High-contrast imaging constraints on gas giant planet formation - The Herbig Ae/Be star opportunity

TL;DR

This paper discusses how high-contrast imaging of Herbig Ae/Be stars' disks can empirically constrain gas giant planet formation, highlighting recent observations of potential young planets and future prospects with advanced telescopes.

Contribution

It emphasizes the advantages of studying Herbig Ae/Be stars for understanding planet formation and reviews recent imaging results that provide direct evidence of young planets in these systems.

Findings

Detection of morphological structures in disks suggestive of planet formation.

Reported direct evidence of very young planets around HD100546 and HD169142.

Outlook on future progress with next-generation high-contrast imagers and ALMA.

Abstract

Planet formation studies are often focused on solar-type stars, implicitly considering our Sun as reference point. This approach overlooks, however, that Herbig Ae/Be stars are in some sense much better targets to study planet formation processes empirically, with their disks generally being larger, brighter and simply easier to observe across a large wavelength range. In addition, massive gas giant planets have been found on wide orbits around early type stars, triggering the question if these objects did indeed form there and, if so, by what process. In the following I briefly review what we currently know about the occurrence rate of planets around intermediate mass stars, before discussing recent results from Herbig Ae/Be stars in the context of planet formation. The main emphasis is put on spatially resolved polarized light images of potentially planet forming disks and how these images - in combination with other data - can be used to empirically constrain (parts of) the planet formation process. Of particular interest are two objects, HD100546 and HD169142, where, in addition to intriguing morphological structures in the disks, direct observational evidence for (very) young planets has been reported. I conclude with an outlook, what further progress we can expect in the very near future with the next generation of high-contrast imagers at 8-m class telescopes and their synergies with ALMA.