Ground-breaking observations have been reported by an international team of astronomers, who is the first to witness the formation of a multiple-star system in its earliest stage. Stella Offner, an astrophysicist from the University of Massachusetts Amherst, had already created model predictions about the way a two- and three-star system forms, and this discovery proves them right.
In an article published in the latest issue of the Nature journal, a team of astronomers from England and United States, led by first time author Jaime Pineda from the Institute for Astronomy at ETH Zurich, talk about the importance of understanding the reasons and the means of the formation of multiple-star systems, because it sheds a clearer light on various phenomena, like planet frequency, star and planet formation and, most importantly, habitability.
Never before has the earliest stage of star formation been so clearly observed, because crucial processes such as determining the number of stars are usually covered in thick waves of dust and gas, making it impossible to study what is happening underneath.
Offner explains how the new studies can help describe how and why some of the pre-stellar gas condensations turn out as binary or multi-star systems, while some cause the formation of systems with only one star, such as ours. Almost half of the existing stars we know of are part of two or more stars systems, among which we count Alpha Centauri, the closest stellar neighbor.
Even with the new observations, astronomers couldn’t find a way to know for sure what shapes the number of stars which will be part of the same system or what are the necessary conditions for developing one type of star system or another. However, the results published this week helped them grasp the importance of such conditions in the case of widely separated stars.
While performing various simulations on original star environments, Offner could predict the enormous distance which will separate stars in a lot of multi-star systems. He estimated a distance of many thousands of times the distance between our sun and the planet Earth. The conditions she studied in the “stellar nursery” of these systems are influenced in a lot of ways by gravity, and most importantly, by gas velocities.
The rising question after studying the initial conditions of other systems was finding out why is our system only with one star, while the nearest system, Alpha Centauri, has three stars? Astronomers have multiple theories competing for the explanation of the origins of multiple star systems.
Pineda and his colleagues report in the new paper that the fortunate discovery of catching the star system in the first act of formation was made possible by pursuing some interesting observations reported by an astronomical radio observatory called the Very Large Array (VLA), and by the world’s largest fully steerable radio telescope, also known as the Green Bank Telescope (GBT).
These high tech instruments have provided high-resolution observations, showing the early stage of gas condensation in three different spots, next to a young star in the process of gaining mass. The estimation given by the astronomers puts the stars in full-formation in about 40,000, which is not very long if you think in astronomical terms. Pineda made sure to explain that without the combined observations provided by both GBT and VLA, these exciting discoveries of young systems in formation would have been impossible.
In the present, the distances between these three gas condensations are massive, multiple times the size of our solar system, but the authors predict that, based on the strong gravitational attraction which exists between the, the stars will eventually come together to form a quadruple star system (including the young star in their vicinity). However, astronomers believe that, in less than a million years, one of the stars will be expelled due to increasing interactions between them, leaving a triple system.
Unfortunately, all the data collected from observing such a young system in formation could not help astronomers find out different locations of other similar situations. Offner notes that the initial GBT observations did not cover the conditions existing before the gas condensations, so scientists do not know what to look for. This is the only time we were able to witness such a phenomenon, and further observations will require a lot more survey work and numerical modeling.
Based on this data, Offner could explain that our sun did not experience the same early conditions as the forming system they are currently observing. Instead, the distribution of planets in our solar system clearly suggests that our sun did not come from a multiple star system, but was likely formed on its own.
Image Source: Sci Tech Daily – the birth of a binary-star system