scholarly journals Multiple Moist Climate Equilibrium States on Arid Rocky M-dwarf Planets: A Last-saturation Tracer Analysis

2021 ◽  
Vol 2 (5) ◽  
pp. 201
Author(s):  
Feng Ding ◽  
Robin D. Wordsworth
Keyword(s):  
Equilibrium States ◽  
Dwarf Planets ◽  
M Dwarf

scholarly journals Red Optical Planet Survey: A radial velocity search for low mass M dwarf planets

2013 ◽  
Vol 47 ◽  
pp. 05002
Author(s):  
J.R. Barnes ◽  
J.S. Jenkins ◽  
H.R.A. Jones ◽  
P. Rojo ◽  
P. Arriagada ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Dwarf Planets ◽  
Low Mass ◽  
M Dwarf

scholarly journals An Astrobiological Experiment to Explore the Habitability of Tidally Locked M-Dwarf Planets

2012 ◽  
Vol 8 (S293) ◽  
pp. 192-196
Author(s):  
Daniel Angerhausen ◽  
Haley Sapers ◽  
Eugenio Simoncini ◽  
Stefanie Lutz ◽  
Marcelo da Rosa Alexandre ◽  
...  
Keyword(s):  
Academic Research ◽  
Environmental Parameters ◽  
Climate Simulation ◽  
Habitable Zone ◽  
Dwarf Stars ◽  
Dwarf Planets ◽  
Late Type Star ◽  
M Dwarf Stars ◽  
M Dwarf ◽  
Simulation Chamber

AbstractWe present a summary of a three-year academic research proposal drafted during the Sao Paulo Advanced School of Astrobiology (SPASA) to prepare for upcoming observations of tidally locked planets orbiting M-dwarf stars. The primary experimental goal of the suggested research is to expose extremophiles from analogue environments to a modified space simulation chamber reproducing the environmental parameters of a tidally locked planet in the habitable zone of a late-type star. Here we focus on a description of the astronomical analysis used to define the parameters for this climate simulation.

scholarly journals Can we detect aurora in exoplanets orbiting M dwarfs?

2019 ◽  
Vol 488 (1) ◽  
pp. 633-644 ◽  
Author(s):  
A A Vidotto ◽  
N Feeney ◽  
J H Groh
Keyword(s):  
Solar System ◽  
Radio Emission ◽  
Stellar Wind ◽  
Engineering Calculation ◽  
M Dwarfs ◽  
Radio Detection ◽  
Dwarf Planets ◽  
M Dwarf ◽  
Host Stars ◽  
New Instruments

ABSTRACT New instruments and telescopes, such as SPIRou, CARMENES, and Transiting Exoplanet Survey Satellite (TESS), will increase manyfold the number of known planets orbiting M dwarfs. To guide future radio observations, we estimate radio emission from known M dwarf planets using the empirical radiometric prescription derived in the Solar system, in which radio emission is powered by the wind of the host star. Using solar-like wind models, we find that the most promising exoplanets for radio detections are GJ 674 b and Proxima b, followed by YZ Cet b, GJ 1214 b, GJ 436 b. These are the systems that are the closest to us (<10 pc). However, we also show that our radio fluxes are very sensitive to the unknown properties of winds of M dwarfs. So, which types of winds would generate detectable radio emission? In a ‘reverse engineering’ calculation, we show that winds with mass-loss rates $\dot{M} \gtrsim \kappa _{\rm sw} /u_{\rm sw}^3$ would drive planetary radio emission detectable with present-day instruments, where usw is the local stellar wind velocity and κsw is a constant that depends on the size of the planet, distance, and orbital radius. Using observationally constrained properties of the quiescent winds of GJ 436 and Proxima Cen, we conclude that it is unlikely that GJ 436 b and Proxima b would be detectable with present-day radio instruments, unless the host stars generate episodic coronal mass ejections. GJ 674 b, GJ 876 b, and YZ Cet b could present good prospects for radio detection, provided that their host stars’ winds have $\dot{M} u_{\rm sw}^{3} \gtrsim 1.8\times 10^{-4} \, {\rm M}_\odot \,{\rm yr}^{-1}\, ({\rm km\,s^{-1}})^{3}$.

scholarly journals THE INTERACTION OF VENUS-LIKE, M-DWARF PLANETS WITH THE STELLAR WIND OF THEIR HOST STAR

2015 ◽  
Vol 806 (1) ◽  
pp. 41 ◽  
Author(s):  
O. Cohen ◽  
Y. Ma ◽  
J. J. Drake ◽  
A. Glocer ◽  
C. Garraffo ◽  
...  
Keyword(s):  
Stellar Wind ◽  
Dwarf Planets ◽  
M 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 Ozone chemistry on tidally locked M dwarf planets

2020 ◽  
Vol 492 (2) ◽  
pp. 1691-1705 ◽  
Author(s):  
Jack S Yates ◽  
Paul I Palmer ◽  
James Manners ◽  
Ian Boutle ◽  
Krisztian Kohary ◽  
...  
Keyword(s):  
Water Vapour ◽  
Atmospheric Transport ◽  
Ozone Layer ◽  
Catalytic Cycle ◽  
Atmospheric Ozone ◽  
Ozone Distribution ◽  
Dwarf Planets ◽  
Stellar Radiation ◽  
Hydrogen Oxide ◽  
M Dwarf

ABSTRACT We use the Met Office Unified Model to explore the potential of a tidally locked M dwarf planet, nominally Proxima Centauri b irradiated by a quiescent version of its host star, to sustain an atmospheric ozone layer. We assume a slab ocean surface layer, and an Earth-like atmosphere of nitrogen and oxygen with trace amounts of ozone and water vapour. We describe ozone chemistry using the Chapman mechanism and the hydrogen oxide (HOx, describing the sum of OH and HO2) catalytic cycle. We find that Proxima Centauri radiates with sufficient UV energy to initialize the Chapman mechanism. The result is a thin but stable ozone layer that peaks at 0.75 parts per million at 25 km. The quasi-stationary distribution of atmospheric ozone is determined by photolysis driven by incoming stellar radiation and by atmospheric transport. Ozone mole fractions are smallest in the lowest 15 km of the atmosphere at the substellar point and largest in the nightside gyres. Above 15 km the ozone distribution is dominated by an equatorial jet stream that circumnavigates the planet. The nightside ozone distribution is dominated by two cyclonic Rossby gyres that result in localized ozone hotspots. On the dayside the atmospheric lifetime is determined by the HOx catalytic cycle and deposition to the surface, with nightside lifetimes due to chemistry much longer than time-scales associated with atmospheric transport. Surface UV values peak at the substellar point with values of 0.01 W m−2, shielded by the overlying atmospheric ozone layer but more importantly by water vapour clouds.

scholarly journals The Direct Detection and Characterization of M-dwarf Planets Using Light Echoes

2018 ◽  
Vol 854 (2) ◽  
pp. 134 ◽  
Author(s):  
William B. Sparks ◽  
Richard L. White ◽  
Roxana E. Lupu ◽  
Holland C. Ford
Keyword(s):  
Direct Detection ◽  
Dwarf Planets ◽  
Light Echoes ◽  
M Dwarf

scholarly journals Rapid formation of super-Earths around low-mass stars

2021 ◽  
Vol 503 (1) ◽  
pp. 1390-1406
Author(s):  
Brianna Zawadzki ◽  
Daniel Carrera ◽  
Eric B Ford
Keyword(s):  
Density Profile ◽  
Surface Density ◽  
Sufficient Information ◽  
Mass Star ◽  
Initial Surface ◽  
Low Mass Stars ◽  
Giant Impact ◽  
Dwarf Planets ◽  
Low Mass ◽  
M Dwarf

ABSTRACT 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 ten sets of N-body planet formation simulations that vary in whether a gas disc is present, initial range of embryo semimajor 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. We find that roughly a quarter of planetary systems experience their final giant impact inside the gas disc, suggesting that some super-Earths may be able to reaccrete an extended gaseous envelope after their final giant impact, though these may be affected by additional processes such as photoevaporation. 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.

scholarly journals Biosignature Anisotropy Modeled on Temperate Tidally Locked M-dwarf Planets

2018 ◽  
Vol 868 (1) ◽  
pp. L6 ◽  
Author(s):  
Howard Chen ◽  
Eric T. Wolf ◽  
Ravi Kopparapu ◽  
Shawn Domagal-Goldman ◽  
Daniel E. Horton
Keyword(s):  
Dwarf Planets ◽  
M Dwarf

scholarly journals Radial velocity studies of cool stars

2014 ◽  
Vol 372 (2014) ◽  
pp. 20130088 ◽  
Author(s):  
Hugh R. A. Jones ◽  
John Barnes ◽  
Mikko Tuomi ◽  
James S. Jenkins ◽  
Guillem Anglada-Escude
Keyword(s):  
Radial Velocity ◽  
Current View ◽  
Velocity Data ◽  
M Dwarfs ◽  
Low Mass Stars ◽  
Robust Detection ◽  
Dwarf Planets ◽  
Low Mass ◽  
M Dwarf ◽  
Radial Velocity Data

Our current view of exoplanets is one derived primarily from solar-like stars with a strong focus on understanding our Solar System. Our knowledge about the properties of exoplanets around the dominant stellar population by number, the so-called low-mass stars or M dwarfs, is much more cursory. Based on radial velocity discoveries, we find that the semi-major axis distribution of M dwarf planets appears to be broadly similar to those around more massive stars and thus formation and migration processes might be similar to heavier stars. However, we find that the mass of M dwarf planets is relatively much lower than the expected mass dependency based on stellar mass and thus infer that planet formation efficiency around low-mass stars is relatively impaired. We consider techniques to overcome the practical issue of obtaining good quality radial velocity data for M dwarfs despite their faintness and sustained activity and emphasize (i) the wavelength sensitivity of radial velocity signals, (ii) the combination of radial velocity data from different experiments for robust detection of small amplitude signals, and (iii) the selection of targets and radial velocity interpretation of late-type M dwarfs should consider H α behaviour.

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