For nearly a century Black holes have been a hot topic, a physical singularity or simply a flawed, all be it brilliant, mathematical concept? Fundamental proof of the existence of black holes lies in the proof of the existence of their event horizons. One such proof lies in the comparison of the X-ray luminosities of black hole and neutron star X

Short period binary white dwarfs may merge within a Hubble time due to gravitational wave radiation. We have begun a targeted survey to find merging white dwarfs systems, and our first results have tripled the number of known merging white dwarf systems. Our sample includes systems with orbital periods as short as 1 hr and with merger times less

In addition to the well-known 11-year solar cycle, the Sun's magnetic activity also shows significant variation on shorter time scales, e.g. between one and two years. We observe a quasi-biennial (2-year) signal in the solar p-mode oscillation frequencies, which are sensitive probes of the solar interior. The signal is visible in Sun-as-a-star data

We analyze simultaneous helioseismic observations collected by the ground- and space-based instruments during solar cycle 23 by computing oscillation frequencies for low- and intermediate-degree p-modes on a time scale of 36 days. We find that the frequency shifts corresponding to different angular degree, ell, indicate different epochs for the

Context. The penumbra of sunspots has a complex magnetic field topology whose three-dimensional organization remains unclear after more than a century of investigation. Aims: I derive a geometrical model of the penumbral magnetic field topology from an uncombed inversion setup designed to reproduce the net circular polarization (NCP) of

Amino acids in Solar system bodies may have played a key role in the chemistry that led to the origin of life on Earth. We present laboratory studies testing the stability of amino acids against high energy radiation. All the 20 chiral amino acids in the levo form found in the proteins of the current terrestrial biochemistry were irradiated in the