József Varga, an astronomer at the Leiden University and the ELKH Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, is the leader of an international research group that discovered a vortex of gas and dust around a young star with the new MATISSE instrument in Chile, which was built with Hungarian contribution. Researchers say it is possible that a nascent planet is also hiding in the vortex. The celestial body HD 163296 under investigation is a much-studied young star located 330 light-years from Earth in the Sagittarius constellation. Earlier, evidence for the presence of three large exoplanets around the star had been found, though they are much farther away from the fourth supposed planet that has now been discovered.

During their observations in March and June 2019, the researchers studied the inner dust disk around the star with their telescopes, during which they observed a ring of warm dust particles at a distance from the star comparable to Mercury’s orbit around our Sun. They were surprised to find that one side of the disk was much brighter than the other. Subsequently, after comparing to previous measurements, it was concluded that this bright cluster is orbiting the star with an orbital period of approximately one month. Astronomers have also used computer simulations to verify their hypothesis that this cluster of hot dust could actually be a vortex. Such vortices have a higher density and pressure of matter (gas and dust) than the rest of the disk, which, according to current planet formation theories, creates the perfect conditions for the birth of a new planet. This is because the formation of a planet originally requires dust particles consisting of small particles like smoke. The grains of dust stick together, forming larger and larger particles, until they eventually form a planet under the influence of gravity. The process of planet formation is still unclear in many respects, but discoveries like this one bring us closer to the understanding the birth of planets such as Earth.

Schematic image of the dust disk around the star HD 163296 in infrared light. The bright part in the upper right is the supposed vortex where a new planet can form. (©) J. Varga et al.

The researchers made their observations leading to the discovery with MATISSE (Multi AperTure mid-Infrared SpectroScopic Experiment). This is the next-generation instrument of the VLTI (Very Large Telescope Interferometer) which is a telescope network at the European Southern Observatory’s (ESO) Paranal Observatory in Chile. VLTI combines the light of four telescopes, creating a virtual telescope of up to 200 meters in diameter. This is necessary because even today’s largest 10-meter-diameter optical telescopes alone would not be able to resolve the now-discovered orbital disk, but by combining the light from multiple telescopes — by increasing the resolution — this becomes possible. MATISSE detects infrared light emitted by the dust in the disk as thermal radiation.

The MATISSE instrument is located at the Paranal Observatory of the European Southern Observatory (ESO). (©)

The MATISSE instrument was largely built in collaboration of research institutes in France, Germany, the Netherlands, and Austria, though engineers from the CSFK Institute of Astronomy also took part in its creation. The contribution by Hungarian engineers included the thermal simulation of the instrument with respect to the thermal load caused by motors operating at temperatures near absolute zero degrees, the design and manufacture of a calibration camera of an instrument unit in Hungary, and the calculation of possible vibrations during the transport of MATISSE. The instrument was mounted on the Chilean telescope system at the turn of 2017-2018, and saw its ‘first light’ in 2018, i.e. it was directed at a celestial object for the first time in that year. In recognition of the Hungarian technical contribution, the researchers at the CSFK Institute of Astronomy were given a guaranteed observation opportunity on the instrument, with the aim to examine young eruptive stars showing large brightness changes. In addition, József Varga, an astronomer at CSFK, who is currently working at Leiden University as an internationally recognized expert in the MATISSE Team, is participating in MATISSE’s large research program on star formation with his Dutch colleagues. The first result of this major research is the discovery of a vortex in a disk around the star HD 163296.

For the astronomers, the first real scientific findings of the MATISSE consortium mark the beginning of further research on star formation. One of their goals is to study even more star systems where the young star is surrounded by a disk of dust and gas, thereby gaining an even better understanding of the formation process of planets like Earth. The research group of the CSFK Institute of Astronomy, led by Péter Ábrahám, continues to participate in the research project, the work of which is supported by NKFIH’s four-year fundamental research grant.

The article on the new results has already been accepted by the journal Astronomy & Astrophysics. The article, which includes the name of József Varga and two other Hungarian astronomers among its authors, will be published soon.

The article is available at:

The asymmetric inner disk of the Herbig Ae star HD 163296 in the eyes of VLTI/MATISSE: evidence for a vortex? J. Varga et. al., accepted for publication in Astronomy & Astrophysics.

Original: https://doi.org/10.1051/0004-6361/202039400

Freely accessible (in English): https://arxiv.org/abs/2012.05697v1

Contact: József Varga; varga@strw.leidenuniv.nl