Asteroid
These may be described as rocks or mountains, of varying
size that orbit the Earth. Majority of them are in a belt between Jupiter and
Mars.
Some of them are larger than 100
km. Some even cross the path of the planets.
(The extinction of the dinosaurs has been attributed to the crashing of
an asteroid.)
Fig. Ida Asteroid and
the satellite captured by Galileo probe.
Ida is about 56 x 24 x 21 km. and has a period of rotation
of 4 hours, 38 minutes the density is between 2.2 and 2.9 g/cm3. Galileo flew
past Ida in August 1993 the greatest discovery was that Ida has a natural
satellite. Dactyl is the first natural satellite of an asteroid ever.
Antimatter and Matter
Matter has mass and occupies space. They consist of atoms.
Even Energy seems to have particles. ( Eg. Light to be made of Photons and
Gravity to be Gravitons) Anti matter is not common in our universe. Particles
in anti-matter have just the opposite properties as in matte except for the
mass. For example an electron will have a positive charge. If matter and anti-matter
come into contact they annihilate producing some rays.
In 1930 Paul Dirac describing the electron to comply with
quantum mechanics and Special theory of Relativity predicted a particle having
the same mass but a plus charge. This
was discovered in 1932 by Carl Anderson. This has been named as a positron.
It was surprise observation that anti matter has been
detected to be coming from thunderclouds during lightning flashes. (Source Scientific:
- American Aug.2012.)
Astronomical Unit (AU or au)
This is the average distance from Earth to the Sun,
approximately 149.6 million km (93 million mi). It is used especially to
measure distances within the solar system.
Big Bang
Prior to space and time ( birth of Universe) all the matter
and energy now spread across the infinite space, had been cramped into a pencil
point of energy .All the forces that we
know existed as a single force Such a colossal conglomeration of a mass has
been termed a singularity. Just within a fraction of a millisecond it violently
exploded producing sub atomic particles and cosmic rays etc, these relays still
come towards us. Universe had been expanding ever since for the last 13.7
billion years. (No sound was heard as there was no matter outside to propagate
sound waves and there was no one to hear either.)
Binary Stars
Our Sun is a loner; but some stars exist in pairs. Usually a large star and a small star orbits
round its centre of mass.
Black Hole
A hole is an empty place. Black is the colour we refer to an
object that will absorb all the visible colours of light. A ‘black hole ‘is neither black nor not
empty. These are gigantic masses which can swallow stars by the force of
gravity. They cannot be seen as they neither reflect nor emanate light. Stephen
Hawkins has shown that they emit some rays which have been verified to be
correct.
Extremely massive stars when they exhaust their Hydrogen for
fusion, die off and remain as black holes gulping down energy and matter from
the surrounding.
Fig. Stephen Hawkins.former Lucasian Professor of
Mathematics at the University of Cambridge (Most recohnised physicist after
Einstein)
Comet
Comets are celestial bodies, much smaller than asteroids,
which follow extremely eccentric orbits with one apogee as the sun. They
usually consist of ice and dust that have not been attracted to stars or
planets for some reason. Most of them come from a region called the Kuiper belt
near Neptune. Shoemaker comet that
visited us probably in 200 years got into Jupiter’s gravitational field
remained as a satellite for a few years and exploded in due to tidal forces.
Some of these fragments crashed on the planet giving our astronomers a chance
to see a collision among celestial bodies.
Fig. Eugene and
Carolyn Shoemaker: Comet hunters ( Courtsey BBC)
They became world famous when in 1993 along with David Levy
discovered Comet Shoemaker-Levy 9. It got torn apart by planetary tides of
Jupiter.in July 1994
First to be buried
outside the Earth.
"I don't think
Gene ever dreamed his ashes would go to the Moon,"
"He would be
thrilled."
Carolyn Shoemaker said shortly before watching Lunar
prospector blast-off in January 1998.
Constellation
From the time the human evolved star gazing may have been
very popular pastime. The position of stars helped them to find directions at
night and the changing of seasons. So
they devised a way of remembering the star maps in the night sky. They connected a group of stars as they saw
them and completed a picture of an animal or a familiar object. These apparent clusters of stars came to be
known as constellations. Astronomers now
have accepted over 80, a few of which are as follows.
Andromeda (The Princess), Orion (The Hunter) Sagittarius
(The Archer) Cassiopeia (The Queen) Cancer (The Crab) Taurus (The Bull)
Aquarius (The Water Bearer), Gemini (The Twins) Scorpius (The Scorpion) Leo
(The Lion)
Corona
This is atmosphere of the Sun where the matter exist in a
plasma state extending to millions of km above the surface.. While the temperature of the surface is about
5800 K the corona temperature is in the millions of degrees. The corona has
been carefully observed during total eclipses.
Cosmic Rays
It may surprise you to know that these are not rays but
sub-atomic particles. 90% of them are protons, which are the nuclei of Hydrogen
atoms. Among others there are charged particles of matter and anti-matter. They
come at a very high speed that the scientists have been baffled as to how they
achieve that. As the name suggests, they come from outside our solar system.
There are some coming from the sun and the other stars in our milkyway. Cosmic
ray collisions with the molecules in the upper atmosphere have given us the
first Hadron Collider. Here the particles have thousand times more energy than
the Large Hadron Collider in Geneva.
Dark Matter
The visible bodies in a galaxy are held together by the
force of gravity. This force is directly
proportional to the mass of the bodies concerned and inversely proportional to
the square of the distance. According to the magnitude of the force scientists
have calculated the mass of matter that has to be present in a galaxy. It has
been discovered that the visible matter and the invisible atoms and all the
energy does not provide the sufficient mass. So they have introduced the
hypothetical substance ‘Dark matter’ that should be pervading the space in
between.
Double Star
Same as Binary stars.
Dwarf Planet
Fig. The orbits of
the dwarf planets Pluto and Eris
A celestial body that orbits the sun, smaller than planets
but has sufficient gravity to maintain spherical shape. (unlike asteroids) There
are 5 recognised at the moment Ceres, Pluto, Haumea, Makemake, and Eris. All
these are in the Kuiper belt.
Galactic Halo
A spherical region of dust-free space surrounding a
galaxy. Unlike the central region, which
has bright and new stars, Halo contains very old feint stars and the mysterious
‘Dark matter’..
Galactic Nucleus
The central part of a galaxy which has a very high density
of new stars. Usually a black hole is present here.
Galaxy
A very large conglomeration of stars. Galaxies are found in
a variety of sizes and shapes. Our own Milky Way galaxy is spiral in shape and contains
several billion stars.
Hawking radiation
A theory first proposed by British physicist Stephen Hawking,
those energy fluctuations from the vacuum causes the generation of
particle-antiparticle pairs near the event horizon of the black hole. One of
the particles falls into the black hole while the other escapes, before they
have an opportunity to annihilate each other. The net result is that, to
someone viewing the black hole, it would appear that a particle had been
emitted.
Hubble's Law
In 1920 Edwin Hubble found that the rate of receding a
galaxy is directly proportional to the distance.
Light Year
An astronomical unit of measure equal to the distance light
travels in a year; it’s about 9.5 trillion km., which is 9,500,000,000,000
kilometers.
Magellanic Clouds
Fig. Our neighboring galaxies seen as clouds.
The two irregular galaxies and Large Megallenic cloud and
Small Magellanic Cloud, found just outside Milky Way; just visible in the
southern skies. They are considered as recent visitors to our Milkyway.
Meteor ( Shooting
stars )
A celestial object smaller than an asteroid. The gravitational
force of the Earth sometimes capture
objects shooting in free space at high speed. As they enter the
atmosphere they get heated due to friction and usually burn and evaporate. Very
rarely some of them crash on the earth and end up as meteorites.
Meteoroid .
A celestial object smaller than an asteroid.
Nebula
Mainly Hydrogen gas present between the stars, which get ionized
by the UV light from the stars. In an emission nebula, electrons re-combine
energy is released. They aggregate to form stars. A reflection nebula is
visible by reflected light.
Courtesy:Hubble
site
Neutrino
Could you believe in one second over sixty billion neutrinos
pass through 1 cm2 of your body exposed to direct sunlight. They traverse
through the planet Earth just like a beam of light passing through a pane of
glass. This is a fundamental particle produced in massive numbers by the
nuclear reactions in stars
"Neuitrino is the most tiny quantity of reality ever
imagined by a human being" said Frederick Reines who
discovered the particle along with Clyde Cowen.
Neutron star
Imagine compressing all the human beings in to the size of a
sugar cube. That’s the type of pressure and density (about 1014 g/cm3) inside a
neutron star. An average n star has a mass of 1.4 times the Sun and a diameter
of about 10 km. It is believed that these are dead carcases of supernova formed
in a similar manner to black holes. Unlike black holes these emit pulses of
energy.
Intense pressure
pushes the orbiting electrons in atoms into the nucleus neutralising the
positive charge of protons.
Proton + electron = neutron + neutrino
This explains why they are predominantly packed with neutrons. The outer 1 km. is solid in spite of the
temperature being in region of millions of degrees.
These stars also have the strongest magnetic fields in the
known universe. The strongest inferred neutron star fields are nearly a hundred
trillion times stronger than Earth's fields, and even the feeblest neutron star
magnetic fields are a hundred million times Ear
The covering of this layer is made of an isotope of iron 56Fe polymerised
due to the intense magnetic field. There are no atoms present the whole mass
can be compared to a single nucleus.
Oort Cloud.
This is a
hypothetical sphere surrounding the solar system starting at a distance
of one light year from us extending to another light year The comets that visit
us from this region give us valuable information as to the conditions there.
Cluster
The stars have been formed in the form of clusters.
Orbit
The path of a celestial body as it moves through space.
Parsec
A parsec equals 3.26 light years.
Perigee
The point in the orbit of the satellite at which it is
closest to the main body.
Perihelion
The point in the orbit of a planet or other body where it is
closest to the Sun.
Planet
A celestial body orbiting a star or stellar remnant that is
massive enough to be rounded by its own gravity is not massive enough to be a
star…
Planet Nebula
When Sir Frederick Wilhelm Herschel, (1738 – 1822) observed
cloud like formations through his telescope, he believed them to be formed around
planets.
Later only he realised that
they were not planets but stars. When a medium sized star consumes the Hydrogen
necessary for fusion, force of gravity overrides the force due to thermal expansion.
This results in a white dwarf and continues to glow due to the high
temperature. It is said that not a single such a star has sufficient time to
cool during the last 13 and a half years. Light gases spread as far as a light
year and diffuse the rays coming from the star giving the appearance of a
cloud.
NGC 6039 Discovered by Hershel .5 Billion yrs old.Color image
Hubble Space Telescope .Courtesy NASA
Quasar (Quasi-Stellar Object)
Brighter than a trillion suns; yet you cannot see them
unaided. They are so far away; billions and billions of light years away. They are black holes surrounded by galaxy
forming matter which emanate large doses of energy…
In these we see almost the beginning of the Universe. It had
taken 12 billion light years to get the light year while the age of the
universe is 13 billion.
Red Giant
The stars derive most of the energy by fusing hydrogen
nuclei into helium nuclei at the central core. When hydrogen gets depleted
there is a setback in supplying the pressure against the matter collapsing due
to force of gravity. Collapsing material
develops a very high temperature and starts to fuse the Hydrogen in the outer
region This increases the luminosity hundredfold and the hot atmosphere expand
swallowing up any planets in the system It has been estimated that when the
time comes our sun will extend up to Jupiter The red colour of these giants is
due to the weakening of rays passing through the gigantic atmosphere.
Solar Flares
The activity of the sun seems to peak in 11 year cycles
which we may experience in next year. Due to the changes in the magnetic field
of the sun the hot plasma gets ejected from the corona. These are called solar
flares and reduce the temperature at the base causing sun spots. These
explosions are million times more violent than volcanic eruptions.
Courtsey Christian
Monitor.
SPRITES
Red flashes that last only for a few miliseconds have been
observed about 80 km above sea level It
is believed that these are produced by
fasts moving stray electrons produced during lightening Source:- Sc Am aug 2012.
TO BE COMPLETED
