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article imageInfant star's molecules suggest life's chemistry universal

By Robert Myles     Apr 8, 2015 in Science
Munich - Using the Chile-based European Southern Observatory’s (ESO) Atacama Large Millimeter/submillimeter Array (ALMA), astronomers have detected the presence of the building blocks of life in an infant star system for the first time.
The discovery of complex organic molecules in material surrounding the infant star MWC 480 points to conditions for the chemistry of life to exist being universal, although such a precursor to life would not, in all cases mean that life itself would subsequently develop.
Using the Chile-based European Southern Observatory’s (ESO) Atacama Large Millimeter/submillimeter Array (ALMA), astronomers detected the presence of complex organic molecules in the protoplanetary disc — material that in the course of time will coagulate to form planets — surrounding a star in its early stages of formation. The discovery will lend further weight to the belief that the conditions that gave birth our Sun and the Earth are by no means unique in the Universe.
With the aid of ALMA, an international team of astronomers examined the nascent star system MWC 480, reckoned to be only about one million years old. The Sun, by comparison, is more than four billion years old. The name MWC 480 is derived from the Mount Wilson Catalog of B and A stars with bright hydrogen lines in their spectra.
The team discovered large amounts of methyl cyanide (CH3CN), a complex carbon-based molecule, in the dust and debris orbiting MWC 480. They estimate there to be enough methyl cyanide circling MWC 480 to fill all of Earth’s oceans.
ALMA can detect the faint millimeter-wavelength radiation naturally emitted by molecules in space. For these most recent observations, researchers used only a portion of ALMA’s 66 antennae when the telescope was in its lower-resolution configuration. Using ALMA’s full capabilities astronomers hope will reveal additional details about the chemical and structural evolution of MWC 480’s protoplanetary disc and that of other young stars and planets.
Both methyl cyanide and another, less complex organic molecule, hydrogen cyanide (HCN) were found in the cold outer reaches of the young star’s newly formed disc. Astronomers believe the location where these organic molecules were found is analogous to our own solar system’s Kuiper Belt. The Kuiper Belt is a region of our solar system beyond the orbit of Neptune containing thousands upon thousands of minute, very cold objects called planetesimals as well as being the realm of comets that occasional wander into the solar system’s inner reaches.
Comets are the USB flash drives of our solar system. They contain a pristine record of the chemistry of the earlier solar system dating from its earliest days when the planets formed. It’s thought comets and asteroids from our solar system’s outer reaches may have seeded Earth, in the earliest times, with water and organic molecules. In so doing, comets were the fertilisers of life on Earth, bringing about the conditions suitable for the development of primordial life.
“Studies of comets and asteroids show that the solar nebula that spawned the Sun and planets was rich in water and complex organic compounds,” explained Karin Öberg, an astronomer with the Harvard-Smithsonian Center for Astrophysics, and lead author of the new paper.
“We now have even better evidence that this same chemistry exists elsewhere in the Universe, in regions that could form solar systems not unlike our own,” she added.
What was particularly intriguing, Öberg noted, was that the molecules found in MWC 480 are also found in similar concentrations in the comets of our solar system.
Astronomers put the size of MWC 480 at about twice that of the Sun. The young star is located 455 light-years from Earth in the Taurus star-forming region.
MWC 480’s surrounding protoplanetary disc is in the very early stages of development, having coalesced from a cold dark nebula of dust and gas. As yet, astronomers have not detected obvious signs of planetary formation within MWC 480’s ring of planetary material but using ALMA’s fuller resolution capabilities may reveal structures similar to the planetary genesis ESO earlier detected from observing another young star, HL Tauri, a system of about the same age as MWC 480.
For some time, astronomers have been aware that, in space, cold, dark, interstellar clouds exist that operate as highly efficient factories for the production of complex organic molecules, including the cyanide family of molecules.
Cyanides, and especially methyl cyanide, play a vital role in how life has come to evolve since they contain carbon-nitrogen bonds. These carbon-nitrogen bonds are essential to the formation of amino acids, which in turn provide the foundations for proteins and the building blocks of life.
But although complex organic molecules were known to exist in the cold, “empty” vastness of space, up till now it wasn’t clear whether these same complex organic molecules could form and survive in the much more frenetic environment associated with newly forming star systems, an environment where shocks and radiation bombardment might easily tear asunder chemical bonds, pulverising these building blocks of life before life even had a chance to develop.
Using ALMA’s sensitivity in detecting faint millimeter-wavelength radiation, researchers established not only that these molecules survived but that they were flourishing. Significantly, Alma scientists found that complex organic molecules in the young MWC 480 system existed in much greater abundance than was the case with interstellar clouds. What this establishes is that far from protoplanetary discs operating as a hostile environment for life to develop, instead, they are very efficient in forming complex organic molecules. In addition, these molecules appear to be formed on relatively short timescales.
This speed of formation is crucial if life is to have a chance to develop. If the pace of molecule formation were slower then forces, such as radiation, would simply break the molecules apart, meaning life would have no chance to develop. The area the molecules were found may also be a factor in ensuring their survival.
Researchers detected complex organic molecules in a relatively tranquil portion of MWC 480’s protoplanetary disc about 4.5 to 15 billion kilometres from the parent star. Compared to our solar system, that’s some way out from the parent star but, scaling up MWC 480’s dimensions puts the area where the molecules were detected slap bang in the middle of what would be MWC 480’s comet-forming zone.
As system MWC 480 continue to evolve, so the theory goes that these organic molecules presently stored far from the stellar centre, would, in the course of time, hitch a lift on comets and other icy bodies and so be transported to inner planets yet to be formed. After cometary bombardment of these planets, some of which might contain the conditions where life could evolve, these complex organic molecules would then provide the ignition spark from which living organisms would eventually develop.
“From the study of exoplanets, we know the Solar System isn’t unique in its number of planets or abundance of water,” commented Öberg, adding, “Now we know we’re not unique in organic chemistry. Once more, we have learnt that we’re not special. From a life in the Universe point of view, this is great news.”
The results, presented in a paper titled, “The Cometary Composition of a Protoplanetary Disk as Revealed by Complex Cyanides,” are published in the April 9 issue of the journal Nature.
More about complex organic molecules, origin of life, building blocks for life, Amino acids, how life started
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