Energy Bubbles.

From all over the universe, bubbles of energy are expanding away from their source and are heading our way.  Some will have passed us by years ago, but there are a lot still coming.  These bubbles are invisible until you stand at their expanding boundary and look back to the way they came.  Then you can see them if there are enough photons left.  There are most properly millions upon millions of bubbles in the universe heading our way, rushing away from the star that formed them at the speed of light.
Now and then a few photons will hit a mirror and be focused onto a detector.  Then they will give up some of their secrets to the scientists examining the way the colours of light and the dark bands hidden within it reveal the formation of different elements millions of light years away and millions of years ago.  Without this information we would not understand the universe as well as we do today.
Many amateurs help in the task of spotting the žrst sign of another bubble of light reaching us from a distance galaxy.  It always amazes me how much can be read from a few photons which can be up to 90% of the age of the universe.  They have travelled on edge of their bubble across the universe.  How many times has the information they preserve in their wave bands been detected and read by alien senses before the bubble as swept on out of reach?

Ivor
Editor

By Mike Frost

(Newcomers to these stories should be aware that I try to stick to known science.
Veterans will know that I don‘t always succeed.)
 

I was sat in the pub, of course, with my old friend Clive, stalwart of the Interplanetary Dangerous Sports Club.  I always look forward to hearing of Clive‘s latest exploits, but sometimes he can be very frustrating.  Like when you‘re trying to tell him your own stories.
”So there we were at Victoria Falls,' I was trying to tell him, 'watching the bungee jumpers'
Clive stifled a yawn. ”Fascinating. . .  Is it your round yet, Frosty?'
I was annoyed.  At times, I could spend hours helping Clive hone his tall stories ™ he should at least indulge me when I wanted to tell him about my own adventures.  Sulkily, I gave up and asked him where he‘d got to lately.
Clive brightened up. ”Europa!'
I was really annoyed.  Clive didn‘t want to know about my trips to the back of beyond, but was quite happy to bore me with journeys into his own back yard.  ”Which bit of Europe?  Majorca?  Moldova?  Schleswig-Holstein?'
Clive tutted.  ”Not Europe, Frosty. Europa; moon of Jupiter.'
”Ooohhhhh‡  Hang on a second!  Isn‘t that moon in quarantine?'
”Exactly!" said Clive, ”So there are people around who are quite prepared to pay very good money for a guided tour."
Well, I wouldn‘t have called it tourism.  More like people trafficking, if you asked me.  But there was no doubt that Clive had stumbled on a lucrative venture.  There were any number of bored millionaires with more money than sense and a burning desire to visit the more obscure bits of the solar system.
But, Europa!  It was one of the few places in  the Solar System that was thought to have any possibility of harbouring life.  Mars, another likely candidate, was only expected to yield fossils; but Europa was known to have an ocean of liquid water, which, for all we knew, was teeming with life.
For that reason, whilst scientists figured out the best way to construct a completely sterile probe, Europa was strictly off-limits to exploration.  I suspected that this would make visiting the moon appealing to a certain category of irresponsible fool.  Two categories, in-fact.  Multi-millionaires seeking to go somewhere nobody else had ever been.
And Clive.
”So who was your client?" I enquired.  Clive shook his head.
”Confidential, I‘m afraid.  Details on a need-to-know basis, and you don‘t need to know.  Let‘s call him Dennis.  He was something big in the city, venture capitalist I think.  Made his money on the Internet start-ups and knew when to cash his share options."
Clive was sounding suspiciously well-informed financially.  It soon became clear why.

* * * * *

”Dennis and I (explained Clive) set off from Earth as inconspicuously as possible.  I‘d filed flight plans to the Moon, but as soon as we were clear of low Earth orbit, I turned on the ion drive and reset course for Jupiter.
Because of the clandestine nature of our journey, I‘d have preferred to stay radio silent.  But for Dennis, this was completely out of the question.
He spent the first week continuously on his mobile phone.
"Nigel!!  Hi!  Yeah, I‘m on the spaceship! How‘s the Citibank deal going??  Great!  Great! Take them for another five million!  OK, gotta ring off — we‘re just coming to the asteroid belt.‘
It was quite exciting at first, Frosty, to be in the presence of so much cashflow, but he never stopped!  And when we did get out of radio range, he turned on to me.
I guess it was just to have someone to talk to, but he only had one topic of conversation — finance!  I‘ll tell you, there wasn‘t much I didn‘t know about OEIC‘s, ISA‘s and TESSA‘s by the time we got to Jupiter.
We had so little in common, you see.  Even the things you‘d think we‘d agree on — like booze.  I was a beer man and he was into imported lagers.  And I could barely eat the things he‘d stocked in the galley — in fact, I could hardly pronounce most of them!
But worst of all was his exercise regime. Frosty, I know you have to keep yourself fit when you‘re in space, otherwise your muscles waste away.  But Dennis was a fanatic — when he wasn‘t on the phone, he‘d spend days on end in our gym.
And you know the very worst thing of all.  HE ONLY HAD ONE PAIR OF SOCKS!!  The whiff, Frosty, it was horrible — I can still smell it.
[I was beginning to understand Clive‘s situation.  Two people locked together in a spaceship can really get on each other‘s nerves. Especially when one of them is Clive.]
Well eventually, Frosty, we reached the Jupiter system — and not a moment too soon.  We started from a wide Jupiter orbit, then swung rapidly in to the inner Jovian system, the better to avoid spending time in Jupiter‘s radiation field.  So I parked us quickly into orbit round Europa, and guided the spaceship gently down on to the surface of Europa, on the side opposite from Jupiter.
Imagine, that, Frosty.  We were the first people ever to land on Europa!  Mind  you, the view wasn‘t exactly stunning — just ridge after ridge of ice, without even Jupiter to look at.
The surface of Europa is made completely of ice sheets, between ten and fifty kilometers thick.  From long range observation, I had identified a landing point where the ice crust was particularly thin.  As soon as we landed, we set up drilling equipment and began to bore our way through the ice crust.
I say ”we" — in fact, I did most of the boring with the drill.  Dennis bored me with statistics.
"You know, Clive, you should really consider the emerging markets for your ISA allowance. Mexico is up thirty percent this fiscal.‘  And all whilst pedaling that darned exercise bike!!  In those darned socks!!
[I was going to ask why, if Dennis was so wealthy, he needed to darn his socks, but I decided not to interrupt Clive mid-rant]
After two days of drilling, the drill bit broke through into the sea beneath the ice-crust.  This, if anywhere, was where we would find life on Europa.  It took another two days to widen out the borehole wide enough to fit our mini-submarine — two days in which I found more about investment trusts than I ever wanted to know.
Finally, we were ready to make the historic first voyage into the oceans of Europa.  Of course, we had taken all the precautions to avoid contamination — I‘d scrubbed the sub all over with Dettol, and even poured a bottle and a half of Domestos over it.
As we descended towards the sea of Europa, Dennis finally seemed to pick up some interest in the mission he‘d paid so much for.
'This will be just so cool to mention to the boys back at the racket club.  They won‘t sneer at me again, I‘ll tell you!‘
At last — the moment when we emerged into the ocean.  I switched on the flash lights, expecting us to see. . . what??  Squid, sharks, jellyfish. . . who could guess?  What we actually saw was . . . nothing at all.  No fish, no plankton, no seaweed.  Nothing at all.  Dennis was not very pleased.
'I‘ve paid a lot of money for this trip, Clive. I‘m expecting a better return on my investment.‘
As though it was my fault!
We spent a week sailing the pitch black deeps of Europa, Frosty, and it was profoundly depressing.  No life at all. Just a completely inert, endless, motionless ocean of water.
We were about to give up, on the point of returning to the borehole, when I spotted something.  Not very exciting,  I‘ll grant you, but we were desparate for anything different.  Our sensors detected a very weak current in the ocean — the only movement in the entire sea not generated by our submarine.
We sailed towards the current, which welled up from the lowest reaches of the ocean, and descended into it.  As we headed downwards, the current grew stronger, and the water temperature began to rise.
For twelve hours, with mounting excitement, we followed the trail back to its source.  Eventually our sonar started to pick up echoes from beneath us — the ocean floor, five hundred kilometers below the ice crust.  And finally, with my heart beating fast, we reached the source of the only current in the Europan ocean.
There in front of us was a hydrothermal vent — a crack in the ocean floor, spewing out boiling  water.  The vent had to stretch down to the molten core of Europa, kept hot by the pummeling of Jupiter‘s tides.
You see, Frosty, this was our luckiest break.  Conditions here were perfect for the formation of life — the warmth rising from the molten interior, the water of the ocean, and a huge variety of chemicals spewed out onto the ocean floor.
If we were going to find life anywhere on Europa, it would surely be here.  I could hardly  control my excitement as I jettisoned our sensors to detect living organisms.
We watched the telemetry for minutes, then hours, with growing frustration.  Not a sign of life.  Not a twitch.  Dennis was not well pleased.
'Pretty poor show, Clive, pretty poor show.  I shouldn‘t have picked you to run this expedition, should I?  I shouldn‘t have listened to her advice.‘
I froze. 'Whose advice shouldn‘t you have listened to??‘
'Oh, thought you knew.  Your old girlfriend Clarissa recommended you.  Well, not exactly  recommended.  She said there‘d never be a dull moment with you around.  Didn‘t I mention her before?  Clarissa and I are an item now, you know.‘

* * * * *******************************************************************************************************************

I could now understand exactly why Clive had taken against Dennis.  For all his protestations, Clive still had a thing for his old girlfriend.  I thought I‘d do well to change the subject.
”This is fascinating, Clive!  It bears out Fred Hoyle‘s theories."
”Fred who?  What theories?"
”Sir Fred Hoyle — famous astronomer.  Very controversial.  He claimed that life didn‘t arise on Earth at all.  It was his opinion that life arrived in comets."
”Comets?!"
”Exactly.  He thought that comets, along much of the rest of the interstellar medium, were made up of organic material — microbes, amino acids and so on — just sitting there in a state of suspended animation.
In the early days of the Earth‘s formation, we were bombarded by millions of comets, which provided the water for our oceans.  Eventually, some of the organic material would find its way down to the Earth‘s hydrothermal vents - where it would thrive."
”Well maybe", said Clive, ”but what has it got to do with Europa?  Comets might hit the surface of Europa, but they would never make it through the ice crust."
”Exactly!!  Europa probably formed without any hydrothermal vents.  An ocean of cometary water formed and froze over, without ever having the chance to nurture any microbes.  All the bugs in the ocean died off billions of years ago.  But much, much, later the tides of Jupiter started to open up hot vents to the molten core.  Too late to be seeded by any organisms from outer space."
Clive nodded sagely.  ”I‘d never heard about Sir Fred‘s theories, but I had come to my own conclusion that the vents were perfect for nurturing life — if only they had some living organisms to start with.  And a thought occurred to me."
I felt a chill go down my spine. "Oh, Clive. . ."
”I figured that here was a chance for immortality.  Any bugs, any microbes, in fact, any organic material at all — would thrive in the hydrothermal vents on Europa.  I could personally kick-start the whole story of life on the moon. . ."
”But Clive," I said, horrified, ”Yes, you could do it — but you‘d be found out.  By the time we  come to explore Europa properly, any DNA you leave behind will still  be there, and still recognizable as Earth-based.  And from the DNA, scientists will be able to trace precisely who vandalized the vents.  You will be found out — shamed — humiliated."
”Exactly." said Clive. ”So I dropped Dennis‘s socks down the vent."

An edited report from off the Web by
Ivor Clarke

The government a short time ago, asked a panel of experts for their thoughts on the possibility of a collision between Earth and other Earth orbit crossing bodies.  This is an edited version of the text of the report recommending that the UK help to fund a program of research into the subject to access the problem and to žnd a solution.
The government a short time ago, asked a panel of experts for their thoughts on the possibility of a collision between Earth and other Earth orbit crossing bodies.  This is an edited version of the text of the report recommending that the UK help to fund a program of research into the subject to access the problem and to žnd a solution.
 

Since its formation four and a half billion years ago, the Earth has been under a constant barrage of objects from space.  These objects come in a very wide range, from dust to moons, with greatly different rates of arrival.  On average, hundreds of tonnes of dust enter the upper atmosphere every day; every year objects of a few meters diameter enter, some having effects on the ground.  Every century or so there are bigger impacts.  For a long time there was an unwillingness to recognise that the Earth was bombarded, but increasing knowledge of the meteoritic flux over the last half century has shown otherwise.
Our understanding of the threat from NEO‘s, asteroids, long and short period comets, is relatively new.  Recently a government task force examined the nature of the asteroids and comets that circulate within the Solar System and looked at the facilities required to identify the orbits and compositions of those objects coming close and how a world-wide effort might be best organised and co-ordinated.
Asteroids and comets are remnants of the formation of the Solar System about 4.5 billion years ago and range in size from pebbles or lumps of ice, to rocky or icy worlds nearly 1,000 kilometres across.  An asteroid or comet will become a NEO if its trajectory intersects the orbit of the Earth or is within 0.3 Astronomical Units.  An object is said to be potentially hazardous when it‘s 150 metres in diameter and its orbit comes even closer, to within 0.05 AU (7.5 million kilometres, or about 20 times the Earth to Moon distance).  So far, 258 potentially hazardous objects have been discovered.
Asteroids are made up of carbonaceous (carbon containing) materials, rocks (silicates) or metal.  They may comprise of piles of boulders held together only by their own very weak gravitational forces, or be solid lumps of stone or slabs of iron.  They are not spherical bodies until they are more than 100 miles in diameter owing to their weak gravity being unable to pull the rocks, ice, dust and other materials into a ball and may spin or tumble as they orbit the sun.  There are many subcategories of asteroids: each behaves differently when entering the Earth‘s atmosphere and in its reaction to countermeasures.
Comets are essentially dirty snow-balls and include many particles of dust.  It is only when a comet comes near the Sun that these gases evaporate, freeing the dust that forms the tail sometimes seen by the naked eye.
Rough estimates of the numbers of Near Earth Objects of different sizes can be made either by direct measurement using ground-based telescopes or inferred from the numbers and sizes of craters on the Moon or the planet Mercury.  The atmosphere protects the surface of the Earth from most small NEO‘s, which burn up or explode at high altitudes.  Whether they survive to impact the surface depends on a number of factors: their size, composition, velocity and angle of approach.
The main effects of impacts are blast waves equivalent in some cases to many megatons of energy, tsunamis (or ocean waves), along with the injection of large amounts of material into the atmosphere, and electromagnetic changes near the surface.  As some two thirds of the Earth‘s surface is covered by the sea, the chances of an ocean impact are greater than on land.
From measurements taken over recent years the orbits of over 400 NEO‘s with a diameter above 1 kilometre (about half the estimated number) are known.  This allows us to hope with some confidence that no object has been identified that is likely to hit the Earth over the next 50 years.  Smaller objects, which can also cause great destruction locally or regionally, are known about even less.
Impacts from NEO‘s with diameters over 10 kilometres would have global consequences, possibly resulting in the extinction of most living organisms, ie, us.  Such events are fortunately very rare.  Impacts of objects with diameters from a few kilometres in diameter to 10 kilometres are also rare , possible only one per million years.
Objects with diameters around 1 kilometre are the most dangerous because they are much more frequent and can give many more casualties per impact than smaller ones.  Impacts of smaller objects, with diameters of a few hundred metres, would have dramatic local consequences, but are unlikely to affect the Earth as a whole.  For objects below about 50 metres in size, the Earth‘s atmosphere usually provides adequate protection with objects exploding at high altitude doing little harm.
By discovering and tracking the most dangerous of these objects, and by studying further the consequences of impacts and the possibilities for mitigation, it may soon be possible to exert some control over further events.
Most measurements can be made with ground-based telescopes and radars, rather than with expensive space-based missions.  While some dedicated facilities are essential, much valuable work can be done by occasional or serendipitous use of telescopes or spacecraft with different prime scientific aims.
Because it is impossible to predict where new objects may come from,  the whole sky must be observe frequently and systematically.  This calls for specially designed wide-angled telescopes with advanced detector arrays coupled to very fast computers.  They need to operate automatically and remotely, and be dedicated to the observations of NEO.
To determine the orbit of an object after its initial discovery, conventional narrow-angle ground-based telescopes are needed in each hemisphere.  Because a newly discovered object rapidly becomes fainter as it moves away from the Earth, follow-up observations must be made within days of discovery.
Uncertainties make it difficult to predict whether a particular asteroid might cause a global or regional catastrophe.  The use of ground-based radar to determine the objects position, velocity, size, shape, gross structure and spin when it is sufficiently near the Earth is possible, but not its mass.  For this, space rendezvous missions are needed.  Relatively inexpensive microsatellites could fulfil this purpose.
The United States is doing far more about NEO than the rest of the world put together.  The Minor Planet Centre is at the hub of observations world-wide.  In addition, military surveillance facilitates in space and on the ground look continuously for objects and explosions in the upper atmosphere.  The only current activity in the Southern Hemisphere is in Australia.
For the first time in the history of the Earth there are possibilities for mitigating the effects of impacts by NEO and even, in the longer term, for deflecting them entirely from collision with the Earth.  But all this depends on first improving our ability to detect such objects well in advance and seeking to measure accurately their orbits and physical properties.
Once an asteroid or comet on a collision course is identified and its orbit tracked, its likely point and time of impact can generally be predicted.  Such accurate prediction is rarely possible for other natural hazards.  Wherever the impact, people could be moved to safety, given sufficient warning and appropriate logistical support.  However, extensive material damage would nevertheless result.
An international effort to look into the practical possibilities of deflection and a number of possible mechanisms have been considered for deflecting or breaking up potentially hazardous NEO.
If ever there was an issue affecting the whole world, it is the threat from Near Earth Objects.  To understand and try to cope with the threat requires an international response.  This response should cover not only understanding the science, so that dangerous Near Earth Objects may be predicted and methods of mitigation assessed; but, equally important, how all aspects of this response should be organised.
The new organisation must cover the identification and coordination of the science, communication with the public and work on measures to react to a possible impact, or to deflect or destroy an incoming object.  At the present time no international institution exists for this purpose.
Spaceguard is a collective term for a variety of activities which have grown up in a number of countries over recent years and which have done much to alert public opinion.  But none has official recognition except for the US Spaceguard Survey (the name given to the NASA survey), and so far there are no specific coordinating mechanisms in any state or government, not even in the United States.
The need for an international approach is essential and at the heart of proposals for action  to confirm the nature of the hazard and potential levels of risk.  The more we studied the subject the more we can see how very little is currently known about Near Earth Objects, despite the efforts of many scientists.  We do not know accurately how many objects of about 1 kilometre diameter there are; and their energies and compositions are very uncertain.
We know very little indeed about smaller objects.  Without this knowledge we have only the roughest idea of the magnitude of the risk.  The science involved is wide-ranging, involving astronomy but also geophysics, oceanography, climatology, biology and the social sciences.
The government Task Force has concluded that the overall needs, worldwide, are as follows:
* For survey and discovery:
At least one dedicated 3 metre-class telescope in the southern hemisphere and one in the northern;  the survey of smaller Near Earth Objects;  the use of data from surveys being made for other purposes;  the use of sky survey archives;  the use of space telescope missions where appropriate;
* For accurate orbit determination:
One large telescope in each hemisphere, preferably dedicated; some time by right on various existing instruments;
* For composition and gross properties:
Access to large telescopes and space rendezvous missions;
* For academic studies:
In particular of Near Earth Objects interactions with the atmosphere, oceans, solid earth, climate and living things, including historical evidence;  the effects on people and society.
What fair contribution should Britain make to fulfilling these needs?  Taking into account  existing telescopes or those under construction in which the United Kingdom is a partner; the skills of British scientists and engineers, industry; and  that partnership with Europe in this task is desirable.
To make a substantial contribution to the need both for surveys in the southern hemisphere and for systematically discovering smaller Near Earth Objects, a proposal to construct an advanced new 3 metre-class telescope on an excellent site seems sensible.  It may possible to  refurbish older existing telescopes for the systematic survey and discovery of these objects, but it may generally be rejected because adapting such equipment would be expensive and the resulting telescopes may not be competitive for very long.  Only a new dedicated telescope would make a satisfactory contribution to the world effort.  Because such a facility would be expensive, this project should be shared with other countries, preferably within Europe.  The recommendations include that arrangements be made for observational data obtained for other purposes by wide-field facilities, such as the new British VISTA telescope, to be searched for Near Earth Objects on a nightly basis.
No current space telescope is dedicated to the discovery of Near Earth Objects.  However, a number of existing and planned missions are, and will be, able to detect objects incidentally when making observations for quite different purposes.  So it is strongly suggested that consideration be given by space agencies to consider the use of space missions for incidental observations of Near Earth Objects.
Apart from existing telescopes, the European Space Agency‘s proposed GAIA mission and NASA‘s SIRTF mission could play a part in surveying the sky for NEO‘s is one of the recommended projects.  The potential in GAIA and SIRTF for Near Earth Object research should and must be considered as a factor in defining the missions and in scheduling their completion.
A particularly urgent requirement is for observations to determine the orbits of NEO‘s discovered by United States telescopes but subsequently lost.  This needs one or more professionally run telescopes about one metre  that could immediately fulfil this need.
Space rendezvous missions to asteroids or comets give a unique insight into the  characteristics of the asteroid or comet being visited.  A systematic assessment of different types needs many missions, perhaps as many as 20 to enable each type subsequently to be recognised by ground-based techniques, of great importance should countermeasures be needed.
For this limited purpose it might be possible to use a series of essentially identical micro satellites, each launched economically piggy-back with other spacecraft; in this way the unit cost should be much below that of current rendezvous missions.  The United Kingdom is a leader in micro satellite technology and a beginning could be made with a single demonstration mission.

What we hope to see

By Paritosh Maulik

In the last article we have seen the construction of the European Southern Observatory  Very Large Telescope Interfometer (VL TI), at Paranal, Chile.  In this article we shall discuss the objects astronomers are interested in studying, and next time the various instruments employed at the facility and briefly discuss the next generation of large telescope.
 

The Very Large Telescope Interferometric (VLTI) array, consisting of 8m Unit Telescopes (UTS) only, is referred as VL TI Main Array (VIMA).  The interferometer consisting of 1.8 m Auxiliary Telescopes (ATs) is called VL TI Sub-Array (VISA).
UTI and UT2 have been in operation from early 2000.  AT1 and AT2 are expected to be on line by early 2002.  Then subjected to the availability of funds all 4 UTs and 3 ATS may begin work in 2003.

WHAT WE HOPE TO SEE
Extra-solar Planets
The presence several extra-solar planets have now been confirmed and this has led to an impetus toward detecting more.  There are two basic methods available.
1) Precise Radial Velocity:  the motion of the star around barycentre of the star™planet system is measured.  This method can not determine the planetary mass and the inclination of the orbit.
2) Astrometric survey:  the planets are viewed pole-on, and from this method it is possible to calculate the planetary mass directly.
To get an idea about the time scale involved in such a project, about 200 target stars will be examined in near infrared with VISA; integration time about 30 minute per star and 30 observations per night for 10 years.  This corresponds to 300 nights over a period of 10 years.  Proper and parallax motion will be studied and this will account for the presence of planets, if any.

Low Mass Star and Brown Dwarfs
Although about 90% of the stars in our galaxy are of mass lower than the sun, our knowledge on these objects is somewhat lacking,  One of the aims of the VLT will be to establish the observational mass ™ luminosity relationship, especially at the lower mass end.

Brown Dwarfs
Until now these have been studied by the broad band photometry method.  This gives an idea about atmosphere of the stars, but the process going on inside the star are primarily determined by its age and mass.  High precision parallax data from Hipparcos and spectroscopy from VISA will yield information on small 0.03% solar mass brown dwarfs.

Young Stellar Objects
These objects often show phenomenon like infrared excess, variation in luminosity and highly collimated jets with velocities of the order of several hundred km/sec.  These phenomena indicate the presence of an accretion process and strong magnetic fields.  Although the VLT would not be able to resolve the innermost part of an accretion disc, the high angular resolution, sensitivity and the infrared response will permit the study the morphology of the disc.  Also disc temperature distribution, relative contribution from the scattered stellar light and thermal disc emission, composition and the properties of the dust grains.
 

Stellar Surface Structures
On the outer surface of stars localised convection cells, convection zones and magnetic fields are present.  These are due to hydro-dynamic and electro-hydrodynamic effects.  These convection zones can be studied by observing surface temperature and line of sight velocity measurements.  These time dependent variations of active areas will give an indication about the processes of the generation of the magnetic fields.  In the disc of the star Betelgeuse some unresolved features have been detected. These are likely to be the hot spots of emission caused by material rising to the surface from the hotter interior.  VL TI will be able to provide us with a clearer picture.  The selected sources will be surveyed in detailed, say every month and also to include their local neighbourhood.

Be Stars
Theses stars show H™emission lines, but the emission pattern is variable and complex.  These are rapidly rotating (around 250 - 400 km/sec) stars with a equatorial disc or ring and it is believed that the emission is from the disc.  The current model assumes that radiation pressure carries the material from the rapidly rotating star to form the disc.  However there appears to be some discrepancies between the observations and the model.  The excellent resolving power of the VLTI will be able to give a clearer image of the point like source and the emitting disc.

Asymptotic Giant Branch (AGB)
These stars are in there giant phase, the helium is exhausted and it is burning in the shell.  These stars show a large convective atmosphere from which material escapes at a rate of 10 8 to 10 4 solar mass per year and this atmospheres appears to expand at a rate of 5™30km/sec.  It is accepted that there is a slowing down of the pulsation and formation of the dust; and radiation pressure ejects the dust.  The mass loss controls the future of the AGB, this dust in the form of chemicals is added to the interstellar dust and finally to the galaxy.
The process of dust formation and the chemical composition of the dust and that of the star is not very well understood.  High resolving power and the mid-infrared range capability of the VLTI will be utilised for this study.

The Galactic Centre
The central region of the Milky Way galaxy, 0.1 pc, will be examined in the infrared range of 2 to 10 micron wavelength.  The presence of the central massive black hole will be carried out by measuring the three-dimensional velocity field of the star cluster centred on IRS16.  It was originally detected as a strong infrared source.  But later lunar occultation studies showed that there are over 24 starts emitting in the 2 micron region.  Detailed analysis suggests perhaps these are blue supergiant stars and emitting in short wavelengths, ultraviolet and visible ranges.  The surrounding dust cloud absorbs the radiation and re-emits it in the infra-red region.  If this is the case, then these stars are young and have formed only 10 million years ago.  All these point to the fact that star formation is going on at the centre of the our galaxy.
Sagittarius A* (Sgr A*), the first radio source to be identified by Carl Jansky, is believed to be at the centre of the Milky Way galaxy.  Radio studies suggest that Srg A*, is in a Keplarian orbit, at a velocity in excess of 1,000 k/sec, about a central massive object of 2.7x10 6 solar mass.  It has also been suggested that black holes of 10 solar masses collapsed to form an enormous black hole at the galactic centre.  As the gasses spiral into the black hole it forms accretion discs and some lost energy is sent out as radio beams. Molecular clouds also surrounds the Srg A*.  The VLT is expected to give a clearer picture of this region.

Active Galactic Nuclei (AGNs)
At the centre of the galaxy there appears to be a black hole of about 10 8 solar mass, accreting gasses.  This object shows both continius and emission lines and also in addition, infrared, radio, or x-ray sources may be present.  These features are more common in the redshift of z - 2 i.e. about 0.8 - 0.9 times of the age of the universe.  Although we are certain that the accretion process is powering the system, the details are not clear.  For example, ultraluminus star bursts, radio sources that are prominent in the elliptical galaxies but not in the spiral galaxies.  Seyfart galaxies behave similar to quasars, but on a much reduced scale.
 

Next time we will look at the telescopes various instruments employed at the facility and briefly discuss the next generation of large telesccopes.