Spacecraft have not only given us spectacular views of the planets, they have also been used to study the stars and galaxies.
Our own star is the Sun and we have been able to obtain spectacular views of it both from the US manned space station Skylab, and from later unmanned craft.
The Sun may look small in our sky, but it is a really huge globe of gas 1.4 million kilometers across. Most of the Sun is hydrogen, and the temperature and pressure are so great at its centre that nuclear fusion takes place. This is what powers the Sun a might nuclear core.
In the Sun, hydrogen atoms are welded together to form helium. While this is happening, a tiny amount of mass is converted to energy, which streams out, causing the Sun to shine.
Because it is gaseous, and spins once in twenty seven days, the Sun often suffers massive explosions on its surface but we are too far away to suffer serious damage from its disturbances. Spacecraft and astronauts are not so lucky. They have to take special precautions to avoid the harmful effects of solar radiation, which can destroy sensitive electronic devices and even more sensitive living tissues.
Wednesday, August 22, 2007
SUN
The case of the missing pilot
On October 21, 1978 Australian pilot Frederich, age 20, took off from Melbourne and headed toward a small island.
It was the young man’s first solo night over water. It was still, clear evening, and from his Cessna aircraft Valentich had perfect view of the sky above and he sea below.
Shortly after taking off, however, Valentich reported to flight controllers in Melbourne that he was being followed by a UFO. “It is a long shape”, “he reported”, with a green light, sort of metallic like, all shiny on the outside. A few minutes later, he told the controllers. That strange aircraft is hovering on top of me again. After that, Valentich stopped talking. For the next fourteen seconds the traffic controllers heard a strange ringing sound. Then silence, Valentich and his plane never reached the island, and no trace of him or aircraft was ever found.
Several members of the public reported seeing strange phenomena in the sky over Melbourne that night. An amateur photographer produced a photo of what looked like a large object surrounded by vapor. A NASA scientist, Richard Haines, Heard about the story and began an investigation. He analyzed Valentich voice on tape and the strange sound heard at the end of the tape. But he concluded that it was “ unidentifiable”. He decided that there were four possible explanations for the mystery surrounding Valentich’s disappearance :
1. Valentich might have become confused and disoriented while flying his plane and finally crashed.
2. He could have staged a deliberate hoax.
3. He could have been the victim of a time of a top secret advanced weapons test.
4. He may have been captured by the occupants of a UFO.
Haines plans to continue with his investigation of the case until the mystery is solved.
Mars
Seen from Earth, Mars is a bright blood red star. This led to its association with war and hence its naming after the ancient war god of the Romans.
Of all the planets Mars is the best known, largely because of the science fiction stories and film featuring it. Many of these were produced long before spacecraft visited Mars, and were based on observations made through Earth based telescopes. These showed a red disc with changeable dark areas and white polar caps, and there was great speculation as to what forms of life could live there. It is amazing just now wrong our ideas of Mars of science fact has turned out to be very different from the Mars of science fiction. It is however in many ways much more fascinating.
It was when the space age arrived with a series of Mars flybys, orbiters and Landers that we found out what things really like on the red planet.
Our most recent knowledge has come mostly from the Viking spacecraft which arrived at Mars in 1976. Two crass were put into orbit round the planet, and mapped the surface in detail. Each orbiter carried a lender, and after careful studies of the landing sites from orbit, these were sent down to the surface.
Plunging through the thin Martian air, and protected by heat shield, the Viking Landers descended to their targets. They went first by parachute and the rocket engines.
The first landing took place on 20th July 1976. that was just seven years after the Apollo moon landing. As the Viking cameras slowly moved along, the bleak rock strewn and red surface of Mars was revealed.
Viking carried instrument to discover what the martin atmosphere was like, and to take readings of the temperature, wind speed and direction. It was our own weather station on Mars.
Viking was soon reporting that the Martian air is very about 100 times thinner than Earth’s it is mostly carbon dioxide with just a tiny trace of nitrogen, oxygen and water vapor. It would be extremely unsuitable for most life as we know it.
Through the Viking cameras mars surface was revealed.
