Far away, in a starless core that scientists call Lynds 1521E, they have discovered complex organic molecules.
Starless cores are among the darkest, coldest, and densest regions in our galaxy to search for signs of star formation. These regions lie within interstellar molecular clouds.
Typical stars like our Sun begin life as dense, but relatively low-mass concentrations of hydrogen, helium, and other trace elements inside large molecular clouds. After the initial kernel emerges from the surrounding gas, matter collapses under gravity into the central region in a relatively ordered fashion via a swirling accretion disk, where eventually planets can form. After enough mass accumulates, nuclear fusion begins at the core and a star is born.
Astronomers have used the ARO 12-m telescope to analyze the young starless core. And the study resulted in the detection of complex organic molecules there.
Determining the level of chemical complexity within dense starless and gravitationally bound prestellar cores is crucial for constructing chemical models, which subsequently constrain the initial chemical conditions of star formation. These regions represent the earliest observable stage of low-mass star formation.
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The new study shows that even in such cold environments, complex organic molecules can be present. Finding these molecules in starless cores could help us better understand the processes of stellar formation and evolution.
Lynds 1521E is a dynamically and chemically young starless core in the Taurus Molecular Cloud. It’s one of the two known in this cloud.
This region has a humble density of around 200,000-300,000 cm−3. Astronomers assume it can only have existed at its present density for less than 100,000 years. This makes it one of the youngest starless cores so far detected and obviously an excellent region to study how complex organic molecules form.
Therefore, a group of astronomers, led by Samantha Thavasa at the University of Arizona, used the Arizona Radio Observatory (ARO) 12-meter telescope to search for complex organic molecules in the Lynds 1521E.
“Molecular line observations were made with the ARO 12m telescope during three separate seasons, two years apart, using two different backend receivers. The first observing shifts between January 12, 2017, and April 27, 2017, with 10 tunings between 84 and 102 GHz (3.6 − 2.9mm),” the researchers explained.
The observations detected dimethyl ether (CH3OCH3), methyl formate (HCOOCH3), and vinyl cyanide (CH2CHCN). Additionally, the study identified eight transitions of acetaldehyde (CH3CHO) and seven transitions of vinyl cyanide.
The analysis confirmed that the estimated chemical age of Lynds 1521E is pretty young. Complex organic molecules there, first peak at about 60,000 years. This is consistent with the carbon monoxide (CO) depletion age of this starless core.
The study members suggest the detected abundances of complex organic molecules for Lynds 1521E are in general underestimated. This suggests that a desorption mechanism is missing. Or maybe further studies need to revise the current description of the already considered mechanisms.
On the whole, the outcome obtained by the group appears to suggest that complex organic molecules found in cold gas formed not only in gas-phase reactions but also on surfaces of interstellar grains. The new findings could also have implications for future analyses of starless cores.
The detection of a rich complex organic molecules chemistry in the young, cold core Lynds 1521E presents an interesting challenge for future modeling eﬀorts, requiring some type of uniﬁed approach combining cosmic-ray chemistry, reactive desorption, and non-diﬀusive surface reactions, the astronomers concluded.
Astronomers detailed the finding in a paper on April 15 on the arXiv pre-print repository.