pebble accretion Archives - Page 2 of 2 - Astrobiology

The ratio of a planet’s surface escape velocity squared v2 esc to its orbital velocity squared v2 K as a function of planet’s orbital distance and mass (equation 12). For v 2 esc/v2 K > 1, ejections are more likely than mergers, which we expect towards large orbital distances where the gravitational potential of the central star is shallower and for larger planet mass which can impart greater kinetic energy through scattering. -- astro-ph.EP

Astrogeology, Exoplanets, -moons, -comets, Status Report

Planet Mass Function Around M Stars At 1-10 au: A Plethora Of Sub-Earth Mass Objects

by Keith CowingOctober 1, 2024October 1, 2024

Small planets (≲1 M⊕) at intermediate orbital distances (∼1 au) represent an uncharted territory in exoplanetary science. The upcoming microlensing survey by the Nancy Grace Roman Space Telescope will be […]

Upper panels: The peak hydrogen envelope mass fraction at the end of accretion, before any mass loss, shown in colour for the slow, medium and fast host star rotators. The time when 90% of the envelope mass is lost due to solar XUV radiation is shown in white contour lines in Myr. Lower panels: The atomic composition of the outgassed atmospheres of the slow, medium and fast rotator simulations at 300 Myr. Values of R/O < 1 (blue) indicate an atmosphere with free oxygen, a value of R/O=1 (green) imply sufficient oxygen to oxidise H to H2O and C to CO2, and values of R/O > 1 (red) indicate reducing conditions (see definition of R/O in equation 8). The white contour lines in the lower panels show a value of R/O = 1.3. The patch of R/O=0 present for the slow rotator is due to the perseverance of the envelope for those high planetary masses even after 300 Myr, with the magma ocean still providing a significant pressure of free oxygen. -- astro-ph.EP

Astrochemistry, Astrogeology, Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Exoplanets, -moons, -comets, Habitable Zones, Lava / magma ocean / Volcanic Worlds, Meteorites & Asteroids, Status Report, Water/Hycean Worlds & Oceanography

Evolution of Gas Envelopes and Outgassed Atmospheres of Rocky Planets Formed via Pebble Accretion

by Keith CowingSeptember 18, 2024September 18, 2024

We present here results of numerical simulations of the formation and early evolution of rocky planets through pebble accretion, with an with an emphasis on hydrogen envelope longevity and the […]

Rasters of Log10(τp,P A/τp,PW ) at t = 0 for a Mars-sized embryo at (a) r = 1 AU and (b) r = 20 AU. In (a), values corresponding to disks with low ˜α and to a lesser extent high ψ are < 1, indicating the dominance of pebble accretion in the mass-doubling growth of the embryo. In (b), values are < 1 across all parameter space. See Section 4.3.2. -- astro-ph.EP

Astrochemistry, Astrogeology, Astronomy & Telescopes, Exoplanets, -moons, -comets, Habitable Zones, Imaging & Spectroscopy, Status Report

Dust-Gas Coupling in Turbulence – and MHD Wind-Driven Protoplanetary Disks: Implications for Rocky Planet Formation

by Keith CowingAugust 10, 2024August 10, 2024

The degree of coupling between dust particles and their surrounding gas in protoplanetary disks is quantified by the dimensionless Stokes number. The Stokes number (St) governs particle size and spatial […]

Confirmed exoplanets around stars with masses 0.08

Astrogeology, Astronomy & Telescopes, Exoplanets, -moons, -comets, Status Report

Rocky Planet Formation In Compact Disks Around M Dwarfs

by Keith CowingJune 13, 2024

Rocky planets in compact configurations are the most common ones around M dwarfs. Many disks around very low mass stars (between 0.1 and 0.5 M⊙) are rather compact and small […]

Radius inflation, Δ𝑅/𝑅 = (𝑅 − 𝑅𝐶𝐸)/𝑅𝐶𝐸, as a function of age (x-axis) and envelope mass (y-axis), for planets with 4.3 M⊕ of silicates. For illustrative clarity we limited the scale of Δ𝑅/𝑅 to 0.25 (red color), but in reality Δ𝑅/𝑅 reaches values up to 1. Dashed curve signifies the maximum radius inflation for each envelope mass. astro-ph.EP

Astrogeology, Exoplanets, -moons, -comets, Status Report

How Planets Form by Pebble Accretion V. Silicate Rainout Delays Contraction of Sub-Neptunes

by Keith CowingMay 17, 2024May 17, 2024

The characterization of Super-Earth-to-Neptune sized exoplanets relies heavily on our understanding of their formation and evolution.

Sketch of a typical disk around a T Tauri star. Thermo-chemical disk models suggest a layered molecular structure with OH and CO at the top, followed by H2O and CO2. HCN and C2H2 peak in abundance deeper in the disk. Theory and observations suggest the possibility of radial transport of icy grains which can affect the inner disk gas composition. The MIRI instrument on board the James Webb Space Telescope probes the inner (≲ 10 au) warm disk surface. -- astro-ph.EP

Astrochemistry, Astrogeology, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report

The Chemical Inventory of the Inner Regions of Planet-forming Disks — The JWST/MINDS Program

by Keith CowingJuly 31, 2023July 31, 2023

The understanding of planet formation has changed recently, embracing the new idea of pebble accretion. This means that the influx of pebbles from the outer regions of planet-forming disks to […]

TRAPPIST-1 Planets

Exoplanets, -moons, -comets, Status Report, TRAPPIST-1

Composition Constraints Of The TRAPPIST-1 Planets From Their Formation

by Keith CowingJuly 13, 2023July 13, 2023

We study the formation of the TRAPPIST-1 (T1) planets starting shortly after Moon-sized bodies form just exterior to the ice line. Our model includes mass growth from pebble accretion and […]