An international team of astronomers has seen inside the spiral structure in the gas and dust that surrounds a newborn star for the first time.
The researchers, led by Laura Pérez from the Max Planck Institute for Radio Astronomy, observed the spiral structure, known as a spiral density wave, around Elias 2-27, a young star about half the mass of the Sun and 453 light-years from Earth.
The spiral is located 100 to 300 times further from this star than Earth is from our Sun, and the discovery could explain how planets form far away from their host star.
“The major implication of these results is that the spiral density waves we found in Elias 2-27 occur at quite large distances from the central star, providing evidence for the first time of a different process than the 'standard' picture of planet formation,” Pérez told IFLScience.
Near a star, planets form by “core accretion”, where a core grows from the accretion of smaller particles. At large distances, the dust and gas are too spread out for planets to form by core accretion, so a different mechanism is necessary.
This observation, reported in the journal Science, is the first example of an alternative system to core accretion.
In the three-decade hunt for exoplanets, humans have discovered a huge variety of systems and it has become increasingly complex to explain the variety of objects and distributions with a single formation scenario.
The Elias 2-27 seen by ALMA and where it's located. NASA/JPL-Caltech/WISE/NRAO/AUI/NSF/ALMA/L Pérez
“We know of a plethora of extrasolar planetary systems that are very different from our own Solar System,” Pérez continued.
“So I think it will not be surprising that we also find a diversity of substructure in protoplanetary disks, where the physical conditions of this disk will determine the eventual formation and architecture of its planetary system.”
The discovery was possible thanks to the power of the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, which spotted the unusual spiral features in the dusty disk. Previous observations were able to spot the disk but only the recent analyses, which were up to 1,000 times more sensitive, allowed the researchers to see the spiral structure.
Other spirals have previously been observed, but this is the first observation that looked at the internal structure of a spiral.
Spiral density waves are a common occurrence in astronomy as they create the characteristic shape we observe in spiral galaxies. Perez pointed out how remarkable it is that we see the similar mechanisms at much smaller scales.