New observations with SPHERE, an advanced exoplanet-hunting instrument on the Very Large Telescope at ESO’s Paranal Observatory, have revealed striking features in protoplanetary disks around three young stars: RX J1615, HD 97048 and HD 135344B.
Artist’s impression of the dust disk and a forming planet around a young star. Image credit: NAOJ.
Interactions between protoplanetary disks and growing planets can shape the disks into various forms: vast rings, spiral arms or shadowed voids. These are of special interest as an unambiguous link between these structures and the sculpting planets is yet to be found; a mystery that astronomers are keen to solve.
Fortunately, specialized capabilities of the SPHERE instrument make it possible for researchers to observe these striking features of protoplanetary disks directly.
For example, RX J1615.3-3255 (RX J1615 for short) is a young star, which lies in the constellation of Scorpius, approximately 600 light-years from Earth.
A team of astronomers led by Leiden Observatory scientist Dr. Jos de Boer found a complex system of concentric rings surrounding RX J1615, forming a shape resembling a giant version of the rings that encircle Saturn.
Using ESO’s SPHERE instrument, J. de Boer et al observed the planetary disk surrounding the star RX J1615 which lies in the constellation of Scorpius, 600 light-years from Earth. The observations show a complex system of concentric rings surrounding the young star, forming a shape resembling a titanic version of the rings that encircle Saturn. Such an intricate sculpting of rings in a protoplanetary disk has only been imaged a handful of times before. The central part of the image appears dark because SPHERE blocks out the light from the brilliant central star to reveal the much fainter structures surrounding it. Image credit: J. de Boer et al / ESO.
Such an intricate sculpting of rings in a protoplanetary disk has only been imaged a handful of times before, and even more excitingly, the entire system seems to be 1.8 million years old. The disk shows hints of being shaped by protoplanets.
The age of the newly detected protoplanetary disk makes RX J1615 an outstanding system, as most other examples of protoplanetary disks detected so far are relatively old or evolved.
The team’s unexpected result was quickly echoed by the findings of a research team led by Dr. Christian Ginski, also of Leiden Observatory.
C. Ginski et al observed HD 97048, a young star approximately 500 light-years away in the constellation of Chamaeleon. Through painstaking analysis, the astronomers found that the juvenile disk around this star has also formed into concentric rings.
C. Ginski et al observed the planet-forming disk surrounding HD 97048, a young Herbig Ae/Be star about 500 light-years away. Image credit: C. Ginski et al / ESO.
The symmetry of these two systems is a surprising result, as most protoplanetary systems contain a multitude of asymmetrical spiral arms, voids and vortexes.
These discoveries significantly raise the number of known systems with multiple highly symmetrical rings.
A particularly spectacular example of the more common asymmetric disk was captured by Dr. Tomas Stolker of the Anton Pannekoek Institute for Astronomy and co-authors.
T. Stolker et al observed the planetary disk surrounding the star HD 135344B, about 450 light-years away. The disk shows prominent spiral arm-like structures. These are thought to have been created by one or multiple massive protoplanets, destined to become Jupiter-like worlds. The central part of the image appears dark because SPHERE blocks out the light from the brilliant central star to reveal the much fainter structures surrounding it. Image credit: T. Stolker et al / ESO.
This disk surrounds HD 135344B, a young star about 450 light-years away.
Although HD 135344B has been well-studied in the past, SPHERE allowed the team to see the star’s protoplanetary disk in more detail than ever before.
The large central cavity and two prominent spiral arm-like structures are thought to have been created by one or multiple massive protoplanets, destined to become Jupiter-like planets.
In addition, four dark streaks, apparently shadows thrown by the movement of material within HD 135344B’s disk, were observed.
Remarkably, one of the streaks noticeably changed in the months between observing periods: a rare example of observing planetary evolution occur in real time, hinting at changes occurring in the inner disk regions that can not be directly detected by SPHERE.
As well as producing beautiful images, these flickering shadows provide a unique way of probing the dynamics of innermost disk regions.
The research of de Boer, Ginski and Stolker and their colleagues in the SPHERE consortium is now accepted for publication in the journal Astronomy and Astrophysics.
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J. de Boer et al. 2016. Multiple rings in the transition disk and companion candidates around RX J1615.3-3255: High contrast imaging with VLT/SPHERE. A&A, in press; doi: 10.1051/0004-6361/201629267
C. Ginski et al. 2016. Direct detection of scattered light gaps in the transitional disk around HD 97048 with VLT/SPHERE. A&A, in press; doi: 10.1051/0004-6361/201629265
T. Stolker et al. 2016. Shadows cast on the transition disk of HD 135344B: Multi-wavelength VLT/SPHERE polarimetric differential imaging. A&A, in press; arXiv: 1603.00481
