Protoplanetary Disks

Protoplanetary discs observed with SPHEREPlanets form from vast disks of gas and dust, known as protoplanetary disks, encircling newborn stars. These disks can extend for billions of kilometers. Over time, the particles in protoplanetary disks collide, combine, and accrete into planet-sized bodies.

Improved observations of the details of the evolution of these planet-forming discs are now being made using ESO’s SPHERE instrument mounted on the Very Large Telescoped, improving our understanding of the enigmatic evolution of fledgling planetary systems. The central parts of the images appear dark because SPHERE blocks out the light from the brilliant central stars to reveal the much fainter structures surrounding them. Bands appear as the forming planets begin to sweep their orbits clean.

Image Credits: ESO

Making Planets?

Boulevard of Broken Rings

This picture was taken using SPHERE (the Spectro-Polarimetric High-contrast Exoplanet REsearch instrument), a planet-hunting instrument mounted on ESO’s Very Large Telescope (VLT) in Chile. It shows a series of disrupted, concentric rings in the inner region of the debris disc surrounding a young star named HD 141569A about 370 light-years away. The image shows what is known as a transition disc, the brief stage between the protoplanetary phase, when planets have not yet formed, and a later time when planets have coalesced, leaving the disc populated only by dusty debris.

The area shown in this image has a diameter of just 200 times the Earth-to-Sun distance. Several features are visible because of the excellent detail from the SPHRE data, including a bright, prominent ring with well-defined edges which is so asymmetric that it appears as a half-ring. We can also see multiple clumps, several concentric ringlets, and a pattern that looks like a spiral arm. These structures are asymmetric, something for which astronomers do not currently have a firm explanation. It is possible that this phenomenon is caused by the presence of planets, but so far planets large enough to do this haven’t been found in the system.

Image Credit: ESO

Dust Rings and Exoplanets

HR4796A Dust RingSPHERE is the Spectro-Polarimetric High-contrast Exoplanet Research instrument, and ithas been installed on ESO’s Very Large Telescope (VLT) at the Paranal Observatory in Chile. This picture is from its first light observations and shows a dust ring around a star known as HR 4796A.

The new instrument uses multiple advanced techniques, yielding dramatically better performance than previously possible. The first is improved adaptive optics to correct for the effects of the Earth’s atmosphere so that images are sharper and the contrast of the exoplanet increased. Second, a coronagraph is used to block out the light from the star and increase the contrast still further. Third, differential imaging exploits differences between planetary and stellar light color or polarization.

Image Credit: ESO