What is K2-141b and Why It Matters
K2-141b is an ultrahot, lava-rich exoplanet detected by the Kepler K2 mission and later characterized by follow-up observations. It orbits extremely close to its host star, completing a revolution in just hours, and presents a streamlined case for studying how intense irradiation reshapes rocky worlds. Its dayside temperatures reach thousands of degrees, producing molten surface conditions that differ in well-defined ways from more temperate super-Earths. This profile clarifies detection methods, physical properties, and the broader relevance of lava worlds to planetary science.
Host Star and Orbital Architecture
M Dwarf Characteristics and Irradiance
The host is an M dwarf, relatively cool but highly active in ultraviolet and X-rays during early evolution. Because K2-141b circles very close to this star, it receives extreme stellar flux, raising equilibrium temperatures that favor vaporized rock and supersonic winds. The system offers insights into how irradiation strength scales with orbital separation.
- Spectral type: late M dwarf
- Apparent magnitude: near-IR bands where M dwarfs peak
- Stellar activity: flares and high-energy emission common in young M dwarfs
Orbital Period and Resonance Context
K2-141b has an orbital period of roughly 0.3 days, placing it well inside the star’s conservative habitable zone’s inner edge. While not currently in mean-motion resonance, its short orbit makes timing variations a promising observational target for future ground-based spectrographs. The compact architecture sets clear bounds on planet formation and migration around low-mass stars.
Physical Properties and Detection Methods
Radius, Mass, and Density Estimates
Early analyses indicate a super-Earth sized body, with radius near ~1.5 Earth radii and mass likely in the low few Earth masses range if the composition is predominantly rocky. Precise mass remains debated due to stellar activity and observational geometry. Density estimates favor a rocky composition with limited volatile envelopes, consistent with planets that experience intense irradiation.
| Attribute | Verified Detail | Source Type |
|---|---|---|
| Radius | Approximately 1.5 Earth radii | Spitzer/K2 photometry |
| Orbital Period | ~0.3 days | Kepler/K2 and follow-up RV |
| Equilibrium Temperature | Several thousand Kelvin | Phase-curve modeling |
| Host Star Type | Late M dwarf | Spectroscopic catalog |
| Surface Conditions | Molten rock, possible magma ocean | Thermal models and emission constraints |
Light Curves and Phase Curves
Kepler K2 observations captured frequent transits, enabling precise period determination and transit depth measurements. Subsequent phase-curve studies mapped the dayside thermal emission, revealing asymmetric brightness patterns driven by strong winds and inefficient heat redistribution. Secondary eclipses help constrain dayside temperature contrasts between the substellar point and the cooler limbs.
Thermal Evolution and Lava Conditions
Dayside Temperatures and Rock Vaporization
Dayside temperatures likely exceed 2,000 K, sufficient to melt silicate rocks and generate widespread lava flows. Under such conditions, rock behaves as a fluid on observable timescales, with evaporation rates substantial enough to produce a tenuous atmosphere of vaporized silicates. Temperature gradients drive powerful winds that transport heat across the surface.
Heat Redistribution and Atmospheric Dynamics
Efficiency of heat redistribution depends on atmospheric opacity, wind speed, and day-night contrast. Models suggest partial redistribution with supersonic flows, resulting in sharp thermal contrasts between the permanent dayside and nightside. Observations of phase curves and secondary depth variations inform whether global magma oceans or thin, dynamic lava regions dominate.
Formation, Migration, and System Context
Inside-Out Formation vs. Late Migration
K2-141b may have formed either in place from a truncated protoplanetary disk or migrated inward after forming farther out. In an inside-out scenario, rapid disk dispersal and high irradiation locked the planet into an ultrashort orbit before substantial gas remained. Alternatively, tidal circularization following planet–planet scattering or disk-driven migration can reproduce tight orbits around M dwarfs. Current data favor a history of strong irradiation regardless of the precise migration pathway.
Multiples and Resonances in the System
No confirmed additional planets have been reported in the K2 light curve, but stellar activity complicates transit timing searches. Future observations could test whether companions exist in or near resonances with K2-141b, shedding light on system architecture and formation history. Comparisons with hotter ultrahot Jupiters and cooler rocky planets highlight how irradiation level correlates with atmospheric properties.
Observational Constraints and Future Tests
Current Limits on Atmosphere and Emissions
Existing studies suggest dayside pressures high enough to sustain vaporized rock, with nightside condensation potentially removing refractory species. Atmospheric escape may be modest but non-negligible over gigayear timescales due to strong XUV flux. Disentangling stellar contamination from planetary signals remains a key challenge with current instruments.
Upcoming Observations and Science Goals
Next-generation spectrographs in the near-IR and mid-IR can refine dayside–nightside temperature contrasts, search for molecular species, and constrain atmospheric scale heights. High-cadence transit and eclipse campaigns, combined with asteroseismology of the host star, will improve radius and mass estimates. Ground-based extremely large telescopes and space-based infrared facilities are expected to sharpen models of lava worlds and their potential diversity.
Comparing Ultrahot Rocky Planets
K2-141b sits among the best-characterized ultrahot rocky bodies, alongside counterparts with similar equilibrium temperatures but slightly larger radii. Comparing this lava planet to hotter gas-dominated cousins helps isolate the effects of irradiation on solid versus gaseous envelopes. Such comparisons emphasize how orbital proximity and stellar type jointly shape observable outcomes.
| Planet | Radius (Earth) | Orbital Period (days) | Dayside Temp (K) | Host Type |
|---|---|---|---|---|
| K2-141b | ~1.5 | ~0.3 | ~2,200–3,000 | M dwarf |
| CoRoT-7b | ~1.7 | ~0.85 | ~2,300–2,500 | F star |
| LHS 3844b | ~1.3 | ~0.47 | ~980–1,300 | M dwarf |
Summary and Status
K2-141b is a well-motivated lava planet studied via Kepler K2 and follow-up campaigns, with an ultra-short orbit around an M dwarf producing extreme dayside temperatures and rock-vaporizing conditions. Current observations point to a rocky composition and significant irradiation-driven dynamics, while uncertainties remain in mass, atmosphere thickness, and night-side behavior. The planet remains a benchmark for ultrahot rocky worlds and a priority for next-generation thermal and spectroscopic monitoring.