Microlensing is the amplification of the light of a background star due to the transit on the line of sight of a massive object, which acts as a gravitational lens. The lens can be another star or a brown dwarf. The light curve of the background star has a typical bell shape, with a duration of a few days. Since microlensing events are very rare, millions of source stars must be monitored every night in order to detect them. (didactic movie)

Microlensing can be used to search for extrasolar planets. In fact, if the lens is a star accompanied by a planet, the light curve of the source contains an anomaly like a secondary peak or a dip. Our group is part of the MiNDSTEp collaboration, looking for extrasolar planets in microlensing observations toward the bulge of our Galaxy. Every year we are leading observations at the Danish telescope at ESO, La Silla (Chile) and at Salerno University Observatory. We have also developed an advanced code for automatic real-time modeling of anomalous microlensing events (RTModel).
Recently, these observations are being supported by the Spitzer and Kepler satellites, which are dedicating an important part of their observing time to microlensing.

Extrasolar planets can also be found by their transits on the disk of the mother-star. Thanks to the defocussing technique, we are reaching precisions of the order of the millimagnitude in these measurements. Observations are currently lead at the Danish telescope at ESO, La Silla (Chile), at Osservatorio Astronomico di Bologna at Loiano, at the Isaac Newton Telescope in Canarian islands and at Calar Alto (Spain).

Microlensing is also a tool for the study of the dark matter halo of our Galaxy and nearby galaxies. In fact, the population of massive dark objects in the halo can be estimated by the number of microlensing events. Our group has led the PLAN collaboration, searching for microlensing events in the Andromeda galaxy M31. We have observed at Osservatorio Astronomico di Bologna at Loiano, at Osservatorio del Toppo di Castelgrande, at Himalayan Chandra Telescope (India) and at the Large Binocular Telescope (USA). (read more)

Gravitational lensing by black holes leads to the spectacular formation of infinite sequences of images very close to the shadow cast by the black hole in the sky. The direct observation of this shadow and of higher order images could soon be accessible by incoming instruments in several electromagnetic bands. The black hole in the center of our Galaxy provides the best candidate for these new observations that will open a new era in gravitational physics. (read more)

Scaling laws in galaxies are important to understand the mechanisms for the formation of the first galaxies. We have found a new law relating the mass of the massive black hole hosted in the center of galaxies and the kinetic energy of stars in the corresponding bulge. It appears that galaxies follow an analogue of the H-R diagram. (TV report)

Early universe cosmology investigates the first instants of our universe. General Relativity is not sufficient to describe the hot quantum universe close to the big bang. String theory and other quantum gravity theories suggest the possibility that the big bang was actually not the beginning of time, but just a transition from a previous pre-big bang collapsing universe to our observed expanding universe.

The Baryon Asymmetry problem refers to the observed asymmetry in the Universe between baryonic and antibaryonic matter. Since the Big Bang should have produced equal amounts of matter and antimatter, it is then expected that some still unkonw mechanism must have acted differently for matter and antimatter during the Universe evolution. This mechanism cannot be explaind within the standard model of particle physics and cosmology, and in fact, modern theories aimed at solving the problem of the baryon asymmetry are based on physics beyond these models.