Astronomy and Space
articles by Martin George of the Launceston Planetarium
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15 November 2009
Remembering Apollo 12
In this fortieth anniversary year of the famous landing on the Moon of the Apollo 11 mission, it's important not to forget that Apollo 11, carrying Neil Armstrong and Edwin ('Buzz') Aldrin to the Moon while Michael Collins orbited overhead in the Command Module, was followed by five more successful lunar landing missions.
It was in November 1969 that the second crewed mission to the Moon, Apollo 12, took place. The anniversary of that launch is today, our time, at 3.22 am.
The Apollo 12 mission, carrying astronauts Pete Conrad, Alan Bean and Richard Gordon, was nearly a disaster just after takeoff. Thirty-six seconds after the giant Saturn V rocket left the launch pad, it was struck by lightning, and was struck again sixteen seconds later. Quick thinking by one of the mission controllers and astronaut Alan Bean brought their onboard instruments back online, saving the mission.
The Apollo 12 Lunar Module, called Intrepid, landed in the Moon's Ocean of Storms a few days later, carrying Bean and Conrad, while Gordon orbited the Moon in the Command Module Yankee Clipper, awaiting their return.
There are, of course, no oceans on the Moon. Long ago, many of the smooth dark features on the Moon were named after seas or oceans because, being large flat areas, they seemed to bear a similarity to the Earth's oceans.
These areas—another example being the Sea of Tranquillity—are huge lava plains caused by impacts or eruptions eons ago.
If you were around in those days but can recall little or nothing about Apollo 12, you are not alone. The mission is, indeed, not well remembered. This is partly because only a few months earlier there had been the excitement of the first lunar landing. It was largely, however, for another, very unfortunate reason: unlike Apollo 11, there was no television coverage from Apollo 12 on the Moon.
Things were certainly not planned that way. However, as astronaut Alan Bean was preparing the television camera for use after the lunar landing, he made a devastating error: he accidentally pointed the camera at the Sun.
Pointing any optical device at the Sun can be hazardous. In the case of the Apollo 12 television camera, its Vidicon tube was quickly destroyed—and there was no backup.
The Apollo 12 mission was, however, a great success. A notable achievement was the pinpoint landing: the lunar module landed, by design, quite close to the USA's Surveyor 3 craft, an uncrewed lander which had reached the surface of the Moon 1967.
In addition, the astronauts took many still pictures during their time on the Moon, including images of Surveyor 3 still sitting on the surface where it had landed
There were four more successful crewed lunar landings, in addition to one that failed—Apollo 13. By the time of Apollo 13 in April 1970, it seemed that lunar landings were becoming commonplace, and little attention was paid to it at first. But after an explosion in space, Apollo 13 made world headlines. That, however, is a story for another time.
by
Martin George, Launceston Planetarium, QVMAG.
Reproduced with permission of the Sunday Tasmanian newspaper
8 November 2009
The Most Distant Object Ever Seen
As a young child I was captivated by the sights of the night sky. I would watch the stars as the sky darkened and one of the first things I wanted to know was how far away they were. My mother gave me an answer that fascinated me: she told me that the stars were so far away that their light has taken a long time to reach us—in some cases, thousands of years. That is quite a distance when one realises that light travels at the amazing speed of 300,000 kilometres every second.
She was quite correct. As we look up to the individual stars we see at night, we are looking back in time anything from several years up to well over a thousand years.
Although these distances seem hard to believe—even the Sun's nearest stellar neighbour is just over 4 light years away, meaning that its light left on its journey to us over 4 years ago—the distances to other galaxies are so much greater that they defy even the imagination. The galaxies in our Local Group of galaxies, which includes our Milky Way Galaxy, are spread across several million light years of space, and the most distant objects we can detect are over 10 billion light years away.
As our instruments and methods have become more sophisticated, astronomers have been able to detect objects at ever-greater distances. Now, they have set a new record. Earlier this year, they recorded a phenomenon called a gamma-ray burst that took place so long ago that its light has been travelling across space for about 13.1 billion years.
Gamma rays have a very short wavelength and are an extremely energetic form of radiation. These Gamma-ray bursts are thought to arise from the catastrophic explosions of very massive stars that existed when the Universe was very young, and studying them helps us to better understand the processes of star formation that took place at that time.
Astronomers estimate the distances to such events by analysing how much the wavelengths of radiation have shifted due to the overall expansion of the Universe. This is an effect called the cosmological redshift. In the case of this event, called Gamma Ray Burst GRB 090423, the wavelengths have a redshift of 8.1, meaning that the wavelengths have expanded by a factor of 9.1 compared with the values they would have if there were no expansion of space between us and the burst.
The age of the Universe is estimated to be about 13.7 billion years, and this is a widely accepted value. This redshift shows, therefore, that the burst occurred when the Universe was relatively quite young—only about 600 million years old.
It's quite amazing to think that we can measure such distances with any degree of confidence at all. It's true that there are uncertainties, but the measurement of distances in astronomy has been one of the great triumphs of science. That's a story, however, that will have to wait for another time!
by
Martin George, Launceston Planetarium, QVMAG.
Reproduced with permission of the Sunday Tasmanian newspaper
1 November 2009
Exoplanet Total Hits 400
There used to be a time when the discovery of a new planet hit the news and captured the attention of the public. Neptune's discovery in 1846 was a triumph of nineteenth-century mathematics, and Pluto's in 1930 also made news all over the world, even though it has lost its planetary status.
Then came the 1995 announcement of the first planet to be found orbiting a star other than our Sun. The star was 51 Pegasi, and its planet was found through careful observation of the star at the Haute Provence observatory in the south of France.
There's scarcely an astronomer around who would not know the reason for the fame of that star or observatory but, since that major breakthrough, there have been very many more found, and now the total is over 400.
That's 50 times as many known planets moving around other stars as are orbiting our Sun, and I have long given up trying to memorise them all!
Bringing the total to over 400 was the recent announcement, by European astronomers, of 30 new planets.
Discoveries of new planets are now coming thick and fast. Our methods for finding them are becoming more varied and refined, but the vast majority of them are still being detected using the 'wobble' technique.
'Extrasolar' planets, or exoplanets, are typically far too faint to be seen, even through powerful telescopes. This is so especially because of the glare of their parent stars. Even Venus, which appears so brilliant to us, is far less bright than our Sun. If we were at a great distance from our Solar System, Venus would be lost to view—bathed in the Sun's brilliant light.
The 'wobble' method relies on the fact that orbiting planets exert a gravitational tug on their stars, causing them to move. The 'back and forth' component of this motion is detectable by watching the change in the wavelengths of light from a star: an approaching star will appear slightly bluer, and a receding one slightly redder. The difference is so slight that highly advanced instruments are needed to make the measurements.
Amazingly, astronomers are now able to measure a star's motion towards or away from us to a precision of about one metre per second. This corresponds to a shift in wavelength of one part in 300 million.
One of the most tedious parts of this type of measurement, however, is allowing for an effect that has nothing to do with the wobble of the star. Rather, it is all to do with our Earth and its motions.
We are not only spinning once per day—the rotational speed here in Tasmania is about 1250 kilometres per hour (350 metres per second)—but the Earth's speed in orbit around the Sun is a whopping 29 kilometres per second. Astronomers also take the gravitational effects on Earth of other planets, especially Jupiter, into account.
Amazingly, astronomers are hoping to improve on this still further, allowing them to detect less massive planets which have only a slight influence on their stars' motions.
We're getting closer and closer to finding planets that have the mass of our Earth. Using either this method or another, I think it's going to happen soon!
by
Martin George, Launceston Planetarium, QVMAG.
Reproduced with permission of the Sunday Tasmanian newspaper
25 October 2009
Article still to come
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
