Astronomers have identified more than 4,000, and counting, confirmed exoplanets -- planets orbiting stars other than the sun -- but only a fraction have the potential to sustain life.
Almost half a century ago the creators of Star Wars imagined a life-sustaining planet, Tatooine, orbiting a pair of stars. Now, 44 years later, scientists have found new evidence that that five known systems with multiple stars, Kepler-34, -35, -38, -64 and -413, are possible candidates for supporting life.
Understanding when global glaciations occur on Earth-like planets is a major challenge in climate evolution research. Most models of how greenhouse gases like CO2 evolve with time on terrestrial planets are deterministic, but the complex, nonlinear nature of Earth's climate history motivates study of non-deterministic climate models.
In the search for small exoplanets orbiting cool stars whose spectral energy distributions peak in the near infrared, the strong absorption of radiation in this region due to water vapour in the atmosphere is a particularly adverse effect for the ground-based observations of cool stars.
In a few years, space telescopes will investigate our Galaxy to detect evidence of life, mainly by observing rocky planets. In the last decade, the observation of exoplanet atmospheres and the theoretical works on biosignature gasses have experienced a considerable acceleration.
The search for water-rich Earth-sized exoplanets around low-mass stars is rapidly gaining attention because they represent the best opportunity to characterize habitable planets in the near future.
A study by scientists at The Australian National University (ANU) on the magnetic fields of planets has found that most planets discovered in other solar systems are unlikely to be as hospitable to life as Earth.
We show that planets around M-dwarfs with M⋆≲0.2M⊙ may not receive enough photons in the photosynthetically active range of 400-750 nm to sustain Earth-like biospheres.
One of the key goals of exoplanet science is the atmospheric characterisation of super-Earths. Atmospheric abundances provide insight on the formation and evolution of those planets and help to put our own rocky planets in context.
One of the unique features associated with the Earth is that the fraction of its surface covered by land is comparable to that spanned by its oceans and other water bodies.
The conditions for life surviving on planets entirely covered in water are more fluid than previously thought, opening up the possibility that water worlds could be habitable, according to a new paper from the University of Chicago and Pennsylvania State University.
The detection of many extrasolar gas giants with high eccentricities indicates that dynamical instabilities in planetary systems are common. These instabilities can alter the orbits of gas giants as well as the orbits of terrestrial planets and therefore eject or move a habitable planet out of the habitable zone.
In an attempt to select stars that can host planets with characteristics similar to our own, we selected seven solar-type stars known to host planets in the habitable zone and for which spectroscopic stellar parameters are available.
Two separate teams of scientists have identified major challenges for the development of life in what has recently become one of the most famous exoplanet systems, TRAPPIST-1.
The TRAPPIST-1, Proxima Centauri, and LHS 1140 systems are the most exciting prospects for future follow-up observations of potentially inhabited planets. All orbit nearby M-stars and are likely tidally locked in 1:1 spin-orbit states, which motivates the consideration of the effects that tidal locking might have on planetary habitability.
On Thursday NASA will announce evidence that hydrothermal activity on the floor of an ice-covered ocean on Saturn's moon Enceladus is most likely creating methane from carbon dioxide. The process is indicative of possible habitable zones within the ocean of Enceladus.
But before we go any further, "habitable" does not mean "inhabited".
Conventional definitions of habitability require abundant liquid surface water to exist continuously over geologic timescales. Water in each of its thermodynamic phases interacts with solar and thermal radiation and is the cause for strong climatic feedbacks.
Hazes are common in known planet atmospheres, and geochemical evidence suggests early Earth occasionally supported an organic haze with significant environmental and spectral consequences. The UV spectrum of the parent star drives organic haze formation through methane photochemistry.
Clouds have a strong impact on the climate of planetary atmospheres. The potential scattering greenhouse effect of CO2 ice clouds in the atmospheres of terrestrial extrasolar planets is of particular interest because it might influence the position and thus the extension of the outer boundary of the classic habitable zone around main sequence stars.
Detecting the atmospheres of low-mass low-temperature exoplanets is a high-priority goal on the path to ultimately detect biosignatures in the atmospheres of habitable exoplanets.