One of the things we talk about is planet formation. Or, more importantly, how we really don’t understand planetary formation. Part of the problem is, we only had one example of a solar system for the nearly 400 years between when Galileo started making scientific observations and when 51 Peg was discovered to have a planet in 1995. Four-hundred years is a lot of years during which theorists could theorize about how to create solar systems just like our own. In the years since extrasolar planets were discovered, people have flailed about trying to explain the great diversity of solar systems we are now finding.
Along the way, lots of contradictory ideas have been put forward. Part of the problem is we don’t have a lot of data to describe the in between steps in solar system formation. We see the big picture of star forming regions becoming star clusters. We see the proplyd step, where baby solar systems are cocooned in gas and dust. With radio telescopes we have started to see disks with what we think are forming planets. With missions like Kepler, we see fully formed solar systems in every possible configuration. What we haven’t had are observations of the intermediate step between proplyd and planetary disk.
At least we haven’t had them until now.
A team of observers using the Very Large Array and the Atacama Large Millimeter Array have now observed more than 300 baby planet forming disks that are just starting to spin up. All these systems are part of the Great Orion Star Forming Region. As astronomers, we will often say things like “all the stars in a star cluster form at the same time” but the truth is, they may gradually come into existence over a million or millions of years, which from the perspective of cosmic time and stellar evolution is only a moment. From the perspective of planet formation, however, a difference of a million years can be the difference between no planets and a mostly-finished solar system. Only by looking at many different young systems did this team have any possibility of catching systems in the act of just starting to form worlds.
Out of their collection of more than 300 systems, the research team identified 4 protostars just starting to turn on; systems estimated to be less than 10,000 years old. These system’s stars have just started to form, and have slow moving jets, and they appear irregular and blobby in radio light. According to team researcher Nicole Karnath, “We think that they are in one of the earliest stages of star formation.” By studying these stars we can begin to build a detailed film of what star systems look like during a new stage of their development.
While it may seem like a waste to observe more than 300 systems to find just 4 special systems, we want to assure you that no piece of data in this survey will go unused. This work has already produced 2 new papers appearing in the Astrophysical Journal, and has detailed how the size of protoplanetary disks evolves as the forming star in each system grows by stealing material away from the disk. It’s literally a star eat planet-forming material universe out there.
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