Infrared diffuse interstellar bands in the Galactic Centre region.

The spectrum of any star viewed through a sufficient quantity of diffuse interstellar material reveals a number of absorption features collectively called 'diffuse interstellar bands' (DIBs). The first DIBs were reported about 90  years ago, and currently well over 500 are known. None of them has been convincingly identified with any specific element or molecule, although recent studies suggest that the DIB carriers are polyatomic molecules containing carbon.

An infrared ring around the magnetar SGR 1900+14.

Magnetars are a special class of slowly rotating (period approximately 5-12 s) neutron stars with extremely strong magnetic fields (>10(14 )G)--at least an order of magnitude larger than those of the 'normal' radio pulsars. The potential evolutionary links and differences between these two types of object are still unknown; recent studies, however, have provided circumstantial evidence connecting magnetars with very massive progenitor stars. Here we report the discovery of an infrared elliptical ring or shell surrounding the magnetar SGR 1900+14.

Pinwheels in the Quintuplet cluster.

The five enigmatic cocoon stars, after which the Quintuplet cluster was christened, have puzzled astronomers since their discovery. Their extraordinary cool, featureless thermal spectra have been attributed to various stellar types from young to highly evolved, whereas their absolute luminosities place them among the supergiants. We present diffraction-limited images from the Keck 1 telescope that resolve this debate with the identification of rotating spiral plumes characteristic of colliding-wind binary "pinwheel" nebulae.

An upper limit to the masses of stars.

There is no accepted upper mass limit for stars. Such a basic quantity eludes both theory and observation, because of an imperfect understanding of the star-formation process and because of incompleteness in surveying the Galaxy. The Arches cluster is ideal for investigating such limits, being large enough to expect stars at least as massive as approximately 500 solar masses (approximately 500 Mo; based on a typical mass function), and young enough for its most massive members to still be visible.