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Astronomers have obtained the first direct image of a protoplanet actively accreting material inside a dark gap of a multi-ring protoplanetary disk. The newborn world, designated WISPIT 2b, was detected by its hydrogen-alpha (H-alpha) emission — light produced when infalling hydrogen gas heats to plasma as it crashes onto the forming planet. This detection confirms a long-suspected explanation for the ring-and-gap architecture seen in many young disks: planets carving gaps as they grow.
Scientific context: why H-alpha matters
Protoplanetary disks are rotating sheets of dust and gas around young stars where planets form. Many of these disks show concentric rings with dark gaps; theory has often pointed to embedded planets as the cause, but direct detections inside those dark gaps had been elusive. H-alpha is a specific visible-wavelength emission created when hydrogen is ionized and then recombines. Accreting protoplanets can produce strong H-alpha, making it a valuable tracer for newborn planets that are otherwise faint in reflected starlight or thermal infrared.
Observations and instruments
The discovery was led by Laird Close (University of Arizona) and Richelle van Capelleveen (Leiden Observatory), using several of the world’s most advanced adaptive-optics systems. Key data came from the University of Arizona’s MagAO-X instrument on the 6.5-meter Magellan Telescope (Chile), optimized for H-alpha imaging, together with infrared follow-up from the 8.4-meter Large Binocular Telescope (Arizona) and supporting SPHERE observations with the European Southern Observatory’s Very Large Telescope (Chile).
The WISPIT-2 system and results
The WISPIT-2 disk shows multiple rings and gaps. In H-alpha images a compact source — WISPIT 2b — appears inside a cleared gap roughly 56 astronomical units (AU) from the host star (1 AU = Earth–Sun distance). A second candidate, CC1, appears inside the inner cavity at about 14–15 AU. Thermal infrared measurements suggest CC1 may be ~9 Jupiter masses and WISPIT 2b about ~5 Jupiter masses, though mass estimates at this stage carry uncertainties due to accretion luminosity and age assumptions.
The team reports that once MagAO-X was engaged, the H-alpha signal 'jumped right out' of the data, enabling a confident detection after combining a few hours of exposure. Parallel infrared detections from SPHERE and the Large Binocular Telescope corroborate the multi-ring architecture and support the interpretation of planets shaping the disk.
This detection demonstrates that forming planets can be located within dark disk gaps and directly observed through their accretion signatures. The WISPIT-2 system offers a rare nearby laboratory to study how gas giants assemble, migrate, and interact with surrounding dust. Comparisons to our early solar system suggest that giant planets like Jupiter and Saturn would have been similarly bright during their accretionary youth, but WISPIT-2’s gas giants appear larger and more widely separated.
Conclusion
The first H-alpha image of a baby planet inside a disk gap strengthens the link between disk structure and planet formation. Continued multiwavelength monitoring and high-resolution spectroscopy will refine mass and accretion estimates and reveal how such systems evolve into mature planetary systems.
Source: scitechdaily
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