Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have uncovered chemical ‘fingerprints’ of three complex organic molecules — methanol (CH3OH), dimethyl ether (CH3OCH3) and methyl formate (CH3OCHO) in the Large Magellanic Cloud, a satellite galaxy to our Milky Way Galaxy. The latter two molecules are the largest organic molecules ever conclusively detected outside the Milky Way.
ALMA detected methanol, dimethyl ether, and methyl formate in the Large Magellanic Cloud. The far-infrared image on the left shows the full galaxy. The zoom-in image shows the star-forming region observed by ALMA. It is a combination of mid-infrared data from Spitzer and visible (H-alpha) data from the Blanco 4-m telescope. Image credit: NRAO / AUI / NSF / ALMA / ESO / NAOJ / Herschel / ESA / NASA / JPL-Caltech / NOAO.
NASA astronomer Marta Sewiło and co-authors discovered the complex organic molecules’ faint millimeter-wavelength ‘glow’ emanating from two dense star-forming embryos in the Large Magellanic Cloud, regions known as ‘hot cores.’
“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 — presumably — elsewhere in the Universe,” the astronomers explained.
“Though methanol is a relatively simple compound compared to other organic molecules, it nonetheless is essential to the formation of more complex organic molecules, like those that ALMA observed, among others.”
“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.”
Dr. Sewiło and her colleagues focused their study on the N113 star-forming region in the Large Magellanic Cloud, 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 revealed a startling concentration of protostars that have just begun to heat their stellar nurseries, causing them to glow brightly in infrared light.
At least a portion of this star formation is due to a domino-like effect, where the formation of massive stars triggers the formation of other stars in the same general vicinity.
The scientists used ALMA to study several young stellar objects in this region to better understand their chemistry and dynamics.
“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,” Dr. Sewiło said.
“Young, primordial galaxies simply didn’t have enough time to become so chemically enriched.”
“Dwarf galaxies like the Large Magellanic Cloud probably retained this same youthful makeup because of their relatively low masses, which severely throttles back the pace of star formation.”
“Due to its low metallicity, the Large Magellanic Cloud offers a window into these early, adolescent galaxies,” said co-author Dr. Remy Indebetouw, from the National Radio Astronomy Observatory.
“Star-formation studies of this galaxy provide a stepping stone to understand star formation in the early Universe.”
The findings are published in the Astrophysical Journal Letters.
_____
Marta Sewiło et al. 2018. The Detection of Hot Cores and Complex Organic Molecules in the Large Magellanic Cloud. ApJL 853, L19; doi: 10.3847/2041-8213/aaa079
