Search Publications
Distance to the Virgo cluster galaxy M100 from Hubble Space Telescope observations of Cepheids
Illingworth, Garth D.; Kennicutt, Robert C.; Madore, Barry F. +11 more
Accurate distances to galaxies are critical for determining the present expansion rate of the Universe or Hubble constant (H0). An important step in resolving the current uncertainty in H0 is the measurement of the distance to the Virgo cluster of galaxies. New observations using the Hubble Space Telescope yield a distance of…
Detection of intergalactic ionized helium absorption in a high-redshift quasar
Boksenberg, A.; Deharveng, J. M.; Jakobsen, P. +3 more
Observations obtained with the recently refurbished Hubble Space Telescope reveal strong absorption arising from singly ionized helium along the line of sight to a high-redshift quasar. The strength of the absorption suggests that it may arise in a diffuse ionized intergalactic medium. The detection also confirms that substantial amounts of helium…
Evidence for a quasar in the radio galaxy Cygnus A from observation of broad-line emission
Antonucci, Robert; Hurt, Todd; Kinney, Anne
ACTIVE galaxies are thought to be powered by the accretion of surrounding dust and gas onto central black holes. The unified model1-3 of active galaxies predicts that narrow-line radio galaxies (NLRGs), which are very luminous at radio wavelengths and have narrow optical emission lines, would appear as quasars—which have broad emission …
Dust formation in Nova Cassiopeiae 1993 seen by ultraviolet absorption
Sonneborn, G.; Hauschildt, P. H.; Shore, S. N. +2 more
The clouds of gas in interstellar space also contain grains of dust, whose properties and origins have been the focus of debate for decades. Some dust formation has been assumed to take place in novae explosions1-5, as was first implied by the observation of a steep decrease in the amount of light emitted by the nova1,2 DQ He…
Discovery of Jovian dust streams and interstellar grains by the Ulysses spacecraft
Forsyth, R.; Balogh, A.; Bame, S. J. +20 more
ON 8 February 1992, the Ulysses spacecraft flew by Jupiter at a distance of 5.4 AU from the Sun. During the encounter, the spacecraft was deflected into a new orbit, inclined at about 80° to the ecliptic plane, which will ultimately lead Ulysses over the polar regions of the Sun1. Within 1 AU from Jupiter, the onboard dust de…
Mechanism for the acceleration and ejection of dust grains from Jupiter's magnetosphere
Horanyi, M.; Grun, E.; Morfill, G.
PERHAPS the most unexpected finding of the Ulysses mission so far has been the detection of quasi-periodic streams of high-velocity, submicrometre-sized dust particles during the spacecraft's encounter with Jupiter1. The impact geometry clearly shows that these small grains originate in the jovian system, but it is surprising that any d…
A large nuclear accretion disk in the active galaxy NGC4261
O'Connell, Robert W.; Ferrarese, Laura; Ford, Holland C. +2 more
THE powerful emissions from the nuclei of active galaxies and quasars are thought to arise from the accretion of matter onto a massive black hole. Angular momentum will prevent matter from falling directly onto the central mass; instead, an 'accretion disk' should form, within which the gravitationally bound material will lose angular momentum and…
Detection of the hydroxyl radical in the Saturn magnetosphere
Shemansky, D. E.; Tripp, T. M.; Matheson, P. +2 more
THE magnetosphere in the vicinity of the orbits of Saturn's icy satellites consists of a low-density plasma, in which the electrons are an order of magnitude cooler than the accompanying heavy ions1. Most models2-12 neglect this fact, even though radiative cooling and diffusive loss rates are both too slow to account for the …
Ejection of dust from Jupiter's gossamer ring
Hamilton, Douglas P.; Burns, Joseph A.
ONE of the most intriguing discoveries of the Ulysses mission so far has been the detection of periodic, collimated streams of high-velocity, submicrometre-sized dust particles emanating from Jupiter1,2. To explain the Ulysses data, Horanyi et al. showed3 that electromagnetic forces within Jupiter's magnetosphere can accelera…
Dust particle impacts during the Giotto encounter with comet Grigg-Skjellerup
Colangeli, L.; Green, S. F.; Greenberg, J. M. +7 more
IN the European Space Agency's 1992 Giotto Extended Mission, the Dust Impact Detection System operated successfully during a fly-by that took the spacecraft within about 200 km of the nucleus of comet Grigg-Skjellerup. During the encounter, three meteoroid impacts were detected on Giotto's front shield. The particle masses were found to be lOO