Maturation expected

The technique used in this case was not interferometry, but coronagraphy. In effect interferometry is a powerful tool for studying, amongst others, the formation and development of planetary systems. It has been made much use of to probe protoplanetary disks. But as far as detecting exoplanets goes, even if it has been envisaged for 15 years, the technique in its current state has reached its limits, as Olivier Absil has demonstrated in a recent study (2). ‘With the aid of three of the VLT’s auxiliary telescopes and their AMBER instrument we used interferometry to observe β-Pictoris. We knew in advance that it was sheltering a companion as it had been observed via coronagraphy. But we were looking to detect it through interferometry. To do so we intensively observed the star for three successive nights, but in vain. This non-detection of the nevertheless avowed companion allowed us to estimate the sensitivity of our instrument: for a companion orbiting between 0.1 and 3 astronomical units, we have a 90% chance of detecting a body with a mass 50 times greater than Jupiter’s mass (MJ), in other words 1500 times greater the mass of our planet. This probability falls to 50% for a body of 35 MJ. We can thus detect companions which are brown dwarfs, but not planets. To enter the domain of planets (less than 13 MJ) we still have to increase our sensitivity by a factor of 5. The technique of interferometry is a complicated one, but it should reach maturity with the new instruments installed at the VLTI (Very Large Telescope Interferometer) in Chile or at the CHARA network (Center for High Angular Resolution Astronomy) at Mount Wilson.’