Old Hole

STScI; Sep 12, 2001; Press Release: "Ancient Black Hole Speeds Through Sun's Galactic Neighborhood, Devouring Companion Star"

Using visual, radio, and X-ray telescopes, astronomers have located a "microquasar" only 6,000 light years from Earth. Discovered by the Rossi X- Ray satellite, the object is designated "XTE J1118+480". Observations indicate that the object is a 7-solar mass black hole that draws material from a companion star and spews out radio emitting jets of subatomic particles. The companion star has been consumed to the point where its inner layers are exposed; it is only one-third the mass of our Sun. This binary object may have been ejected from a globular cluster where the black hole began life as a gigantic star. Such clusters contain the oldest stars in our galaxy and orbit the center of the Milky Way at an inclination to the galactic plane. Astronomers estimate ancient black holes from the first burst of star formation in the galaxy may number in the hundreds of thousands.

Orbit of black hole "microquasar" around the galaxy.   STScI image.

Very Long Baseline Array radio telescope observations and Palomar Observatory Sky Survey images -- taken 43 years apart -- helped determine the nature and motion of the object. "This also is the first time that a black hole's motion through space has been measured," says astrophysicist Felix Mirabel, who is affiliated with the Institute for Astronomy and Space Physics of Argentina and the French Atomic Energy Commission. Mirabel believes the black hole formed inside a globular cluster before our galaxy's disk was established. "What we're doing here is the astronomical equivalent of archaeology, seeing traces of the intense burst of star formation that took place during an early stage of our Galaxy's development."

Six-Way Lens

Space.com; Aug 27, 2001; Astronomy: "Astronomers Discover Six-Image Gravitational Lens"

Hubble image of lensed B1359+154 (white objects) and galaxy cluster (orange objects) -- STScI

Eleven billion light-years from Earth, in the direction of the constellation Bootes, lies a galaxy called CLASS B1359+154. This galaxy appears to contain a massive black hole in its core and exhibits signs of recent star formation. In the precise, same line of sight as this galaxy, but only 7-billion light-years away, is an unrelated cluster of three foreground galaxies. How do we know anything concerning the CLASS object apparently hidden by this cluster -- you may ask?  When you discover that CLASS is the acronym for Cosmic Lens All-Sky Survey, you'll understand that B1359+154 is actually made visible by gravitational lensing due to the foreground cluster that might obscure it.

First suggested by Einstein, this is an example of gravitational lensing acting as a tool to observe distant, unobservable objects. The manifestation of the lensed object allows us to also learn about the foreground objects doing the lensing. In the case of B1359+154 there are an intriguing six images of the galaxy -- the first example of a six-way image produced by a small cluster of galaxies. Larger galaxy clusters have produced more multiple images of a background object, but the number of galaxies in the cluster makes it hard to decipherer the physics of the lensing effect. With this relatively simple system, it is easier to construct computer models that predict the six images.

Creating better computer models of gravitational lensing will allow researchers to gain insight in the evolution and distribution of various forms of matter in the universe.

Missing Streaker

Space.com; Aug 30, 2001; Solar System - Meteorites: "Bright, Booming Meteor Vanishes in Colorado Mountains"

RockyMountainNews.com; Aug 24, 2001; Local: "Fireball Sighting Snowballs into 800 Reports in 5 states"

"It was 10 times brighter than the Moon," says Mike Valdez of Monte Vista, Colorado, of the August 17 fireball that streaked through the La Garita Mountain range at 10:44 that evening. A team from the Denver Museum of Nature & Science has interviewed 200 witnesses in an attempt to track down the attention-getting meteor. Though it was brilliant, trailing sparks, and causing sonic booms, remnants on the ground have not been located.

The museum had been inundated with 800 telephone and e-mail reports of the fireball from five states.  Some estimated the red-orange object was 40-times brighter than the Moon and posed a threat of forest fire. 

It is believed that the meteor was composed of a ton of iron and entered the atmosphere at 40,500 mph. This data was supplied by Los Alamos National Laboratory and based on the steep angle of the object's descent. It was hoped chunks of iron meteorite would be found in the rugged La Garita Mountains.

Flaming Cold Star

MIT; Sep 6, 2001; Press Release: "Star in Deep Freeze Chills Theory, MIT Researchers Report"

Illustration of neutron star (left) accreting from star.   NASA

A neutron star is the mind boggling, compact core of a star that blew-off its outer shells -- an event we see as a supernova. The core remains have a diameter measured in mere miles. When such a star exists in a binary system with a normal hydrogen-burning star, the intense gravity of the neutron star siphons off some of the companion star's material. Gas spirals around the neutron star and reaches its surface. This unleashes nuclear reactions that are visible from Earth as X-rays.

Some such binary systems flare in a periodic manner lasting weeks to years. In order to confirm neutron star models, scientists are keen on determining the temperature of the neutron star during the quiescent period between flare-ups.

Using the Chandra X-ray Observatory, Dr. Rudi Wijnands, of MIT's Center for Space Research, measured the temperature of a neutron star designated "KS 1731-260", a few months after the end of a 12-year period of flaring. Astonishingly, the 12-years of thermonuclear surface reactions left the neutron star no hotter than less-active neutron stars. According to Wijnands: "Twelve years of constant thermonuclear explosions: One would think that would heat things up." He continued, "This leaves us wondering whether some neutron stars are in the freezer for a much longer time than previously thought and consequently take a long time to heat up, or whether they cool down incredibly fast. Either explanation has profound implications for our field."

Models of neutron star temperature fluctuation predicted the star would be 10 times hotter than the 3.5-million degrees actually measured. According to theory, the low temperature could be explained if KS 1731-260 was dormant for a thousand years prior to the 12-year active episode. This is an usually long time. If true, KS 1731-260 could be the first of a new type of neutron star that stays dormant for very long periods of time.