Astronomers using the Mid-Infrared Instrument (MIRI) on the NASA/ESA/CSA James Webb Space Telescope have detected a variety of molecules ranging from relatively simple ones like methane to complex compounds like ethanol (alcohol) and acetic acid in interstellar ices toward one low- and one high-mass protostar: NGC 1333 IRAS 2A and IRAS 23385+6053, respectively.
This image, taken by Webb’s MIRI instrument, shows a region near the IRAS 23385+6053 protostar. Image credit: NASA / ESA / CSA / W.R.M. Rocha, LEI.
Complex organic molecules (COMs) are molecules with six atoms or more, including at least one atom of carbon.
They are intrinsically important to comprehend the chemical complexity developed in star-forming regions since these materials are the feedstock for future exoplanetary systems.
When made available in primitive planetary systems, this material can potentially promote the habitability of planets.
In a new study, Leiden University astronomers Will Rocha, Harold Linnartz and their colleagues used Webb’s Mid-Infrared Instrument to explore the COMs ice signatures in two protostars: NGC 1333 IRAS 2A and IRAS 23385+6053.
They were able to identify a variety of COMs like ethanol (alcohol) and likely acetic acid (an ingredient in vinegar).
“Our finding contributes to one of the long-standing questions in astrochemistry,” Dr. Rocha said.
“What is the origin of COMs in space? Are they made in the gas phase or in ices? The detection of COMs in ices suggests that solid-phase chemical reactions on the surfaces of cold dust grains can build complex kinds of molecules.”
“As several COMs, including those detected in the solid phase in our research, were previously detected in the warm gas phase, it is now believed that they originate from the sublimation of ices.”
“Sublimation is to change directly from a solid to a gas without becoming a liquid.”
“Therefore, detecting COMs in ices makes us hopeful about improved understanding of the origins of other, even larger molecules in space.”
This graphic shows the spectrum of the NGC 1333 IRAS 2A protostar. Image credit: NASA / ESA / CSA / Leah Hustak, STScI.
The researchers also detected simpler molecules, including formic acid, methane, formaldehyde, and sulfur dioxide.
“Sulfur-containing compounds like sulfur dioxide played an important role in driving metabolic reactions on the primitive Earth,” they said.
“Of particular interest is that one of the sources investigated, NGC 1333 IRAS 2A, is characterized as a low-mass protostar.”
“NGC 1333 IRAS 2A may be similar to the early stages of our own Solar System.”
“As such, the chemicals identified around this protostar may have been present in the first stages of development of our Solar System and later delivered to the primitive Earth.”
“All of these molecules can become part of comets and asteroids and eventually new planetary systems when the icy material is transported inward to the planet-forming disk as the protostellar system evolves,” said Dr. Ewine van Dishoeck, an astronomer at Leiden University.
“We look forward to following this astrochemical trail step-by-step with more Webb data in the coming years.”
The team’s paper was published in the journal Astronomy & Astrophysics.
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W.R.M. Rocha et al. 2024. JWST Observations of Young protoStars (JOYS+): Detecting icy complex organic molecules and ions. I. CH4, SO2, HCOO−, OCN−, H2CO, HCOOH, CH3CH2OH, CH3CHO, CH3OCHO, and CH3COOH. A&A 683, A124; doi: 10.1051/0004-6361/202348427