So far, roughly 40 quasars with redshifts greater than z = 6 have been discovered. Each quasar contains a black hole with a mass of about one billion solar masses (10(9) M Sun symbol). The existence of such black holes when the Universe was less than one billion years old presents substantial challenges to theories of the formation and growth of black holes and the coevolution of black holes and galaxies. Here we report the discovery of an ultraluminous quasar, SDSS J010013.02+280225.8, at redshift z = 6.30. It has an optical and near-infrared luminosity a few times greater than those of previously known z > 6 quasars. On the basis of the deep absorption trough on the blue side of the Lyman-α emission line in the spectrum, we estimate the proper size of the ionized proximity zone associated with the quasar to be about 26 million light years, larger than found with other z > 6.1 quasars with lower luminosities. We estimate (on the basis of a near-infrared spectrum) that the black hole has a mass of ∼1.2 × 10(10) M Sun symbol, which is consistent with the 1.3 × 10(10) M Sun symbol derived by assuming an Eddington-limited accretion rate.

Context. The DANCe survey provides photometric and astrometric (position and proper motion) measurements for approximately 2 million unique sources in a region encompassing ∼80 deg 2 centered on the Pleiades cluster. Aims. We aim at deriving a complete census of the Pleiades and measure the mass and luminosity functions of the cluster. Methods. Using the probabilistic selection method previously described, we identified high probability members in the DANCe (i ≥ 14 mag) and Tycho-2 (V 12 mag) catalogues and studied the properties of the cluster over the corresponding luminosity range. Results. We find a total of 2109 high-probability members, of which 812 are new, making it the most extensive and complete census of the cluster to date. The luminosity and mass functions of the cluster are computed from the most massive members down to ∼0.025 M . The size, sensitivity, and quality of the sample result in the most precise luminosity and mass functions observed to date for a cluster. Conclusions. Our census supersedes previous studies of the Pleiades cluster populations, in terms of both sensitivity and accuracy.

We discussthe proposalrelating the origin of someof the diffuse interstellar bands (DIBs) to neutral and ionized polycyclic aromatic hydrocarbons(PAHs) presentin interstellar clouds. Laboratory spectra of severalPAHs, isolated at low temperature in inert gas matrices, are comparedwith an extensiveset of astronomical spectra of reddened,early type stars. From this comparison,it is concludedthat PAH ions are good candidatesto explain someof the DIBs.Unambiguousassignmentsare difficult, however,dueto the shift in wavelengths and the band broadeninginducedin the laboratory spectra by the solid matrix." Definitive band assignmentsand, ultimately, the test of the of the proposal that PAH ions carry someof the DIB must await the availability of gas-phase measurementsin the laboratory. The presentassessment offers a guideline for future laboratory experimentsby allowing the preselectionof PromisingPAH moleculesto be studied in jet expansions.