Since its launch on 24 April 1990 the Hubble Space Telescope has provided a stunning view of the universe as well as of the objects in our Solar System. It has made many discoveries. I remember reading in 1930, what a very venturesome astronomer had to say about the view, is that earthbound astronomers get of Mars. The Planet is very small and very far away and the Earth's atmosphere spoils the clarity of the image obtained photographically. He wrote that, perhaps in two or three hundred years it might become possible to launch a telescope into an orbit around the Earth outside the Earth's atmosphere. Crazy coot! What is the operating astronomer going to stand on out there beyond the atmosphere? What is he going to breathe for air? How is he going to keep warm in the cold of space at -273° C? That's what I thought. Now, only 60 years later, not two or three hundred years, the orbiting space telescope has become an accomplished fact.

In its eight years of space exploration the 12.5 tonne Hubble Telescope has set many milestones, among others:

Circling Earth every 90 minutes, the Hubble Telescope has travelled about 1,9 milliard kilometres, more than 55 times to the Sun and back.

Astronomers, using Hubble data have published 170 000 scientific papers.

The total amount of Hubble data placed in archives is 4.4 terabytes, which fills 710 thirty centimetre optical discs each containing 6.66 GB

The telescope has taken about 120 000 exposures.

Hubble has observed 10 000 astronomical targets.

Hubble has looked at least four times deeper into space than any other telescope.

Hubble has looked more than 10 million lightyears to galaxies in their infancy and has found a bewildering assortment of about 2 000 galaxies at various stages of evolution.

Hubble knows these distances because all it has to do is to measure the redshifts of the objects, the amounts by which the lines in their spectra are shifted to the red. The further away the galaxies lie, the greater are their redshifts and the greater are their speeds of recession. The formula of the law devised by the astronomer E P Hubble is

V = H₀D,

where V is the velocity of recession and D is the distance. H₀ is the Hubble constant. Certainty about this constant has not yet been reached, but its value lies between 55 and 100 kilometres per second per mega-parsec (km.s^-1.Mpc^-1) A megaparsec is a million parsecs.

The Hubble telescope has been able to monitor Cepheid variables at much greater distances than other telescopes and to standardise the corresponding redshifts of objects at these distances.

The deepest, most detailed optical view of the universe is called the Hubble Deep Field. For 10 consecutive days in 1995 the Hubble telescope was pointed on to a spot in the Constellation Ursa Major, a spot 2½ arc minutes (one twelfth the diameter of the Moon) in size. In this area the telescope revealed 1 500 galaxies to distances as far as 10 million lightyears. Many of these galaxies have never been seen by any other telescope. These data will yield invaluable information with regard to the evolution of galaxies.

Hubble's information shows that the Big Bang must have been followed by an intense and all-pervading burst of star formation even before the galaxies came into existence.

The radiation from distant supernovae indicates that the expansion of the universe has continued unabated. One of these supernova must have erupted 7.7 million years ago. This indicates that the most probable age of the universe is 15 million years (10⁹⁾

Hubble has found that must quasars lie at the nuclei of distant galaxies, both spiral and elliptical. The light variability of these quasars is very short, showing that the quasars occupy very small regions of space. The quasars may therefore be groups of supernovae erupting at short intervals, hence the short periods of variability. This indicates that galaxies have masses of supernovae at their nuclei. The end product of these supernovae is bound to be black holes or gravitational vortices, which is a better name than Black Holes. Hubble has succeeded in measuring the speeds at which super-heated gases revolve in accretion discs around the nuclei of the distant galaxies. The gravitational vortices, on their part, may play a salient tie in the firing off of quasars.

The most energetic blasts of radiation ever observed, have been the so-called gamma rays. These have been monitored by Hubble, the indication being that they come from supernovae. The Space Telescope Imaging spectrograph (STIS), has measured the speeds of the revolving gases in the accretion disc of a gravitational vortex in the galaxy M84 in Virgo at a distance of 50 million light years. It found speeds of 400 kilometres per second. It seems that all large galaxies have massive gravitational vortices in their centres.

Hubble has also monitored the collision taking place in the Antennae galaxies, so called because the arms of stellar matter and gas which have been flung into space, resemble the antennae of insects. The many young globular clusters it has found in the arms of the Antennae, indicate that globular clusters are not, as hitherto thought, very old, but may still be in the process of formation. These images produced by Hubble, will help to unravel the secrets of the formation of globular clusters and the effects of galactic collisions.

Hubble images have provided dramatically clear views of the birth of planetary systems by revealing the discs of gas which surround many stars. These discs have been called proto-planetary discs because it is supposed that planets will condense out of the gas and dust in the discs.

Hubble's Wide Field Planetary Camera 2 (WFPC2) and the STIS have shown that the debris from Supernova 1987A has slammed into a ring of material around the dying star. This "ring" is actually a bubble of gas and dust, which must have been cast off from the star Sanduleak -69° 202 when it is in its supergiant stage. Hubble has also revealed the existence of an hourglass bubble around Eta Carinae. This bubble must have been formed in Eta Carina's 1843 outburst.

Besides monitoring the crash of the 21 fragments of the comet Shoemaker-Levy 9 into Jupiter in 1994, Hubble has also discovered a giant crater on the Asteroid Vesta, 450km in size. Hubble actually caught the giant mushroom-shaped plumes of gas and dust caused by the crashes into the atmosphere of Jupiter, as these rotated around the limb of the planet.

Something else which has never been seen before is the aurora which hover over each of Jupiter's poles. It has actually photographed vapour trails left by Jupiter’s moon Io. It has found that Ganymede is manufactured ozone so that Ganymede must contain some oxygen. The other Jovian satellite Europa does have a very thin atmosphere of oxygen.

The surface of Pluto has a mottled appearance.

Hubble produced fantastic views of Saturn revealing details of hazes in the clouds girdling the planet. The white stripes and ovals in Saturn's clouds appear to consist of fine crystals of ammonia. The very dark region at Saturn's south pole is a hole in the cloud system. The red and orange stripes indicate clouds reaching high into the otherwise clear atmosphere.

Although the Hubble Space Telescope is far and away the most expensive telescope ever built, it is certainly producing the goods.

One can now start looking forward to the launching of two infrared telescope into an orbit between the orbits of Uranus and Neptune, so as to get away from the Sun's heat and so as to receive the infrared radiation from individual planets of the nearby stars. Two such telescopes can act interferometrically and thus obtain the greatest amount of resolution which is needed to reveal individual planets. When will this be done? It is a pity that one has to live in the present primitive times before these things come to pass.

Eben van Zyl