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Two distinct sequences of blue straggler stars in the globular cluster M 30
Dalessandro, E.; Beccari, G.; Ferraro, F. R. +7 more
Stars in globular clusters are generally believed to have all formed at the same time, early in the Galaxy's history. `Blue stragglers' are stars massive enough that they should have evolved into white dwarfs long ago. Two possible mechanisms have been proposed for their formation: mass transfer between binary companions and stellar mergers result…
A high stellar velocity dispersion for a compact massive galaxy at redshift z = 2.186
van Dokkum, Pieter G.; Franx, Marijn; Kriek, Mariska
Recent studies have found that the oldest and most luminous galaxies in the early Universe are surprisingly compact, having stellar masses similar to present-day elliptical galaxies but much smaller sizes. This finding has attracted considerable attention, as it suggests that massive galaxies have grown in size by a factor of about five over the p…
Observed variations of methane on Mars unexplained by known atmospheric chemistry and physics
Lefèvre, Franck; Forget, François
The detection of methane on Mars has revived the possibility of past or extant life on this planet, despite the fact that an abiogenic origin is thought to be equally plausible. An intriguing aspect of the recent observations of methane on Mars is that methane concentrations appear to be locally enhanced and change with the seasons. However, metha…
Early assembly of the most massive galaxies
Hilton, Matt; Stott, John P.; West, Michael J. +15 more
The current consensus is that galaxies begin as small density fluctuations in the early Universe and grow by in situ star formation and hierarchical merging. Stars begin to form relatively quickly in sub-galactic-sized building blocks called haloes which are subsequently assembled into galaxies. However, exactly when this assembly takes place is a…
A binary origin for `blue stragglers' in globular clusters
Sills, Alison; Knigge, Christian; Leigh, Nathan
Blue stragglers in globular clusters are abnormally massive stars that should have evolved off the stellar main sequence long ago. There are two known processes that can create these objects: direct stellar collisions and binary evolution. However, the relative importance of these processes has remained unclear. In particular, the total number of …
The changing phases of extrasolar planet CoRoT-1b
de Mooij, Ernst J. W.; Albrecht, Simon; Snellen, Ignas A. G.
Hot Jupiters are a class of extrasolar planet that orbit their parent stars at very short distances. They are expected to be tidally locked, which can lead to a large temperature difference between their daysides and nightsides. Infrared observations of eclipsing systems have yielded dayside temperatures for a number of transiting planets. The day…
Saturn's rotation period from its atmospheric planetary-wave configuration
Read, P. L.; Dowling, T. E.; Schubert, G.
The rotation period of a gas giant's magnetic field (called the System III reference frame) is commonly used to infer its bulk rotation. Saturn's dipole magnetic field is not tilted relative to its rotation axis (unlike Jupiter, Uranus and Neptune), so the surrogate measure of its long-wavelength (kilometric) radiation is currently used to fix the…
A single sub-kilometre Kuiper belt object from a stellar occultation in archival data
Zucker, S.; Gal-Yam, A.; Sari, R. +5 more
The Kuiper belt is a remnant of the primordial Solar System. Measurements of its size distribution constrain its accretion and collisional history, and the importance of material strength of Kuiper belt objects. Small, sub-kilometre-sized, Kuiper belt objects elude direct detection, but the signature of their occultations of background stars shoul…
Global circulation as the main source of cloud activity on Titan
Sotin, Christophe; Barnes, Jason W.; Le Mouélic, Stéphane +11 more
Clouds on Titan result from the condensation of methane and ethane and, as on other planets, are primarily structured by circulation of the atmosphere. At present, cloud activity mainly occurs in the southern (summer) hemisphere, arising near the pole and at mid-latitudes from cumulus updrafts triggered by surface heating and/or local methane sour…
Storms in the tropics of Titan
Brown, M. E.; Schaller, E. L.; Roe, H. G. +1 more
Methane clouds, lakes and most fluvial features on Saturn's moon Titan have been observed in the moist high latitudes, while the tropics have been nearly devoid of convective clouds and have shown an abundance of wind-carved surface features like dunes. The presence of small-scale channels and dry riverbeds near the equator observed by the Huygens…