Longitudinal Range Control For A Lifting Vehicle Entering A Planetary Atmosphere

1962 ◽  
pp. 241-270
Keyword(s):  
Planetary Atmosphere

scholarly journals GJ 436b and the stellar wind interaction: simulations constraints using Lyα and Hα transits

2020 ◽  
Author(s):  
Carolina Villarreal D’Angelo ◽  
Aline A Vidotto ◽  
Alejandro Esquivel ◽  
Gopal Hazra ◽  
Allison Youngblood
Keyword(s):  
Mass Loss ◽  
Stellar Wind ◽  
Planetary System ◽  
Neutral Hydrogen ◽  
Hydrogen Atmosphere ◽  
Planetary Atmosphere ◽  
Hydrodynamic Simulations ◽  
Stellar Disc ◽  
Planetary Mass ◽  
Best Fit

Abstract The GJ 436 planetary system is an extraordinary system. The Neptune-size planet that orbits the M3 dwarf revealed in the Lyα line an extended neutral hydrogen atmosphere. This material fills a comet-like tail that obscures the stellar disc for more than 10 hours after the planetary transit. Here, we carry out a series of 3D radiation hydrodynamic simulations to model the interaction of the stellar wind with the escaping planetary atmosphere. With these models, we seek to reproduce the $\sim 56\%$ absorption found in Lyα transits, simultaneously with the lack of absorption in Hα transit. Varying the stellar wind strength and the EUV stellar luminosity, we search for a set of parameters that best fit the observational data. Based on Lyα observations, we found a stellar wind velocity at the position of the planet to be around [250-460] km s−1 with a temperature of [3 − 4] × 105 K. The stellar and planetary mass loss rates are found to be 2 × 10−15 M⊙ yr−1 and ∼[6 − 10] × 109 g s−1, respectively, for a stellar EUV luminosity of [0.8 − 1.6] × 1027 erg s−1. For the parameters explored in our simulations, none of our models present any significant absorption in the Hα line in agreement with the observations.

scholarly journals Direct observation of long-lived cyanide anions in superexcited states

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Xiao-Fei Gao ◽  
Jing-Chen Xie ◽  
Hao Li ◽  
Xin Meng ◽  
Yong Wu ◽  
...  
Keyword(s):  
Direct Observation ◽  
Electron Attachment ◽  
Planetary Atmosphere ◽  
Interstellar Space ◽  
Dissociative Electron Attachment ◽  
Circumstellar Envelopes ◽  
Vibrational States ◽  
Cyanide Anion ◽  
Exceptional Stability ◽  
Electronic Ground

AbstractThe cyanide anion (CN−) has been identified in cometary coma, interstellar medium, planetary atmosphere and circumstellar envelopes, but its origin and abundance are still disputed. An isolated CN− is stabilized in the vibrational states up to ν = 17 of the electronic ground-state 1Σ+, but it is not thought to survive in the electronic or vibrational states above the electron autodetachment threshold, namely, in superexcited states. Here we report the direct observation of long-lived CN− yields of the dissociative electron attachment to cyanogen bromide (BrCN), and confirm that some of the CN− yields are distributed in the superexcited vibrational states ν ≥ 18 (1Σ+) or the superexcited electronic states 3Σ+ and 3Π. The triplet state can be accessed directly in the impulsive dissociation of BrCN− or by an intersystem transition from the superexcited vibrational states of CN−. The exceptional stability of CN− in the superexcited states profoundly influences its abundance and is potentially related to the production of other compounds in interstellar space.

scholarly journals Stellar activity and magnetic shielding

2009 ◽  
Vol 5 (S264) ◽  
pp. 385-394 ◽  
Author(s):  
J.-M. Grießmeier ◽  
M. Khodachenko ◽  
H. Lammer ◽  
J. L. Grenfell ◽  
A. Stadelmann ◽  
...  
Keyword(s):  
Dipole Moment ◽  
Magnetic Dipole ◽  
Magnetic Dipole Moment ◽  
Direct Interaction ◽  
Planetary Atmosphere ◽  
Stellar Activity ◽  
Planetary Environment ◽  
Atmospheric Loss ◽  
Planetary Magnetic Field ◽  
Planetary Habitability

AbstractStellar activity has a particularly strong influence on planets at small orbital distances, such as close-in exoplanets. For such planets, we present two extreme cases of stellar variability, namely stellar coronal mass ejections and stellar wind, which both result in the planetary environment being variable on a timescale of billions of years. For both cases, direct interaction of the streaming plasma with the planetary atmosphere would entail servere consequences. In certain cases, however, the planetary atmosphere can be effectively shielded by a strong planetary magnetic field. The efficiency of this shielding is determined by the planetary magnetic dipole moment, which is difficult to constrain by either models or observations. We present different factors which influence the strength of the planetary magnetic dipole moment. Implications are discussed, including nonthermal atmospheric loss, atmospheric biomarkers, and planetary habitability.

scholarly journals Metallicity effect and planet mass function in pebble-based planet formation models

2018 ◽  
Vol 619 ◽  
pp. A174 ◽  
Author(s):  
N. Brügger ◽  
Y. Alibert ◽  
S. Ataiee ◽  
W. Benz
Keyword(s):  
Internal Structure ◽  
Planet Formation ◽  
Large Fraction ◽  
Mass Function ◽  
Planetary Atmosphere ◽  
Population Synthesis ◽  
Core Accretion ◽  
Mass Functions ◽  
Synthesis Approach ◽  
Gaseous Envelope

Context. One of the main scenarios of planet formation is the core accretion model where a massive core forms first and then accretes a gaseous envelope. This core forms by accreting solids, either planetesimals or pebbles. A key constraint in this model is that the accretion of gas must proceed before the dissipation of the gas disc. Classical planetesimal accretion scenarios predict that the time needed to form a giant planet’s core is much longer than the time needed to dissipate the disc. This difficulty led to the development of another accretion scenario, in which cores grow by accretion of pebbles, which are much smaller and thus more easily accreted, leading to more rapid formation. Aims. The aim of this paper is to compare our updated pebble-based planet formation model with observations, in particular the well-studied metallicity effect. Methods. We adopt the Bitsch et al. (2015a, A&A, 575, A28) disc model and the Bitsch et al. (2015b, A&A, 582, A112) pebble model and use a population synthesis approach to compare the formed planets with observations. Results. We find that keeping the same parameters as in Bitsch et al. (2015b, A&A, 582, A112) leads to no planet growth due to a computation mistake in the pebble flux (2018b). Indeed a large fraction of the heavy elements should be put into pebbles (Zpeb∕Ztot = 0.9) in order to form massive planets using this approach. The resulting mass functions show a huge amount of giants and a lack of Neptune-mass planets, which are abundant according to observations. To overcome this issue we include the computation of the internal structure for the planetary atmosphere in our model. This leads to the formation of Neptune-mass planets but no observable giants. Furthermore, reducing the opacity of the planetary envelope more closely matches observations. Conclusions. We conclude that modelling the internal structure for the planetary atmosphere is necessary to reproduce observations.

Sign in / Sign up

Export Citation Format

Share Document