The M.A.S. Newsletter

Journal of the Mauritius Astronomical Society

October 2000

The Next Meeting:

The next meeting will be due Friday 27^th of October at 19:30 at Collège du Saint Esprit, Quatre Bornes. There will be a slide show on Cosmology given by Mr. R. Auckbur.

The sky this month:

On the night of the 16^th, the moon is in conjunction with the planet Jupiter, visible in the east at about 23:00. Mars is visible in the constellation of Leo and moving towards Virgo. At dawn on the 24^th the moon is in conjunction this time with the planet Mars at magnitude 1.8, visible in the east. On the evening of the 27^th, Venus is at its closest to the main star of Scorpius, Antares. On the 30^th the moon is again in conjunction, this time with the planet Venus, visible just after sunset in the west. The planet Mercury is in inferior conjunction with the Sun (between the Earth and the Sun) on the 30^th.

Pics of the Moon
by Serge Florens

Click on thumbnail to enlarge...

Telescope: Celestron 5 with an eyepiece projection of 25 mm

Film: Kodacolor 100

Date: 6 September

Occultation:

In the early hours of the 26^th the planet Saturn passes in front of a 10.6 magnitude star (visible only through a telescope). The event is expected to start at 04:27, but since the star first passes behind the rings, it is worth starting the observation a few minutes earlier. The planet is now visible in the constellation of Taurus.

News:

Researchers using data from NASA's Transition Region and Coronal Explorer (TRACE) spacecraft concluded that the heating in the lower regions of the corona provided the energy to heat the gas in the corona, although they have yet to identify the mechanism that heats it. The discovery came from studies of coronal loops, streams of gas that rise hundreds of thousands of kilometers high - large enough to encompass 30 Earths - before falling back to the solar photosphere at speeds of 100kms- ¹. The TRACE data revealed that the loops are actually composed of a number of individual loops bundled together, and that, on average, the temperature of the individual loops varies much less than predicted by uniform heating hypotheses. Astronomers have spent decades trying to understand why the corona can reach temperatures of millions of degrees, while the photosphere, or solar "surface", is far cooler, at less than 6 000° C. Discovering that the heating of the corona is taking place at relatively low altitudes is the first step towards understanding the mechanism that heats the corona. Some scientists believe that the Sun's magnetic field is involved with the heating of the corona.  In 1997 scientists found that electrical currents travelling along magnetic loops extending high into the corona provided more than enough energy to heat the corona, but were unable to describe both how the magnetic loops formed and how the energy would be transferred from the current loops to the gas. TRACE studies the Sun at ultraviolet wavelengths from a polar low-Earth orbit using a 30 cm telescope.

Astronomers in Arizona have started using a new, larger telescope to search for near-Earth objects.  The 1.8 metre Spacewatch telescope started observations of asteroids last month atop Kitt Peak, Arizona.   After several days of testing, the telescope took what scientists called the "first data with potentially scientific value" when it observed a very fast-moving asteroid, 2000 RD53, on September 20.  The telescope, believed to be the largest in the world dedicated to asteroid searches, should allow astronomers to discover asteroids that are fainter and smaller than those that can be seen with the existing 0.9 metre telescope also at Kitt Peak.  "The telescopes will be complementary," said Robert McMillan, Spacewatch director.  "The smaller telescope, when upgraded [next year with improved instruments], will get a much wider field of view, or cover 10 times as much sky. The 1.8 metre will concentrate on finding the very faint objects."

The interior of Io, the volcanic inner large moon of Jupiter, has a differentiated mantle much like the Earth's, according to a recent report by planetary scientists.  Measurements of the composition of volcanic plumes, derived from spectra taken by the HST, have allowed scientists to infer the conditions within the interior of the geologically-active moon, concluding that its mantle is rich in sulphur but poor in iron. Mikhail Zolotov of Washington University in St. Louis believes that water may have oxidised the iron the moon originally had and help transport it into its core, a process similar to what occurred in Earth's early history.

Astronomers believe observations of a collision between a stream of particles powered by a black hole and a nearby gas cloud may prove to be the "missing link" towards a better understanding of black holes and active galaxies.  Astronomers used the Very Long Baseline Array (VLBA), a collection of 10 radio telescopes, to study a jet of particles emitted in the vicinity of the black hole in the heart of galaxy 3C120 over the course of 16 months. "Blobs" in the jet would turn on and off over that time, as the jet apparently collided with a nearby gas cloud.   "This cloud, about 25 light-years away from the black hole, represents a 'missing link' that will help us understand the complex regions around the central black holes in active galaxies," said Jose-Luis Gomez of the Astrophysical Institute of Andalucia in Granada, Spain.

Serge Florens, Secretary

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