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Photometry and spectroscopy of the object Cha H[Alpha] 1, located in the Chamaeleon I star-forming cloud, show that it is a ~[10.sup.6]-year-old brown dwarf with spectral type M7.5 to M8 and 0.04 ± 0.01 solar masses. Quiescent x-ray emission was detected in a 36-kilosecond observation with 31.4 ± 7.7 x-ray photons, obtained with the Rontgen Satellite (ROSAT), with 9 Σ detection significance. This corresponds to an x-ray luminosity of 2.57 x [10.sup.28] ergs per second and an x-ray to bolometric luminosity ratio of [10.sup.-3.44]. These are typical values for late M-type stars. Because the interior of brown dwarfs may be similar to that of convective late-type stars, which are well-known x-ray sources, x-ray emission from brown dwarfs may indicate magnetic activity., A brown dwarf (BD) is an object with a mass [is less than or equal to] 0.08 solar masses (M??), which is insufficient to sustain nuclear fusion of hydrogen (1). [...]

Among the great astronomical discoveries of the 1960s was the totally unexpected finding by Giacconi et al. (1) of a bright x-ray star, now known as Scorpio X-1. Because cosmic [...]

The soft x-ray spectra of the Virgo and Coma clusters cannot be modeled by emission from the well-known hot intracluster medium attenuated by photoelectric absorption along the line of sight in our galaxy. If the excess soft emission is due to thermal emission in the clusters from gas at about 1 million kelvin, then the gas should be rapidly cooling. The high rate of cooling poses problems for the origin of the gas and its sink. A model in which the component is due to turbulent mixing layers around clouds scattered throughout the intracluster medium may explain the excess emission. The gas in the mixing layer is reheated after cooling, so that the total mass remains relatively small., Lieu et al. (1) report excess soft x-ray emission in the Virgo and Coma clusters, greater than that expected from the known hot intracluster medium in those clusters. The excess [...]

The Hague--You wouldn't want to get too close to a quasar, but astronomers would love to get a better view of these enigmatic beasts. Seen only in the farthest reaches [...]

X-ray astronomers are burning the candle at both ends these days, thanks to the appearance of a bizarre and brilliant x-ray emitter that is doing its own kind of double [...]

The night sky,, seemingly serene, is abuzz with signals from our cosmic neighborhood: light, radio waves, and other radiation from stars and gas within our galaxy. This cosmic buzz tends [...]

It may not look like the sun, but the image at right shows what the Japanese satellite Yohkoh saw when it trained its instruments on the sun's surface just 2 [...]