Chapter 29:

Supernova 1987A Is Blazing Out

This image, taken Nov. 28, 2003 by the Advanced Camera for Surveys aboard NASA's Hubble Space Telescope, shows many bright spots along a ring of gas, like pearls on a necklace. These cosmic "pearls" are being produced as a supersonic shock wave unleashed during the explosion slams into the ring at more than a million miles per hour. The collision is heating the gas ring, causing its innermost regions to glow. Curiously, one of the bright spots on the ring [at 4 o'clock] is a star that happens to lie along the telescope's line of sight.

Astronomers detected the first "hot spot" in 1996, but now they see dozens of them all around the ring. The temperature of the flares surges from a few thousand degrees to a million degrees Fahrenheit. Individual hot spots cannot be seen from ground-based telescopes. Only Hubble can resolve them.

And, more hot spots are coming. In the next few years, the entire ring will be ablaze as it absorbs the full force of the crash. The glowing ring is expected to become bright enough to illuminate the star's surroundings, thus providing astronomers with new information on how the star ejected material before the explosion.

The elongated and expanding object in the middle of the ring is debris from the supernova blast. The glowing debris is being heated by radioactive elements, principally titanium 44, that were created in the supernova explosion. The debris will continue to glow for many decades.

The ring, about a light-year across, already existed when the star exploded. Astronomers believe the star shed the ring about 20,000 years before the supernova blast.

The violent death of a star 20 times more massive than the Sun, called a supernova, created this stellar drama. The star actually exploded about 160,000 years ago, but it has taken that long for its light to reach Earth. The supernova resides in the Large Magellanic Cloud, a nearby small galaxy that is a satellite or our Milky Way galaxy.

Since its launch in 1990, the Hubble telescope has watched the supernova drama unfold, taking periodic snapshots of the gradually fading ring. Now, the orbiting observatory will continue to monitor the ring as it brightens from this collision.

Credit: NASA, P. Challis, R. Kirshner (Harvard-Smithsonian Center for Astrophysics) and B. Sugerman (STScI)

Huge Cosmic Ray Detector Advances

Press contact: Kurt Riesselmann, Fermilab Public Affairs, 630-840-3351, kurtr@fnal.gov

Batavia, Ill.- With the completion of its hundredth surface detector, the Pierre Auger Observatory, under construction in Argentina, this week became the largest cosmic-ray air shower array in the world. Managed by scientists at the Department of Energy's Fermi National Accelerator Laboratory, the Pierre Auger project so far encompasses a 70-square-mile array of detectors that are tracking the most violent-and perhaps most puzzling-processes in the entire universe.

Cosmic rays are extraterrestrial particles-usually protons or heavier ions-that hit the Earth's atmosphere and create cascades of secondary particles. While cosmic rays approach the earth at a range of energies, scientists long believed that their energy could not exceed 1020 electron volts, some 100 million times the proton energy achievable in Fermilab's Tevatron, the most powerful particle accelerator in the world. But recent experiments in Japan and Utah have detected a few such ultrahigh energy cosmic rays, raising questions about what extraordinary events in the universe could have produced them.

"How does nature create the conditions to accelerate a tiny particle to such an energy?" asked Alan Watson, physics professor at the University of Leeds, UK, and spokesperson for the Pierre Auger collaboration of 250 scientists from 14 countries. "Tracking these ultrahigh-energy particles back to their sources will answer that question."

Scientific theory can account for the sources of low- and medium-energy cosmic rays, but the origin of these rare high-energy cosmic rays remains a mystery. To identify the cosmic mechanisms that produce microscopic particles at macroscopic energy, the Pierre Auger collaboration is installing an array that will ultimately comprise 1,600 surface detectors in an area of the Argentine Pampa Amarilla the size of Rhode Island, near the town of MalargUe, about 600 miles west of Buenos Aires. The first 100 detectors are already surveying the southern sky.

"These highest-energy cosmic rays are messengers from the extreme universe," said Nobel Prize winner Jim Cronin, of the University of Chicago, who conceived the Auger experiment together with Watson. "They represent a great opportunity for discoveries."

The highest-energy cosmic rays are extremely rare, hitting the Earth's atmosphere about once per year per square mile. When complete in 2005, the Pierre Auger observatory will cover approximately 1,200 square miles (3,000 square kilometers), allowing scientists to catch many of these events.

"Our experiment will pick up where the AGASA experiment has left off," said project manager Paul Mantsch, Fermilab, referring to the Akeno Giant Air Shower Array (AGASA) experiment in Japan. "At highest energies, the astonishing results from the two largest cosmic-ray experiments appear to be in conflict. AGASA sees more events than the HiRes experiment in Utah, but the statistics of both experiments are limited."

The Pierre Auger project, named after the pioneering French physicist who first observed extended air showers in 1938, combines the detection methods used in the Japanese and Utah experiments. Surface detectors are spaced one mile apart. Each surface unit consists of a 4-foot-high cylindrical tank filled with 3,000 gallons of pure water, a solar panel, and an antenna for wireless transmission of data. Sensors register the invisible particle avalanches, triggered at an altitude of six to twelve miles just microseconds earlier, as they reach the ground. The particle showers strike several tanks almost simultaneously.

In addition to the tanks, the new observatory will feature 24 HiRes-type fluorescence telescopes that can pick up the faint ultraviolet glow emitted by air showers in mid-air. The fluorescence telescopes, which can only be operated during dark, moonless nights, are sensitive enough to pick up the light emitted by a 4-watt lamp traveling six miles away at almost the speed of light.

"It is a really beautiful thing that we have a hybrid system," said Watson. "We can look at air showers in two modes. We can measure their energy in two independent ways."

Source of White-Dwarf-Type Supernovae Identified

Astronomers have finally identified the progenitor star system of a Type Ia supernova. The culprit that triggered the stellar explosion is a surprisingly normal star just a few times more massive than the Sun.

Type Ia supernovae are luminous objects that have been used as cosmological beacons to study the expansion and geometry of the Universe. Two separate teams have reported on-going observations of distant supernovae of this type that indicate the presence of a repulsive force, termed dark energy, causing the expansion of the Universe to accelerate.

"A great worry in this work has been that astronomers do not understand exactly how these supernovae are produced," says Mario Hamuy, a Hubble fellow at the Carnegie Observatories in Pasadena, CA, lead author of a paper in the August 7 issue of Nature magazine. "We have been searching for a progenitor system for two decades, and now we finally have a suspect clearly identified."

The generally accepted model for a Type Ia supernova consists of a binary system with a white dwarf star (a dense and dim stellar object near the end of its life) that undergoes a sudden thermonuclear explosion. But no one had observed anything about the companion star or the processes which ultimately lead to the explosion.

"In theory, some transfer of mass must occur between the companion star and the white dwarf before the explosion," Hamuy explains, "yet no evidence has ever been found for gas around a Type Ia supernova."

Based on a strong signal of hydrogen in ground-based spectroscopic observations of Supernova 2002ic from Las Campanas Observatory, scientists in Chile and the U.S. have concluded that the source of this Type Ia supernova consisted of a white dwarf that suddenly exploded after gaining hydrogen gas blown off by its gravitational partner.

"The amount of hydrogen-rich circumstellar gas detected is considerable," says Nicholas Suntzeff, an astronomer at the Cerro Tololo Inter-American Observatory in Chile and a co-author of the paper.

"The most reasonable conclusion is that the stellar system was made up of a white dwarf and a common asymptotic giant branch star about three to seven times the mass of the Sun, which proceeded to lose a large amount of its hydrogen in the form of a wind, due to instabilities in the late stages of its evolution," Suntzeff adds. "Some of this hydrogen settled on the companion white dwarf, driving its mass up to the point where the white dwarf incinerated within just a few seconds in a potent thermonuclear event."

Type Ia supernovae are important explosions in the buildup of heavy elements in the Universe. More than half of the iron peak elements in the Solar System, such as iron and nickel, come from the ashes of previous Type Ia explosions.

"We can't understand the buildup of the elements in the stars in galaxies unless we know precisely what is blowing up - what it is made of, and how long it takes to get to the point of the explosion," explains astronomer Mark Phillips of Carnegie Observatories, a co-author of the paper.

So far, the extremely faint galaxy that spawned the system which led to Supernova 2002ic has not been identified.

The redshift of the light from the supernova, however, allowed the astronomers to measure the distance to the explosion at 945 million light-years (290 megaparsecs) from Earth.

"The search for a progenitor for Type Ia supernovae has gone on for so long that it almost became a point of embarrassment for scientists in the field," Suntzeff notes. "Supernova 2002ic may not be the prototype for all Type Ia's, but it is certainly the first crack in the puzzle."

The first identified progenitor of any supernova was massive star Sn-69 202, which was the source of the famous Supernova 1987A, a nearby example of the "core collapse" class of supernovae known as Type II, which begin with stars at least 10 times as massive as the Sun. Five more progenitors of these core collapse-type of supernovae have been found since then.

Las Campanas Observatory is operated by the Carnegie Observatories, founded in 1904 by George Ellery Hale. It is one of six departments of the private, nonprofit Carnegie Institution of Washington (www.CarnegieInstitution.org), a pioneering force in basic scientific research since 1902.

Gamma-Ray Burst Breakthrough

Scientists have pieced together the key elements of a gamma-ray burst, from star death to dramatic black hole birth, thanks to a "Rosetta stone" found on March 29, 2003.

This telling March 29 burst in the constellation Leo, one of the brightest and closest on record, reveals for the first time that a gamma-ray burst and a supernova -- the two most energetic explosions known in the Universe -- occur simultaneously, a quick and powerful one-two punch.

The results appear in the June 19 issue of Nature. The burst was detected by NASA's High-Energy Transient Explorer (HETE) and observed in detail with the European Southern Observatory's Very Large Telescope (VLT) at the Paranal Observatory in Chile.

"We've been waiting for this one for a long, long time," said Dr. Jens Hjorth, University of Copenhagen, lead author on one of three Nature letters. "The March 29 burst contains all the missing information. It was created through the core collapse of a massive star."

The team said that the "Rosetta stone" burst also provides a lower limit on how energetic gamma-ray bursts truly are and rules out most theories concerning the origin of "long bursts," lasting longer than two seconds.

Gamma-ray bursts temporarily outshine the entire Universe in gamma-ray light, packing the energy of over a million billion suns. Yet these explosions are fleeting -- lasting only seconds to minutes - -- and occur randomly from all directions on the sky, making them difficult to study.

A supernova is associated with the death of a star about eight times as massive as the Sun or more. Its core implodes, forming either a neutron star or (if there is enough mass) a black hole. The star's surface layers blast outward, forming the colorful patterns typical of supernova remnants. Scientists have suspected gamma-ray bursts and supernovae were related, but they have had little observational evidence, until March 29.

"The March 29 burst changes everything," said co-author Dr. Stan Woosley, University of California, Santa Cruz. "With this missing link established, we know for certain that at least some gamma-ray bursts are produced when black holes, or perhaps very unusual neutron stars, are born inside massive stars. We can apply this knowledge to other burst observations."

GRB 030329, named after its detection date, occurred relatively close, approximately 2 billion light years away (at redshift 0.1685). The burst lasted over 30 seconds. ("Short bursts" are less than 2 seconds long.) GRB 030329 is among the 0.2 percent brightest bursts ever recorded. Its afterglow lingered for weeks in lower-energy X-ray and visible light.

With the VLT, Hjorth and his colleagues uncovered evidence in the afterglow of a massive, rapidly expanding supernova shell, called a hypernova, at the same position and created at the same time as the afterglow. The following scenario emerged:

A bluish Wolf-Rayet star -- containing about 10 solar masses worth of helium, oxygen and heavier elements -- rapidly depleted its fuel, triggering the Type Ic supernova / gamma-ray burst event. The core collapsed, without the star's outer part knowing. A black hole formed inside surrounded by a disk of accreting matter, and, within a few seconds, launched a jet of matter away from the black hole that ultimately made the gamma-ray burst.

The jet passed through the outer shell of the star and, in conjunction with vigorous winds of newly forged radioactive nickel-56 blowing off the disk inside, shattered the star. Meanwhile, collisions among pieces of the jet moving at different velocities, all very close to light speed, created the gamma-ray burst. This "collapsar" model, introduced by Woosley in 1993, best explains the observation of GRB 030329, as opposed to the "supranova" and "merging neutron star" models.

"This does not mean that the gamma-ray burst mystery is solved," Woosley said. "We are confident that long bursts involve a core collapse, probably creating a black hole. We have convinced most skeptics. We cannot reach any conclusion yet, however, on what causes short gamma-ray bursts."

Short bursts might be caused by neutron star mergers. A NASA-led international satellite named Swift, to be launched in January 2004, will "swiftly" locate gamma-ray bursts and may capture short-burst afterglows, which have yet to be detected.

The VLT is the world's most advanced optical telescope, comprising four 8.2-meter reflecting Unit Telescopes and, in the future, four moving 1.8-meter Auxiliary Telescopes for interferometry. HETE was built by MIT as a mission of opportunity under the NASA Explorer Program, with collaboration among U.S. universities, Los Alamos National Laboratory, and scientists and organizations in Brazil, France, India, Italy and Japan. For new gamma-ray burst animation, refer to:

European Southern Observatory Results on the March 29 GRB

Within 90 min, a new, very bright light source (the "optical afterglow") was detected in the same direction by means of a 40-inch telescope at the Siding Spring Observatory (Australia) and also in Japan. The gamma-ray burst was designated GRB 030329, according to the date.

And within 24 hours, a first, very detailed spectrum of this new object was obtained by the UVES high-dispersion spectrograph on the 8.2-m VLT KUEYEN telescope at the ESO Paranal Observatory (Chile). It allowed to determine the distance as about 2,650 million light-years (redshift 0.1685).

Continued observations with the FORS1 and FORS2 multi-mode instruments on the VLT during the following month allowed an international team of astronomers [1] to document in unprecedented detail the changes in the spectrum of the optical afterglow of this gamma-ray burst. Their detailed report appears in the June 19 issue of the research journal "Nature".

The spectra show the gradual and clear emergence of a supernova spectrum of the most energetic class known, a "hypernova." This is caused by the explosion of a very heavy star - presumably over 25 times heavier than the Sun. The measured expansion velocity (in excess of 30,000 km/sec) and the total energy released were exceptionally high, even within the elect hypernova class.

From a comparison with more nearby hypernovae, the astronomers are able to fix with good accuracy the moment of the stellar explosion. It turns out to be within an interval of plus/minus two days of the gamma-ray burst. This unique conclusion provides compelling evidence that the two events are directly connected.

These observations therefore indicate a common physical process behind the hypernova explosion and the associated emission of strong gamma-ray radiation. The team concludes that it is likely to be due to the nearly instantaneous, non-symmetrical collapse of the inner region of a highly developed star (known as the "collapsar" model).

The March 29 gamma-ray burst will pass into the annals of astrophysics as a rare "type-defining event", providing conclusive evidence of a direct link between cosmological gamma-ray bursts and explosions of very massive stars.

What are Gamma-Ray Bursts?

Despite major observational efforts, it is only within the last six years that it has become possible to pinpoint with some accuracy the sites of some of these events. With the invaluable help of comparatively accurate positional observations of the associated X-ray emission by various X-ray satellite observatories since early 1997, astronomers have until now identified about fifty short-lived sources of optical light associated with GRBs (the "optical afterglows").

Most GRBs have been found to be situated at extremely large ("cosmological") distances. This implies that the energy released in a few seconds during such an event is larger than that of the Sun during its entire lifetime of more than 10,000 million years. The GRBs are indeed the most powerful events since the Big Bang known in the Universe, cf. ESO PR 08/99 and ESO PR 20/00.

During the past years circumstantial evidence has mounted that GRBs signal the collapse of massive stars. This was originally based on the probable association of one unusual gamma-ray burst with a supernova ("SN 1998bw", also discovered with ESO telescopes, cf. ESO PR 15/98). More clues have surfaced since, including the association of GRBs with regions of massive star-formation in distant galaxies, tantalizing evidence of supernova-like light-curve "bumps" in the optical afterglows of some earlier bursts, and spectral signatures from freshly synthesized elements, observed by X-ray observatories.

VLT observations of GRB 030329

The corresponding distance is about 2,650 million light-years. This is the nearest normal GRB ever detected, therefore providing the long-awaited opportunity to test the many hypotheses and models which have been proposed since the discovery of the first GRBs in the late 1960's.

With this specific aim, the ESO-lead team of astronomers [1] now turned to two other powerful instruments at the ESO Very Large Telescope (VLT), the multi-mode FORS1 and FORS2 camera/spectrographs. Over a period of one month, until May 1, 2003, spectra of the fading object were obtained at regular rate, securing a unique set of observational data that documents the physical changes in the remote object in unsurpassed detail.

The hypernova connection

This is based on the gradual "emergence" with time of a supernova-type spectrum, revealing the extremely violent explosion of a star. With velocities well in excess of 30,000 km/sec (i.e., over 10% of the velocity of light), the ejected material is moving at record speed, testifying to the enormous power of the explosion.

Hypernovae are rare events and they are probably caused by explosion of stars of the so-called Wolf-Rayet" type [4]. These WR-stars were originally formed with a mass above 25 solar masses and consisted mostly of hydrogen. Now in their WR-phase, having stripped themselves of their outer layers, they consist almost purely of helium, oxygen and heavier elements produced by intense nuclear burning during the preceding phase of their short life.

"We have been waiting for this one for a long, long time", says Jens Hjorth, "this GRB really gave us the missing information. From these very detailed spectra, we can now confirm that this burst and probably other long gamma-ray bursts are created through the core collapse of massive stars. Most of the other leading theories are now unlikely."

A "type-defining event"

The astronomers determined that the hypernova explosion (designated SN 2003dh [2]) documented in the VLT spectra and the GRB-event observed by HETE-II must have occurred at very nearly the same time. Subject to further refinement, there is at most a difference of 2 days, and there is therefore no doubt whatsoever, that the two are causally connected.

"Supernova 1998bw whetted our appetite, but it took 5 more years before we could confidently say, we found the smoking gun that nailed the association between GRBs and SNe" adds Chryssa Kouveliotou of NASA. "GRB 030329 may well turn out to be some kind of 'missing link' for GRBs."

In conclusion, GRB 030329 was a rare "type-defining" event that will be recorded as a watershed in high-energy astrophysics.

What really happened on March 29 (or 2,650 million years ago)?

Thousands of years prior to this explosion, a very massive star, running out of hydrogen fuel, let loose much of its outer envelope, transforming itself into a bluish Wolf-Rayet star [4]. The remains of the star contained about 10 solar masses worth of helium, oxygen and heavier elements.

In the years before the explosion, the Wolf-Rayet star rapidly depleted its remaining fuel. At some moment, this suddenly triggered the hypernova/gamma-ray burst event. The core collapsed, without the outer part of the star knowing. A black hole formed inside, surrounded by a disk of accreting matter. Within a few seconds, a jet of matter was launched away from that black hole.

The jet passed through the outer shell of the star and, in conjunction with vigorous winds of newly formed radioactive nickel-56 blowing off the disk inside, shattered the star. This shattering, the hypernova, shines brightly because of the presence of nickel. Meanwhile, the jet plowed into material in the vicinity of the star, and created the gamma-ray burst which was recorded some 2,650 million years later by the astronomers on Earth. The detailed mechanism for the production of gamma rays is still a matter of debate but it is either linked to interactions between the jet and matter previously ejected from the star, or to internal collisions inside the jet itself.

This scenario represents the "collapsar" model, introduced by American astronomer Stan Woosley (University of California, Santa Cruz) in 1993 and a member of the current team, and best explains the observations of GRB 030329.

"This does not mean that the gamma-ray burst mystery is now solved", says Woosley. "We are confident now that long bursts involve a core collapse and a hypernova, likely creating a black hole. We have convinced most skeptics. We cannot reach any conclusion yet, however, on what causes the short gamma-ray bursts, those under two seconds long."

Notes

New Movie of the Crab's Center

Chandra X-ray Observatory Press Release, 9/19/02

Just when it seemed like the summer movie season had ended, two of NASA's Great Observatories have produced their own action movie. Multiple observations made over several months with NASA's Chandra X-ray Observatory and the Hubble Space Telescope captured the spectacle of matter and antimatter propelled to near the speed of light by the Crab pulsar, a rapidly rotating neutron star the size of Manhattan.

NASA Press release 02-178

Just when it seemed the summer movie season had ended, two of NASA's Great Observatories have produced their own action movie. Multiple observations made over several months with NASA's Chandra X-ray Observatory and the Hubble Space Telescope captured the spectacle of matter and antimatter propelled to nearly the speed of light by the Crab pulsar, a rapidly rotating neutron star the size of Manhattan.

"Through this movie, the Crab Nebula has come to life," said Jeff Hester of Arizona State University in Tempe, lead author of a paper in the September 20 issue of The Astrophysical Journal Letters. "We can see how this awesome cosmic generator actually works."

The Crab was first observed by Chinese astronomers in 1054 A.D. and has since become one of the most studied objects in the sky. By combining the power of Chandra and Hubble, the movie reveals features never before seen in still images. By understanding the Crab, astronomers hope to unlock the secrets of how similar objects across the universe are powered.

Bright wisps can be seen moving outward at half the speed of light to form an expanding ring, visible in both X-ray and optical images. These wisps appear to originate from a shock wave that shows up as an inner X-ray ring. This ring consists of about two dozen knots that form, brighten and fade, jitter around, and occasionally undergo outbursts that give rise to expanding clouds of particles, but remain in roughly the same location.

"These data leave little doubt that the inner X-ray ring is the location of the shock wave that turns the high-speed wind from the pulsar into extremely energetic particles," said Koji Mori of Penn State University in University Park, a coauthor of the paper.

Another dramatic feature of the movie is a turbulent jet that lies perpendicular to the inner and outer rings. Violent internal motions are obvious, as is a slow motion outward into the surrounding nebula of particles and magnetic field.

"The jet looks like steam from a high-pressure boiler," said David Burrows of Penn State, another coauthor of the paper, "except when you realize you are looking at a stream of matter and anti-matter electrons moving at half the speed of light!"

The inner region of the Crab Nebula around the pulsar was observed with Hubble on 24 occasions between August 2000 and April 2001 at 11-day intervals, and with Chandra on eight occasions between November 2000 and April 2001. The Crab was observed with Chandra's Advanced CCD Imaging Spectrometer and Hubble's Wide-Field Planetary Camera. http://chandra.harvard.edu/photo/2002/0052/

Highest-Energy Cosmic Ray Source Found

NASA Goddard Press Release, April 22, 2002

They are old but not forgotten. Nearby "retired" quasar galaxies, billions of years past their glory days as the brightest beacons in the Universe, may be the current source of rare, high-energy cosmic rays, the fastest-moving bits of matter known and whose origin has been a long-standing mystery, according to scientists at NASA and Princeton University.

The scientists have identified four elliptical galaxies that may have started this second career of cosmic-ray production, all located above the handle of the Big Dipper and visible with backyard telescopes. Each contains a central black hole of at least 100 million solar masses that, if spinning, could form a colossal battery sending atomic particles, like sparks, shooting off towards Earth at near light speed.

These findings were discussed April 22, 2002, in a press conference at the joint meeting of the American Physical Society and the High Energy Astrophysics Division of the American Astronomical Society in Albuquerque, N.M. The team includes Dr. Diego Torres of Princeton University and Drs. Elihu Boldt, Timothy Hamilton and Michael Loewenstein of NASA's Goddard Space Flight Center in Greenbelt, Md.

Quasar galaxies are thousands of times brighter than ordinary galaxies, fueled by a central black hole swallowing copious amounts of interstellar gas. In galaxies with so-called quasar remnants, the black hole nucleus is no longer a strong source of radiation.

"Some quasar remnants might not be so lifeless after all, keeping busy in their later years," said Torres. "For the first time, we see the hint of a possible connection between the arrival directions of ultra-high energy cosmic rays and locations on the sky of nearby dormant galaxies hosting supermassive black holes."

Ultra high-energy cosmic rays represent one of astrophysics' greatest mysteries. Each cosmic ray -- essentially a single sub-atomic particle such as a proton traveling just shy of light speed -- packs as much energy as a major league baseball pitch, over 40 million trillion electron volts. (The rest energy of a proton is about a billion electron volts.) The particles' source must be within 200 million light years of Earth, for cosmic rays from beyond this distance would lose energy as they traveled through the murk of the cosmic microwave radiation pervading the Universe. There is considerable uncertainty, however, over what kinds of objects within 200 million light years could generate such energetic particles.

"The very fact that these four giant elliptical galaxies are apparently inactive makes them viable candidates for generating ultra high-energy cosmic rays," said Boldt. Drenching radiation from an active quasar would dampen cosmic-ray acceleration, sapping most of their energy, Boldt said.

The team concedes it cannot determine if the black holes in these galaxies are spinning, a basic requirement for a compact dynamo to accelerate ultra-high energy cosmic rays. Yet scientists have confirmed the existence of at least one spinning supermassive black hole, announced in October 2001. The prevailing theory is that supermassive black holes spin up as they accrete matter, absorbing orbital energy from the infalling matter.

Ultra-high-energy cosmic rays are detected by ground-based observatories, such as the Akeno Giant Air Shower Array near Yamanashi, Japan. They are extremely rare, striking the Earth's atmosphere at a rate about one per square kilometer per decade. Construction is underway for the Auger Observatory, which will cover 3,000 square kilometers (1,160 square miles) on an elevated plain in western Argentina. A proposed NASA mission called OWL (Orbiting Wide-angle Light-collectors) would detect the highest-energy cosmic rays by looking down on the atmosphere from space.

Loewenstein joins NASA Goddard's Laboratory for High Energy Astrophysics as a research associate with the University of Maryland, College Park. Hamilton, also a member of the Lab, is a National Research Council fellow.

For images of the "retired" quasar galaxies, refer to:
http://universe.gsfc.nasa.gov/press/images/cosmic_ray/.

AMANDA on line

The Antarctic Muon and Neutrino Detector Array (AMANDA) has detected its first neutrinos. AMANDA ( http://amanda.berkeley.edu) uses the clear ice under the south pole to provide interactions with incoming neutrinos.

A nice article, "Antarctic Dreams," about the project appeared in The Sciences, March/April 1999, pp. 19-24.