1.ASTEROIDS

» these are smaller planets also known as “planetoids”» found between the orbits of Mars and Jupiter» believed to be of the particles of an exploded planet» about 2,000 of them have been discovered;» revolves around the sun just like the planets with an average of 3- 6 years revolution time.» In 1801, Ceres, the first and largest was discovered by Piazzi;» Has a diameter of 480 miles, most of them however, have diameter under 64 miles.» An important among the planetoids is Hermes, discovered in 1937.

2.COMETS

» they are bizarre, awe – inspiring heavenly bodies, considered to be visitors from outer space;

» most of them are seen only with the aid of a telescope but some are readily visible to the naked eye;

» have a long “hairy” tail which it forms as it approximates the sun which it loses as it leaves the sun;

Composition and behavior:

A well –formed comet consist of a solid nucleus embedded in a rightly luminiferous coma or head which is about several thousand of miles in diameter, and a long magnificent tail.

The nucleus of the comet, according to F.L. Whipples is a porous mixture of frozen methane, ammonia and water with metallic and stony pieces of material embedded in it. When the comet approaches the sun, the ices evaporate, causing the gas to be ejected in all directions. The material ejected towards the sun is turned back by streams of charged particles radiated outward from the sun. This “solar wind” pushes the material back into the shell, or coma, around the comet’s nucleus on the opposite side of the sun, forming a tail of 5 to 50 million miles long. Much of the light we see is due to the ionization of the particles of the head.

Three things that may happen as a comet as it comes nearer the sun:

» If it falls straight towards the sun, it will become a part of the sun.

» If it falls close to the sun, but is not caught by the whirl of gases from the latter, it will start off in the general direction from where it came. The sun will continue exerting a force upon it as it stops and returns. In this case, the attraction of the sun has captured it and it becomes a part of the solar system, visiting the sun at regular intervals.

» As it approaches the sun, it is somehow deviated from its path that it flies off into the space and never to return.

Halley’s comet has been the most celebrated comet in the 20th century. It has become a regular visitor of our solar system. It is calculated to appear every 75 to 76 years. The last time it appeared was May 1910 and is expected to be back in 1985 or 1986. Several smaller and less celebrated comets have graced our skies such as Kohoutek, Lobayashi – Milton – Berger comets.

Halley's Comet Seen Through the 24-Inch Telescope at Table Mountain

Observatory

3. METEORS AND METEORITES

The universe seems to be littered with chunks of stones and metals which fly through space at high speeds. These particles of heavenly bodies of stone and iron traveling through space are called meteors. Some astronomers believe them to be particles of exploded comets. When the meteors actually penetrates the atmosphere and lands on the ground, it is termed meteorites. These are usually black, as a result of the burning that occurs due to friction with particles of the atmosphere. Their sizes are varied from particles of dust to boulders weighing forty tons. All of the various kinds of meteorites that have been found to fall are of three types:

» those of metal, called the siderites;» those of stones, called serolites» those which are mixture of metals and stones, called

siderolites.

This crater in Arizona was caused by a 30 m wide, 100,000 ton meteor. The

impact crater is 1.1 kilometers wide and 200 m deep.

A Leonid Fireball Meteor from 1966.

The siderites were used in making tools such as Atilla’s sword or arrowheads of certain South American Indians. The age of meteorites has been calculated on the basis of the ratios of the numbers of atoms of radioactive potassium to the number of argon atoms found in the meteorites.

Meteoroids are tiny particles of matter that travels at high velocities and enter earth’s outer atmosphere in vast numbers. They are observed to occur in large numbers at certain dates of the year. The events are called meteor showers. The principal meteors shows during the year occur as follows:

NAME OF SHOWER DATEBootids (Quadratids) -------------------- January 2 – 3Lyrids -------------------- April 19 -22Perseids --------------------- August 9 – 14 Orionids --------------------- October 16 – 20Leonids --------------------- November 14 – 18Andromenids --------------------- November 17 – 23Gemenids -------------------- December 9 -12

4. STARS» are huge globular masses of hot gases held together by its own gravitational attraction.» produce their own light and twinkle when viewed with the naked eye. The nuclear transformation of hydrogen to helium produces the light.» method of measuring distances is by means of light year, the distance traveled by light in one year at the speed of 186,000 miles per second equaling to 5.86 x 10» movement is independent of each other. Due to its distance, they do not seem to move at all. After a long period of time, a shift in their position becomes apparent.» space velocities for the most part is more than 100 miles / second» brightness is expressed in magnitude which is affected by age» sizes ranges from the small white dwarfs to such giants as Antares and Mira; Giant stars’ diameter is up to 2 billion miles. The smallest stars have diameters of about 10,000 miles (dwarfs)

Example of stars:

1. Sirius- is the brightest star in the nighttime sky. It is located in the constellation Canis Major. It is situated in the eye of the greater dog Canis Major, therefore it is known as the “Dog Star”. It is also called the watchdog of the river Nile since its appearance serves as a warning that the Nile would soon be flooded. It is 8.6 light years away.

2. Bernard star - the fastest moving star. It appears to move in 20 years, a distance slightly greater than the diameter of the full moon.

3. Alpha Centauri - is a special star, not because it is the closest stellar system to the sun but because it is one of the relatively few places in the Milky Way Galaxy that may offer terrestrial life conditions. If humanity looks for intelligent life elsewhere, then Alpha Centauri is an excellent

candidate. It lies 4.35 light years from the sun. 4. Antares –the 15th brightest star in the sky. It got its name from the

ancient Greek which means anti-ares. Ares, is the Greek god of War who is called Mars by the Romans. Antares is linked to the

planet Mars because they are both about the same color and the same brightness, so it is easy to get them confused.

SIRIUS ALPHAR CENTAURI

ANTARES

5. THE SOLAR SYSTEM

» it is a family which includes the sun as the central body, the planets, their moons or satellite, a number of asteroids, comets, meteors and meteorites.» it is a system wherein the movement of its members is determined by the gravitational attraction of influence of the sun.» most accepted theory regarding the formation or origin is:

Nebular Hypothesis – first proposed by Immanuel Kant but was further elucidated by Marquis de la Place to whom the credit for he hypothesis goes. It claims that the solar system envolved from a slowly rotating gaseous cloud, that when it cooled by radiation and eventually contracted, causing the gaseous cloud, that when it cooled by radiation and eventually contracted, causing the gaseous material to assume a disk like form.

The production of energy by the sun results from atomic fussion which is the combination of 4 hydrogen nuclei to form one helium nucleus. Such theory are based on H.A. Bethe’s work and is an outgrowth of the theory relatively. The mass loss of 0.03 atomic mass units is converted into heat energy. According to Einstein, the sun losses mass at the rate of 4.5 x 10 to the power of 6 tons per second in order to produce its present rate of radiation.