The moon in the news...
Friday 22 July 2011
object: THE MOON
The Moon is the closest astronomical object to the Earth. With the Earth it forms what is almost a double planet as no other planet has a satellite which is as large in comparison to its own size.
The Moon has a diameter of 3476 km and orbits the Earth at a mean distance of 384,000 km. It orbits the Earth in 27.322 days and always keeps the same face pointed towards the Earth.
The Moon shines by reflecting the light from the Sun and shows the characteristic phases during each orbit of the Earth. Near New Moon, when the sunlit portion of the Moon is small, the phenomenon of 'the old Moon in the young Moon's arms' is often seen. This is caused by sunlight being reflected towards the Moon by the Earth and being reflected back again to the Earth. We are seeing Earthshine, the equivalent of moonlight on the Earth.
The orbital plane of the Moon is inclined to that of the Earth about the Sun and so eclipses are only seen when New Moon or Full Moon occur when the Moon is near to the crossing points of these planes.
The gravitational pull of the Moon and the Sun are responsible for the tides.
The Moon has no atmosphere. Any early atmosphere that the Moon might have had has escaped from the Moon's feeble gravitational pull. This is only one sixth that at the surface of the Earth. Because of the lack of any atmosphere the temperature of the Moon's surface varies between -180°C and +110°C. The Moon offers little protection from the solar wind, cosmic rays or micrometeorites and so it is not surprising that there is no form of life on the Moon.
Man in the Moon
The Moon's surface is characterised by light mountainous regions interspersed with dark maria. The 'Man in the Moon' is formed from patches of these two types of terrain. The maria are vast impact basins which have been filled with basaltic rocks some 3000 million years ago. Much of the Moon's surface is covered with craters. These are the result of impacts by meteors. The largest are about 200 km in diameter, the smallest are only about a metre across. Most of these craters were formed between 3000 and 4000 million years ago.
Much of our knowledge of the structure of the lunar surface and the geology of the Moon comes from the landings of the Apollo series and the samples of lunar material brought back to Earth. Despite this we are still not sure how the Moon was formed. In recent years, the most widely-accepted theory is that the Earth was struck by a Mars-sized body early in its history. Part of the resulting debris then coalesced into the Moon.
Viewing the Moon
The Moon is probably the most satisfying object to look at through any telescope. The craters and mountains can be seen with even a small telescope. The best place to look is near the terminator, where the Sun is either rising or setting. Here the shadows cast by mountains and crater walls are longest and can give very dramatic views. After as short a time as an hour changes in the shadows can be seen as the sunlight reaches or leaves peaks near the terminator.
Recently two probes completed successful missions to map and determine the composition of the Moon. The Clementine probe mapped the surface over two months in 1994 and hinted at the presence of water ice in some of the permanently shadowed craters at the poles.
Lunar Prospector found strong evidence for up to 300 million tons of water ice deposits at both poles as well as mapping lunar magnetic fields and determining the abundances of many elements.
During the Clementine mission, observations of TLPs by amateur astronomers were followed up by direct imaging by the orbiting spaceprobe. On 23 April 1994, there were reports of an obscuration over the so-called Cobrahead feature on a region called the Aristarchus plateau. Clementine images taken on 3 March and again on 27 April do indeed show a change as part of the region is a slightly different colour.
Confirmation of this tentative discovery would be very significant as the Aristarchus region is one of the youngest regions of the Moon. The Cobrahead feature is a collapsed lava tube that came from a volcano that had its heyday billions of years ago. It is also a region where TLPs have been seen in the past. Perhaps pockets of gas seep up through the ground and, when caught by the bright rays of the lunar dawn, glow in reds and blues. Or perhaps heating effects cause sub-surface explosions.
Lunar Prospector found strong evidence for up to 300 million tons of water ice deposits at both poles as well as mapping lunar magnetic fields and determining the abundances of many elements.
Transient lunar phenomena
Many amateur astronomers look for 'transient lunar phenomena' (TLPs). These are outbursts of some kind which give rise to short-lived colour or brightness changes in small areas. It is not clear how many of these are real or what causes them.
During the Clementine mission, observations of TLPs by amateur astronomers were followed up by direct imaging by the orbiting spaceprobe. On 23 April 1994, there were reports of an obscuration over the so-called Cobrahead feature on a region called the Aristarchus plateau. Clementine images taken on 3 March and again on 27 April do indeed show a change as part of the region is a slightly different colour.
Confirmation of this tentative discovery would be very significant as the Aristarchus region is one of the youngest regions of the Moon. The Cobrahead feature is a collapsed lava tube that came from a volcano that had its heyday billions of years ago. It is also a region where TLPs have been seen in the past. Perhaps pockets of gas seep up through the ground and, when caught by the bright rays of the lunar dawn, glow in reds and blues. Or perhaps heating effects cause sub-surface explosions.
Thursday 21 July 2011
The brief...
SUMMER BRIEF - WHAT IS GOOD? - Research
'GOOD' depends on your perspective, ethics, creative preferences, likes and dislikes (amongst other things). It is a matter of opinion rather than a statement of fact. You need to decide what is ‘good’ & design something that communicates your opinion, supports your argument or delivers your point of view.
'GOOD' depends on your perspective, ethics, creative preferences, likes and dislikes (amongst other things). It is a matter of opinion rather than a statement of fact. You need to decide what is ‘good’ & design something that communicates your opinion, supports your argument or delivers your point of view.
BRIEF
Identify, research and present your opinions of what is ‘good’.
Identify, research and present your opinions of what is ‘good’.
TASKS
Select 1 object, 1 place, 1 activity, 1 opinion AND 1 concept that you think are good
Select 1 object, 1 place, 1 activity, 1 opinion AND 1 concept that you think are good
Subscribe to:
Posts (Atom)