Search Publications
Gravitational microlensing by low-mass objects in the globular cluster M22
Casertano, Stefano; Livio, Mario; Albrow, Michael D. +4 more
Gravitational microlensing offers a means of determining directly the masses of objects ranging from planets to stars, provided that the distances and motions of the lenses and sources can be determined. A globular cluster observed against the dense stellar field of the Galactic bulge presents ideal conditions for such observations because the pro…
Space physics: Rhythms of the auroral dance
Newell, Patrick T.
Earlier this year, the four satellites of the Cluster mission passed through part of the electric circuit that causes aurorae. Their observations support the view that intense aurorae form in regions largely devoid of electrons.
Rossby waves on the Sun as revealed by solar `hills'
Kuhn, J. R.; Bush, R. I.; Scherrer, P. +1 more
It is a long-standing puzzle that the Sun's photosphere-its visible surface-rotates differentially, with the equatorial regions rotating faster than the poles. It has been suggested that waves analogous to terrestrial Rossby waves, and known as r-mode oscillations, could explain the Sun's differential rotation: Rossby waves are seen in the oceans …
Interception of comet Hyakutake's ion tail at a distance of 500 million kilometres
Balsiger, H.; Geiss, J.; Schwadron, N. A. +6 more
Remote sensing observations and the direct sampling of material from a few comets have established the characteristic composition of cometary gas. This gas is ionized by solar ultraviolet radiation and the solar wind to form `pick-up' ions, ions in a low ionization state that retain the same compositional signatures as the original gas. The pick-u…
Identification of comet Hyakutake's extremely long ion tail from magnetic field signatures
Balogh, André; Jones, Geraint H.; Horbury, Timothy S.
Observations of the varying orientations of comet tails led to the suggestion of the existence of the solar wind-a continuous outflow of ionized material from the Sun. It is now well established that gas from comets is ionized by several processes and joins the solar wind, forming an ion (plasma) tail that points away from the Sun. The plasma envi…
Evidence against a redshift z > 6 for the galaxy STIS123627+621755
Dey, Arjun; Stanford, S. A.; Spinrad, Hyron +5 more
The identification of galaxies at extreme distances provides the most direct information about the earliest phases of galaxy formation. But at redshifts z > 5 even the most luminous galaxies appear faint; the interpretation of low signal-to-noise ratio data is difficult and misidentifications do occur. Here we report optical and near-infrared o…
Discovery of a comet by its Lyman-α emission
Bertaux, Jean-Loup; Laakso, Harri; Lallement, Rosine +6 more
Several searches for near-Earth objects have recently been initiated, as a result of increased awareness of the hazard of impacts on the Earth. These programs mainly search for asteroids, so amateur astronomers can still contribute to the discovery of comets, especially out of the orbital plane of the Solar System. An ideal way to search for comet…
Unusual spectral energy distribution of a galaxy previously reported to be at redshift 6.68
Chen, Hsiao-Wen; Lanzetta, Kenneth M.; Pascarelle, Sebastian +1 more
Observations of distant galaxies are important both for understanding how galaxies form and for probing the physical conditions of the Universe at early times. It is, however, very difficult to identify galaxies at redshifts <italic>z</italic> > 5, because they are so faint and have few spectral characteristics. We previously report…
The afterglow, redshift and extreme energetics of the γ-ray burst of 23 January 1999
Kelson, D. D.; Malkan, M. A.; Harrison, F. A. +26 more
Long-lived emission, known as afterglow, has now been detected from about a dozen γ-ray bursts. Distance determinations place the bursts at cosmological distances, with redshifts, z, ranging from ~1 to 3. The energy required to produce these bright γ-ray flashes is enormous: up to ~10 53erg, or 10 per cent of the rest-mass energy of a n…
A giant periodic flare from the soft γ-ray repeater SGR1900+14
Cline, T.; Hurley, K.; Golenetskii, S. +11 more
Soft γ-ray repeaters are transient sources of high-energy photons; they emit sporadic and short (about 0.1s) bursts of `soft' γ-rays during periods of activity, which are often broken by long stretches of quiescence. These objects are associated with neutron stars in young supernova remnants. The event of 5 March 1979 was the most intense burst to…