Inside the swirling cloud of gas and dust that surrounds a newborn star, scientists say they've found an organic molecule that's a very early ingredient for life.
It's the gaseous form of methanol, a relatively large and complex organic compound that is needed to make things like amino acids, which in turn are used to build proteins. And that swirling cloud isn't just any old mess of mass — it's a protoplanetary disc, the cluster of matter from which planets form, surrounding a star that looks very much like our own Sun would have in its youth.
The discovery "proves there's definitely complexity that we can see around a very young star ... and its some of the same chemical components we see in our solar system," said Ryan A. Loomis, a graduate student at the Harvard-Smithsonian Center for Astrophysics and co-author of a report on the find in the Astrophysical Journal.
The newborn star in question, TW Hydrae, is of particular interest to scientists because it's so nearby and so closely resembles a 4-billion-years-younger version of the Sun. The orange dwarf star is about 176 lightyears from Earth and roughly 10 million years old — a mere infant in cosmic terms.
That makes it an excellent window into the early stages of our own solar system, Loomis explained. As it stands, the vast majority of what we know about the solar system 4 billion years ago comes from comets and meteorites, which act as geological time capsules from that era. Their composition attests to the molecules that were around at the time.
"What we know right now ... is kind of like paleontology," Loomis said. By comparison, examining TW Hydrae is like traveling back in time.
Working with the world's most powerful telescope — the Atacama Large Milimeter/submillimeter Array, in Chile — Loomis and his colleagues parsed the microwave emissions coming from the protoplanetary disc around TW Hydrae in search of a particular frequency characteristic of methanol molecules. They found it, in spades.
"It’s not coming from just one or two molecules it's coming from a very large collection of them," Loomis said.
This is the first time methanol has been detected in a protoplanetary disc.
Because the molecule can only form as a solid, rather than in the gas phase, the researchers believe that the molecules must be forming in the ice that coats the very tiny dust particles making up the protoplanetary disc. If they found signatures of a great deal of methanol gas in the disc, then there must be even more of those molecules locked up in the ice.
"That's really important, because these dust grains are going to be the particles that collide and come together to form the planetesimals and comets," he said. "And we know from comets in our own system ... they're going to have methanol as one of their components."
That's significant, the researchers say, because it helps connect the dots of comet and planet formation, linking this very early dust cloud stage to what we see in our solar system today. It also indicates that the chemistry of our corner of the universe isn't unique when it comes to creating the early ingredients for life.
The detection of methanol is still a very long way away from finding living things outside our solar system, Loomis cautioned.
"These aren't prebiotic molecules," he said. "But the precursors are there." And that's a start.