Rafael Barrena

GLANCING VIEWS OF THE EARTH: FROM A LUNAR ECLIPSE TO AN EXOPLANETARY TRANSIT

It has been posited that lunar eclipse observations may help predict the in-transit signature of Earth-like extrasolar planets. However, a comparative analysis of the two phenomena addressing in detail the transport of stellar light through the planets atmosphere has not yet been presented. Here, we proceed with the investigation of both phenomena by making use of a common formulation. Our starting point is a set of previously unpublished near-infrared spectra collected at various phases during the August 2008 lunar eclipse. We then take the formulation to the limit of an infinitely distant observer in order to investigate the in-transit signature of the Earth-Sun system as being observed from outside our Solar System. The refraction-bending of sunlight rays that pass through the Earths atmosphere is a critical factor in the illumination of the eclipsed Moon. Likewise, refraction will have an impact on the in-transit transmission spectrum for specific planet-star systems depending on the refractive properties of the planets atmosphere, the stellar size and the planets orbital distance. For the Earth-Sun system, at mid-transit, refraction prevents the remote observers access to the lower ~12-14 km of the atmosphere and, thus, also to the bulk of the spectroscopically-active atmospheric gases. We demonstrate that the effective optical radius of the Earth in transit is modulated by refraction and varies by ~12 km from mid-transit to 2nd contact. The refractive nature of atmospheres, a property which is rarely accounted for in published investigations, will pose additional challenges to the characterization of Earth-like extrasolar planets. Refraction may have a lesser impact for Earth-like extrasolar planets within the habitable zone of some M-type stars.

Around the Clock Observations of the Q0957+561A,B Gravitationally Lensed Quasar

An observing campaign with 10 participating observatories has undertaken to monitor the optical brightness of the Q0957 gravitationally lensed quasar for 10 consecutive nights in 2000 January. The resulting A image brightness curve has significant brightness fluctuations and makes a photometric prediction for the B image light curve for a second campaign planned for 2001 March 12-21. The ultimate purpose is to determine the gravitational lens time delay to a fraction of an hour and to seek evidence of rapid microlensing.

Gravitational lensing detection of an extremely dense environment around a galaxy cluster

Galaxy clusters form at the highest-density nodes of the cosmic web1,2. The clustering of dark matter halos hosting these galaxy clusters is enhanced relative to the general mass distribution, with the matter density beyond the virial region being strongly correlated to the halo mass (halo bias)3. Halo properties other than mass can further enhance the halo clustering (secondary bias)4–7. Observational campaigns have ascertained the halo bias8–10, but efforts to detect this secondary bias for massive halos have been inconclusive11–13. Here, we report the analysis of the environment bias in a sample of massive clusters, selected through the Sunyaev–Zel’dovich effect by the Planck mission14,15, focusing on the detection of the environment dark matter correlated to a single cluster, PSZ2 G099.86+58.45. The gravitational lensing signal of the outskirts is very large and can be traced up to 30 megaparsecs with a high signal-to-noise ratio (about 3.4), implying environment matter density in notable excess of the cosmological mean. Our finding reveals this system to be extremely rare in the current paradigm of structure formation and, implies that enhancing mechanisms around high-mass halos can be very effective. Future lensing surveys will probe the surroundings of single haloes, enabling the study of their formation and evolution of structure.The strong gravitational lensing signal around the massive cluster PSZ2 G099.86+58.45 indicates environment matter density in notable excess of the cosmological mean and implies that enhancing mechanisms around high-mass halos can be very effective.