An article published in the journal “Science” describes a research about the structure around the young star Elias 2-27. A team led by astronomer Laura Perez of the Max Planck Institute for Radio Astronomy in Bonn, Germany, used the ALMA radio telescope to detect the spiral-shaped structure around the star, the first of its kind ever observed.

Elias 2-27 is a star with an estimated age of just a million years, practically a baby in astronomical terms, about 450 light-years away from Earth. As is normal for a star so young, it’s surrounded by a protoplanetary disk which turned out to be really massive considering that Elias 2-27’s mass is about half the Sun’s.

That’s not an isolated solar system in formation because Elias 2-27 is a member of a much wider star-forming region called rho-Ophiuchus. It’s very interesting to study because there are several possible mechanisms that lead to the formation of planets from smaller particles.

The dust disk around the star Elias 2-27 extends beyond the equivalent of Neptune’s orbit. Beyond the disk, the ALMA radio telescope identified a dark band which suggests a reduced presence of dust. In that area, there might be a planet in formation. But the real peculiarity is that from there two spiral arms extend that reach more than 10 billion kilometers (almost 6 billion miles) from Elias 2-27.

The spiral arms resemble those of galaxies which are the best known. The ones found in the protoplanetary disk are the first direct evidence of density waves that cause a shock inside it. They show that density instabilities are possible within the disk and they may lead to planet formation.

If the protoplanetary disk was too homogenous, it would be stable so the formation of any little bodies would be very slow. Only when bodies of at least one meter (a little more than 3′) size start forming the instabilities that can speed up the birth of the planets can be generated. This leads scientists to wonder whether density waves are the result of planet formation or their cause.

The ALMA radio telescope, inaugurated in March 2013, allowed to perform much more detailed observations than those possible in the past with other, less sensitive, instruments. However, this research is only the beginning because more studies are needed to understand the mechanisms in place in the spiral arms of protoplanetary disks such as the one around the star Elias 2-27.