WE have covered quite a long distance in our journey across the realm of astronomy. But the fact is that we have barely begun, or, as they say, just scratched the surface. It is like a few million miles (read kilometres!) into the expanse yet close to the home base.

Take the moon, for instance. It has barely been reached in our own time (1969) though it is a measly quarter million miles away — actually an average of 384,400km. The conquest of moon seems like a long time in the past. We have since gone across Neptune-Pluto system and are nearing the edge of the Solar System; although, crossing the ‘real’ edge will take us yet quite a while, still one does not know for certain what will follow next. Whether our craft will be taken up by another gravitational field losing our diktat in the process, or it will be swamped by forces yet unclear to us, refusing to conform to our commands altogether.

Like any fateful journey, the journey of astronomy begins with the first step (misquoting the famous Chinese proverb to suit my purpose). Nevertheless, a journey it is all the same. We have only taken the first small step. Astronomical Parlance will turn out to be a similar journey. Hence we must continue from where we left off for our knowledge of astronomy to leapfrog.

Atmosphere

A THIN envelope of gases held in place around the Earth by the gravitational pull of the planet’s mass. Early on, the Earth’s original atmosphere was composed of methane and ammo nia. It was only some 200 million years ago that an atmosphere resembling the modern composition evolved because of changing physical conditions on Earth’s surface, and evolution and proliferation of plant life.

Today’s atmosphere (written as ATM), apart from water vapour and pollutants, consists of 78 per cent nitrogen and just over 20 per cent oxygen with carbon dioxide, aragon, helium, krypton, methane, neon and ozone taking up the rest.

Oxygen is the primary part of the atmosphere today because of life and the process of photosynthesis, that is, the ability of early plant life to thrive by harnessing the energy of sunlight. A waste product of photosynthesis is gaseous oxygen — photosynthetic organisms take in carbon dioxide and release oxygen. All components of ATM are essential to all life and the ecosystem. Any alteration, manmade or by nature (such as massive volcanic eruption etc,) can have serious consequences for the Earth’s life (eco) system.

Atom

ALL forms of matter in the universe are made up of atoms which are the fundamental units of a chemical element. Thus, whether it is wood, whale, water, trees, the Sun, us humans and stars, everything is composed of atoms, usually billions, trillions or more of them, packed close to each other. Each atom has a central, positively charged centre, or nucleus with only a small fraction of atom’s volume but most of its mass, surrounded by a cloud of much lighter, negatively charged electrons.

The number of electrons in an atom matches the number of charged particles, or protons in the nucleus and determines how the atom will link to the other atoms to form molecules. Electrically neutral particles, in the nucleus add to the mass but do not affect the number of electrons and therefore have virtually no affect on the atom’s link to other atoms.

While combination of atoms makes a molecule for instance, a molecule of water is made of two atoms of hydrogen bound to one atom of oxygen. Other molecules are much more complex than water.

There is more to come! Keep the ‘astronomical parlance’ preserved in your memory, or any other form of record, and it will serve you in good stead in times to come.

Asteroids

WE have been through the world of asteroids earlier. But there seems no harm in going over them once again. They are small compared to our Earth, or even the moon. Asteroids are solid objects, they orbit the Sun and shine by its reflected light. More than nine out of ten are located in the asteroid belt between the orbits of Mars and Jupiter. But there are some that have managed to break the shackles and have become independent of the so-called strip where they once resided with others of their ilk. They total in hundreds of thousands but their total mass is a pitiable fraction of the Earth’s.

On their own they would add up to the size of a small moon, not a planet. Most are less than a kilometre across, to the largest one (named Ceres) which is about 1,000km wide.

Actually, their size can be confusing to the extent that it is hard to decide which ones qualify as the next largest. Still, asteroid Pallas and 4 Vesta may be at the top of the heap. With their dimensions ranging from 582 by 556 and 572 by 557 respectively, they are enough to harass the most patient astronomers seeking to graduate them according to size. Strangely though, Ceres has since been elevated to the status of a planetoid leaving others to work out between themselves the question of their sizes!

Hygeia and Intermania are the ‘also-rans’ whereas, some others follow closely.

Asteroids mostly tell the story of their composition from studies by various space probes but also by their albedos. But they present a possible hazard to the Earth or another unwary planet. A roving body, having strayed from its prescribed orbit and turned into a rogue may strike the Earth. In fact, one almost did so when in January 1991, it came to within 170,000km of the unsuspecting Earth but caused no damage. The tiny asteroid could have obliterated a city square resulting in sizeable harm. But its intrusion had long been predicted and arrangements were in the offing should it venture too close for comfort.

The one (either an asteroid or a comet) that struck the Earth some 65 million years ago obliterated most of the dinosaurs. This, albeit the damage that it caused, ushered in its wake the ‘Age of Mammals’ through which we are privileged to be prospering. It is apprehended that an asteroid may strike the Earth once every quarter million years. Have a nice time meanwhile! Nevertheless have a nice day. God bless.