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.
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.
|Part of the Milky Way
||The Andromeda Galaxy|
The Solar System
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.
Scientists use a three tier system to classify solar flares; Class X are the largest and most powerful, Class M are medium but still considered very large, while Class C are the weakest.
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.
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.
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.
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 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 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.
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.
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.".
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 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.
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.
China National Space Agency
European Space Agency (ESA)
Hubble Space Telescope
Japanese Aerospace Exploration Agency (Jaxa)
Russian Space Web
Indian Space Research Organisation
Space Telescope Institute
Student Space Exploration and Technology Initiative
Careers in Space
The European Southern Observatory
British National Space Centre
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 Australia to host the Square Kilometer Array (SKA), an array of radio telescopes, sponsored by a 16-nation consortium, which will be situated near Carnarvon in the Northern Cape. This $1.5 billion project will be 100 times larger than the largest existing radio wave receiving surface and will thus be the largest radio telescope in the world. South Africa already has a radio telescope at the Hartebeeshoek Radio Astronomy Observatory. South Africa would be partnering with eight other African nations to build the SKA on this site which is 1,000 meters above sea-level and behind the Cape mountain range, preventing radio waves and other interference.
The radio telescope, when completed, will consist of 3,000 towering antenna dishes, working collectively, like a giant zoom lens, and numerous ground-based receiver tiles acting like a wide-angle lens, to see back in time for billions of years - almost to the time of the creation of the universe. Many scientists believe it has the potential to determine whether extra-terrestrial life does, in fact, exist, and it will also be able to finally validate (or invalidate) Einstein's Theory of Relativity. The furthermost stations of the project would be based in Ghana and Madagascar.
A final decision on SKA will be reached in mid-2012 and it is expected to receive initial space observations by 2019, and be fully operational by 2024.
South Africa has also 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.