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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.
A Leonid Fireball Meteor from 1966.
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.
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
Bootids (Quadratids)
Lyrids
Perseids
Orionids
Leonids
Andromenids
Gemenids
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DATE
January 2 – 3
April 19 -22
August 9 – 14
October 16 – 20
November 14 – 18
November 17 – 23
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.