astronomy


The Beginning of the Universe

The universe was formed about 10 to 20 billion years ago.

At that time, interstellar dust was widely dispersed throughout the universe with densities as low as 1 atom per cubic meter and consisting probably only of hydrogen particles. Scientists speculate that some event caused the dust to begin a process of accretion through the force we know as gravity.

This accumulation of all matter formed into a large mass, which is commonly called the 'cosmic egg'. The huge gravitational forces present inside this mass caused an atomic reaction to begin, which culminated in a gigantic explosion, hurling matter out into empty space.

This event became known as the 'big bang'.



The universe had been born.

The temperature, at the point of the big bang, within the first second of this event, has been calculated by scientists as being about 1000 billion degrees centigrade. Subsequent cooling over the last 10 billion years has reduced the average temperature of the universe to just 3 degrees above absolute zero. The matter dispersed in this primal event has been analysed at roughly 90% hydrogen and 10% helium. Heavier metals have subsequently been formed by stars in supernova events.

There is much debate about the about the nature of the universe, and there are two main theories, namely the solid-state universe and the expanding universe theories, i.e. the conservation of matter theory, or the theory that matter is being continously created. The nature of space-time relationships and the behaviour of matter has been contemplated by humans since ancient times, in search of a grand unified theory to explain the events we observe in our universe. Many theories have been devised including Newton's laws of planetary motion, Einstein's Theory of Relativity, Quantum Mechanics and the 'sum over histories' theory which synthesizes particle probabilities and imaginary time.

Later theories include the possibility that the big bang was itself the result of a black hole being created in another universe. Some writers have remarked on the similarity between the structure of atoms and the structure of star systems. Our universe is ultimately a mystery. It appears to be expanding as a result of the primal big bang event. All galaxies are receding outwards from the center of the universe at measurable speeds. The further away the galaxies are, the faster they appear to be travelling. It is believed that the light from some of these outer galaxies may never reach us, we will therefore never be able to see them and that these galaxies are, as a result, at the very edge of our knowable universe, the so-called particle horizon. See the quantum field theory.

Astronomical distances in space are huge and for convenience's sake are usually measured in light-years or parsecs.

1 light-year is the distance a beam of light will travel in one year.

1 parsec = 3.2616 light years.

The Next 15 Billion Years - The Birth of the Galaxies

Some time after the 'big bang' event, gravitational processes drew matter together to create what we know today as galaxies. Galaxies are huge clusters of stars which are born and die over periods of millions of years. Over time, galaxies spawn planets, moons, asteroids, meteorites and comets, all of which are known as celestial bodies.

Galaxies can also contain glowing clouds of dust or gas called nebulae. Most of the 'stars' that we see at night are actually galaxies or nebulae. Galaxies emit energy. The first system of classification for galaxies was introduced by Edwin Hubble in 1925, using a collection of photographs he obtained at the Mount Wilson observatory. There are many millions of galaxies in the observable universe.

Types of galaxies that have been classified by humans include Active Galaxies(Normal, Seyfert, Markarian, or Compact), Radio Galaxies and Quasars.

Recent observations of supernova variants have led to our constantly evolving theory on double stars, pulsars and the nature and role of dark matter in the Universe.


Our own galaxy is of the type giant intermediate normal spiral galaxy and is known as the 'Milky Way'. It measures 30 kiloparsecs in diameter and contains approximately 100 billion stars. Objects in the Milky Way orbit the galactic center, much like the planets orbit the sun in our solar system. Light from a star on one edge of our galaxy takes about 100,000 years to reach the opposite side of the galaxy. The center of the galaxy is characterised by a thick swarm of red and orange suns known as the galactic bulge.

The spirals of the Milky Way galaxy are called 'arms' and are named as follows, from the galactic center outwards: 3KPC Arm, Norma Arm, Scutum Arm, Crux Arm, Sagittarius Arm, Carina Arm, Orion Arm, Perseus Arm and the Outer Arm. Our solar system is positioned on the Orion Arm of our spiral galaxy. Our galaxy has several dwarf galaxies for neighbours. A galaxy that is less than 10% as luminous as the Milky way is called a dwarf galaxy, as luminosity is mostly a result of the total number of stars in the galaxy.

By looking at the Milky Way in the constellation of Sagittarius, we are looking towards the galactic center.

Part of the Milky Way
   The Andromeda Galaxy

Stellar 19100 Galaxy
Nebula

Types of Stars

The stars that are nearest to our solar system are found within a radius of twenty light years, with Proxima Centauri being the closest. See the Star Neighbourhood. There are many different types of stars, ranging from brown dwarfs to yellow, blue and red supergiants as well as black holes.

Black holes are stars or galaxies whose mass is so great that they collapse on themselves, forming a gravity well from which not even light can escape, collectively known as collapsars. The point at which there is no escape for light from the black hole is called the event horizon, also known as the Schwarzchild radius. Although black holes are difficult to see, their existence has been confirmed by observing the effect of their gravity on nearby, more visible, bodies. There are two type of black holes, those formed during the Big Bang, called primordial , and those formed after.

It is believed that there is a large primordial black hole at the very center of our galaxy, the Milky Way, concealed at the very center of the galactic bulge.

Generally, the size of a star will determine it's type and density. Many stars, but not all, consist chiefly of hydrogen which is converting by atomic reaction to helium, but other heavy metals can exist, particularly if the atomic reactions are violent. Our yellow sun contains a variety of elements including hydrogen, helium, sodium and gold. For a full list of all known elements, see the periodic table of elements.

Stars are classified according to size, temperature, brightness and distance from earth. The smaller stars are more stable and last for perhaps 10 billion years, like our star, the sun. Smaller stars tend to burn out quietly at the end of their lives, becoming barren lumps of dead matter.

Giant stars have a very different evolutionary cycle. Stars that are very massive tend to have more intense nuclear reactions, creating more elements, and they last for a much shorter period of time. At the end of their giant phase they explode spectacularly in an event called a supernova. This event can result in the creation of white dwarf stars, neutron stars, pulsars or even black holes.

Neutron stars are small dense bodies, much smaller than white dwarfs. They typically have a radius of about 10 miles and a density of hundreds of millions of tons per square inch. Neutron stars emit powerful radiation caused by repulsion between the protons and neutrons of their matter. There are two types of neutron stars - pulsars and magnetars. Pulsars rotate with a cone shaped magnetic field that causes a magnetic pulse to be emitted and magnetars generate spontaneous and random magnetic fields through a series of eruptions.

The History of Astronomy

From the earliest civilizations, in order to find and name more easily the stars they saw, observers of the night sky imagined them to be grouped in shapes, according to arbitrary recognisable figures. This gave rise to the concept of constellations, which were given the names of heroes, animals or objects associated with myths and legends e.g. Andromeda, Hercules, Centarus, Sagittarius and Cassiopeia.

There are two sets of constellations, one for the northern hemisphere and one for the southern hemisphere, totalling 88 constellations in all.

Chaldea, Egypt and China are the three oldest centers of astronomy on Earth. The Chaldeans (circa 4000 BC) lived on the plains of Mesopotamia, between the Tigris and Euphrates rivers, and their civilization spread out from there. From about 600 BC, Greek scientific rationalism from philosophers like Plato began to supercede magical and supernatural interpretations of celestial events and this was the beginning of astronomy's emergence as a science. The word planet, from the Greek planetes, means a wanderer, and refers to any heavenly body that orbits a star, such as our sun, Sol.

In Europe, early astronomical observation began with stone monuments, or megaliths, which are found chiefly in Brittany, Scotland, the south of England and Scandinavia. It is estimated that they were built between 3000 and 6000 years ago. There are four main kinds of megaliths: menhirs (single upright stones), groups of menhirs (cromlechs), funeral chambers (dolmens) and megalithic temples. The most famous of these ancient astronomical sites is at Stonehenge. A 32-cm gold and bronze disc depicting 32 stars from the constellation of Pleiades has been dated back to the bronze age, about 3600 years ago. The artefact, discovered in the Ziegelroda forest on the Mittelberg in Germany, near the town of Nebra, is known as the Nebra disc, and is said to be the world's oldest star map.

Astronomers are constantly searching for new planets outside of our solar system, and to date about 250 distant planets have been identified. These planets are known as exoplanets. Some systems have multiple planets, like our own solar system, and some even have water. Researchers tell us that, based on their observations, there could be billions of inhabitable planets throughout the universe. For information on the latest discoveries of exoplanets, visit exoplanets.org.


The Solar System
Sol
Our sun which is called Sol, is a smallish yellow star. The internal temperature is estimated to be 15 million degrees centigrade. The sun is 149,600,000 kilometers from earth. It is estimated to be about 5 billion years old. It consists of 92 percent hydrogen, 7.8 percent helium and .2 percent heavier elements. The sun has a 22 year magnetic cycle in which the solar magnetic field reverses it's polarity every 11 years. This coincides with increased sunspot activity. See the Solar Observatory. The sun is 330,000 times as massive as the earth.

The nine planets of our solar system, as well as many asteroids and comets revolve in various orbits around our sun, Sol.

The orbital path of these celestial bodies is usually an elliptical one, i.e. they are closer to the sun at some points than others. The closest point of an orbit to the center is called the perihelion. The furthest point from the center is called the aphelion.

For a perspective on mineral surveys in the solar system, see Astrogeology. For geographical features of the moon and planets, see Planetary Cartography.


Mercury
Mercury
The first planet in our solar system, Mercury revolves around the sun at a distance of only 58 million kilometers from the sun. It completes it's solar orbit in only 88 days and therefore it's movement in the sky appears very rapid to an observer on earth. For this reason, it was named Mercury : 'Messenger of the gods'.

The gravitational force of the sun is so strong on Mercury that 'tidal' rock formations exist on it's surface. As the atmosphere on Mercury is negligible, the surface temperatures vary tremendously, from 400 degrees C in the day, to 180 degrees C at night. Mercury is smaller than many of the moons in our solar system.


Venus
Venus
The second planet in our solar system, Venus, is the brightest object in the sky after the sun and the moon. It has also been called the Sister planet and the Shepherds Star. It orbits the sun every 225 days.

Ancient Roman and Greek civilizations identified the planet with their goddesses of love, Venus and Aphrodite. As Aphrodite was worshipped on the island of Cythera, the adjective Cytherean is often applied to Venus. To the ancient Greeks, Venus was also two stars: Phosphorus, the morning star and and Hesperus, the evening star.

Venus is about 67 million kilometers from the sun.

Venus does not have the pleasant atmosphere it's name would suggest. The clouds of Venus are composed of sulphuric acid and the greenhouse atmosphere is 96% carbon dioxide. Surface temperatures average around 480 degrees C.

Atmospheric pressure on the surface of the planet is more than ninety times that at sea level on earth.

Each day on Venus (243 Earth days) lasts longer than it's year(225 Earth days), and the sun rises in the west and sets in the east. See the Map of Venus.


Earth
Earth
Our planet earth is the third planet from the sun. The earth rotates from west to east around a polar axis, and is tilted to one side. Earth revolves around the sun in 365 and a quarter days. Light from the sun takes 8 minutes to reach the earth, which is 93 million miles away. The mass of the Earth is about 5.98 septillion kilograms and it has a diameter of 12, 756 km. It is currently the only known planet in the universe that has sentient life.

Earth is nearly spherical, but not exactly so, in fact, it is an oblate spheroid, i.e., it bulges slightly at the equator. The equatorial radius is 13 miles greater than the polar radius; not much in a total radius of about 3950 miles.


The Moon
Moon
The earth has one satellite which we call the moon. The mass of the moon is about 1/81st that of the earth and it has a diameter of about 3500 km. The study of the earth's moon is known as selenography. The moon's gravitational pull causes the tides of the earth's oceans. Periodic eclipses of the sun and moon occur to observers on earth, because of the orbital path's of the sun, earth and moon. For more information on eclipses, click here.

The first map of the moon was drawn in about 1610 by the Italian astronomer Galileo, after he invented the telescope. Later astronomers with better telescopes saw details more clearly, and, in 1647, the German astromer, Johannes Hevelius, published an atlas of the Moon's surface called Selenographia. Following the view that the moon was a smaller earth, he transferred the names of terran geographical mountain ranges to selenographical mountain ranges. Thus the moon's mountains have names like the Alps, Appenines, and so on. Dark area's on the moon's surface are called 'maria', which is Latin for sea's, even though there is no water on the moon. For more information on the surface of the moon, see Planetary Cartography.

NASA is developing a new Apollo rocket to be tested in space by 2014, and plans to establish a permanent base on the moon by 2018/2020.


Mars
Mars


Mars is known as the last of the terrestrial planets. It was named after the god of war because of it's reddish color which resembles blood. Mars comes within 56 million kilometers of the earth during the course of it's solar orbit. It is believed that Mars could be 'terraformed' to create an environment that could sustain human life. It takes 687 days to orbit the sun. See Mars Tracker.

Mars has two moons, or satellites, called Phobos (Greek, fear) and Deimos (Greek, terror). The surface of Mars consists primarily of oxidized particles and it has polar caps of frozen carbon dioxide. The atmosphere is thin with very little water, but sometimes morning clouds appear. Ice has been observed on the highest peak of Mars, Olympus Mons, at altitudes of six to eight kilometers. Rocks collected from Mars suggest that flooding waters once ravaged parts of the planet. NASA is planning a manned landing on Mars by 2022. Mars is named after the Greek god of war.


Jupiter
Jupiter
More than 99.5 % of the solar system's planetary mass lies beyond the orbit of Mars.

This region is dominated by planets having very different characteristics from those of the aforegoing telluric planets. Their dimensions are much larger, ranging between 4 and 11 times that of the earth ; their average density is, however, much lower. Jupiter, for example, is a gas giant.

They have very fast rotation periods, ranging from 10 to 16 hours, creating a 'flattening' effect upon their shape. The largest and most massive of these giant planets is also the closest: Jupiter.

Jupiter has several satellites or moons. The four so-called Galilean satellites, Io, Europa, Callisto and Ganymede, have planetary proportions. The largest, Ganymede, is bigger than Mercury.

Jupiter's surface is characterised by a huge fifteen thousand mile-wide storm which never ends, known as the Red Spot. Frequent cyclones and winds of up to 400 km/hr occur in various layers of the atmosphere. Jupiter takes almost twelve years to orbit the sun.


Saturn
Saturn
Beyond Jupiter lies Saturn, the second largest planet of our solar system. Saturn's main peculiarity is the vast system of rings that surround the planet, and there are actually more than one hundred thousand ringlets. The major rings are labelled E, G, F , A, B, C and D as you approach the planet. The rings consist chiefly of ice, rock and frozen gas. The gap between ring A and ring B is called the Cassini division and contains five fainter rings.

Saturn rotates so fast that a day lasts only 10 hours and thirty-nine minutes. It is estimated that winds blowing on Saturn reach 1800 kilometers per hour at the equator. Saturn orbits the sun every 29.5 years. It is 9.41 times larger than earth.

Saturn has at least 18 satellites or moons, and may have up to 14 more. The moons include Dione and Janus, and the largest satellite is called Titan. The moon called Enceladus in the outermost ring of Saturn is active, has heat and water and periodically ejects plumes of water vapour called "cryo-volcanoes.".


Uranus
Uranus
This planet lies, on average, 2,875 million kilometers from the sun. The planet has an aquamarine color indicating the presence of helium and methane. It orbits the sun every 85 years. Uranus is topsy-turvy in that it's poles are where it's equator should be and vice-versa. There are at least 24 rings encircling the planet.

Uranus has 17 known satellites, most of which are named after female characters in Shakespeare such as Titania, Miranda, Rosalind, Portia, Juliet, Desdemona, Ophelia, Cordelia, Umbriel, Mab and Ariel. The largest moon is called Oberon.


Neptune
Neptune
Neptune lies about 4500 million kilometers from the sun, and it's orbit is almost circular. It takes about 165 years to orbit the sun. The surface temperature is estimated to be about -228 degrees centigrade.

Neptune has eight moons, the largest being Triton and Nereid, and also has four rings circling the planet. Neptune has a great Dark Spot which is about the size of Earth, and winds there gust to about 1800 km/hr. It is thought to be slowly fracturing because of it's intense gravity.


Pluto
Pluto
Even today, the orbit of Pluto is still not known with as much precision as that of the other planets. Pluto's existence was predicted even before it was seen for the first time. Pluto takes about 248.5 years to revolve around the sun.

At it's perihelion, the planet is 4,425 million kilometers from the sun, dipping into the orbit of Neptune. At it's aphelion, this frigid world is 7,400 million kilometers from the sun. Pluto has recently been downgraded to the status of a dwarf planet, a new classification meaning a really small planet..

Pluto has one large moon called Charon, which is only slightly smaller than Pluto itself. Pluto and Charon are locked gravitationally so that the same hemispheres always face each other - like two dancers gazing into each other's eyes. The latest images from the Hubble space telescope have shown that Pluto has another two smaller moons, orbiting at twice the distance of Charon. These moons have been named Nix and Hydra, Nyx after the Greek goddess of darkness, Nyx, and Hydra the nine-headed monster, both associated with Pluto, the god of the underworld.

Since it was first discovered in 1915, Pluto has not yet completed a full orbit of the sun.


A small tenth planet has been discovered even further away than Pluto, and has not yet been named. Proposed names for the new planet include Persephone and Xena. Persephone was a Greek goddess kidnapped by Pluto, according to Greek mythology. The planet has a diameter of about 2600 km, thus, also a dwarf planet. See planet diameter size comparisons.





Space Agencies

China National Space Agency

European Space Agency (ESA)

Hubble Space Telescope

Japanese Aerospace Exploration Agency (Jaxa)

N.A.S.A.

Russian Space Web

Indian Space Research Organisation

Space Telescope Institute

Space-X

Student Space Exploration and Technology Initiative

Careers in Space

The European Southern Observatory

British National Space Centre

Astronomy ebooks


South African Astronomy Links

South African involvment in space began in 1820 with the establishment of the Royal S.A. Observatory at Observatory in Cape Town. The headquarters of the observatory have remained there while the telescopes have moved to Sutherland in the Northern Cape. There are several telescopes at Sutherland with mirrors ranging from 0.5 meters to 1.9 meters in diameter. A much bigger telescope called SALT has been constructed at Sutherland which is now in operation. The telescope consists of 91 hexagonal 1 meter mirrors which provides an effective mirror diameter of 11 meters, making it the largest telescope in the Southern hemisphere. It records images of distant galaxies, stars and quasars a billion times too faint to be seen with naked eye.
See S.A. Large Telescope.

Click here for larger and more recent images from SALT

South Africa is also competing with several other countries to host the Square Kilometer Array (SKA), an array of radio telescopes to be situated in the Northern Cape. This $1.5 billion project will be 100 times larger than the largest existing radio wave receiving surface and will be the largest radio telescope in the world. South Africa already has a radio telescope at the Hartebeeshoek Radio Astronomy Observatory.

South Africa has signed bilateral agreements with the Russian Space Agency, which has expressed an interest in launching satellites from South Africa, as well as partnership agreements with ESA and NASA.

A facility for studying the earth's magnetosphere exists at the Hermanus Magnetic Observatory, which studies and models changes in the earth's magnetic field.

Gamma rays are studied at the Hess Observatory which is situated between Windhoek and Walvis Bay, Namibia. The High Energy Stereoscopic System (Hess) consists of an array of four telescopes which measure the direction and intensity of gamma rays.

The CSIR provides services and products related to satellite tracking, imaging and other space industries at the
Satellite Applications Center (SAC), situated at Hartebeeshoek.

The third largest telescope in South Africa, featuring a 1.5 m reflector is situated at Boyden Observatory, just outside Bloemfontein. The observatory also has a solar telescope.

The National Astrophysics and Space Science Program, N.A.S.S.P, offers postgraduate degrees hosted at the University of Cape Town. The African Institute for Mathematical Sciences (AIMS) runs workshops.

The South African government signed a bill in 2009 to set up a South African space agency. The agency will oversee development of space missions, develop technology platforms, and acquire, assimilate and disseminate space satellite data. It will coordinate the launch of SA's second indigenous satellite, Sumbandilasat.

For news and events see the South African Department of Science & Technology or the S.A. Space Portal websites. Stellenbosch University uses staff and post-graduates to develop satellite systems, see Sunspace.

The South African Rocketry Association caters for amateur rocket enthusiasts.


For more astronomy websites, see Astronomy Links. For shareware and free astronomy applications software, visit the Astronomy Shareware website. Get news of the latest astronomical events from U.K. based Astronomy Now magazine and New Scientist Space.

For free software to view the night sky and constellations, see Stellarium.


S.E.T.I. run a website where internet users can assist in the search for extraterrestrial intelligence by processing data from the Arecibo, Puerto Rico radio telescope observatory via a screensaver. You can also assist by analyzing some of the 1.5 million images of stardust brought back by the U.S. spaceship Stardust, see Berkeley Stardust. Another way to contribute is by helping to classify galaxies from a list of over a million galaxies, see the Galaxy Zoo.


Where Do We Go From Here ...

The Earth is running out of resources - fast! - man needs to look to other planets for resources and expansion. But even sending men to the closest (barely) inhabitable planet of Mars and ensuring their safe return is a hugely expensive exercise, running into billions of dollars. The logistics of providing the food, oxygen and other life support systems to the astronauts, from the physical to the psychological, are hugely expensive, and far, in terms of cost, outweigh the benefits of seeing a few astronauts walking around on the barren surface of Mars. We have already had soil samples, temperature readings, seismographic, spectographic and topographical data from Mars, and seen endless photographs from (relatively) inexpensive robotic probes and missions. I think we can be sure that there is not an alien race of giraffes running around on Mars. And even if there are, they may just have to take their chances, because we need the space.

If we are serious about our future (and I don't think we have choice, unless we institute immediate birth control measures on Earth), it should be obvious to all that we need to start with a planned expansion into space right now. This process would consist of firing cheap one-way rockets filled with fertile soil, plants, algae, bacteria, and water at Mars, designed to crash on the surface and split open, releasing all those ingredients onto the surface at random or targeted locations. In about 20-50 years we can send a spacecraft with a large team of colonists on a one way trip to start a new world. By that time, there will be oxygen, some global warming (required in Mar's case), plants growing and an infant ecology that can support life as we know it. If we had done this 30 years ago, we could have been selling tourism and real estate, as well as farming and mining minerals, on Mars already.

We need to start now, not only with the greening of Mars, but with the design of a forward-looking and budgeted modus operandi, that will allow us to expand to the stars as cost-effectively as possible. We must identify other likely planets with all speed, probe them and green them, if they are suitable, as soon as possible.

Protocols should be developed for possible encounters with aliens. Seriously. We have no idea what we will find out there. Universities should teach basic Space Science and Survival Techniques. The challenges that expansion to space present to the human race are immense, and are therefore ripe with opportunity. Employment for young people as colonists, miners, geologists, nurses, teachers, pyschologists, engineers, farmers and dentists will arise. Energy must be audited and conserved so that costs are contained.

The Earth has been conquered by Man, and now, that same indomitable spirit that explored the Amazon, that defied Everest, that reached the Poles, that plumbed the depths of the world's oceans, must be called upon to colonise new worlds and help us survive to achieve our destiny in the Universe.


Related Links

Antarctica eBooks Geophysics Science





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