Some of the Milky Way's "celebrity stars" opulent, attention-getting, and short-lived can be found in this Hubble Space Telescope image of the glittering star cluster called Trumpler 14. It is located 8,000 light-years away in the Carina Nebula, a huge star-formation region in our galaxy. Because the cluster is only 500,000 years old, it has one of the highest concentrations of massive, luminous stars in the entire Milky Way. Like some Hollywood celebrities, the stars will go out in a flash. Within just a few million years they will burn out and explode as supernovae. But the story's not over. The blast waves will trigger the formation of a new generation of stars inside the nebula in an ongoing cycle of star birth and death.
A prevalence of dynamo-generated magnetic fields in the cores of intermediate-mass stars
Nature 529, 7586 (2016). doi:10.1038/nature16171
Authors: Dennis Stello, Matteo Cantiello, Jim Fuller, Daniel Huber, Rafael A. García, Timothy R. Bedding, Lars Bildsten & Victor Silva Aguirre
Magnetic fields play a part in almost all stages of stellar evolution. Most low-mass stars, including the Sun, show surface fields that are generated by dynamo processes in their convective envelopes. Intermediate-mass stars do not have deep convective envelopes, although 10 per cent exhibit strong surface fields that are presumed to be residuals from the star formation process. These stars do have convective cores that might produce internal magnetic fields, and these fields might survive into later stages of stellar evolution, but information has been limited by our inability to measure the fields below the stellar surface. Here we report the strength of dipolar oscillation modes for a sample of 3,600 red giant stars. About 20 per cent of our sample show mode suppression, by strong magnetic fields in the cores, but this fraction is a strong function of mass. Strong core fields occur only in red giants heavier than 1.1 solar masses, and the occurrence rate is at least 50 per cent for intermediate-mass stars (1.6–2.0 solar masses), indicating that powerful dynamos were very common in the previously convective cores of these stars.
Exposed water ice on the nucleus of comet 67P/Churyumov–Gerasimenko
Nature 529, 7586 (2016). doi:10.1038/nature16190
Authors: G. Filacchione, M. C. De Sanctis, F. Capaccioni, A. Raponi, F. Tosi, M. Ciarniello, P. Cerroni, G. Piccioni, M. T. Capria, E. Palomba, G. Bellucci, S. Erard, D. Bockelee-Morvan, C. Leyrat, G. Arnold, M. A. Barucci, M. Fulchignoni, B. Schmitt, E. Quirico, R. Jaumann, K. Stephan, A. Longobardo, V. Mennella, A. Migliorini, E. Ammannito, J. Benkhoff, J. P. Bibring, A. Blanco, M. I. Blecka, R. Carlson, U. Carsenty, L. Colangeli, M. Combes, M. Combi, J. Crovisier, P. Drossart, T. Encrenaz, C. Federico, U. Fink, S. Fonti, W. H. Ip, P. Irwin, E. Kuehrt, Y. Langevin, G. Magni, T. McCord, L. Moroz, S. Mottola, V. Orofino, U. Schade, F. Taylor, D. Tiphene, G. P. Tozzi, P. Beck, N. Biver, L. Bonal, J-Ph. Combe, D. Despan, E. Flamini, M. Formisano, S. Fornasier, A. Frigeri, D. Grassi, M. S. Gudipati, D. Kappel, F. Mancarella, K. Markus, F. Merlin, R. Orosei, G. Rinaldi, M. Cartacci, A. Cicchetti, S. Giuppi, Y. Hello, F. Henry, S. Jacquinod, J. M. Reess, R. Noschese, R. Politi & G. Peter
Although water vapour is the main species observed in the coma of comet 67P/Churyumov–Gerasimenko and water is the major constituent of cometary nuclei, limited evidence for exposed water-ice regions on the surface of the nucleus has been found so far. The absence of large regions of exposed water ice seems a common finding on the surfaces of many of the comets observed so far. The nucleus of 67P/Churyumov–Gerasimenko appears to be fairly uniformly coated with dark, dehydrated, refractory and organic-rich material. Here we report the identification at infrared wavelengths of water ice on two debris falls in the Imhotep region of the nucleus. The ice has been exposed on the walls of elevated structures and at the base of the walls. A quantitative derivation of the abundance of ice in these regions indicates the presence of millimetre-sized pure water-ice grains, considerably larger than in all previous observations. Although micrometre-sized water-ice grains are the usual result of vapour recondensation in ice-free layers, the occurrence of millimetre-sized grains of pure ice as observed in the Imhotep debris falls is best explained by grain growth by vapour diffusion in ice-rich layers, or by sintering. As a consequence of these processes, the nucleus can develop an extended and complex coating in which the outer dehydrated crust is superimposed on layers enriched in water ice. The stratigraphy observed on 67P/Churyumov–Gerasimenko is therefore the result of evolutionary processes affecting the uppermost metres of the nucleus and does not necessarily require a global layering to have occurred at the time of the comet’s formation.
Evidence grows for giant planet on fringes of Solar System
Nature 529, 7586 (2016). http://www.nature.com/doifinder/10.1038/529266a
Author: Alexandra Witze
Gravitational signature hints at massive object that orbits the Sun every 20,000 years.
Astronomy: Brightest-ever supernova
Nature 529, 7586 (2016). doi:10.1038/529259d
A supernova has been spotted that is twice as luminous as the previous record holder — at its peak it blazed brighter than 570 billion Suns.Subo Dong at Peking University in Beijing and his colleagues spotted the exploding star, called ASASSN-15lh, in June last