASA’s Spitzer Space Telescope and ESA’s Herschel Space Observatory showed a suprising concentration of young stellar objects, called protostars, that have just begun to heat their stellar incubators, causing them to glow brightly in infrared light.
Sewiło and her colleagues used ALMA to study several young stellar objects in this region to better understand their chemistry and dynamics
. The ALMA data surprisingly revealed the telltale spectral signatures of dimethyl ether and methyl formate, molecules that have never been detected so far from Earth.
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