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Heidelberg, Germany

Kaltenegger L.,MPIA | Kaltenegger L.,Harvard - Smithsonian Center for Astrophysics | Sasselov D.,Harvard - Smithsonian Center for Astrophysics
Astrophysical Journal Letters

This Letter outlines a simple approach to evaluate habitability of terrestrial planets by assuming different types of planetary atmospheres and using corresponding model calculations. Our approach can be applied for current and future candidates provided by the Kepler mission and other searches. The resulting uncertainties and changes in the number of planetary candidates in the HZ for the Kepler 2011 February data release are discussed. To first order, the HZ depends on the effective stellar flux distribution in wavelength and time, the planet albedo, and greenhouse gas effects. We provide a simple set of parameters which can be used for evaluating future planet candidates from transit searches. © 2011. The American Astronomical Society. All rights reserved. Source

Van Der Laan T.P.R.,MPIA
Journal of Physics: Conference Series

Circumnuclear starburst rings are effective barriers against gas inflow. The large 'pile-up' of gas leads to distinct star forming events in the rings of NGC 5248 and NGC 6951. In our work, the rings are distinctly seen as the locations where the bulk of the central kiloparsec star formation in the last 2 Gyr has taken place. This in turn has direct implications for the large scale bars that have driven the formation of the circumnuclear rings in these galaxies. They have to be at least as old. The system of large-scale bar and circumnuclear ring has therefore ample time to stop gas inflow on the scale of the last 100 pc. The stars formed in the ring will help build the (pseudo-)bulge and eventually alter the gravitational potential. Source

Rugheimer S.,Harvard - Smithsonian Center for Astrophysics | Rugheimer S.,Center for Astrophysics | Kaltenegger L.,Harvard - Smithsonian Center for Astrophysics | Zsom A.,MPIA | And 3 more authors.

We present model atmospheres for an Earth-like planet orbiting the entire grid of main sequence FGK stars with effective temperatures ranging from T eff=4250 K to Teff=7000 K in 250 K intervals. We have modeled the remotely detectable spectra of Earth-like planets for clear and cloudy atmospheres at the 1 AU equivalent distance from the VIS to IR (0.4 to 20 μm) to compare detectability of features in different wavelength ranges in accordance with the James Webb Space Telescope and future design concepts to characterize exo-Earths. We have also explored the effect of the stellar UV levels as well as spectral energy distribution on a terrestrial atmosphere, concentrating on detectable atmospheric features that indicate habitability on Earth, namely, H2O, O3, CH4, N2O, and CH3Cl. The increase in UV dominates changes of O3, OH, CH4, N2O, and CH3Cl, whereas the increase in stellar temperature dominates changes in H2O. The overall effect as stellar effective temperatures and corresponding UV increase is a lower surface temperature of the planet due to a bigger part of the stellar flux being reflected at short wavelengths, as well as increased photolysis. Earth-like atmosphere models show more O3 and OH but less stratospheric CH 4, N2O, CH3Cl, and tropospheric H2O (but more stratospheric H2O) with increasing effective temperature of main sequence stars. The corresponding detectable spectral features, on the other hand, show different detectability depending on the wavelength observed. We concentrate on directly imaged planets here as a framework to interpret future light curves, direct imaging, and secondary eclipse measurements of atmospheres of terrestrial planets in the habitable zone at varying orbital positions. Copyright © 2013, Mary Ann Liebert, Inc. 2013. Source

Kaltenegger L.,MPIA | Haghighipour N.,University of Hawaii at Manoa | Haghighipour N.,University of Tubingen
Astrophysical Journal

We have developed a comprehensive methodology for calculating the boundaries of the habitable zone (HZ) of planet-hosting S-type binary star systems. Our approach is general and takes into account the contribution of both stars to the location and extent of the binary HZ with different stellar spectral types. We have studied how the binary eccentricity and stellar energy distribution affect the extent of the HZ. Results indicate that in binaries where the combination of mass-ratio and orbital eccentricity allows planet formation around a star of the system to proceed successfully, the effect of a less luminous secondary on the location of the primary's HZ is generally negligible. However, when the secondary is more luminous, it can influence the extent of the HZ. We present the details of the derivations of our methodology and discuss its application to the binary HZ around the primary and secondary main-sequence stars of an FF, MM, and FM binary, as well as two known planet-hosting binaries α Cen AB and HD 196886. © 2013. The American Astronomical Society. All rights reserved.. Source

Haghighipour N.,University of Hawaii at Manoa | Haghighipour N.,University of Tubingen | Kaltenegger L.,MPIA
Astrophysical Journal

We have developed a comprehensive methodology for calculating the circumbinary habitable zone (HZ) in planet-hosting P-type binary star systems. We present a general formalism for determining the contribution of each star of the binary to the total flux received at the top of the atmosphere of an Earth-like planet and use the Sun's HZ to calculate the inner and outer boundaries of the HZ around a binary star system. We apply our calculations to the Kepler's currently known circumbinary planetary systems and show the combined stellar flux that determines the boundaries of their HZs. We also show that the HZ in P-type systems is dynamic and, depending on the luminosity of the binary stars, their spectral types, and the binary eccentricity, its boundaries vary as the stars of the binary undergo their orbital motion. We present the details of our calculations and discuss the implications of the results. © 2013. The American Astronomical Society. All rights reserved.. Source

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