2. • heavenly bodies which are cloudy in appearance revolving around the Sun.
• They contain a nucleus inside a cloud-like coma.
• As they come near the Sun, they develop a tail due to the melting of icy
constituents and dusts blown away by the solar wind.
• The tails points away from the Sun.
• As it moves away from the Sun, the tail disappears.
• Comets are seen periodically.
3. EXAMPLE
ENCKE’S COMET
Comet 2P/Encke was first
discovered by Pierre F. A. Mechain on
Jan. 17, 1786. Other astronomers
located this comet in subsequent
passages, but these sightings were
not defined as the same comet until
Johann Franz Encke calculated its
orbit.
It takes 3.30 years for Enke to
orbit the sun once.
4. EXAMPLE
HALLEY’S COMET
Halley was last seen in Earth's skies in
1986 and was met in space by an
international fleet of spacecraft. It will
return in 2061 on its regular 76-year
journey around the Sun.
Comets are usually named for their
discoverer(s) or for the name of the
observatory/telescope used in the
discovery. Since Halley correctly
predicted the return of this comet — the
first such prediction — it is named for
him to honor him. The letter "P" indicates
that Halley is a "periodic" comet. Periodic
comets have an orbital period of less
than 200 years.
5. EXAMPLE
COMET C/1995 O1 (HALE-
BOPP)
was discovered in July 23,
1995, independently, by both
Alan Hale and Thomas Bopp.
Hale-Bopp was discovered at
the amazing distance of 7.15
AU. One AU is equal to about
150 million km (93 million miles).
6. • They have nebulous appearance and
elongated orbits.
• The nucleus is the only part that can
be seen with a large telescope even
when still far away from the Sun.
• This cometary nucleus is an irregularly
shaped mass composed of largely
frozen water mixed with substantial
amounts of carbon the form of fine
dust.
7. ORIGIN OF COMETS
• Comets are as old as the solar system
and are the remnant of the building
blocks that produced the giant planets.
• Hundreds of millions of comet nuclei
exist in a spherical region called Oort
Cloud that surrounds the solar system.
8. TWO TYPES OF COMETS
1. Short-period comets are those that are periodically observed in less than two
hundred (200) years. Comet Halley with an average period of 76 years is the
only one that returns in a single lifetime. It is among those comets that can be
easily seen with the naked eye.
2. Long-period comets are those with periods of more than or 2 000 years.
Comets bodies were investigated for the first time with spacecraft during
the mid-1980s.
• 1985 – US Probe known as ICE (International Cometary Explorer) passed through
the dust tail of comet Giacobini-Zinner.
• 1986 – Spacecraft launched by Japan and USSR along with the Giotto Probe of
ESA (European Space Agency) flew by Comet Halley, transmitting many useful
data about its composition and sending pictures of its nucleus.
9. • any interplanetary object of relatively small
size that enters the Earth’s atmosphere.
• vast majority of meteroids burn up in the
upper atmosphere, but occasionally one of
relatively large mass survives.
10. • the resultant luminous phenomena, due to
the collision with the atoms and molecules
of the atmosphere at high velocity, the
object begins to burn up and heats the air
around.
• Also known as a shooting star or falling star
and can be seen as a streak of light in the
sky.
11. • object survives its plunge through the
atmosphere and strikes the ground.
• Termed used to similar objects reaching
the surface of other planets or satellite.
12. • Studies suggest that the majority of meteroids re fragments of asteroids
produced by collisions between objects in the asteroid belt lying between
the orbits of Mars and Jupiter.
• Evidences says that some meteroids are of cometary origin.
• Some of the meteroids entering the Earth’s atmosphere came from the dust
embedded in a comet.
• Meteor showers become visible when the Earth encounters swarms of
meteroids moving together.
• Eta Aquarid is meteor shower which can be seen every year in early May,
has been identified with Comet Halley. The meteoroids in the swarm
producing this shower are thought to be debris ejected from the comet
along its orbit.
13. • rocky bodies that move in elliptical orbits
around the Sun like planets do.
• Most asteroids rotate on their axis.
• Most of them are found between Mars and
Jupiter, known as Asteroid belt which
separates the inner planets from the outer
planets.
• The bigger ones are Ceres, Pallas, and Vesta.
In 1992, an asteroid was found between
Neptune, one of the first of the Kuiper belt
(Edgeworth-Kuiper belt).
• In 1996, asteroids near the earth were
discovered. One of the largest near-Earth
asteroid is Eros.
14. • also known as planetoids or minor
planets being smaller, rocky
astronomical objects than any of the
eight planets of the Solar System.
• By the 1990s, more than 7000 asteroids
had been observed and 5 000 of them
had been assigned numbers, done as
soon as accurate orbital elements have
been determined.
• There are about 30 few large asteroids
having a diameter of more than 300
kilometers (km).
15. • Ceres – the largest known asteroid
discovered in 1801, has a diameter of
roughly 935 km.
• Pallas – the second sie, measures 535
km across.
16. • Approximately 250 asteroids have a diameter of at least 100 km. it is
estimated that millions of asteroids of boulder size exist in the solar system.
• In 1993-1994 images were produced by spacecraft Galileo passing through
the asteroid belt on its way to Jupiter showing an asteroid that has its own
tiny moon. As potato-shaped asteroid named Ida with a length of about 56
km is orbited at a distance of roughly 100 km by a rock that is about 1.5 km
in diameter and is the smallest known natural satellite in the solar system.
