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Ultra-relativistic electrons in Jupiter's radiation belts
Johnson, W. T. K.; Klein, M.; Hofstadter, M. +18 more
Ground-based observations have shown that Jupiter is a two-component source of microwave radio emission: thermal atmospheric emission and synchrotron emission from energetic electrons spiralling in Jupiter's magnetic field. Later in situ measurements confirmed the existence of Jupiter's high-energy electron-radiation belts, with evidence for elect…
Transient aurora on Jupiter from injections of magnetospheric electrons
Clarke, J. T.; Waite, J. H.; Mauk, B. H. +3 more
Energetic electrons and ions that are trapped in Earth's magnetosphere can suddenly be accelerated towards the planet. Some dynamic features of Earth's aurora (the northern and southern lights) are created by the fraction of these injected particles that travels along magnetic field lines and hits the upper atmosphere. Jupiter's aurora appears sim…
The binary Kuiper-belt object 1998 WW31
Parker, Joel Wm.; Tholen, David J.; Holman, Matthew J. +6 more
The recent discovery of a binary asteroid during a spacecraft fly-by generated keen interest, because the orbital parameters of binaries can provide measures of the masses, and mutual eclipses could allow us to determine individual sizes and bulk densities. Several binary near-Earth, main-belt and Trojan…
The dusk flank of Jupiter's magnetosphere
Gurnett, D. A.; Dougherty, M. K.; Hospodarsky, G. B. +8 more
Limited single-spacecraft observations of Jupiter's magnetopause have been used to infer that the boundary moves inward or outward in response to variations in the dynamic pressure of the solar wind. At Earth, multiple-spacecraft observations have been implemented to understand the physics of how this motion occurs, because they can provide a snap…
Planetary science: Magnetic moments at Jupiter
Hill, Thomas W.
The coming together of two spacecraft near Jupiter provided a unique opportunity to investigate the giant planet's magnetic field -- and the results, collected in this issues, are stunning
Direct detection of a microlens in the Milky Way
Alcock, C.; Allsman, R. A.; Alves, D. R. +22 more
The nature of dark matter remains mysterious, with luminous material accounting for at most ~25 per cent of the baryons in the Universe. We accordingly undertook a survey looking for the microlensing of stars in the Large Magellanic Cloud (LMC) to determine the fraction of Galactic dark matter contained in massive compact halo objects (MACHOs). Th…
An auroral flare at Jupiter
Desai, S.; McComas, D. J.; Young, D. T. +8 more
Jupiter's aurora is the most powerful in the Solar System. It is powered largely by energy extracted from planetary rotation, although there seems also to be a contribution from the solar wind. This contrasts with Earth's aurora, which is generated through the interaction of the solar wind with the magnetosphere. The major features of Jupiter's au…
Discovery of X-rays from the protostellar outflow object HH2
Maeda, Yoshitomo; Bally, John; Feigelson, Eric D. +3 more
Herbig-Haro (HH) objects have been known for 50 years to be luminous condensations of gas in star-forming regions, but their underlying physical nature is still being elucidated. Previously suggested models encompass newborn stars, stellar winds clashing with nebular material, dense pockets of interstellar gas excited by shocks from outflows, and …
Temporal evolution of the electric field accelerating electrons away from the auroral ionosphere
Balogh, A.; André, M.; Buchert, S. +10 more
The bright night-time aurorae that are visible to the unaided eye are caused by electrons accelerated towards Earth by an upward-pointing electric field. On adjacent geomagnetic field lines the reverse process occurs: a downward-pointing electric field accelerates electrons away from Earth. Such magnetic-field-aligned electric fields in the collis…
Substantial reservoirs of molecular hydrogen in the debris disks around young stars
Thi, W. F.; Natta, A.; van Dishoeck, E. F. +7 more
Circumstellar accretion disks transfer matter from molecular clouds to young stars and to the sites of planet formation. The disks observed around pre-main-sequence stars have properties consistent with those expected for the pre-solar nebula from which our own Solar System formed 4.5Gyr ago. But the `debris' disks that encircle more than 15% of n…