A team of researchers from the University of Liège and Monash University has confirmed the existence of a protoplanet, named HD169142 b, located 374 light years away from Earth.
Utilizing the SPHERE instrument of the European Southern Observatory (ESO), the international team, including Valentin Christiaens from the University of Liège, conducted a thorough analysis of data and developed advanced image processing tools at the PSILab of the University of Liège. The results, published in the Monthly Notices of the Royal Astronomical Society (MNRAS), confirm the presence of a new protoplanet.
Protoplanets are celestial bodies in the early stages of planet formation, originating from material clusters within protoplanetary disks surrounding young stars. Prior to this discovery, only two protoplanets, PDS 70 b and c, were definitively identified, both orbiting the star PDS 70. With the confirmation of HD169142 b, the number of identified protoplanets has increased to three, located within the gas and dust disk surrounding the star HD 169142.
A protoplanet represents an embryonic stage of a planet’s formation, emerging from the concentration of gas and dust in a protoplanetary disk encircling a recently formed star. As these materials gather and coalesce, the protoplanet grows by attracting additional matter through its gravitational pull.
To confirm the presence of HD169142 b, observations were conducted using the SPHERE instrument of the European Southern Observatory’s Very Large Telescope (VLT) between 2015 and 2019. Infrared images of HD 169142 were captured to detect the thermal signature associated with the formation of planets. These data verified the existence of HD169142 b, positioned approximately 37 astronomical units (AU) away from its star, slightly beyond the orbit of Neptune.
Previously, in 2020, a research team led by R. Gratton postulated that a compact source observed in their images could be indicative of a protoplanet. The current study not only confirms this hypothesis through a re-analysis of the previously used data but also incorporates new, higher-quality observations.
Images obtained from the VLT’s SPHERE instrument between 2015 and 2019 reveal the planet HD169142 b in motion within its orbit, accompanied by a prominent spiral arm generated from the dynamic interaction between the planet and its surrounding disk. By employing a combination of optical components and image processing techniques, the signal from the star, which is approximately 100,000 times brighter than the planet, was effectively subtracted. These images provide valuable insights into the planet’s evolution.
Furthermore, the recent images corroborate the predictions made by models, indicating that HD169142 b has created a distinct gap within the disk. Polarized light observations of the disk clearly illustrate this gap.
In addition, the research team’s measurements of the infrared spectrum and polarized light strongly suggest that the planet is enveloped in a significant amount of dust acquired from the protoplanetary disk. This dust accumulation may take the form of a circumplanetary disk—a small disk encircling the planet—potentially leading to the formation of moons. This groundbreaking discovery demonstrates the possibility of directly imaging and detecting planets in their early stages of formation.
Valentin Christiaens remarks on the significance of this finding, stating that while there have been numerous false positives in the identification of forming planets, apart from the protoplanets within the PDS 70 system, the authenticity of other candidates remains highly debated within the scientific community. HD169142 b exhibits distinct properties from the protoplanets in the PDS 70 system, implying that it was captured in a younger stage of its formation and is still concealed within or surrounded by substantial amounts of dust.
Considering the scarcity of confirmed forming planets, the discovery of HD169142 b and subsequent investigations will contribute significantly to understanding the formation of planets, particularly giant planets like Jupiter.
Further study and independent confirmation of the protoplanet can be achieved through future observations using the James Webb Space Telescope (JWST). The high sensitivity of JWST to infrared light holds the potential to detect thermal emissions emanating from the hot dust encompassing the planet.
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Frequently Asked Questions (FAQs) about protoplanet discovery
What is HD169142 b?
HD169142 b is a protoplanet located 374 light years away from Earth. It is an embryonic planet in the process of formation within a protoplanetary disc surrounding its parent star.
How was the existence of HD169142 b confirmed?
The existence of HD169142 b was confirmed by a team of researchers using the SPHERE instrument of the European Southern Observatory’s Very Large Telescope (VLT). They analyzed data obtained between 2015 and 2019, utilizing advanced image processing tools developed by the University of Liège.
How many confirmed protoplanets are there?
Prior to the discovery of HD169142 b, only two protoplanets had been definitively identified: PDS 70 b and c. With the confirmation of HD169142 b, the number of confirmed protoplanets increased to three.
What is a protoplanetary disc?
A protoplanetary disc is a flat, rotating disk of dense gas and dust that surrounds a newly formed star. It plays a crucial role in the formation and growth of planets, as protoplanets emerge from the material within these discs.
How does HD169142 b affect its surrounding disc?
HD169142 b has carved a gap in its protoplanetary disc, as predicted by models. The presence of a prominent spiral arm in the wake of the planet indicates dynamic interactions between the planet and the disc.
Can planets be detected in their early stages of formation?
Yes, the discovery of HD169142 b demonstrates the possibility of directly imaging and detecting planets at a very early stage of their formation. This finding opens up new avenues for studying the early evolution of planets.
More about protoplanet discovery
- Monthly Notices of the Royal Astronomical Society: Letters
- European Southern Observatory (ESO)
- University of Liège
- Monash University
- SPHERE instrument
- PDS 70 system
- James Webb Space Telescope (JWST)
