Search Publications
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…
A distance of 133-137 parsecs to the Pleiades star cluster
Kulkarni, S. R.; Shao, M.; Pan, Xiaopei
Nearby `open' clusters of stars (those that are not gravitationally bound) have played a crucial role in the development of stellar astronomy because, as a consequence of the stars having a common age, they provide excellent natural laboratories to test theoretical stellar models. Clusters also play a fundamental part in determining distance scale…
Compact sources as the origin of the soft γ-ray emission of the Milky Way
Strong, A. W.; Walter, R.; Ubertini, P. +16 more
The Milky Way is known to be an abundant source of γ-ray photons, now determined to be mainly diffuse in nature and resulting from interstellar processes. In the soft γ-ray domain, point sources are expected to dominate, but the lack of sensitive high-resolution observations did not allow for a clear estimate of the contribution from such sources.…
A test of general relativity using radio links with the Cassini spacecraft
Iess, L.; Tortora, P.; Bertotti, B.
According to general relativity, photons are deflected and delayed by the curvature of space-time produced by any mass. The bending and delay are proportional to γ + 1, where the parameter γ is unity in general relativity but zero in the newtonian model of gravity. The quantity γ - 1 measures the degree to which gravity is not a purely geometric e…
An extended upper atmosphere around the extrasolar planet HD209458b
Lecavelier des Etangs, A.; Ferlet, R.; Vidal-Madjar, A. +4 more
The planet in the system HD209458 is the first one for which repeated transits across the stellar disk have been observed. Together with radial velocity measurements, this has led to a determination of the planet's radius and mass, confirming it to be a gas giant. But despite numerous searches for an atmospheric signature, only the dense lower atm…
A class of compact dwarf galaxies from disruptive processes in galaxy clusters
Ferguson, H. C.; Hilker, M.; Drinkwater, M. J. +5 more
Dwarf galaxies have attracted increased attention in recent years, because of their susceptibility to galaxy transformation processes within rich galaxy clusters. Direct evidence for these processes, however, has been difficult to obtain, with a small number of diffuse light trails and intra-cluster stars being the only signs of galaxy disruption.…
An energetic stellar outburst accompanied by circumstellar light echoes
Munari, U.; Sparks, William B.; Bond, Howard E. +6 more
Some classes of stars, including novae and supernovae, undergo explosive outbursts that eject stellar material into space. In 2002, the previously unknown variable star V838 Monocerotis brightened suddenly by a factor of ~104. Unlike a supernova or nova, it did not explosively eject its outer layers; rather, it simply expanded to become…
The magnetic field of an isolated neutron star from X-ray cyclotron absorption lines
Caraveo, P. A.; Bignami, G. F.; Mereghetti, S. +1 more
Isolated neutron stars are highly magnetized, fast-rotating objects that form as an end point of stellar evolution. They are directly observable in X-ray emission, because of their high surface temperatures. Features in their X-ray spectra could in principle reveal the presence of atmospheres, or be used to estimate the strength of their magnetic …