Discovering the origin of life depends on our understanding of how, when, and where complex molecules form in the universe.

New observations by the Atacama Large Millimeter/submillimeter Array (ALMA) show that when stars begin to form, they are already surrounded by intricate chemicals – an indication that organic molecules were transported from interstellar space.

Now, an international team led by Yoko Oya, a graduate student from the University of Tokyo, has studied a solar-type protostar called IRAS 16293-2422A. The astronomers observed a ring structure 7.5 billion kilometers (4.7 billion miles) away that shows carbonyl sulfide (OCS) molecules spiraling in towards a more compact region rich in methanol (CH₃OH) and methyl formate (HCOOCH₃), a non-toxic chemical that smells of lemon.

"When we measured the motion of the gas containing methyl formate by using the Doppler effect, we found a clear rotation motion specific to the ring structure," Oya said in a statement.

Although the researchers observed the molecules distributed in rotating rings, they were not able to resolve the most detailed structure. These complex molecules are trapped within the so-called centrifugal barrier, a separation zone where the infalling interstellar gas "slams" into the spinning protoplanetary disk.

In the paper, published in the Astrophysical Journal, the team reports how this centrifugal barrier could play a crucial role in the chemical enrichment of the protoplanetary disk. Complex molecules are carried by ice and dust grains that melt due to both the heat from the young star as well as the accretion shocks found at the centrifugal barrier. More detailed observations are necessary to understand the exact intensity of the different forces.

The team has previously found a similar ring structure around another Solar-type protostar L1527, with a flow of complex molecules coming from beyond the star system and a ring of sulfur monoxide at the centrifugal barrier.

Considering the two findings together, the abundance of life-supporting molecules might be different from star to star, and it is necessary to include a higher level of complexity when we consider the origin of the Solar System. This "lemon-smelling" star might have given us a big clue on where life comes from.