Individual Planets Research Articles

Investigating the Atmospheric Mass Loss of the Kepler-105 Planets Straddling the Radius Gap

An intriguing pattern among exoplanets is the lack of detected planets between approximately 1.5 R ⊕ and 2.0 R ⊕. One proposed explanation for this “radius gap” is the photoevaporation of planetary atmospheres, a theory that can be tested by studying individual planetary systems. Kepler-105 is an ideal system for such testing due to the ordering and sizes of its planets. Kepler-105 is a Sun-like star that hosts two planets straddling the radius gap in a rare architecture with the larger planet closer to the host star (R b = 2.53 ± 0.07 R ⊕, P b = 5.41 days, R c = 1.44 ± 0.04 R ⊕, P c = 7.13 days). If photoevaporation sculpted the atmospheres of these planets, then Kepler-105b would need to be much more massive than Kepler-105c to retain its atmosphere, given its closer proximity to the host star. To test this hypothesis, we simultaneously analyzed radial velocities and transit-timing variations of the Kepler-105 system, measuring disparate masses of M b = 10.8 ± 2.3 M ⊕ (ρ b = 3.68 ± 0.84 g cm−3) and M c = 5.6 ± 1.2 M ⊕ (ρ c = 10.4 ± 2.39 g cm−3). Based on these masses, the difference in gas envelope content of the Kepler-105 planets could be entirely due to photoevaporation (in 76% of scenarios), although other mechanisms like core-powered mass loss could have played a role for some planet albedos.

Spatially resolving the volatile sulfur abundance in the HD 100546 protoplanetary disc

ABSTRACT Volatile elements play a crucial role in the formation of planetary systems. Their abundance and distribution in protoplanetary discs provide vital insights into the connection between formation processes and the atmospheric composition of individual planets. Sulfur, being one of the most abundant elements in planet-forming environments, is of great significance, and now observable in exoplanets with JWST. However, planetary formation models currently lack vital knowledge regarding sulfur chemistry in protoplanetary discs. Developing a deeper understanding of the major volatile sulfur carriers in discs is essential to building models that can meaningfully predict planetary atmospheric composition, and reconstruct planetary formation pathways. In this work, we combine archival observations with new data from the Atacama Large sub-Millimeter Array (ALMA) and the Atacama Pathfinder EXperiment (APEX), covering a range of sulfur-bearing species/isotopologs. We interpret this data using the dali thermo-chemical code, for which our model is highly refined and disc-specific. We find that volatile sulfur is heavily depleted from the cosmic value by a factor of ∼1000, with a disc-averaged abundance of S/H ∼ 10−8. We show that the gas-phase sulfur abundance varies radially by ≳3 orders of magnitude, with the highest abundances inside the inner dust ring and coincident with the outer dust ring at r ∼ 150–230 au. Extracting chemical abundances from our models, we find OCS, H2CS, and CS to be the dominant molecular carriers in the gas phase. We also infer the presence of a substantial OCS ice reservoir. We relate our results to the potential atmospheric composition of planets in HD 100546, and the wider exoplanet population.

Using helium 10 830 Å transits to constrain planetary magnetic fields

ABSTRACT Planetary magnetic fields can affect the predicted mass-loss rate for close-in planets that experience large amounts of ultraviolet irradiation. In this work, we present a method to detect the magnetic fields of close-in exoplanets undergoing atmospheric escape using transit spectroscopy at the 10 830 Å line of helium. Motivated by previous work on hydrodynamic and magnetohydrodynamic photoevaporation, we suggest that planets with magnetic fields that are too weak to control the outflow’s topology lead to blueshifted transits due to dayside-to-nightside flows. In contrast, strong magnetic fields prevent this day-to-night flow, as the gas is forced to follow the magnetic field’s roughly dipolar topology. We post-process existing 2D photoevaporation simulations, computing synthetic transit profiles in helium to test this concept. As expected, we find that hydrodynamically dominated outflows lead to blueshifted transits of the order of the sound speed of the gas. Strong surface magnetic fields lead to unshifted or slightly redshifted transit profiles. High-resolution observations can distinguish between these profiles; however, eccentricity uncertainties generally mean that we cannot conclusively say that velocity shifts are due to the outflow for individual planets. The majority of helium observations are blueshifted, which could be a tentative indication that close-in planets generally have surface dipole magnetic field strengths $\lesssim \!\! 0.3$ G. More 3D hydrodynamic and magnetohydrodynamic simulations are needed to confirm this conclusion robustly.

The Possibility of Detecting our Solar System through Astrometry

Searching for exoplanets with different methods has always been the focus of astronomers over the past few years. Among multiple planet detection techniques, astrometry stands out for its capability to accurately determine the orbital parameters of exoplanets. In this study, we examine the likelihood of extraterrestrial intelligent civilizations detecting planets in our solar system using the astrometry method. By conducting injection-recovery simulations, we investigate the detectability of the four giant planets in our solar system under different observing baselines and observational errors. Our findings indicate that extraterrestrial intelligence could detect and characterize all four giant planets, provided they are observed for a minimum of 90 yr with signal-noise ratios exceeding 1. For individual planets such as Jupiter, Saturn, and Neptune, a baseline that surpasses half of their orbital periods is necessary for detection. However, Uranus requires longer observing baselines since its orbital period is roughly half of that of Neptune. If the astrometry precision is equal to or better than 10 μas, all 8707 stars located within 30 pc of our solar system possess the potential to detect the four giant planets within 100 yr. Additionally, our prediction suggests that over 300 stars positioned within 10 pc from our solar system could detect our Earth if they achieve an astrometry precision of 0.3 μas.

Machine-learning Inferences of the Interior Structure of Rocky Exoplanets from Bulk Observational Constraints

Characterizing the interiors of rocky exoplanets is important to understand planetary populations and further investigate planetary habitability. New observable constraints and inference techniques have been explored for this purpose. In this work, we design and train mixture density networks (MDNs) to predict the interior properties of rocky exoplanets with large compositional diversity. In addition to measurements of mass and radius, bulk refractory elemental abundance ratios and the static Love number k 2 are used to constrain the interior of rocky exoplanets. It is found that the MDNs are able to infer the interior properties of rocky exoplanets from the available measurements of exoplanets. Compared with powerful inversion methods based on Bayesian inference, the trained MDNs provide a more rapid characterization of planetary interiors for each individual planet. The MDN model offers a convenient and practical tool for probabilistic inferences of planetary interiors.

Experimental investigation of moving contact pattern in helical planetary gearboxes

Planetary gear sets combine the characteristics of high-power density and compact design which are beneficial for a wide range of high-performance applications. Embedded in the efforts for resource efficiency and cost reduction, new challenges arise regarding a lightweight design. An accurate prediction of the load sharing on the individual planetary gears and especially of the load distribution of the meshing gears is of major importance. A uniform load distribution enables the design of the individual tooth meshes without load increases and oversizing. However, a varying load distribution has been observed in planetary gearboxes with respect to the rotation of the carrier which is caused by misaligned central shafts of the gearbox. This behavior is influenced by several factors, such as manufacturing and assembly deviations, the rigidity of shafts, housing and bearings, the number of planets, the quality of the gear wheels and the operating conditions. To determine the exact load distribution, detailed simulations or extensive experimental prototype tests are required. In an early design phase, these detailed boundary conditions are not yet defined and their effect on a moving contact pattern therefore cannot be reliably considered.Thus, in this paper an experimental investigation of the influencing factors on a varying load distribution with regard to the carrier rotation is presented. Based on experimental data recommendations for the design of planetary gearboxes are derived.

Expanding the inventory of spectral lines used to trace atmospheric escape in exoplanets

Escaping exoplanet atmospheres have been observed as deep transit signatures in a few specific spectral lines. Detections have been made in the hydrogen Ly-αline, the metastable helium line at 10 830 Å, and some UV lines of metallic species. Observational challenges, unexpected nondetections, and model degeneracies have generally made it difficult to draw definitive conclusions about the escape process for individual planets. Expanding on the suite of spectral tracers used may help to mitigate these challenges. We present a new framework for modeling the transmission spectrum of hydrodynamically escaping atmospheres. We predict far UV to near infrared spectra for systems with different planet and stellar types and identify new lines that can potentially be used to study their upper atmospheres. Measuring the radius in the atmosphere at which the strongest lines form puts them into context within the upper atmospheric structure. Targeting a set of complementary spectral lines for the same planet will help us to better constrain the outflow properties.

Numerical modelling of relative contribution of planetary waves to the atmospheric circulation

Abstract. Using the general circulation model of the middle and upper atmosphere (MUAM), a number of numerical scenarios were implemented to study the impact of individual planetary waves (PWs) on the global atmospheric circulation, including zonal wind, temperature, and residual meridional circulation (RMC). The calculations were performed for the winter conditions of the Northern Hemisphere (January–February). We show the contribution to the formation of the dynamic and temperature regimes of the MUAM made by equatorial Kelvin waves propagating to the east, as well as atmospheric normal modes (NMs) with periods from 4 to 16 d. In particular, it is demonstrated that the impact of a 5 d PW and an ultra-fast Kelvin wave (UFKW) can change the speed of circulation flows by up to 6 % in the areas of their amplitude maxima. At the same time, this effect can be significantly enhanced in certain periods of time. The presented research results are important for a deeper understanding of the mechanisms of large-scale atmospheric interactions. Despite the obviousness and simplicity of the problem, such work has not been carried out yet.

Framework for the architecture of exoplanetary systems

We present a novel, model-independent framework for studying the architecture of an exoplanetary system at the system level. This framework allows us to characterise, quantify, and classify the architecture of an individual planetary system. Our aim in this endeavour is to generate a systematic method to study the arrangement and distribution of various planetary quantities within a single planetary system. We propose that the space of planetary system architectures be partitioned into four classes: similar, mixed, anti-ordered, and ordered. We applied our framework to observed and synthetic multi-planetary systems, thereby studying their architectures of mass, radius, density, core mass, and the core water mass fraction. We explored the relationships between a system’s (mass) architecture and other properties. Our work suggests that: (a) similar architectures are the most common outcome of planet formation; (b) internal structure and composition of planets shows a strong link with their system architecture; (c) most systems inherit their mass architecture from their core mass architecture; (d) most planets that started inside the ice line and formed in-situ are found in systems with a similar architecture; and (e) most anti-ordered systems are expected to be rich in wet planets, while most observed mass ordered systems are expected to have many dry planets. We find, in good agreement with theory, that observations are generally biased towards the discovery of systems whose density architectures are similar, mixed, or anti-ordered. This study probes novel questions and new parameter spaces for understanding theory and observations. Future studies may utilise our framework to not only constrain the knowledge of individual planets, but also the multi-faceted architecture of an entire planetary system. We also speculate on the role of system architectures in hosting habitable worlds.

A Study on Astrometeorological Relationship between Planet Azimuth and Temperature

Temperature is one of the key weather parameters, which is a necessity for all life on Earth. Any variation from the normal can impede the physical, chemical, and biological processes of life. Extremes would produce permanent changes that would halt the plant's growth and may cause complete withering. Advance information on temperature events will be helpful in protecting the plant and sustain the productivity under any temperature related disasters. Astrometeorology is one of the oldest organized knowledge systems that interplay between planetary movement and weather. In Tamil Nadu Agricultural University (TNAU), Astrometeorological weather forecast rules for rainfall, wind speed and cyclone events were already well defined. In continuation of this research, identification of Astrometeorological rules for the temperature events had been taken up during 2021-2022 at Agro climate Research Centre, TNAU, Coimbatore. Hourly temperature data from 2011-2016 was collected for 30 districts of Tamil Nadu. In each districts one particular location is selected and is correlated with ephemeris developed for a particular location using Alcyone ephemeris calculator. The findings clearly demonstrated the differential impact of individual planets and their azimuth on the temperature events. The study revealed that low temperature events were influenced when most planets are away (271- 300 degree azimuth) whereas the high temperature events were influenced by the planets that are directly above the location (91 to 120 degrees azimuth) and the in between temperature events were influenced by both 61-90 and 241-270 degrees. The specific azimuth of the Sun, Mercury, Venus, Jupiter, Saturn, Uranus, and Neptune had a makeable influence on a particular temperature event, however all the azimuths of the Moon and Mars had only a mild effect on any temperature event. Based on the results, Astrometeorological rules for the temperature events could be defined and used for the development of hybrid forecasting by overlapping the astromet forecast output on the numerical forecast output. This will produce more accuracy than individual forecast, reduce missing forecast, falls alarms, and improve the usability of forecast.

Five Key Exoplanet Questions Answered via the Analysis of 25 Hot-Jupiter Atmospheres in Eclipse

Population studies of exoplanets are key to unlocking their statistical properties. So far, the inferred properties have been mostly limited to planetary, orbital, and stellar parameters extracted from, e.g., Kepler, radial velocity, and Gaia data. More recently an increasing number of exoplanet atmospheres have been observed in detail from space and the ground. Generally, however, these atmospheric studies have focused on individual planets, with the exception of a couple of works that have detected the presence of water vapor and clouds in populations of gaseous planets via transmission spectroscopy. Here, using a suite of retrieval tools, we analyze spectroscopic and photometric data of 25 hot Jupiters, obtained with the Hubble and Spitzer Space Telescopes via the eclipse technique. By applying the tools uniformly across the entire set of 25 planets, we extract robust trends in the thermal structure and chemical properties of hot Jupiters not obtained in past studies. With the recent launch of the James Webb Space Telescope and the upcoming missions Twinkle and Ariel, population-based studies of exoplanet atmospheres, such as the one presented here, will be a key approach to understanding planet characteristics, formation, and evolution in our galaxy.

Stacked Periodograms as a Probe of Exoplanetary Populations

Abstract Ongoing, extreme-precision Doppler radial-velocity (RV) surveys seek planets with masses less than several M ⊕; population-level studies to determine the distribution of planetary masses, however, remain difficult due to the required observational time investment, as well as challenges associated with robustly detecting the lowest-mass planets. We outline a novel approach that leverages extensive, existing RV data sets to constrain masses of exoplanet populations: stacking periodograms of RV time series across many targets. We show that an exoplanet population may be statistically identifiable in the stacked periodogram, even when individual planets do not pass the threshold of detection. We discuss analytical, statistical properties of the stacked periodogram, perform simulations to demonstrate the efficacy of the method, and investigate the influence of semistructured window functions and stellar activity. Analysis of the Lick–Carnegie Exoplanet Survey data set reveals a marginally significant (1.6σ) signal consistent with a population of exoplanets occupying 3–7 days periods with typical K between 1.6–5.1 m s−1. More detailed investigation of signals associated with stellar activity and yearly systematics may be necessary to confirm this result or detect other underlying Keplerian contributions.

Fundamental challenges to remote sensing of exo-earths

ABSTRACT Inferring the climate and surface conditions of terrestrial exoplanets in the habitable zone is a major goal for the field of exoplanet science. This pursuit will require both statistical analyses of the population of habitable planets as well as in-depth analyses of the climates of individual planets. Given the close relationship between habitability and surface liquid water, it is important to ask whether the fraction of a planet’s surface where water can be a liquid, χhab, can be inferred from observations. We have produced a diverse bank of 1874 3D climate models and computed the full-phase reflectance and emission spectrum for each model to investigate whether surface climate inference is feasible with high-quality direct imaging or secondary eclipse spectroscopy. These models represent the outcome of approximately 200 000 total simulated years of climate and over 50 000 CPU-hours, and the roughly 100 GB model bank and its associated spectra are being made publicly available for community use. We find that there are correlations between spectra and χhab that will permit statistical approaches. However, spectral degeneracies in the climate observables produced by our model bank indicate that inference of individual climates is likely to be model-dependent, and inference will likely be impossible without exhaustive explorations of the climate parameter space. The diversity of potential climates on habitable planets therefore poses fundamental challenges to remote sensing efforts targeting exo-Earths.

Applications of a Gaussian process framework for modelling of high-resolution exoplanet spectra

ABSTRACT Observations of exoplanet atmospheres in high resolution have the potential to resolve individual planetary absorption lines, despite the issues associated with ground-based observations. The removal of contaminating stellar and telluric absorption features is one of the most sensitive steps required to reveal the planetary spectrum and, while many different detrending methods exist, it remains difficult to directly compare the performance and efficacy of these methods. Additionally, though the standard cross-correlation method enables robust detection of specific atmospheric species, it only probes for features that are expected a priori. Here, we present a novel methodology using Gaussian process (GP) regression to directly model the components of high-resolution spectra, which partially addresses these issues. We use two archival CRyogenic Infra-Red Echelle Spectrograph (CRIRES)/Very Large Telescope (VLT) data sets as test cases, observations of the hot Jupiters HD 189733 b and 51 Pegasi b, recovering injected signals with average line contrast ratios of ∼4.37 × 10−3 and ∼1.39 × 10−3, and planet radial velocities ΔKp = 1.45 ± 1.53 $\mathrm{km\, s^{-1}}$ and ΔKp = 0.12 ± 0.12 $\mathrm{km\, s^{-1}}$ from the injection velocities, respectively. In addition, we demonstrate an application of the GP method to assess the impact of the detrending process on the planetary spectrum, by implementing injection-recovery tests. We show that standard detrending methods used in the literature negatively affect the amplitudes of absorption features in particular, which has the potential to render retrieval analyses inaccurate. Finally, we discuss possible limiting factors for the non-detections using this method, likely to be remedied by higher signal-to-noise data.

The Posttransit Tail of WASP-107b Observed at 10830 Å

Abstract Understanding the effects of high-energy radiation and stellar winds on planetary atmospheres is vital for explaining the observed properties of close-in exoplanets. Observations of transiting exoplanets in the triplet of metastable helium lines at 10830 Å allow extended atmospheres and escape processes to be studied for individual planets. We observed one transit of WASP-107b with NIRSPEC on Keck at 10830 Å. Our observations, for the first time, had significant posttransit phase coverage, and we detected excess absorption for over an hour after fourth contact. The data can be explained by a comet-like tail extending out to ∼7 planet radii, which corresponds to roughly twice the Roche lobe radius of the planet. Planetary tails are expected based on three-dimensional simulations of escaping exoplanet atmospheres, particularly those including the interaction between the escaped material and strong stellar winds, and have been previously observed at 10830 Å in at least one other exoplanet. With both the largest midtransit absorption signal and the most extended tail observed at 10830 Å, WASP-107b remains a keystone exoplanet for atmospheric escape studies.

Experimental investigation of the dynamic load sharing of planetary gearboxes

Due to their compactness and power density, planetary gearboxes are used for a wide range of high-performance applications in the automotive, aviation and marine sector. Aerospace applications in particular benefit from a full use of the load capacity potential to meet the requirements for lightweight construction and efficiency. Against this background, the load sharing between the individual planetary gears plays a decisive role. A uniform load sharing enables the design of the single tooth meshes without load increases and oversizing. However, due to manufacturing and assembly deviations, a perfect load sharing is technically not feasible. These load increases are taken into account in the standard calculation of the load capacity of planetary gearboxes by the mesh load factor Kγ. The load sharing in planetary gearboxes is influenced by a number of factors, such as the rigidity of shafts, housing and bearings, the number of planets, the quality of the gear wheels and the operating conditions. Detailed simulations or extensive experimental measurements are required to determine the exact load sharing. For new designs of planetary gearboxes, there are only simplified assumptions available, based on the number of planets and a rough estimation of the operating range. Especially additional dynamic forces, due to operation in high-speed ranges or near resonance frequencies, can lead to a considerable change of the dynamic load sharing compared to the static load sharing and cause an uncertainty in the design. Thus, in this paper the dynamic load sharing behaviour is investigated from 0 to 6800 rpm sun speed for different loads. Based on the experimental data recommendations for the design of planetary gearboxes under consideration of the operating conditions are derived.

System-level Fractionation of Carbon from Disk and Planetesimal Processing

Abstract Finding and characterizing extrasolar Earth analogs will rely on interpretation of the planetary system’s environmental context. The total budget and fractionation between C–H–O species sensitively affect the climatic and geodynamic state of terrestrial worlds, but their main delivery channels are poorly constrained. We connect numerical models of volatile chemistry and pebble coagulation in the circumstellar disk with the internal compositional evolution of planetesimals during the primary accretion phase. Our simulations demonstrate that disk chemistry and degassing from planetesimals operate on comparable timescales and can fractionate the relative abundances of major water and carbon carriers by orders of magnitude. As a result, individual planetary systems with significant planetesimal processing display increased correlation in the volatile budget of planetary building blocks relative to no internal heating. Planetesimal processing in a subset of systems increases the variance of volatile contents across planetary systems. Our simulations thus suggest that exoplanetary atmospheric compositions may provide constraints on when a specific planet formed.

Caught in the act: core-powered mass-loss predictions for observing atmospheric escape

ABSTRACT Past studies have demonstrated that atmospheric escape by the core-powered mass-loss mechanism can explain a multitude of observations associated with the radius valley that separates the super-Earth and sub-Neptune planet populations. Complementing such studies, in this work, we present a shortlist of planets that could be losing their atmospheres today if their evolution is indeed primarily dictated by core-powered mass-loss. We use Bayesian inference analysis on our planet evolution and mass-loss model to estimate the posteriors of the parameters that encapsulate the current state of a given planet, given their published masses, radii, and host star properties. Our models predict that the following planets could be losing their atmospheres today at a rate ≳107 g s−1 at 50 per cent confidence level: pi Men c, Kepler-60 d, Kepler-60 b, HD 86226 c, EPIC 249893012 b, Kepler-107 c, HD 219134 b, Kepler-80 e, Kepler-138 d, and GJ 9827 d. As a by-product of our Bayesian inference analysis, we were also able to identify planets that most-likely harbour either secondary atmospheres abundant with high mean-molecular weight species, low-density interiors abundant with ices, or both. The planets belonging to this second category are WASP-47 e, Kepler-78 b, Kepler-10 b, CoRoT-7 b, HD 80653 b, 55 Cnc e, and Kepler-36 b. While the aforementioned lists are by no means exhaustive, we believe that candidates presented here can serve as useful input for target selection for future surveys and for testing the importance of core-powered mass-loss in individual planetary systems.

Orbital eccentricity–multiplicity correlation for planetary systems and comparison to the Solar system

ABSTRACT The orbit eccentricities of the Solar system planets are unusually low compared to the average of known exoplanetary systems. A power-law correlation has previously been found between the multiplicity of a planetary system and the orbital eccentricities of its components, for systems with multiplicities above two. In this study we investigate the correlation for an expanded data sample by focusing on planetary systems as units (unlike previous studies that have focused on individual planets). Our full data sample contains 1171 exoplanets, in 895 systems, and the correlation between eccentricity and multiplicity is found to follow a clear power law for all multiplicities above one. We discuss the correlation for several individual subsamples and find that all samples consistently follow the same basic trend regardless of e.g. planet types and detection methods. We find that the eccentricities of the Solar system fit the general trend and suggest that the Solar system might not show uncommonly low eccentricities (as often speculated) but rather uncommonly many planets compared to a ‘standard’ planetary system. The only outlier from the power-law correlation is, consistently in all the samples, the one-planet systems. It has previously been suggested that this may be due to additional unseen exoplanets in the observed one-planet systems. Based on this assumption and the power-law correlation, we estimate that the probability of a system having eight planets or more is of the order of 1 per cent, in good agreement with recent predictions from analyses based on independent arguments.

GJ 273: on the formation, dynamical evolution, and habitability of a planetary system hosted by an M dwarf at 3.75 parsec

Context.Planets orbiting low-mass stars such as M dwarfs are now considered a cornerstone in the search for planets with the potential to harbour life. GJ 273 is a planetary system orbiting an M dwarf only 3.75 pc away, which is composed of two confirmed planets, GJ 273b and GJ 273c, and two promising candidates, GJ 273d and GJ 273e. Planet GJ 273b resides in the habitable zone. Currently, due to a lack of observed planetary transits, only the minimum masses of the planets are known:Mbsinib= 2.89M⊕,Mcsinic= 1.18M⊕,Mdsinid= 10.80M⊕, andMesinie= 9.30M⊕. Despite its interesting character, the GJ 273 planetary system has been poorly studied thus far.Aims.We aim to precisely determine the physical parameters of the individual planets, in particular, to break the mass–inclination degeneracy to accurately determine the mass of the planets. Moreover, we present a thorough characterisation of planet GJ 273b in terms of its potential habitability.Methods.First, we explored the planetary formation and hydration phases of GJ 273 during the first 100 Myr. Secondly, we analysed the stability of the system by considering both the two- and four-planet configurations. We then performed a comparative analysis between GJ 273 and the Solar System and we searched for regions in GJ 273 which may harbour minor bodies in stable orbits, that is, the main asteroid belt and Kuiper belt analogues.Results.From our set of dynamical studies, we find that the four-planet configuration of the system allows us to break the mass–inclination degeneracy. From our modelling results, the masses of the planets are unveiled as: 2.89 ≤Mb≤ 3.03M⊕, 1.18 ≤Mc≤ 1.24M⊕, 10.80 ≤Md≤ 11.35M⊕, and 9.30 ≤Me≤ 9.70M⊕. These results point to a system that is likely to be composed of an Earth-mass planet, a super-Earth and two mini-Neptunes. Based on planetary formation models, we determine that GJ 273b is likely an efficient water captor while GJ 273c is probably a dry planet. We find that the system may have several stable regions where minor bodies might reside. Collectively, these results are used to offer a comprehensive discussion about the habitability of GJ 273b.