Astronomers Detect Organic Molecules in Starless and Prestellar Regions of Nearby Stellar Nursery

Astronomers have detected the signatures of two complex organic molecules, methanol and acetaldehyde, in starless and prestellar cores of the Taurus Molecular Cloud, a star-forming region located about 440 light-years away from Earth in the constellation of Taurus.

An artist’s illustration of complex organic molecules in space. Image credit: Jenny Mottar / NASA.

Prestellar or starless cores are so-named because while they do not yet contain any stars, they mark regions in space where cold dust and gases coalesce into the seeds that will give rise to stars and possibly planets.

Taurus Molecular Cloud | Mt. Lemmon SkyCenter

Each core can stretch over a distance that would cover up to 1,000 solar systems lined up next to each other.

Compared to other objects in the Universe, like galaxies, they form on rather short timescales, with lifespans of less than a million years.

Driven by processes like turbulence and gravitational forces, the gas and dust in a molecular cloud collapses to form filaments, and it is within those filaments that the denser cores form.

“The Taurus Molecular Cloud is especially interesting because it provides a glimpse into different evolutionary stages between cores,” said lead author Samantha Scibelli, a doctoral student with the Steward Observatory at the University of Arizona.

“Not all cores may form stars; there is a lot of uncertainty involved. We think many of the cores are in early stages, which is why we don’t see them forming stars right now.”

Using the Arizona Radio Observatory’s 12-m dish telescope on Kitt Peak, southwest of Tucson, Scibelli and Steward Observatory astronomer Yancy Shirley conducted a large sample survey of 31 starless and prestellar cores in the Taurus Molecular Cloud.

“These starless cores we looked at are several hundred thousand years away from the initial formation of a protostar or any planets,” Dr. Shirley said.

“This tells us that the basic organic chemistry needed for life is present in the raw gas prior to the formation of stars and planets.”

The researchers looked for the tell-tale signatures of methanol (CH3OH) and acetaldehyde (CH3CHO) during an observation campaign totaling almost 500 hours of observing time.

They detecting methanol in 100% of the cores targeted and acetaldehyde in 70%.

They interpret these results as evidence that complex organic molecules are much more widespread in nascent star-forming regions than previously thought.

The findings challenge traditional theories of how prebiotic molecules form, because they assume a scenario in which the heat from newborn stars provides the necessary environment for organic molecules to form.

The abundance of complex organic molecules in clouds of extremely cold gas and dust that are still a long way away from such conditions means other processes must be at work.

“Inside these cores, which we think of as birthplaces, cocoons and nurseries of low-mass stars similar to our Sun, the conditions are such that it’s hard to even create these molecules,” Scibelli said.

“By doing surveys like this, we can understand better how precursors to life come into existence, how they migrate and enter solar systems at later stages of star formation.”

The results were published in the Astrophysical Journal.