An article published in “The Astrophysical Journal Letters” describes a research about what used to be a multiple system in the Orion Nebula. A team of researchers led by Kevin Luhman of Penn State University used the Hubble Space Telescope to discover a runaway star that was part of the original system with two other stars already known that are also traveling at high speeds. The three stars were part of a single system untile about 540 years ago.

The stars protagonists of this research were discovered decades away from each other. The first one, called Becklin-Neugebauer (BN), was discovered in 1967 by examining infrared images but was recognized as a runaway star only in 1995 thanks to radio observations that allowed to estimate its speed at about 96,500 km/h (60,000 mph).

The second star, called source I, was detected only through radio observations because it’s located far inside the Kleinmann-Low Nebula, near the center of the Orion Nebula. This makes it nearly invisible at optical and infrared frequencies while radio waves can pass through the nebula’s gas and dust. Its speed was estimated at about 35,500 km/h (22,000 mph).

The third star, called source x, was detected in the course of another study that had the purpose to find planets in the Orion Nebula. Kevin Luhman was part of the team of researchers who were using the Hubble Space Telescope and during an analysis of infrared detections based on comparison of new images taken in 2015 and others taken in 1998 he realized that source x had moved significantly compared to the stars nearby. Its speed was estimated at about 210,000 km/h (130,000 mph).

After its discovery, the researchers followed the trajectory of source x to find its origin and discovered that is the same area from which they BN and source I left about 540 years earlier. Probably the gravitational influences exerted by the three stars ended up disrupting the system pushing them on their way out of the Kleinmann-Low Nebula.

The discovery of source x solves a problem that concerned the couple BN – source I. They seemed part of a single system that was somehow disrupted but their combined energy was too low to push them in opposite directions at those speeds. For this reason, scientists had speculated that that system had included at least one more star that turned out to be source x.

These three stars are the youngest example of disrupted system because they’re likely to have an age of just some hundred thousands of years, virtually newborns in astronomical terms. They’re so young that the infrared images show around them residues of the disks of materials from which they formed. All these factors make them particularly interesting for future research also with next generation telescopes.