The M.A.S. Newsletter
Journal of the Mauritius Astronomical Society
June 2000
The Next Meeting:
The next meeting will be due on the 30th of June at Collège du Saint Esprit at 19:30 for a slide show about the planets.
The sky this month:
Mixed News:
One of the scientific instruments on NASA's NEAR Shoemaker spacecraft has malfunctioned and been shut down, project officials said Wednesday 7th. Engineers first noticed problems with the Near-Infrared Spectrometer (NIS) on the spacecraft on May 13, when the instrument inexplicably began to draw extra current from the spacecraft's power supply and stopped collecting data. The instrument was turned off at that time while engineers tried to understand the problem. Technicians turned NIS on again on Monday for one minute to collect housekeeping and diagnostic data from the instrument. That test showed the problem persisted, and officials have now decided to leave the instrument off indefinitely. The loss of NIS is a blow to scientists, who had been collecting a bounty of information about the mineral composition of the asteroid Eros, which NEAR Shoemaker has been orbiting since February 14. By the time NIS started malfunctioning, the instrument had taken more than 58,000 spectra of the asteroid, covering 60 percent of its surface.
Newly-released observations of comet Hale-Bopp indicate that it formed much farther from the Sun than previously thought, astronomers said at a conference Monday 5th. A team of astronomers led by S. Alan Stern of the Southwest Research Institute (SwRI) took spectra of the comet at ultraviolet wavelengths during a sounding rocket flight in late March of 1997, when the comet was at the perihelion of its orbit around the Sun. Those spectra revealed the existence of the noble element argon, the first time it has been detected in a comet. Noble gases like argon have weak spectral signals; argon was detected in Hale-Bopp through a combination of advanced instrumentation and the brightness of the comet. "The detection of argon would not have been possible except for Hale-Bopp's unusually high brightness," said coinvestigator David Slater of SwRI. The argon discovery is of considerable scientific importance. Since argon and other noble elements don't combine chemically with other constituents, their presence in comets implies they have been there since the comet formed in the early history of the solar system.
Astronomers announced Wednesday 7th
that they have created a three-dimensional map of 100,000 galaxies in the Universe,
providing an independent measure of the mass density of the Universe. The first results of
the 2dF Galaxy Redshift Survey, the largest survey of galaxies yet performed, were
released Wednesday at a meeting of the American Astronomical Society in Rochester, New
York. The survey was conducted with a wide-field spectrograph, capable of seeing an area
of the night sky two degrees across -four times the diameter of the Moon- at a given time,
hence the "2dF" name. The spectrograph can take spectra of 400 galaxies
simultaneously and 3,000 over the course of a single night, allowing astronomers to
measure the redshift of the galaxies as they move away from Earth, and hence their
distance. The observations were made with the Anglo-Australian Telescope (AAT) in
Australia. This information, coupled with existing images of the galaxies, has been
combined into a 3-D map with a volume of some 13 billion billion cubic light-years,
covering 1/20th of the night sky out to a distance of 4 billion light-years. The results
confirm existing concepts of the structure of the Universe, where galaxies are combined
into huge superclusters and stretched out along long filaments, with huge areas devoid of
any galaxies. The origin of these structures dates back to the Big Bang itself,
astronomers said.
Serge Florens, Secretary