Museum of Freemasonry - Masonic Library
Collins English Dictionary defines asteroid as a ‘minor planet or planetoid’.

The early observers of the heavens had to make do with naked-eye sightings until the development of the telescope as the primary tool of Astronomers. The early observers of the heavens would never have discovered asteroids without the telescope.

On 1st January 1801 at Palermo in Sicily, Giuseppe Piazzi noticed an unknown point of light against a background of known stars. Please note that the point of light was not moving and only subsequent sightings on 41 consecutive nights could prove that it had moved. This object was named Ceres to honour the patron saint of Sicily.

Ceres is too small to be seen with the naked eye having a diameter of only 1003 kilometres. Subsequently, Pallas was discovered in 1802 and Juno in 1804, then Vesta in 1807. Together these four bodies became known as the minor planets, or asteroids. In 1845 Astraea was spotted, then in 1847, Hebe, Iris and Flora were found followed by Metis in 1849.

Since then, over 2000 asteroids have now been found and studied sufficiently for their orbits to be plotted and many more still remain undetected. One estimate of the small planets, is 44000, but Russian sources believe the number could be as high as 100,000. As stated earlier, the first discoveries were made by ordinary visual observations of the star fields, night after night, to pick up apparent movement, using telescopes that were rapidly being improved in quality.

Later, when telescopes were adapted to take photographs, this new innovation was responsible for finding asteroids more readily and in rapidly increasing numbers. By utilising time-exposure plates to obtain clearer definition of star-fields, any asteroid passing through the field of vision betrayed its passing and its type by leaving a streak of light when the plate was exposed. This technique discovered asteroids in such numbers that they were called by some, ‘the vermin of the skies’

The first stars which formed from primordial hydrogen and helium produced in the big bang, cannot have had any planets, because there were no heavy elements available from which they could be built up. Planetary systems are all second-generation (or later) systems, made from the previous generations of stars in which the heavy elements had been built up by nucleosynthesis and scattered through space in stellar explosions, or supernovae.

Before the initial creation of the solar system, the slowly spinning primordial cloud would have been dusted, from time to time with, with fragments of matter containing the higher elements. These would have originated in nearby supernovae in our galaxy, and blasted across time and space, to the cloud from which our solar system formed.

After the Sun formed, the swirls became the planets, but those nearer the Sun contained the bulk of the heavier elements, the lighter elements being blown away from the Sun and then from the inner planets.

As the parent cloud of gas and dust, began to shrink, any rotation it possessed made it spin faster and faster, and as the core of the cloud collapsed to form a star, some of the material from which it had formed was held out from the centre of the cloud by residual spin, and the material settled down into a dusty disc around the young star.

Closest to the young star, the lightest material in the disc, comprising mainly hydrogen and helium gas, was blown away by the heat of the star. The material left behind was made up of billions of tiny grains of dust that collided and stuck together, building up larger lumps. The lumps of matter may have been a few millimetres across and were settling into a thinner disc around the star. The process of accretion – lumps growing by sticking together carried on until the original dust grains had become lumps of rock about one kilometre across, similar to the asteroids that orbit in profusion between Mars and Jupiter today.

Once the pieces of rock reached this size, they began to tug on each other significantly through gravitation, which pulled them into swarms that orbited around the star together, bumping into one another from time to time. Gravitation pulled the pieces more and more tightly together, with the largest lumps (which had the strongest gravitational pull) attracting more and more material, growing to become planets and their moons, or more correctly speaking, their satellites.

In our solar system, there are four rocky planets close to the Sun, each formed in the way just described – Mercury, Venus, Earth and Mars. Then there is a belt of cosmic rubble (the asteroid belt), a ring representative in many ways of the kind of material from which the inner planets formed. The material in this ring could never settle down to become a planet itself because it is continuously being disturbed by the gravitational influence of Jupiter, the largest planet in the solar system. Beyond the asteroid belt, there are four “gas giant” planets, Jupiter, Saturn, Uranus and Neptune. These are probably typical of planets that form at larger distances from the parent star, planets in which the primordial volatile material has been retained, so that even though they may contain a small rocky core, they are mostly made of gas and ices.

Even after the four main bodies that were to become the inner planets had formed in the disc of material around the young Sun, there were many smaller pieces of rubble in the inner solar system, following their own orbits around the Sun and being swept up by the four planets as they passed through the swarm. The battered face of the Moon shows the effect of the bombardment that continued after the planets had been formed: similar cratering has been photographed by space probes visiting Mercury, which (like the Moon) has no atmosphere to erode the traces of the ancient bombardment.

In the original disc of material around the Sun from which the planets formed, the region that is now occupied by the asteroid belt would have contained enough matter to make a planet about four times heavier than Earth. Originally, particles in this region, like those closer to the Sun where the inner planets formed, would have been moving around the young star in almost circular orbits, alongside each other, so that collisions between them would have been fairly gentle, encouraging them to stick together. But as Jupiter began to grow by accretion nearby, its gravitational influence would have disturbed the orbits of these objects in the asteroid belt. As these orbits became more elliptical, they criss-crossed one another in a confused tangle. As a result, any lumps of rock that had grown up in this region smashed together at higher speeds, so hard that instead of sticking together to make larger objects (and eventually a single planet) they broke apart. As many as eight super-asteroids, each as large as Mars, may have formed in what is now the asteroid belt before being broken up in this way.

In the inner part of the solar system, as far out as the asteroids, it was hot enough for volatile material to be evaporated and blown away, so that small, rocky planets and the asteroids, themselves formed. Beyond the orbit of Jupiter, it was cold enough for ices (frozen water, frozen methane, frozen ammonia, and other materials) to stay frozen. So from the very beginning, when particles stuck together to make larger lumps, the lumps they made contained a lot of ices, like a dirty snowball. Many of these dirty snowballs stuck together and grew, to make the giant gas planets. There, the heat released in the collisions eventually vaporized the ices, but the strong gravity of the giant planets held on to some of the primordial hydrogen and helium. All these gases together gave the gas giants their present structure.

None of the asteroids has an atmosphere, even the larger ones having a diameter of 1000 kilometres or so, because they do not have a strong enough gravitational attraction to retain the lighter gases.

Its possible that some asteroids may be the remains of a former planet that met with disaster. It is more probable that the bulk, were formed from the debris left over after the planets had been formed, as previously described.

Because asteroids are so small and of so little mass (relatively speaking), their gravitational attractions are weak, and a man standing on a small one could jump clear off, that is if he wanted to.

There are two groups of asteroids which move in almost the same orbit as Jupiter and these are called the Trojan Asteroids. They are positioned at the Lagrange points of Jupiter, i.e. one sixth of an orbit ahead of, and behind, Jupiter. Each of these Lagrange Points is a point of gravitational equilibrium and would be the third corner of an equilateral triangle formed by drawing lines between the point, the planet, and the Sun.

Collisions taking place in the crowded traffic lanes of the asteroid belt may cause some fragments resulting from the impact, to be flung off in revised orbits that may intersect that of Earth and the other inner planets. There are even a few asteroids known to have a similar orbit to that of Earth.

Early in their formation, some asteroids underwent internal heating and melting which caused differentiation of their structure. It seems that a number of the larger asteroids in the asteroid belt also underwent internal melting and segregation, but only briefly because they were not big enough for the process to last.

Occasional impacts between these bodies must have demolished some of them so that fragments from their metallic interiors and their stony exteriors occasionally arrive on Earth as meteorites, some 4600 million years after their creation.

All the asteroids that have been tracked orbit around the Sun in the same West to East direction as the Earth and other planets. This supports the theory of them all having formed from the same revolving cloud of matter.

Asteroids sometimes come close enough to Earth to collide with it. Approximately 1500 boulder sized asteroids enter the atmosphere each year, as meteors and those that do not disintegrate or vaporize, reach the surface as meteorites. Fully fledged flying-mountains are thought to strike much less frequently, perhaps once in each 10,000 years, on average. If, and when they do, the Earth acts like soft mud and swallows them explosively into the surface with incredible forces being released. These astroblemes (or star wounds) are eventually erased by the combined effects of the atmosphere and the healing power of vegetation, erosion and the effects of mountain building. Without these, Earth would be as pock-marked as the Moon and Mercury.

Even though they are essentially erased, traces of the outlines of some large astroblemes can still be seen from space, for example, the Vredefort Structure in South Africa which has a diameter of over three hundred kilometres. I have a list of the larger ones for your interest.

Eros, an asteroid as big as the island of Manhattan, has an unusual orbit bringing it inside Mars, and within 24 million kilometres of Earth. In February 2001, the probe NEAR Shoemaker performed a remarkable feat. It landed on the asteroid Eros, a rocky lump only about 33 kilometres long after orbiting the asteroid for a year.

In 1937, Hermes, a dwarf world, passed us at a distance of only 776,000 kilometres, less than twice as far as the Moon.

Given that the extinction of the dinosaurs 65 million years ago is widely regarded as resulting from the impact of an asteroid approximately 15 kilometres across, with an impact energy of 100 million megatons, the detection of near-Earth objects and the consideration of how to defend against them, is clearly of importance.

Near-Earth asteroids include the types known as Amors, Atens and Apollos (named after a typical asteroid of each type), which are characterised by their orbits.

Amor asteroids have orbits with a perihelion (the point of orbit closest to the Sun) between the orbits of Mars and Earth, while Apollos and Atens have orbits which cross that of Earth. Gravitational perturbations by the planets can, however, change one type of orbit into another over time, so all are potentially hazardous to Earth, given enough time.

Apart from an Aten object designated 2003 CP20, the near-Earth asteroid that comes closest to the Sun is the Apollo asteroid Phaethon which is about five Km. wide, and whose perihelion distance is about 22 million Km. The mean distance of the Earth from the Sun is 150 million Km., so Phaethon comes well inside our orbit.

The metallic asteroids are rich in iron, as well as nickel and other metals that are comparatively rare on Earth. Metals in asteroids exist in pure form, not in ores as on Earth, and this makes them much easier to extract. So when supplies of the rarer metals start to run out, we might send astronauts or robotic mining into space to mine the asteroids and send their materials back to Earth. Near-Earth asteroids that come closest to our planet with a high metal content, would be the first targets for mining.

Asteroids are considered by Astronomers to be the least interesting of the many celestial bodies which decorate and adorn the universe, but I do hope that the few details I have been able to share with you, my Masonic audience were of interest as these objects have had an effect on Earth in the past and, most probably, will again in the future. Therefore we must regard them as dynamic astronomical objects that can greatly affect the future of man and finally, that we can consider this, your acquisition of Astronomical knowledge for today.

VW Bro Robert Taylor