Article Posted on : - Apr 13, 2009

(Left) This image shows the zooming into the centre of the Orion star-forming region with four bright Trapezium stars. A high-resolution image of Theta1 Orionis C (lower right) has been captured. (Right) The orbit of the binary system (grey line) was derived using position measurements obtained over the past 12 years (yellow points). The size of the orbit of Jupiter around Sun is shown for comparison. – Image credit : Astronomy & Astrophysics Journal

PARIS (BNS): Astronomers have captured the sharpest image of the young binary star – Theta1 Orionis C – in the Orion Trapezium cluster, which they believe, would help them conducting an in-depth study of the system.


The Astronomy & Astrophysics journal, which has published the new image, said that a team of astronomers, led by Stefan Kraus and Gerd Weigelt (MPIfR, Bonn, Germany), using the AMBER instrument installed at the ESO/Very Large Telescope Interferometer (VLTI), obtained the image.


The new image has enabled scientists to clearly distinguish the two young, massive stars of the system, the journal said in a statement. Using Kepler's third law, they have also derived the masses of the two stars at 38 and 9 solar masses.


The high-resolution image has helped them calculate the distance to the system, hence to the centre of the Orion star-forming region, which is estimated to be 1350 light-years. These various measurements are essential for improving theoretical models of massive star formation, the journal said.


The Orion Trapezium cluster is the nearest region from Earth where massive stars are formed. Located at about 1350 light-years from Earth, it provides a unique laboratory for studying the formation process of massive stars in detail.


The binary star Theta1 Ori C is the brightest of the four Trapezium stars in the Orion nebula. It is the most massive star in the nearest region where high-mass stars are forming. The intense radiation of the star ionizes the entire Orion nebula. Its strong wind also shapes the famous Orion proplyds, young stars that are still surrounded by their protoplanetary dust disks, according to astronomers.


Theta1 Ori C is a bright, naked-eye star, but its companion is so close (20 milli-arcseconds) that it was not detected until 1999.


Thus, a high-angular resolution was needed for an in-depth study of the system. The image that is now published has a sharpness of 2 milli-arcseconds, the journal said. Combining AMBER observations with position measurements of the system over the past 12 years, the team of astronomers was able to compute the orbital period of the system which is 11 years.