scholarly journals Prevalent externally driven protoplanetary disc dispersal as a function of the galactic environment

2019 ◽  
Vol 491 (1) ◽  
pp. 903-922 ◽  
Author(s):  
Andrew J Winter ◽  
J M Diederik Kruijssen ◽  
Mélanie Chevance ◽  
Benjamin W Keller ◽  
Steven N Longmore
Keyword(s):  
Planet Formation ◽  
Solar Neighbourhood ◽  
Related Factor ◽  
Low Mass Stars ◽  
Stellar Feedback ◽  
Low Mass ◽  
Far Ultraviolet ◽  
Birth Environment ◽  
Stellar Density ◽  
Key Questions

ABSTRACT The stellar birth environment can significantly shorten protoplanetary disc (PPD) lifetimes due to the influence of stellar feedback mechanisms. The degree to which these mechanisms suppress the time and mass available for planet formation is dependent on the local far-ultraviolet (FUV) field strength, stellar density, and ISM properties. In this work, we present the first theoretical framework quantifying the distribution of PPD dispersal time-scales as a function of parameters that describe the galactic environment. We calculate the probability density function for FUV flux and stellar density in the solar neighbourhood. In agreement with previous studies, we find that external photoevaporation is the dominant environment-related factor influencing local stellar populations after the embedded phase. Applying our general prescription to the Central Molecular Zone of the Milky Way (i.e. the central $\sim 250~\mbox{${\rm pc}$}$), we predict that $90{{\ \rm per\ cent}}$ of PPDs in the region are destroyed within 1 Myr of the dispersal of the parent molecular cloud. Even in such dense environments, we find that external photoevaporation is the dominant disc depletion mechanism over dynamical encounters between stars. PPDs around low-mass stars are particularly sensitive to FUV-induced mass-loss, due to a shallower gravitational potential. For stars of mass ∼1 M⊙, the solar neighbourhood lies at approximately the highest gas surface density for which PPD dispersal is still relatively unaffected by external FUV photons, with a median PPD dispersal time-scale of ∼4 Myr. We highlight the key questions to be addressed to further contextualize the significance of the local galactic environment for planet formation.

scholarly journals A Decreased Probability of Habitable Planet Formation around Low‐Mass Stars

2007 ◽  
Vol 669 (1) ◽  
pp. 606-614 ◽  
Author(s):  
Sean N. Raymond ◽  
John Scalo ◽  
Victoria S. Meadows
Keyword(s):  
Planet Formation ◽  
Low Mass Stars ◽  
Low Mass ◽  
Habitable Planet

scholarly journals Terrestrial planet formation in extra-solar planetary systems

2007 ◽  
Vol 3 (S249) ◽  
pp. 233-250 ◽  
Author(s):  
Sean N. Raymond
Keyword(s):  
Final Stage ◽  
Planet Formation ◽  
Giant Planet ◽  
Terrestrial Planet ◽  
Circumstellar Disks ◽  
Giant Planets ◽  
Terrestrial Planets ◽  
Low Mass Stars ◽  
Low Mass ◽  
Rocky Planets

AbstractTerrestrial planets form in a series of dynamical steps from the solid component of circumstellar disks. First, km-sized planetesimals form likely via a combination of sticky collisions, turbulent concentration of solids, and gravitational collapse from micron-sized dust grains in the thin disk midplane. Second, planetesimals coalesce to form Moon- to Mars-sized protoplanets, also called “planetary embryos”. Finally, full-sized terrestrial planets accrete from protoplanets and planetesimals. This final stage of accretion lasts about 10-100 Myr and is strongly affected by gravitational perturbations from any gas giant planets, which are constrained to form more quickly, during the 1-10 Myr lifetime of the gaseous component of the disk. It is during this final stage that the bulk compositions and volatile (e.g., water) contents of terrestrial planets are set, depending on their feeding zones and the amount of radial mixing that occurs. The main factors that influence terrestrial planet formation are the mass and surface density profile of the disk, and the perturbations from giant planets and binary companions if they exist. Simple accretion models predicts that low-mass stars should form small, dry planets in their habitable zones. The migration of a giant planet through a disk of rocky bodies does not completely impede terrestrial planet growth. Rather, “hot Jupiter” systems are likely to also contain exterior, very water-rich Earth-like planets, and also “hot Earths”, very close-in rocky planets. Roughly one third of the known systems of extra-solar (giant) planets could allow a terrestrial planet to form in the habitable zone.

scholarly journals Low-mass Star Formation: Observations

2010 ◽  
Vol 6 (S270) ◽  
pp. 25-32 ◽  
Author(s):  
Neal J. Evans
Keyword(s):  
Star Formation ◽  
Molecular Clouds ◽  
Planet Formation ◽  
Mass Star ◽  
Low Mass Stars ◽  
Chemical Changes ◽  
Open Questions ◽  
Low Mass ◽  
Over Time ◽  
The Imf

AbstractI briefly review recent observations of regions forming low mass stars. The discussion is cast in the form of seven questions that have been partially answered, or at least illuminated, by new data. These are the following: where do stars form in molecular clouds; what determines the IMF; how long do the steps of the process take; how efficient is star formation; do any theories explain the data; how are the star and disk built over time; and what chemical changes accompany star and planet formation. I close with a summary and list of open questions.

scholarly journals Astrometry in the Service of Planet Formation Studies: Disk Lifetimes in Nearby Star Forming Regions and a Planet Candidate around a Mature Brown Dwarf

2013 ◽  
Vol 8 (S299) ◽  
pp. 230-231
Author(s):  
Alycia J. Weinberger ◽  
Alan P. Boss ◽  
Guillem Anglada-Escudé
Keyword(s):  
Planet Formation ◽  
Circumstellar Disks ◽  
Giant Planets ◽  
Brown Dwarf ◽  
Low Mass Stars ◽  
Nearby Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Low Mass ◽  
Stellar Associations

AbstractWe present preliminary astrometric results aimed at understanding the lifetime of circumstellar disks and potential for planet formation. We have obtained parallaxes to stars in the TW Hydrae, Upper Scorpius, and Chamaeleon I stellar associations. These enable new estimates for the ages of the stars. We are also performing the Carnegie Astrometric Planet Search of nearby low mass stars for gas giant planets on wide orbits. We have our first candidate around a mature brown dwarf.

scholarly journals Rapid Formation of Super-Earths Around Low-Mass Stars

2020 ◽  
Author(s):  
Brianna Zawadzki
Keyword(s):  
Density Profile ◽  
Surface Density ◽  
Planet Formation ◽  
Secondary Process ◽  
Sufficient Information ◽  
Initial Surface ◽  
Low Mass Stars ◽  
Dwarf Planets ◽  
Low Mass ◽  
M Dwarf

<p>NASA's TESS mission is expected to discover hundreds of M dwarf planets. However, few studies focus on how planets form around low-mass stars. We aim to better characterize the formation process of M dwarf planets to fill this gap and aid in the interpretation of TESS results. We use six sets of N-body planet formation simulations which vary in whether a gas disc is present, initial range of embryo semi-major axes, and initial solid surface density profile. Each simulation begins with 147 equal-mass embryos around a 0.2 solar mass star and runs for 100 Myr. We find that planets form rapidly, with most collisions occurring within the first 1 Myr. The presence of a gas disc reduces the final number of planets relative to a gas-free environment and causes planets to migrate inward. Because planet formation occurs significantly faster than the disc lifetime, super-Earths have plenty of time to accrete extended gaseous envelopes, though these may later be removed by collisions or a secondary process like photo-evaporation. In addition, we find that the final distribution of planets does not retain a memory of the slope of the initial surface density profile, regardless of whether or not a gas disc is present. Thus, our results suggest that present-day observations are unlikely to provide sufficient information to accurately reverse-engineer the initial distribution of solids.</p>

scholarly journals Abundances and Chemical Evolution of the Galactic Center

1977 ◽  
Vol 45 ◽  
pp. 79-101
Author(s):  
Jean Audouze
Keyword(s):  
Chemical Evolution ◽  
Gamma Rays ◽  
Molecular Clouds ◽  
Galactic Center ◽  
Solar Neighbourhood ◽  
Interstellar Matter ◽  
Low Mass Stars ◽  
Element Abundances ◽  
The Galaxy ◽  
Low Mass

AbstractFrom observations of the galactic center using various techniques radioastronomy, millimeter waves (molecules) – infrared and gamma rays, the interstellar matter of this region* appears to have been strongly processed into stars : the gas density is much lower than in the solar neighbourhood. From CO measurements one knows that there are many molecular clouds such as SgrB2 where stars are forming now. From IR measurements, there are some indication that low mass stars are relatively more numerous in such regions than in the external regions of the galaxy. Finally the heavy element abundances show three important features (i) the possibility of strong enhancements in elements such as N and in a less extent 0 and Ne (the so called abundance gradients), (ii) Some specific enhancements of isotopes such43C,44N and also47O relative to42C,45N and43O (iii) Deuterium seems to have a lower abundance than in other parts of the galaxy such as the solar neighbourhood. Simple models of chemical evolution have been designed to account for such features and are rewiewed here.

scholarly journals The Milky Way evolution under the RAVE perspective

2015 ◽  
Vol 11 (S317) ◽  
pp. 320-323
Author(s):  
Georges Kordopatis ◽  
Keyword(s):  
Radial Velocity ◽  
Milky Way ◽  
Solar Neighbourhood ◽  
Low Mass Stars ◽  
Medium Resolution ◽  
Low Mass

AbstractThe RAdial Velocity Experiment (RAVE) collected from 2003 to 2013 medium resolution spectra for 5ċ105 low-mass stars of our Galaxy, improving our understanding of the Milky Way evolution and of its properties outside the Solar neighbourhood. This proceeding gives an overview of RAVE results obtained in the last two years.

Low-Mass Stars and Accretion at the Ages of Planet Formation in the Cepheus OB2 Region

2004 ◽  
Vol 128 (2) ◽  
pp. 805-821 ◽  
Author(s):  
Aurora Sicilia-Aguilar ◽  
Lee W. Hartmann ◽  
César Briceño ◽  
James Muzerolle ◽  
Nuria Calvet
Keyword(s):  
Planet Formation ◽  
Low Mass Stars ◽  
Low Mass

scholarly journals Diverse outcomes of planet formation and composition around low-mass stars and brown dwarfs

2019 ◽  
Author(s):  
Y Miguel ◽  
A Cridland ◽  
C W Ormel ◽  
J J Fortney ◽  
S Ida
Keyword(s):  
Planet Formation ◽  
Planetary Systems ◽  
Brown Dwarfs ◽  
Population Synthesis ◽  
Optimal Conditions ◽  
Low Mass Stars ◽  
Water Fraction ◽  
Low Mass ◽  
M Stars ◽  
Mass Form

Abstract The detection of Earth-size exoplanets around low-mass stars –in stars such as Proxima Centauri and TRAPPIST-1– provide an exceptional chance to improve our understanding of the formation of planets around M stars and brown dwarfs. We explore the formation of such planets with a population synthesis code based on a planetesimal-driven model previously used to study the formation of the Jovian satellites. Because the discs have low mass and the stars are cool, the formation is an inefficient process that happens at short periods, generating compact planetary systems. Planets can be trapped in resonances and we follow the evolution of the planets after the gas has dissipated and they undergo orbit crossings and possible mergers. We find that formation of planets above Mars mass and in the planetesimal accretion scenario, is only possible around stars with masses M⋆ ≥ 0.07Msun and discs of Mdisc ≥ 10−2 Msun. We find that planets above Earth-mass form around stars with masses larger than 0.15 Msun, while planets larger than 5 M⊕ do not form in our model, even not under the most optimal conditions (massive disc), showing that planets such as GJ 3512b form with another, more efficient mechanism. Our results show that the majority of planets form with a significant water fraction; that most of our synthetic planetary systems have 1, 2 or 3 planets, but planets with 4,5,6 and 7 planets are also common, confirming that compact planetary systems with many planets should be a relatively common outcome of planet formation around small stars.

scholarly journals A giant exoplanet orbiting a very-low-mass star challenges planet formation models

Science ◽  
2019 ◽  
Vol 365 (6460) ◽  
pp. 1441-1445 ◽  
Author(s):  
J. C. Morales ◽  
A. J. Mustill ◽  
I. Ribas ◽  
M. B. Davies ◽  
A. Reiners ◽  
...  
Keyword(s):  
Near Infrared ◽  
Planet Formation ◽  
Giant Planet ◽  
Mass Star ◽  
Low Mass Stars ◽  
Migration Rates ◽  
Low Mass ◽  
And Migration ◽  
Core Accretion ◽  
Planet Accretion

Surveys have shown that super-Earth and Neptune-mass exoplanets are more frequent than gas giants around low-mass stars, as predicted by the core accretion theory of planet formation. We report the discovery of a giant planet around the very-low-mass star GJ 3512, as determined by optical and near-infrared radial-velocity observations. The planet has a minimum mass of 0.46 Jupiter masses, very high for such a small host star, and an eccentric 204-day orbit. Dynamical models show that the high eccentricity is most likely due to planet-planet interactions. We use simulations to demonstrate that the GJ 3512 planetary system challenges generally accepted formation theories, and that it puts constraints on the planet accretion and migration rates. Disk instabilities may be more efficient in forming planets than previously thought.

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