THE FIRST SNAPSHOT OF AN EXTRASOLAR PLANET? The existence of extrasolar planets around several stars has been inferred from the wobble in the stars' emissions, but the planets themselves have not been seen amid the glare of the parent stars. Now, the Hubble Space Telescope has taken a picture of an object (named TMR-1C) that might, depending on how the data is interpreted, be either a brown dwarf star or a protoplanet (perhaps with a mass several times that of Jupiter). The object, about 450 light years away and glowing in infrared light, was glimpsed at all because it has apparently been ejected from a nearby binary-star system, and therefore stands apart from any stellar brilliance. This and the object's youth (it might be only 100,000 years old) might redirect thinking on how gas giant planets form. According to NASA scientist Edward Weiler, "If the planet interpretation stands up to the careful scrutiny of future observations, it could turn out to be the most important discovery by Hubble in its 8-year history." (NASA press release, 28 May 1998.)
A PULSAR WITH A MAGNETIC FIELD OF 8 x 1014 GAUSS has been studied with the Rossi X Ray Telescope (RXTE). Referred to as a soft gamma-ray repeater (SGR1806-20) since it is a source of recurring bursts of low-energy gamma-rays (whereas gamma ray bursters don't emit higher energy gammas and don't repeat), this neutron star rotates with a period of about 7.4 seconds. The size of the magnetic field, 100 times larger than that of ordinary radio pulsars, is deduced from the rotation period and the slowdown of that rotation. Such a highly magnetized neutron star has been called a "magnetar." The huge field (the largest magnetic field ever measured) puts the star's surface under great stress. According to one theory, the observed high energy bursts of radiation come about when the neutron star's crust cracks open. (C. Kouveliotou et al., Nature, 21 May 1998.)
TUMBLE AND FLUTTER: how paper falls to the ground is impossible to describe exactly with the laws of physics because of the mathematically intractable equations governing the fluid flow of air. To gain at least some understanding, scientists beginning in the 19th century, have modeled this problem in 2 dimensions. Now, experiments at the Weizmann Institute in Israel (Andrew Belmonte, University of Pittsburgh, 412-624-9385) have provided the first quantitative tests of these 2-D theories. In the experiment, researchers dropped thin strips of metal, plastic, and brass into a thin fluid-filled tank, which forced the strips to move in a two-dimensional plane. What determined whether the falling strips predominantly oscillated from side to side (flutter) or rotated end over end (tumble) was the Froude number, the ratio of the time it takes for the strip to fall its own length to the time it takes for the strip to move from side to side. Longer or lighter strips, which have a low Froude number (like an 8.5 x 11" page) flutter while smaller or heavier strips (e.g., a business card) tend to tumble. (Try it yourself.) The vortices set up by the falling strips may be relevant to the question of how airplanes stall, and may be exploited by insects to enable them to fly with great efficiency. (Upcoming article in Physical Review Letters.)
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