Astronomy and Space
articles by Martin George of the Launceston Planetarium
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18 October 2009
Mercury and the Moon in the Spotlight
Our Moon and the planet Mercury, two superficially similar worlds, have been in the spotlight lately because of visits by spacecraft—although they were visits of quite different kinds.
A few weeks ago, NASA's MESSENGER craft made its third flyby of Mercury. Its two previous flybys were in January and October 2008, and now MESSENGER has imaged more parts of Mercury that have never been seen before.
Of special interest is a bright patch on Mercury that is so prominent that it has actually been seen in telescopic observations made from Earth.
There are bright patches on the Moon, generally formed by relatively recent impacts on its surface. This one on Mercury is rather curious, though, because at its centre is some kind of depression that may have been formed through a volcanic process. There is no suggestion that Mercury necessarily has active volcanoes today, but closer study of this area may reveal a lot about Mercury's past, and this part of the planet will certainly be a major target of study after MESSENGER is finally placed into orbit around Mercury in 2011. When that happens, we shall finally have placed spacecraft into orbit around all of the planets that are clearly visible with the unaided eye.
Our Moon has captured a lot of attention lately, too, because of an event that took place on the evening of October 9, our time. A Centaur rocket stage was deliberately crashed into a crater called Cabeus, near the Moon's south pole. Four minutes later, the spacecraft called LCROSS—the Lunar Crater Observation and Sensing Satellite—plummeted into the same crater.
The LCROSS mission's aim was to analyse the plume of material resulting from the impact of the rocket stage, with the specific hope of finding direct evidence of water on the Moon.
All seems to have gone well. The rocket stage reached its target at 10.30 pm our time, and for four precious minutes the little spacecraft, also heading for destruction on impact, transmitted information that will be of great value to scientists. Then, right on schedule, LCROSS stopped transmitting—a sure sign of its impact with the Moon.
There were, however, many disappointed people. There had been a possibility that the impact of the rocket stage would produce a plume large enough, and bright enough, to be visible through amateur telescopes, provided that they had diameter of at least 25 centimetres. However, even the great 5-metre-diameter Hale Telescope in the USA failed to reveal the plume.
It may be some time before the data returned by LCROSS are analysed thoroughly enough to be able to say whether there was, or was not, a detection of water. However, the evidence so far, produced by two previous spacecraft called Clementine and Lunar Prospector, was strong. I think that the water, which would be in the form of ice inside craters that never receive direct sunlight, will eventually be found. Let's hope that it is LCROSS, now in a crumpled heap on the lunar surface, that has come up with the goods.
by
Martin George, Launceston Planetarium, QVMAG.
Reproduced with permission of the Sunday Tasmanian newspaper
11 October 2009
Launceston Planetarium Reopens
Tomorrow night will see the official reopening, by his worship the Mayor of Launceston Albert van Zetten, of the Launceston Planetarium, after its move from the Queen Victoria Museum's Royal Park site to its Inveresk site. Having been involved with the Planetarium for such a long time, it is a very exciting development for me. It's also a great development for the Launceston City Council, the people of Tasmania, and for visitors from interstate and overseas.
The Planetarium began operation at the Museum's Royal Park site, in Wellington Street, in January 1968. By 1972 it was housed in a specially constructed section of the building. It entertained hundreds of thousands of people over its first 40 years of operation.
With the decision to convert the Royal Park site into a superb new art gallery, the Planetarium closed its doors in February 2008 and the long moving process began.
Now, the new facility is complete and ready to go—and there is far more on offer than ever before!
The Planetarium now has full dome video capability, which covers the dome with astronomy and space related digital video. The opening show, Dawn of the Space Age, is an exciting programme taking the audience from the first artificial satellite to the manned landings on the Moon and beyond, and includes amazing sequences showing some of the things that didn't go quite right!
In a few weeks time, the Planetarium will be opening its new, in-house programme entitled What Happened to Pluto? which has been a question on everyone's lips ever since its demotion from planetary status in 2006—an event for which, I have to admit, I am partly responsible!
In addition to the new video capability, the Planetarium's ageing Zeiss ZKP1 projector has been replaced with a much more modern ZKP3 model. The new projector, purchased from the Stardome Planetarium in New Zealand with the kind support of the Grote Reber Foundation, gives a superb rendition of the starry night sky, and has projection capabilities far beyond those of the much-loved old ZKP1.
Martin George (right) and Chris Arkless adjusting the Launceston Planetarium's new projector. PHOTO: Lisa Gershwin, QVMAG
The old projector will soon be reassembled and placed on public display within the Inveresk site.
As well as running programmes for the public, the Launceston Planetarium also caters for group bookings. The vast majority of visiting groups are school classes and, indeed, over the Planetarium's many years of operation, about half of all visitors have been from within school groups.
There are several thousand planetariums around the world, but only seven open to the public on a regular basis within Australia.
The Launceston Planetarium is the most southerly fixed-dome planetarium in the world. It's wonderful to have such a facility in Tasmania, giving us the opportunity to run shows explaining the superb views we have of the southern night sky. Tasmania is also, of course, the best place in the country to observe the aurora australis, also called the southern lights.
I'm looking forward to welcoming you all to the new Launceston Planetarium, where you'll really feel as if you are outside at night. In the Planetarium, however, we never have a cloudy sky!
by
Martin George, Launceston Planetarium, QVMAG.
Reproduced with permission of the Sunday Tasmanian newspaper
4 October 2009 Impact Site Chosen for Lunar Spacecraft
Today is a famous date in space history. It was on 4 October 1957 that the Soviet Union successfully launched the first artificial satellite, Sputnik. This was much to the dismay of the United States, which remained behind in the 'space race' for several years.
Each year, as this date comes around, I reflect on the great achievements that humans have made in the effort to explore space, and to use space-based instruments to learn more about our Solar System, and indeed our whole Universe.
There's plenty to think about at the moment, though, in relation to a current spacecraft that is about to have a rather spectacular arrival on the surface of the Moon!
Earlier this year, NASA launched two craft to the Moon. One, the Lunar Reconnaissance Orbiter, is orbiting the Moon and has returned some great pictures and data about the Moon and its surface. The other, called LCROSS, or the Lunar Crater Observation and Sensing Satellite, is a separate mission designed to learn more about the Lunar surface by what some may call 'brute force'.
The LCROSS mission involves sending the upper stage of its Centaur rocket crashing into the Moon, with the main spacecraft following four minutes later. As the spacecraft flies through the debris cloud caused by the impact, it will measure the composition of that cloud. It may even confirm, once and for all, something that scientists have long suspected—that there is water, in the form of ice, near the lunar poles in craters whose interiors never receive any sunlight.
Recently, it was announced that the target crater for the LCROSS impact is one called Cabeus A1, at a lunar latitude of 81.5 degrees south. It is a 17-kilometre-diameter crater near the much larger main crater called Cabeus, which is named after Niccolo Cabeo (1586-1650), who was an Italian mathematician, philosopher and astronomer.
The big crash is scheduled to take place this coming Friday, 9 October, at about 10.30 pm our time.
Unfortunately, the Moon will still be well below our Tasmanian horizon at the time of impact, and will not rise until after midnight. However, there is a possibility that amateur astronomers with reasonably large telescopes, located at longitudes well to the east of ours, will be able to spot the debris plume not long after the impact. They will be more suitably placed, as the Moon will be above their horizons.
This is not the first time that a spacecraft has been deliberately sent crashing onto the Moon. In the 1960s, the US sent its Ranger probes to the Moon with the aim of impacting the Moon and sending back pictures as they descended. Some ascent stages of Lunar modules were also returned to the Moon by the Apollo astronauts in this way once they were no longer of any use. Much more recently, NASA's Lunar Prospector craft met its end in the same way in the first attempt to 'dig up' some lunar debris and form a plume of material for study from Earth.
This time, however, the study will be much, much, closer up!
by
Martin George, Launceston Planetarium, QVMAG.
Reproduced with permission of the Sunday Tasmanian newspaper
