Search Publications
Old galaxies in the young Universe
Cimatti, A.; Daddi, E.; Rodighiero, G. +8 more
More than half of all stars in the local Universe are found in massive spheroidal galaxies, which are characterized by old stellar populations with little or no current star formation. In present models, such galaxies appear rather late in the history of the Universe as the culmination of a hierarchical merging process, in which larger galaxies ar…
The massive binary companion star to the progenitor of supernova 1993J
Smartt, Stephen J.; Kudritzki, Rolf P.; Podsiadlowski, Philipp +2 more
The massive star that underwent a collapse of its core to produce supernova (SN)1993J was subsequently identified as a non-variable red supergiant star in images of the galaxy M81 taken before explosion. It showed an excess in ultraviolet and B-band colours, suggesting either the presence of a hot, massive companion star or that it was embedded in…
The binary progenitor of Tycho Brahe's 1572 supernova
Filippenko, Alexei V.; Foley, Ryan J.; Ibata, Rodrigo +8 more
The brightness of type Ia supernovae, and their homogeneity as a class, makes them powerful tools in cosmology, yet little is known about the progenitor systems of these explosions. They are thought to arise when a white dwarf accretes matter from a companion star, is compressed and undergoes a thermonuclear explosion. Unless the companion star is…
A large population of `Lyman-break' galaxies in a protocluster at redshift z ~ 4.1
White, Richard L.; Franx, Marijn; Illingworth, Garth D. +35 more
The most massive galaxies and the richest clusters are believed to have emerged from regions with the largest enhancements of mass density relative to the surrounding space. Distant radio galaxies may pinpoint the locations of the ancestors of rich clusters, because they are massive systems associated with `overdensities' of galaxies that are brig…
Reconstructing galaxy histories from globular clusters
Jordán, Andrés; Marzke, Ronald O.; Côté, Patrick +1 more
Nearly a century after the true nature of galaxies as distant `island universes' was established, their origin and evolution remain great unsolved problems of modern astrophysics. One of the most promising ways to investigate galaxy formation is to study the ubiquitous globular star clusters that surround most galaxies. Globular clusters are compa…
An interplanetary shock traced by planetary auroral storms from the Sun to Saturn
Vourlidas, Angelos; Hansen, Kenneth C.; Prangé, Renée +4 more
A relationship between solar activity and aurorae on Earth was postulated long before space probes directly detected plasma propagating outwards from the Sun. Violent solar eruption events trigger interplanetary shocks that compress Earth's magnetosphere, leading to increased energetic particle precipitation into the ionosphere and subsequent auro…
The interstellar N2 abundance towards HD 124314 from far-ultraviolet observations
Andersson, B. -G.; McCandliss, Stephan R.; Knauth, David C. +1 more
The abundance of interstellar molecular nitrogen (N2) is of considerable importance: models of steady-state gas-phase interstellar chemistry, together with millimetre-wavelength observations of interstellar N2H+ in dense molecular clouds predict that N2 should be the most abundant nitrogen-bearing molecu…