Cosmic birth: Congratulations, it’s a planet

Birth is always an amazing, powerful event. If people pass out and cry at a single human birth, imagine what they’d do if they’d learn that at this moment we’re watching the birth of an entire solar system for the first time.

The Atacama Large Millimeter/submillimeter Array (ALMA) is an array of international antennae in Chile. North America joined the array back in 2009. With 66 antennae in formation, the observatory mainly watches star and planet formation. The astronomers in Chile, led by Simon Casassus, studied a young two million year-old star  about 450 light years from Earth named HD 142527.

Gas and cosmic dust beginning to surround a young star. Image from NBC News.
Gas and cosmic dust beginning to surround a young star. Image from NBC News.

Stars form in massive clouds of dust and gas. The gravitational pull may eventually grow strong enough to collapse these clouds and form the core of what will one day become a star, and what components from the cloud aren’t taken up expand into a disk to continue feeding it throughout its growth and form planets.  HD 142527’s growth slows down as it approaches maturity. Right now, it’s about twice the size of our sun and surrounded by a disk of dust and gas leftover from its birth, from which baby planets broke into an inner and outer disk.

Until now, scientists never witnessed the early stages of a new planet, called a planetesimal. Specifically, they never saw the crucial step they’re witnessing now. Planetesimals form from the disk around a parent star and pull in nearby gas and dust with their gravity, increasing their mass and leaving long gaps in the disk. By measuring the gap around HD 142527, scientists believe several planetesimals dwell near the star.

With the planetesimals between separating the star and the outer disk, debris must be channeled by the baby planets in order to maintain the star’s growth for now. Once the channels run out, the planets will arrange themselves and settle into their places as fully-functioning members of a solar system.