The Monthly Journal
of the Johannesburg Centre of the
Astronomical Society of Southern Africa

Box 93145 Yeoville 2143 - 18a Gill Street Observatory

Notice is hereby given that the Annual General Meeting of the Johannesburg centre of the Astronomical Society will take place at 8pm in the Sir Herbert Baker Library, in the grounds of the former Republic Observatory, 18a Gill Street, Observatory.

Tom Budge hosts the next lesson in the beginner's course starting at 7pm on Wednesday 9 July 1997, just before the AGM.

To be advised.

A telescope in "good-condition" is offered to society members. The owner is not a society member and is offering us a commission on the sale of the telescope. The committee decided to sell the telescope to the highest bid received by post.

The following information is available. Its diameter = 114mm (4½ inches) F = 900mm packed in a case lined with Styrofoam. It comprises tripod, accessory shelf, balance weights, flexible cables, sighting scope, main tube, Barlow lens and four eyepieces. To quote the owner: "The telescope is in good condition and I don't think it has been used much."

There is a reserve price of R1000.00 (one thousand Rand).

If you are interested in acquiring this instrument you should send a written offer to The Secretary at the P. O. Box listed above. The offer must list your name, address, telephone number and the amount you are prepared to offer. You must sign the offer. Envelopes must be clearly marked "POSTAL TENDER".

Envelopes will be opened at the August committee meeting. The closing date is the night of the August monthly meeting -- 13 August 1997.

Sorry for the lack of an article last month, but the dreaded beast called work attacked me with all its force, and enslaved me with chains of deadlines.

I guess the highlight of this months astro-activities has to be the weekend down in Swinbourne. I packed the car up on Thursday night, and left Johannesburg on Friday afternoon, arriving at Swinbourne at about 16:00.

It is a pleasant enough place, consisting of a nice bar/dining room and a cluster of old buildings in which we all slept.

As darkness fell on Friday, we all rushed to set up our scopes, and then went for supper. The food was good wholesome home cooking just like Grandma made.

Anyway, after the food, we went back out to the dark sky, and I saw parts of the Milky Way that I last saw whilst on Veld School in Std 8. Really nice.

I spent a good 4 hours moving the scope around aimlessly, and enjoying the feast of nebulae, clusters.

Jupiter was a splendid object to view, I could see the striations very clearly, and the moons spread out in a straight line like cosmic pearls.

I went to a really cold bed at about 00:30.

We all woke up to a really miserable Saturday morning. True gluevine weather. But fortunately after a miserable day the optimism that Chris showed paid off and the skies cleared up nicely.

I set up the scope before supper, went to eat, and horror of horrors the scope was covered by a layer of ice. It was brass monkey cold. I took off the front cover off the scope and within 4 minutes the corrector plate had frozen up solid. So that put an end to using my scope to view the sky.

Chris and company took out their 6" scopes, and we took turns looking at pretty objects.

We had a look at Saturn which rose at about 01:45, and packed in at about 01:30.

Many thanks to Ed for organising the whole weekend, putting up with the cold was worth it, but next time we should try to find a place where there are absolutely no lights.

As far as the other projects are concerned, I have nearly finished the stepper controller circuits, and should be able to test them within the next two weeks or so ( work allowing).

I have collect all the electronic components for the CCD camera now, with the exception of the TC245 CCD chip which I will attempt to import shortly.

That is it for this month.

Inferences from Two Galileo Encounters

Doppler data generated with the Galileo spacecraft's radio carrier wave during two Europa encounters on 19 December 1996 and 20 February 1997 were used to measure Europa's external gravitational field. The measurements indicate that Europa has a predominantly water ice-liquid outer shell about 100 to 200 kilometers thick and a deep interior with a density in excess of about 4000 kilograms per cubic meter. The deep interior could be a mixture of metal and rock or it could consist of a metal core with a radius about 40 percent of Europa's radius surrounded by a rock mantle with a density of 3000 to 3500 kilograms per cubic meter. The metallic core is favored if Europa has a magnetic field.

One effect the Comet Hale-Bopp had on Earthlings was a renewed general interest in astronomy and an increase in Planetarium visits from the public -- over 3000 people attended the "Comet Show", and many were spotted doing the Hale-Bopp Salute" with Tom Budge. We counted 300 telephonic queries about the comet before we installed a temporary "star-line" answering machine to avoid insanity among the Planetarium staff. Among other unusual objects spotted recently was a flock of "glowing ducks" (1am near Pietersburg).

The second annual Wits University Open Day attracted thousands of people and was generally judged successful by participants. The Planetarium offered free trips "Round the Sun in 12 Minutes", built miniature comet nuclei and organised rocket-launching competitions. The only disappointed visitor appeared to be one expecting to see "a rocket that goes around the Sun in twelve minutes". Thanks to Peter, Trevor and Chris for displaying telescopes and Tom for all the hard work.

We have had some staff changes in the last couple of months -- our long-suffering Admin. Officer, Gail Harber, left us -- Constant Volschenk joined our staff in May as her replacement. We also bid farewell to the keeper of the Zeiss Star-projector, Frank Flowers. Frank will however still be involved with the Planetarium as a weekend lecturer.

Our current show, "Return to Mars", is timed to coincide with the arrival at Mars of the Pathfinder.

Observed with the Infrared Space Observatory at 2.9 Astronomical Units from the Sun

Comet Hale-Bopp was observed at wavelengths from 2.4 to 195 micrometers with the Infrared Space Observatory when the comet was about 2.9 astronomical units (AU) from the sun. The main observed volatiles that sublimated from the nucleus ices were water, carbon monoxide, and carbon dioxide in a ratio (by number) of 10:6:2. These species are also the main observed constituents of ices in dense interstellar molecular clouds; this observation strengthens the links between cometary and interstellar material. Several broad emission features observed in the 7- to 45-micrometer region suggest the presence of silicates, particularly magnesium-rich crystalline olivine. These features are similar to those observed in the dust envelopes of Vega-type stars.

Scientists have triggered a miniature explosion that may resemble a tiny supernova by enticing a newly created form of matter, called Bose-Einstein condensate, to collapse in the lab. The phenomenon, described here yesterday at a meeting of the American Physical Society, could be a boon to physicists probing mysterious interactions of atoms when they are suddenly crammed together.

Bose-Einstein condensates are dense collections of certain atoms cooled to a fraction of a degree above absolute zero, where their identities merge and they act as a single particle. Members of a team led by Randall Hulet of Rice University found that they were unable to load more than 1400 atoms into their condensate, created from chilled lithium trapped in a magnetic field. The researchers believe that when too many atoms are in the trap, all the lithium atoms rush together and somehow spin off from the magnetic trap. "It's like the lithium is digging a deeper and deeper hole," says Robert Dodd, a physicist at the University of Maryland. "When the hole is deep enough, they all rush in."

The lithium condensate behaves this way because lithium atoms have a peculiar property: They attract each other when close together, instead of repelling each other, as most other elements do. "They want to suck together rather than push each other apart," says team member Charles Sackett, a physicist at Rice University. Nobody is sure why lithium acts this way, says Eise Tiesinga, a physicist at the National Institute of Standards and Technology. "There's no 'why'--it just is," he says.

Until the number of atoms in the trap reaches a threshold, however, the zero-point energy--quantum-mechanical fluctuations of energy that are a consequence of the Heisenberg uncertainty principle--helps prop up the condensate. But when there are too many atoms in the trap, their attraction overwhelms the zero-point energy and the condensate collapses.

The heat generated by the collapse warms the atoms enough to muck up the condensate, says Sackett. That process of collapse and expansion resembles what happens when the core of a giant star collapses into a black hole or neutron star, triggering a supernova. Stars collapse when gravity overcomes the pressure exerted by electrons obeying the Pauli exclusion principle, a law of quantum mechanics that says that certain particles cannot be in the same place at the same time. The lithium condensate collapse "is the exact same thing," says Dodd. "You're just overcoming Heisenberg instead of Pauli."

Bursts of hard radiation called gamma-rays coming from the sky, have been one of the most intractable mysteries of modern astronomy. A multinational research team reporting in the 17 April issue of the science magazine Nature may, at last, provide some explanation for the origins of these puzzling visitors from space.

The 'gamma-ray bursters', or 'GRBs', were first discovered by spy satellites designed to detect nuclear explosions. The very existence of GRBs was kept secret for about five years, until scientists decided that they simply could not figure out what they were. More than a thousand theories have been concocted, ranging from collisions between comets to the exhaust emissions from the warp-drive engines of alien spaceships. The absence of any visible counterpart to the bursts has been a serious stumbling block, because astronomers have had no idea what type of object makes the burst. Now, almost twenty-five years after their discovery was announced, researchers have the first hint of what may be causing GRBs.

Dr Jan van Paradijs of the University of Alabama at Huntsville, Alabama and his team of international collaborators [mainly from the Netherlands and Italy] think they have found an optical counterpart that faded quickly after the burst of gamma rays. This fading source appears to be located in a faint, distant galaxy.

Until 1991, when NASA launched an astronomical satellite called the Compton Gamma-ray observatory (a kind of gamma-ray counterpart to the Hubble space telescope), it was generally assumed that the objects giving rise to the bursts of gamma-rays were located relatively close to the Sun, and certainly within our Galaxy. That view was challenged seriously in 1992, when Dr Chuck Meegan of Marshall Space Flight Centre in the United

States and colleagues reported that the bursts seemed to be distributed uniformly across the sky. If they were located in our Galaxy, there should have been a pronounced surplus of bursts along the line of the Milky Way.

Soon after that, various theories were put forward suggesting that instead of being quite local, the bursts were instead coming from objects far outside the Galaxy, halfway or more to the edge of the observable Universe. The most favoured theory was the collision and merger of two super-dense neutron stars, which would release enormous quantities of hard radiation such as gamma rays, potentially detectable at cosmic distances. Other astronomers suggested that GRBs came from sources much closer, from a 'halo' of objects associated with our own Galaxy.

Opinion has polarized between these two views -- do GRBs originate close to our own Galaxy, or much further away? A public debate was held on the issue on 22 May, 1995, at the auditorium of the National Museum of Natural History in Washington DC: [75 years after a similar debate about whether 'spiral nebulae' were objects within our Galaxy, or more distant objects (we now know the second option to be true).] The debate pitted Dr Bohdan Paczynski of Princeton University against Dr Don Lamb from the University of Chicago, the main proponents of the 'cosmological' and 'local' distance scales, respectively. Any source at a 'cosmological' distance is presumed to reside inside a distant galaxy.

The evidence presented by Dr van Paradijs is at this stage only suggestive, and other astronomers are trying to confirm the identification of the source as a faint galaxy, using the Keck telescope in Hawaii and the Hubble space telescope. Dr Paczynski remains somewhat skeptical, but many astronomers are convinced that they have at last found the critical evidence needed to determine the origin of GRBs. The next few weeks should see this issue settled.

The discovery was made thanks to a Italian-Dutch satellite called BeppoSAX, which was designed to observe X-rays (which are less energetic than gamma-rays). This satellite is able to report the position of a GRB within hours of detection -- rather than days or weeks as had been the case previously -- allowing astronomers to direct optical telescopes to the source before it fades from view. Dr van Paradijs and colleagues found the fading optical source only 21 hours after BeppoSAX reported the GRB.

Should the identification of a galaxy hold up, there is still a lot more to be learned. For example, it will make a difference to theorists if future bursts occur mainly in spiral galaxies (meaning that they may come mostly from young objects), or from elliptical galaxies, in which case they are most probably caused by old objects. Although the colliding-neutron-star theory is currently looking like a good bet, more data may tell us something completely unexpected -- as unexpected as the original discovery itself.

The long-running mystery of gamma-ray bursts (GRBs)--flashes from somewhere in space that periodically set detectors screaming--has taken another dizzying twist. After astronomers thought they had tracked a recent burst to a faraway source, a new analysis of observations by the Hubble Space Telescope suggests that the source may in fact be a fast-moving object a stone's throw away.

The question is whether GRBs originate in or near our galaxy or billions of light-years away, at cosmological distances, which would make them the brightest outpourings in the universe. Astronomers thought they were on the verge of an answer when an Italian-Dutch satellite saw a fading source of x-rays that seemed to be the afterglow of a GRB the satellite had detected on 28 February. Because x-ray detectors have much better spatial resolution than those for gamma rays, that helped pin down the burst's position for further observation. Hopes shot even higher when ground-based telescopes aimed at the spot then fished out both a point of light and a faint fuzzy patch next to it--possibly the GRB source and its host galaxy in the distant universe (Science, 21 March, p. 1738). The cosmological alternative seemed poised to carry the day. But then the Hubble got into the act.

The latest results of its scrutiny of the proposed source, reported on the Internet in International Astronomical Union (IAU) circulars, have thrown the debate wide open again. Patrizia Caraveo at the Istituto di Fisica Cosmica in Milan, Italy, and several collaborators claim to have found something startling: The point source was moving across the sky. The angular motion was so quick, they say, that the object might have to be within a few hundred light-years of Earth--much closer than even the proponents of a galactic origin for GRBs have been suggesting recently. The fuzzy object could then be a transient cloud of gas associated with the burst or a background galaxy, aligned by chance with the pointlike object.

Another group--looking at the same data--saw nothing of the kind. An analysis by Kailash Sahu of the Space Telescope Science Institute (STScI) in Baltimore and several collaborators suggests the point source is stationary. "We cannot reproduce what Caraveo says in the IAU circular in spite of our best efforts," Sahu told ScienceNOW.

Resolving these issues, experts say, is likely to require a third Hubble observation when the point source, now drawing close to the sun, reemerges from its glow in a few months. If the object is still visible, the next glimpse of it should settle the question of whether it's moving. In the meantime, many astronomers share the sentiments of Chryssa Kouveliotou of NASA's Marshall Space Flight Center in Huntsville, Alabama: "I'm more confused than anything," she says.

Alex Richter is the manager of the Aloe Ridge Conference Center and Game Park, and Lu and myself were invited out there by him a couple of weeks ago to listen to a proposal and offer some snippets of advice about setting up an Astronomical Observatory.

Oh, for those who don’t know, the Aloe Ridge is situated along D.F.Malan drive, out past the Krugersdorp/Pretoria Highway and near the Heiea(?) Safari Lodge.

He has Ordered: a Meade 16" LX200 telescope with a Permanent Pier; a Meade 1616 CCD Camera - which is the biggest one they make; Meade Epoch 2000 Software; all the eyepieces & filters available and a powerful Commercial PC to drive all of this.

What he plans to do is: sell time at the observatory to both professionals and amateurs for whom the 16" would be suitable; offer Astronomical Sessions ( ± 1 hour ) as an attraction to Conference delegates & Visitors. These sessions would consist of a leader doing an astronomical tour of the heavens which would be screened from a PC via a Barco or Proxima projector. There would be complete computer control of the 16" telescope and Camera, and there could be both live and pre-recorded segments in the Session. Offer longer Astronomical Sessions to interested parties (such as ourselves) the Astro Sessions obviously at a specified rate per hour or session.

He needs persons to run these sessions and was going to look for Professional parties to do this. I suggested that, as he is an interested Amateur, he should rather approach the ASSA to supply the session leaders and pay a nominal ( but not too nominal ) fee to the society for the use of their members in this role. I guess that ± R150-00 per session would not be too unreasonable.

If he sells an average of 4 of these sessions a week, we could be looking at an amount well in excess of R2000-00 per month coming into the Society’s coffers, and I’m sure these funds would be very welcome. I can think of a couple of projects which would benefit and I’m sure that the committee has many, many more projects in mind which cannot be initiated due to a lack of funds.

From our side, we would obviously need several members who would be able to spare an evening once every couple of weeks just for the love of Astronomy - and our society of course. For an hour or two’s time every couple of weeks, each of these members would be generating some significant income for the Jo’burg Centre.

Alex has a person coming out from the States to install and implement the whole set-up and is paying this guy to train some bodies to run it. He would like these 3 or 4 people to be from the Society. They in turn could teach the balance of the session leaders how to run the setup. The guy from the States will be here from mid-June for about 2 weeks and that is when we would need to spend some learning time out at Aloe Ridge.

I’m sure that he would be happy to have brochures promoting the ASSA and the Planetarium that could be handed out after the sessions and of course we would have a vested interest in promoting his after-dinner sessions as well.

Personally, I can hear opportunity knocking at the door and I think we should open up and let it in.

"May 29, 1997 -- It’s vindication for University of Iowa scientist Louis Frank. Eleven years ago, the scientific community rebuffed Frank when he proposed that the earth’s atmosphere was being bombarded by giant snowballs. Yesterday, he showed a meeting of the American Geophysical Union satellite photos to support his theory."

The balls are a couple of miles across and hit the earth’s atomosphere at the rate of 20/min. It has been calculated that in the 2 billion years that the earth has been around, the balls could easily account for the water in the sea. Amazing huh!!!

For those of you with sound cards, there is a great interview with Frank on National Public Radio to listen to over the net using Real Audio. Just go to www.npr.org and find the story called Snowballs From Space.

I have back copies of Sky & Telescope magazine dating from 1987 to 1993, including the 50^th Anniversary Issue of November 1991. There are approximately 75 magazines in all. The cover price was US$2.50. What offers?

Call Larry Green on 786-6660/3916 (home) or 334-3935 (work).

For sale or swop: Celestron Classic C8 (orange), w/ 23mm 1.25" eyepiece & prism, camera adapter, 240V RA Drive, equatorial mount & tripod. Sell: R3500, swop for Meade 4" EXT or C5+ or something equivalent. Contact Grant Hillebrand 011 651 6781 (w) 011 462 2066 (h) or by e-mail at granth@duvi.eskom.co.za

I am still unable to interpret the newsletter as the so-called attachments are embedded in the e-mail itself and not attached to it. I have not discovered any way of extracting them. I have tried saving the contents to separate files but my application program says "out of memory" even with 16Mb of RAM!

Graham at Grantt@ilink.nis.za

Applicants should have electronic, mechanical and computer expertise. An interest in and knowledge of Astronomy would be an advantage.

For more information contact Joan Francis at (011)716-3596 or Dr. Claire Flanagan at 111FLAN@cosmos.wits.ac.za

It's been my pleasure preparing and publishing Canopus for several years but the time has come for me to take my bow and leave the committee and hand over the editorial reigns to my successor. We don't know who this will be but I'm sure that the new committee will find a willing soul.

The experience was interesting and at times frustrating. The new electronic dispatch was the most exciting part of the task -- pioneering at the forefront of today's technology.

For all those members who supplied articles and material -- thank you.

It has been fun and I look forward to my new role as reader of Canopus in the months and years to come.