Star and Planet Formation and Evolution, and the Search for Life

Green Bank Ammonia Survey in the Perseus molecular cloud at 32’’ resolution (Black contours, Pineda et al. arXiv:2510.0607). The color scale shows N(H2) derived from Herschel.

The NRAO facilities continued to enable major discoveries in the areas of star and planet formation, and the physics of the interstellar medium, through the unique capabilities to study the gas, dust, and star formation on scales of AU to kiloparsecs. One major advance this year was the final data release of the Green Bank Ammonia Survey, mapping all significant star forming regions in the Gould Belt. The survey reveals close correlation between the NH3 emission with the dust distribution derived by Herschel observations, with NH3 extending beyond the typical 0.1 pc length scales of dense cores, into the transition zone between dense cores and turbulent clouds. The higher column density regions typically display subsonic non-thermal velocity dispersions. Maps of the gas kinematics, temperature, and NH3 column density show that the velocity dispersion and kinetic temperature increase with increasing star formation activity. 

Figure: Green Bank Ammonia Survey in the Perseus molecular cloud at 32’’ resolution (Black contours, Pineda et al. arXiv:2510.0607). The color scale shows N(H2) derived from Herschel.

Left: VLA image of the region around the massive protostar IRAS 18162–2048 at 5 GHz, 6” resolution (Cheriyan et al. 2025 ApJ 988, L9). Right: color scale now shows the stokes V circular polarization

Magnetic fields play a key role in stellar evolution and stellar atmospheres, but to date, no direct measurement has been made of field strengths near the photospheres of massive protostars. The VLA has, for the first time, detected circularly polarized emission from a massive protostar, IRAS 18162–2048. The fractional CP varies between 3–5% across the observed frequency range of 4–6 GHz. Possible physical origins for this emission include gyrosynchrotron emission and/or Faraday conversion due to turbulence in the magnetic medium, both arising from mildly relativistic electrons. The results provide the first estimate of the magnetic field strength of B ~ 20 to 35 G in the immediate vicinity of the surface of the massive protostar. The Lorentz factor of the low-energy electrons is estimated to be in the range –7 for gyrosynchrotron emission, and 80–100 for Faraday conversion.

Figure: Left: VLA image of the region around the massive protostar IRAS 18162–2048 at 5 GHz, 6” resolution (Cheriyan et al. 2025 ApJ 988, L9). Right: color scale now shows the stokes V circular polarization

ALMA observations of linearly polarized emission from aligned dust grains at 230 GHz in protostellar cores and clumps in NGC6334, down to 0.4” resolution (Zhang et al. 2025, ApJ 992, 103).

On scales of molecular protostellar cores and clumps, a recent survey of 17 massive protostellar cores and clumps at 230 GHz with ALMA down to 0.4” resolution (1000 AU) shows linearly polarized thermal emission from aligned dust grains. A bimodal distribution is seen for the implied magnetic field orientation relative to the dust structural elongation: either parallel or perpendicular. The parallel systems are typically seen at the highest column density (> 1023 cm−2). The underlying cause of this bimodal distribution is likely gravitational collapse at higher gas densities, which drags and reorients the magnetic field, consistent with an initially sub-Alvenic cloud that becomes magnetically supercritical and super-Alvenic as the cloud collapses to form stars.

Figure: ALMA observations of linearly polarized emission from aligned dust grains at 230 GHz in protostellar cores and clumps in NGC6334, down to 0.4” resolution (Zhang et al. 2025, ApJ 992, 103).

The seven-ring PAH Cyanocoronene structure and GBT GOTHAM (black) + laboratory (orange) spectra. This is the largest PAH discovered outside the solar system to date (Wenzel et al. 2025 ApJ 984, L36).

Radio studies lead the field of large molecule astrochemistry and the search for organic and pre-biotic molecules. Key to these studies are parallel laboratory experiments to determine the spectra of such complex molecules. The GBT Observations of TMC-1: Hunting Aromatic Molecules (GOTHAM) program at the GBT represents the state-of-the-art for such studies, combining laboratory experiments and GBT high resolution broadband spectroscopy. This program has unambiguously identified the seven-ring polycyclic aromatic hydrocarbon (PAH) cyanocoronene (C24H11CN), in the Torus Molecular Cloud. PAHs are critical to ISM chemistry because they sequester up to 25% of the interstellar carbon. The derived column density is 2.7x1012 cm-2, and the temperature is 6.0 K. Cyanocoronene is the largest PAH discovered in space to date, and yet its column density is comparable to smaller PAHs, defying the trend of decreasing abundance with increasing molecular size and complexity found for carbon chains. Comparisons to organics in the Murchison meteorite and in return samples from the asteroid Ryugu suggest a substantial inheritance of PAH from the ISM, possibly produced in the cold (T∼10 K) conditions that occur ∼1 Myr before the birth of the Sun. PAHs represent a promising source of carbon for forming terrestrial worlds, to which carbon is supplied in the form of solid-state organics in the natal clouds.

Figure: The seven-ring PAH Cyanocoronene structure and GBT GOTHAM (black) + laboratory (orange) spectra. This is the largest PAH discovered outside the solar system to date (Wenzel et al. 2025 ApJ 984, L36).

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The NSF National Radio Astronomy Observatory and NSF Green Bank Observatory are facilities of the U.S. National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

Founded in 1956, the NSF NRAO provides state-of-the-art radio telescope facilities for use by the international scientific community. NSF NRAO telescopes are open to all astronomers regardless of institutional or national affiliation. Observing time on NSF NRAO telescopes is available on a competitive basis to qualified scientists after evaluation of research proposals on the basis of scientific merit, the capability of the instruments to do the work, and the availability of the telescope during the requested time. NSF NRAO also provides both formal and informal programs in education and public outreach for teachers, students, the general public, and the media.

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