Earth as a planetary system

This chapter describes how the first found exoplanets presented puzzles: they orbited where they should not have formed or where they could not have survived the death of their stars. The Solar System had its own puzzles to add: Mars is smaller than expected, while Venus, Earth, and Mars had more water—at least at one time—than could be understood. This chapter shows how astronomers worked through the combination of these puzzles: now we appreciate that planets can change their orbits, scatter water-bearing asteroids about, steal material from growing planets, or team up with other planets to stabilize their future. The special history of Jupiter and Saturn as a pair bringing both destruction and water to Earth emerged from the study of seventeenth-century resonant clocks, from the water contents of asteroids, and from experiments with supercomputers imposing the laws of physics on virtual worlds.

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DESTINY: Database for the Effects of STellar encounters on dIsks and plaNetary sYstems

Computational Astrophysics and Cosmology ◽

10.1186/s40668-019-0030-3 ◽

2019 ◽

Vol 6 (1) ◽

Cited By ~ 2

Author(s):

Asmita Bhandare ◽

Susanne Pfalzner

Keyword(s):

Planetary System ◽

Planetary Systems ◽

Gravitational Effect ◽

Parameter Study ◽

Orbital Inclination ◽

Particle Properties ◽

Disk Size ◽

Stellar Group ◽

Cluster Environment ◽

Parabolic Orbits

Abstract Most stars form as part of a stellar group. These young stars are mostly surrounded by a disk from which potentially a planetary system might form. Both, the disk and later on the planetary system, may be affected by the cluster environment due to close fly-bys. The here presented database can be used to determine the gravitational effect of such fly-bys on non-viscous disks and planetary systems. The database contains data for fly-by scenarios spanning mass ratios between the perturber and host star from 0.3 to 50.0, periastron distances from 30 au to 1000 au, orbital inclination from 0∘ to 180∘ and angle of periastron of 0∘, 45∘ and 90∘. Thus covering a wide parameter space relevant for fly-bys in stellar clusters. The data can either be downloaded to perform one’s own diagnostics like for e.g. determining disk size, disk mass, etc. after specific encounters, obtain parameter dependencies or the different particle properties can be visualized interactively. Currently the database is restricted to fly-bys on parabolic orbits, but it will be extended to hyperbolic orbits in the future. All of the data from this extensive parameter study is now publicly available as DESTINY.

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

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3867 ◽

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.

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III. On the nature and construction of the sun and fixed stars

Philosophical Transactions of the Royal Society of London ◽

10.1098/rstl.1795.0005 ◽

1795 ◽

Vol 85 ◽

pp. 46-72 ◽

Cited By ~ 13

Keyword(s):

Central Body ◽

Planetary System ◽

Considerable Progress ◽

The Sun ◽

Great Satisfaction ◽

The Earth ◽

The World ◽

Celestial Bodies ◽

The Universe ◽

Made In

Among the celestial bodies the sun is certainly the first which should attract our notice. It is a fountain of light that illuminates the world! it is the cause of that heat which maintains the productive power of nature, and makes the earth a fit habitation for man! it is the central body of the planetary system; and what renders a knowledge of its nature still more interesting to us is, that the numberless stars which compose the universe, appear, by the strictest analogy, to be similar bodies. Their innate light is so intense, that it reaches the eye of the observer from the remotest regions of space, and forcibly claims his notice. Now, if we are convinced that an inquiry into the nature and properties of the sun is highly worthy of our notice, we may also with great satisfaction reflect on the considerable progress that has already been made in our knowledge of this eminent body. It would require a long detail to enumerate all the various discoveries which have been made on this subject; I shall, therefore, content myself with giving only the most capital of them.

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An unusually low density ultra-short period super-Earth and three mini-Neptunes around the old star TOI-561

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3728 ◽

2020 ◽

Author(s):

G Lacedelli ◽

L Malavolta ◽

L Borsato ◽

G Piotto ◽

D Nardiello ◽

...

Keyword(s):

Transit Time ◽

Time Variation ◽

Planetary System ◽

Radial Velocities ◽

Low Density ◽

Outer Planets ◽

Short Period ◽

The Stability

Abstract Based on HARPS-N radial velocities (RVs) and TESS photometry, we present a full characterisation of the planetary system orbiting the late G dwarf After the identification of three transiting candidates by TESS, we discovered two additional external planets from RV analysis. RVs cannot confirm the outer TESS transiting candidate, which would also make the system dynamically unstable. We demonstrate that the two transits initially associated with this candidate are instead due to single transits of the two planets discovered using RVs. The four planets orbiting TOI-561 include an ultra-short period (USP) super-Earth (TOI-561 b) with period Pb = 0.45 d, mass Mb = 1.59 ± 0.36 M⊕ and radius Rb = 1.42 ± 0.07 R⊕, and three mini-Neptunes: TOI-561 c, with Pc = 10.78 d, Mc = 5.40 ± 0.98 M⊕, Rc = 2.88 ± 0.09 R⊕; TOI-561 d, with Pd = 25.6 d, Md = 11.9 ± 1.3 M⊕, Rd = 2.53 ± 0.13 R⊕; and TOI-561 e, with Pe = 77.2 d, Me = 16.0 ± 2.3 M⊕, Re = 2.67 ± 0.11 R⊕. Having a density of 3.0 ± 0.8 g cm−3, TOI-561 b is the lowest density USP planet known to date. Our N-body simulations confirm the stability of the system and predict a strong, anti-correlated, long-term transit time variation signal between planets d and e. The unusual density of the inner super-Earth and the dynamical interactions between the outer planets make TOI-561 an interesting follow-up target.

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HD 76920 b pinned down: A detailed analysis of the most eccentric planetary system around an evolved star

Publications of the Astronomical Society of Australia ◽

10.1017/pasa.2021.8 ◽

2021 ◽

Vol 38 ◽

Author(s):

C. Bergmann ◽

M. I. Jones ◽

J. Zhao ◽

A. J. Mustill ◽

R. Brahm ◽

...

Keyword(s):

Spectroscopic Analysis ◽

Planetary System ◽

Continuous Phase ◽

Minimum Mass ◽

Orbital Elements ◽

Stellar Envelope ◽

Orbital Decay ◽

Fundamental Stellar Parameters ◽

Transit Probability ◽

Gaia Dr2

Abstract We present 63 new multi-site radial velocity (RV) measurements of the K1III giant HD 76920, which was recently reported to host the most eccentric planet known to orbit an evolved star. We focused our observational efforts on the time around the predicted periastron passage and achieved near-continuous phase coverage of the corresponding RV peak. By combining our RV measurements from four different instruments with previously published ones, we confirm the highly eccentric nature of the system and find an even higher eccentricity of $e=0.8782 \pm 0.0025$ , an orbital period of $415.891^{+0.043}_{-0.039}\,\textrm{d}$ , and a minimum mass of $3.13^{+0.41}_{-0.43}\,\textrm{M}_{\textrm{J}}$ for the planet. The uncertainties in the orbital elements are greatly reduced, especially for the period and eccentricity. We also performed a detailed spectroscopic analysis to derive atmospheric stellar parameters, and thus the fundamental stellar parameters ( $M_*, R_*, L_*$ ), taking into account the parallax from Gaia DR2, and independently determined the stellar mass and radius using asteroseismology. Intriguingly, at periastron, the planet comes to within 2.4 stellar radii of its host star’s surface. However, we find that the planet is not currently experiencing any significant orbital decay and will not be engulfed by the stellar envelope for at least another 50–80 Myr. Finally, while we calculate a relatively high transit probability of 16%, we did not detect a transit in the TESS photometry.

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