Stellar Astronomy and Planetary Systems

Stellar astronomy examines the life cycles of stars from their birth in dense molecular clouds to their ultimate fates as white dwarfs, neutron stars or black holes. Turbulence and gravity sculpt filaments in molecular gas, where cores collapse under hydrostatic equilibrium into protostars surrounded by accretion discs and bipolar outflows. Nuclear fusion ignites at the core, releasing energy that diffuses outward or is carried by convection, and sustains a star in the Hertzsprung–Russell diagram’s main sequence for millions to billions of years. Post-main-sequence evolution—red-giant expansion, shell burning and mass loss—reconfigures stellar structure and enriches the interstellar medium. Planetary systems form as a by-product of star formation. Dust grains in the protostellar disc coagulate and grow into planetesimals, assembling into terrestrial worlds and giant planets. Disc–planet interactions drive migration and resonance capture, while stellar irradiation and winds shape planetary atmospheres. Over the past quarter-century, thousands of exoplanets have been discovered, revealing a diversity of architectures—hot Jupiters, compact super-Earths, wide-orbit giants—and atmospheric compositions. A combination of Doppler spectroscopy, transit photometry, direct imaging and high-contrast coronagraphy probes planetary masses, radii, orbital dynamics and atmospheric spectra. Studies of atmospheric escape, radiative transfer and chemical evolution underpin our understanding of habitability and volatile inventories on temperate worlds.

Research from Nature Portfolio

New self-consistent models of atmospheric evolution on temperate terrestrial exoplanets show that hydrogen-rich primary envelopes do not always lead to barren outcomes. Coupling magma-ocean solidification, mantle redox chemistry, climate modelling and thermal escape, researchers demonstrate that planets in low-mass-star habitable zones can retain thick, secondary atmospheres enriched in water, even after extensive hydrogen loss. This overturns the assumption that complete envelope erosion precludes surface volatiles, and suggests that early hydrogen–rock interactions may promote water inventories.

Medium-resolution (R ≈ 600) transmission spectroscopy of the Saturn-mass exoplanet WASP-39b between 3 and 5 μm using JWST NIRSpec G395H has achieved near-photon-noise-limited precision. The spectrum reveals strong absorption from CO₂ and H₂O, and the first unambiguous detection of SO₂ in an exoplanet atmosphere. Retrievals indicate metallicities of 3–10 × solar and sub-solar to solar C/O ratios. These results showcase JWST’s capability to characterise atmospheric chemistry and provide a template for future time-series studies of temperate and giant exoplanets.

Stellar Astronomy and Planetary Systems publication trend

The graph below shows the total number of articles in stellar astronomy and planetary systems across all publications each year (not limited to Nature Index journals).

Technical terms

Primary atmosphere: The original H₂/He-rich envelope accreted from the protoplanetary disc around a young planet.

Secondary atmosphere: A later envelope generated by outgassing, photochemistry or surface reactions, often dominated by heavier molecules such as CO₂, N₂ or H₂O.

Lyapunov time: The characteristic timescale over which nearby trajectories in a dynamical system diverge exponentially, indicating the onset of chaos.

Gaussian process regression: A non-parametric Bayesian method for modelling correlated noise in time-series data, widely used to disentangle stellar activity from exoplanet signals.

Transmission spectrum: The wavelength-dependent absorption of starlight passing through a planet’s atmosphere during transit, used to infer atmospheric composition.

References

1. The erosion of large primary atmospheres typically leaves behind substantial secondary atmospheres on temperate rocky planets. Nature Communications (2024).
2. Early Release Science of the exoplanet WASP-39b with JWST NIRSpec G395H. Nature (2023).
3. Gaussian Process Regression for Astronomical Time Series. Annual Review of Astronomy and Astrophysics (2023).
4. Timescales of Chaos in the Inner Solar System: Lyapunov Spectrum and Quasi-integrals of Motion. Physical Review X (2023).
5. SPHERE: the exoplanet imager for the Very Large Telescope. Astronomy & Astrophysics (2019).