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22 May 1998 - Experts say asteroid danger is real
(AP) - A mile-wide asteroid capable of killing millions of people could strike the Earth without warning because threatening objects in space are not being cataloged, an expert says. A mountain-sized space rock "could hit tomorrow and we wouldn't even know it was coming," Clark R. Chapman, an asteroid expert with the Southwest Research Institute, told a congressional subcommittee Thursday. He said a mile-wide asteroid would send so much dust into the atmosphere the sun could be blotted out for a year, destroying food crops, triggering starvation and killing millions directly or indirectly. Such a catastrophe would "threaten the future of modern civilization," he said. Chapman said such an asteroid would gouge a crater bigger than Washington, D.C., and deeper than 20 Washington Monuments piled on top of each other. He said the chances of such an asteroid striking the Earth next year are one in a few hundred thousand, but this "is more likely to happen than that the next poker hand you are dealt will be a royal flush." The scientist said an asteroid much smaller than a mile wide exploded over Tunguska, Siberia, in 1908 and the shock wave flattened trees across an area larger than New York City.
03 July 1998 - Newly-found asteroid points to unseen danger
Astronomers said Thursday they had found an asteroid in a place where they have never been found before, orbiting entirely between the Earth and the sun, and warned there may be more out there. They say this asteroid is nothing to worry about - it does not seem to be on a collision course with the Earth. But because it was so hard to spot, there could be others in orbit that no one would see until the last minute. Most asteroids orbit in an ellipse that extends at least partly outside the Earth's orbit. That means there is a point in the orbit during which the asteroid can be easily spotted. (Reuters)
PHYSICS NEWS UPDATE The American Institute of Physics Bulletin of Physics News Number 374 June 3, 1998, by Phillip F. Schewe and Ben Stein 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 10^14 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.)
PHYSICS NEWS UPDATE The American Institute of Physics Bulletin of Physics News Number 379 June 25, 1998, by Phillip F. Schewe and Ben Stein
Nearest Extra-Solar Planet
The existence of a planet around the star Gliese 876, only 15 light years distant from Earth, was announced this week by planeteer Geoffrey Marcy of San Francisco State University at a meeting in Victoria, British Columbia. The star, whose presence is inferred not from direct observation but by the wobble it imparts to the star, has a mass about 1.6 that of Jupiter. Gliese itself only has a mass of about one third that of our sun, making it the lightest known star to have a planet. The planet circles the star every 61 days at a radius of one-fifth the Earth-Sun distance. The discovery was soon confirmed by other astronomers. (Science News, 27 June 1998.) Still other extra-solar planets (perhaps a half dozen) will be presented by several observing teams at a meeting a week from now in Santa Barbara. (Science NOW, 24 June 1998.)
Life Extinctions by Cosmic Ray Jets
Several reasons have been put forward to explain past periods of mass extinction on the Earth. An asteroid, for example, is thought to have killed off the dinosaurs in the Cretaceous/Tertiary era 60 million years ago. A new theory by physicists at the Technion in Israel suggests that jets of cosmic rays coming from the collapse of neutron stars or the merger of two such stars could initiate a lethal batch of muons in our atmosphere. They argue that the ensuing ionizing radiation might have affected the biosphere in two ways---by killing many species outright and by causing the sort of mutations that might result in the abrupt appearance of many new species in the aftermath of the jet event. Furthermore, the coming of the cosmic rays might be heralded a few days before by the arrival of a gamma ray burst (GRB), presumably from the same energetic source. The mechanism behind GRBs is itself now the subject of intense astronomical scrutiny. (Arnon Dar et al., Physical Review Letters, 29 June; Arnon Dar, arnon@physics. technion.ac.il, 011-972-4-829-3529.)
The Moon Was the First Object of Pure Science,
according to Martin Gutzwiller of IBM (gutzwil@watson.ibm.com). The Babylonians (c1000 BC) recorded the comings and goings of the Moon arithmetically without understanding the geometry. The Greeks (c200 BC) went further; they viewed the solar system as sitting in an immense vacuum surrounded by the fixed stars. But even the clever Greeks knew nothing about the underlying physics of the solar system. This fell to Newton (1687) in the "Principia," and the 18th century mathematician/physicists such as Laplace. These thinkers proposed the principle of universal gravitation and tried to check it out on the complicated Moon-Earth-Sun system. The study of this oldest of three-body problems is the true subject of Gutzwiller's article in the April 1998 issue of Review of Modern Physics. In many physics problems, the dynamics of two interacting bodies (a planet and a star or two electrical charges, say) is easy. Add a third body and things get complicated, indeed chaotic, which is why Newton and his 18-century followers were largely stumped in their efforts to nail down the Earth-Sun-Moon dynamics. Gutzwiller compares the study of this problem with the history of particle physics: the amassing of cross sections, branching ratios and other particle properties (the kinds of things published in tables) corresponds to the "Babylonian phase," while the advent of the standard model represents the "Greek phase." The third, or Newtonian, age, in which the masses of the quarks and fundamental parameters such as the fine structure constant will be explained, has not yet arrived. (For a study of the 3-body problem with ions, see Update 372)
PHYSICS NEWS UPDATE The American Institute of Physics Bulletin of Physics News Number 386 August 26, 1998, by Phillip F. Schewe and Ben Stein
Black Holes Cannot Serve as Portals to Other Universes
That is the conclusion of Shahar Hod and Tsvi Piran (tsvi@vms.huji.ac.il, 011-972-2-6584233), two Hebrew University physicists who have performed the first detailed calculations tracing a black hole from the prelude of its formation to the development of its inner structure. Black holes have such large amounts of gravity that they irretrievably attract all objects that are closer than a point-of-no-return known as the event horizon. As Roger Penrose and Stephen Hawking first showed, the insides of black holes must contain a singularity, which in its simplest form is a region of infinite density. Associated with a singularity is a boundary known as a "Cauchy horizon" beyond which it becomes impossible to predict the future trajectory of a particle with any reliability. Previously, some theorists have suggested the possibility that matter passing through the Cauchy horizon may encounter an "asymptotically flat" region, a region of relatively weak gravity such as our own, and then travel to other universes rather than get caught in a singularity. However, Hod and Piran have now supported previous indications showing that these Cauchy horizons are unstable; small disturbances in the black hole instantly transform them into singularity regions. In fact, their calculations suggest that generic black holes contain two singularities that are connected to each other so that all infalling matter reaches one or the other. (Hod and Piran, Physical Review Letters, 24 August 1998)
PHYSICS NEWS UPDATE The American Institute of Physics Bulletin of Physics News Number 391 September 15, 1998, by Phillip F. Schewe and Ben Stein
Anomalous acceleration
Data from several spacecraft, including Pioneer 10 and 11, Galileo, and Ulysses, provide evidence for an unexplained, weak, long-range acceleration, a new report shows. Position and velocity information is derived from radio signals sent from the craft to the Deep Space Network back on Earth. Any change in velocity over time can be ascribed to a variety of known sources: the sun and planets, the solar wind, the Milky Way, the Kuiper belt, etc. But even after taking this all into account, as well as other possibilities such as the presence of dark matter in the solar system (only a millionth of a solar mass of dark matter could reside within the orbit of Uranus, it is estimated) or gas leakage from the vehicles themselves, a small acceleration in the direction of the Sun---8 x 10^-8 cm/sec^2 for Pioneer 10---remains unaccounted for. Signs of this anomaly first appeared in the Pioneer tracking as long ago as 1980; Pioneer 10 was launched in 1972 and is presently 70 astronomical units from Earth. Now six space scientists, armed with many years of Pioneer data, supplemented with trajectory information from Galileo and Ulysses, have carried out the first thorough analysis of the problem and find the anomaly to be as persistent as ever. (The Voyager spacecraft are less useful for determining acceleration anomalies.) The researchers doubt but do not rule out the possibility of a novel gravitational effect or other kind of new physics. Alternative explanations include subtle systematic errors in the data analysis or unexpected aspects of space navigation. Further work on this problem may extend to the observed motions of planets, comets, and the proposed Pluto Express craft. (John D. Anderson et al., Physical Review Letters, tentatively 5 October 1998) .
PHYSICS NEWS UPDATE The American Institute of Physics Bulletin of Physics News Number 392 September 22, 1998, by Phillip F. Schewe and Ben Stein
Do cosmic rays come from quasars?
Cosmic ray particles, which crash into Earth's atmosphere setting up huge showers of particles detected on the ground, have mysterious origins. Looking at the five most energetic events ever recorded (energies above 10^20 eV), Glennys Farrar of NYU (farrar@physics.nyu.edu) and Peter Bierman of the Max Planck Institute for Radio Astronomy in Bonn have found that all the events are consistent with the cosmic rays having originated in radio-loud quasars with redshifts in the range 0.3-2.2, and propagating undeflected and unattenuated in energy through the intervening thousands of Mpc (Physical Review Letters, tentatively 19 October 1998). If the particles (conventionally assumed to be protons) are indeed coming from a great distance then how do they evade the Greisen-Zatsepin-Kuzmin (GZK) cutoff, according to which cosmic rays with energies above about 10^19.5 eV would be sapped of their energy through interactions with cosmic microwave background photons if they traveled much more than 20 Mpc (roughly 60 million light years)? Such interactions would typically produce pions and electron-positron pairs. Some speculate that the high-energy particles are not protons at all but some exotic new particle. One explanation is that energetic neutrinos make the long cosmic journey and then annihilate relatively near the Earth with massive dark-matter neutrinos to create the cosmic ray primary particle. Farrar herself is partial to the notion that the primary is the neutral S particle, an amalgam of three quarks and a gluino (one of the shadow particles associated with supersymmetry theory; see Updates 86 and 265). With a mass two or three times that of the proton, the S would not as readily produce pions in interactions with microwave photons, thus ensuring for itself a more robust passage through the cosmos. Thus the highest energy cosmic rays could be produced at cosmological distances but still survive the trip to Earth. (Physics Today, October 1998.) Future measurements determining whether the primary is a photon or hadron will help decide the question of whether the correlation between cosmic rays and quasars holds up.
The 25 greatest astronomical findings of all time
According to the editors of Astronomy magazine (October 1998), they are as follows: Discovery of quasars (1963); Cosmic microwave background (1965-66); Pulsars (1967); Galileo's observations of the phases of Venus, Jupiter's moons, and craters on the moon (c 1609); Extrasolar planets (1992); Supermassive black holes (early 1990s); Newton's Principia, formulating the mathematics of our heliocentric system (1687); Discovery of Uranus (1781); First known asteroid (1801); Discovery of Pluto (1930); Discovery of Neptune (1846); Spectroscopic proof that nebulae are gaseous in nature (1864); Recognition of galaxies beyond our own (1923); Advent of radio astronomy (1931-32); Studies of globular clusters help to map the Milky Way (1918); Cometary explosion over Siberia (1908); Accurate measurement of the speed of light (1675); Southern Hemisphere celestial objects cataloged (1834-38); Cepheid-variable period-luminosity relationship worked out (1912); Copernicus' De Revolutionibus sets forth the heliocentric system (1543); Laplace's theory on how the solar system formed (1796); Transit of Venus suggesting that Venus has an atmosphere (1761); Hertzsprung-Russell diagram for understanding how stars age (1913); Scheme for classifying star types (1890); Use of parallax for finding a star's distance from Earth (1838).
PHYSICS NEWS UPDATE The American Institute of Physics Bulletin of Physics News Number 393 September 28, 1998, by Phillip F. Schewe and Ben Stein
Two new extrasolar planets found
The extrasolar planet parade continues with the discovery of two new planets with unique features. As before, astronomers Geoffrey Marcy (San Francisco State) and Paul Butler (Anglo-Australian Observatory) have inferred the presence of the planets from their observed influence on the companion star. One of the new objects orbits its star (HD187123) in a mere three days in an orbit 9 times closer than Mercury's around our sun. The other new planet has a very Earth-like orbit of 437 days around star HD21027. This comes as a reassurance to those who were beginning to wonder whether Earth was an anomaly; all previously discovered extrasolar planets have had orbits much smaller or much larger than Earth's. (San Francisco State University press release, 23 September 1998.)
PHYSICS NEWS UPDATE The American Institute of Physics Bulletin of Physics News Number 394 October 1, 1998, by Phillip F. Schewe and Ben Stein
A BLAST OF GAMMA LIGHT, representing the largest batch of energy to arrive at Earth from a star beyond our solar system, struck the upper reaches of our atmosphere on 27 August 1998. The 5-minute pulse of high-energy radiation momentarily disrupted some terrestrial radio traffic and sent detectors on several spacecraft off scale. The source of the blast is believed to be a neutron star previously known for its intermittent gamma and x-ray emissions. The potency of the August event, however, would seem to characterize the star as a very rare type of object that has come to be known as a magnetar, so named because the star's magnetic field is expected to be in the vicinity of 10^15 gauss, 100 times larger than ordinary neutron stars, and essentially the largest known magnetic field in the universe. The gammas probably arise when magnetic forces crack open the star's crust. Ionized particles above the star ride the magnetic fields, spewing radiation as they go, creating a much more potent version of the solar flares seen on our sun. (Science News, 12 September 1998.)
PHYSICS NEWS UPDATE The American Institute of Physics Bulletin of Physics News Number 397 October 15, 1998, by Phillip F. Schewe and Ben Stein
Nulled Starlight
Under the right circumstances light from two separated telescopes can be combined to create a signal whose spatial resolution is better than that for either of the single telescopes. This interferometry technique can also be used in reverse: the light paths for the two beams can be adjusted to create not a maximum but a minimum. Thus the star's light can be nulled out. Astronomers have demonstrated this principle by canceling the image of the star Betelgeuse, leaving behind the faint glow of a surrounding dust nebula. The researchers expect that with adaptive optics, a ground-based nulling system could be used to image Jupiter-sized planets around nearby stars beyond the sun by subtracting the distracting stellar glare. (Hinz et al., Nature, 17 September 1998.)
PHYSICS NEWS UPDATE The American Institute of Physics Bulletin of Physics News Number 401 November 9, 1998, by Phillip F. Schewe and Ben Stein
Influence of Cosmic Rays on Earth's Climate
Do small changes in solar activity translate into climate change on our planet? One possible linkage is the sun's influence over the local flux of galactic cosmic rays (GCR); as the solar magnetic field gets stronger, fewer cosmic rays are able to penetrate to the inner solar system and Earth. And because the GCR are the biggest ionizer of air molecules in the lower atmosphere, they might play a role in processes like cloud formation. Henrik Svensmark, a physicist now at the Danish Meteorological Institute (011-45-3-536-2475, hsv@dsri.dk), has studied the connection between GCR flux, solar activity, and climate on Earth. He finds that during the past 11-year solar cycle, Earth's cloud cover was more closely correlated with the GCR flux than with other solar activity parameters, such as solar radiance, the main energy emitted by the sun. Svensmark concludes that climate seems to be influenced by solar activity via the GCR-cloud connection. In other words, climate is partly affected by processes in deep space. (Physical Review Letters, 23 November 1998; see figure at www.aip.org/physnews/graphics.)
PHYSICS NEWS UPDATE The American Institute of Physics Bulletin of Physics News Number 405 December 7, 1998, by Phillip F. Schewe and Ben Stein
The topography of Mars
The Mars Global Surveyor laser altimeter, with its 30-cm precision, is rendering the best topographic maps yet for the red planet. Two highlights from a series of articles in the 15 December issue of Geophysical Research Letters---Mars is less flattened than was thought: its mean equatorial and polar radii are measured to be 3396 and 3373 km; and a possible shoreline of a presumed ancient polar ocean was studied.
PHYSICS NEWS UPDATE The American Institute of Physics Bulletin of Physics News Number 406 December 11, 1998, by Phillip F. Schewe and Ben Stein
Space Weather Exerts Itself in Several Ways
Here are two examples, from reports given at this week's American Geophysical Union (AGU) meeting in San Francisco, of how a hurricane of particles from the sun can push things around here at Earth. First, Geoffrey Reeves of Los Alamos described new data recorded by a number of orbiting spacecraft which suggests that Earth's own magnetic field is more important than the solar wind in supplying electrons and whipping them to high speeds in the Van Allen Belts. Electron energies and densities in the belts change too quickly, Reeves argued, to be responding directly to solar eruptions. Another report, delivered by Thomas Moore of NASA Goddard, confirmed with new observations by the Polar satellite the idea that blasts of solar wind can greatly enhance the escape of oxygen, helium, and hydrogen ions from Earth's upper atmosphere. This exodus of ions contributes to near-Earth space storms and promotes a charge buildup on nearby spacecraft.
Contact with spacecraft restored - Dec 23, 1998
WASHINGTON (AP) - Jubilant, yet exhausted, scientists who have restored communications with a robot spacecraft tracking a giant asteroid millions of miles from Earth now are busily trying to figure out what happened during the 27 hours they lost contact with the craft. The problem likely will cause the Near Earth Asteroid Rendezvous to delay its Jan. 10 mission to begin circling the asteroid named Eros more than 200 million miles from Earth - the first attempt in history to orbit an asteroid. "We're not getting as much data back as we had hoped so it looks like it will be the first week in February before there's an encounter to lock into orbit around Eros," said a spokeswoman for the Johns Hopkins University Applied Physics Laboratory. Scientists lost contact with NEAR about 5 p.m. ET Sunday (Dec 20) as the craft's speed was being boosted by a series of rocket engine firings so it could catch and begin its orbit around Eros.