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In 1995, the South African Broadcasting Corporation (SABC-3) commissioned this astronomy television series, in which Thomas Budge visited key astronomical sites, interviewed many prominent astronomers, and taught the television audience how to get the most from their viewing the night sky.

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Outline

Boyden Observatory | Bloemfontein | University of the Orange Free State | Rockefeller Telescope | Uriah Boyden | Dr John Stefanos Paraskevopoulos | Professor Tony Farrell | University of Cape Town | Cape Town Planetarium | Large-scale Structures in the Universe | The Virgo Cluster of Galaxies | The Centauri Great Wall | First Xhosa Planetarium Show | The Lamont-Hussey Observatory | Conference of the Astronomical Society | Dr Robert Stobie | Solar System Formation | The Oort Cloud | Kepler's Laws | Newton's Laws | Planetary Motion | Possibility of Planets orbiting other Stars | How to find the Planets in the Night Sky | Planetary Motion around the Sun | The Ecliptic | Retrograde Motion | Observing Venus, Mars and Jupiter | Planetary Conjunction of Venus, Mars and Jupiter.

Video transcription

Hi, and welcome to Out of This World.

I'm here at the Boyden Observatory, not too far outside of Bloemfontein on this wonderful, rocky outcrop. In this program, we are going to be talking to some eminent astronomers, and also discussing the solar system.

The Boyden Observatory lies 24 kilometres to the northeast of the city on a rocky hill near the Modderrivier. Presently owned by the University of the Orange Free State, it is under severe financial and environmental threat. The fast growing Thabanchu and other areas, only some 35 kilometres away, and an industrial area only 10 kilometres away, threaten the dark skies with chemical and light pollution.

Hopefully, the municipal and provincial authorities can be persuaded to install sensible lighting to enable faint star observing to continue here at Boyden.

This is Boyden's largest telescope, the Rockefeller telescope. A 60 inch reflecting mirror at its base weighs about four tons, just the glass alone. This telescope was installed in 1933, and in fact, was used right up until the closure of Boyden.

It did some very good work, and do you know that this telescope is the second largest telescope in South Africa?

The telescope was purchased by Harvard in 1904 to continue their visual photometry program of very faint stars in southern latitudes. The definition was rather unsatisfactory and had to be refigure in the twenties to continue the research on the limits of the visible universe. It was a troublesome telescope as the ratio of the mirror's thickness to its diameter was too small. In the late sixties, it was entirely refurbished with a new housing and a new primary mirror.

In 1879, a Boston mechanical engineer left a small fortune to the Harvard College, a sum of $238,000. He was Uriah Boyden. With this money, the Harvard College Observatory built their facility in Arequipa, Peru. Because of administrative difficulties, it was relocated to Bloemfontein in 1927.

Dr John Stefanos Paraskevopoulos was Boyden's director in Peru and continued as such in Bloemfontein until 1951. After some years without a director, Professor Allen Jarrett, from the university, served in this capacity until 1976. In that year, Boyden closed its doors and handed ownership to the university.

In the shadow of the impressive Rockefeller dome, lie some smaller domes with roll off roofs. They contain some excellent equipment like this 13 inch refracting telescope. The other equipment known to have been at Boyden has since been removed. It is a great pity that this facility lost the support of the international community due to South Africa's political status at the time. The administrative building still houses a well-equipped library containing some very interesting and historically important documentation. Here I spoke with Professor Farrell.

 

Professor Farrell, thank you for joining me here in the Boyden Library.

You are Associate Professor of Astronomy at the University of Cape Town, and also the Planetarium Director, associated with the SA Museum. I believe that your area of special interest is large scale structures in the universe.

That that's my particular baby that I serve, but to explain large scale structures is going to need a little bit of a change of scale. Thom, what would you say is home sweet home to you?

Oh, I have a nice farm just to the west of Pretoria.

You are thinking on too smaller scale, a little bit larger, South Africa perhaps? Perhaps Earth?

Earth, yes.

Solar system? Yes?

Yes.

Okay. I still need to take you incredibly larger than that. Most people know the solar system. Astronomers can often describe the size of the solar system, maybe in light travel time. If you had to send a message to someone, say in Neptune, it would take about four to five hours to get it there. So that, that sort of is a feel as to how big it is. Maybe 10 light hours in all in diameter.

Outside the solar system, you've got lots of other stars. Those stars could each and themselves have their own solar systems, and there's a collection of let's say, about a million million stars and maybe solar systems in our galaxy.

Now, if you asked me what's home, sweet home, I would've said the Milky Way galaxy. It's estimated, if we could, you know, look throughout our universe, you could detect something like about a hundred thousand million galaxies.

Goodness.

Now each one of those possibly has a million, million stars in them, and uh, just one star is a star like our sun. So, it does kind of put you in perspective.

Makes them really feel insignificant.

Yes. Oh, yes. I mean, your everyday worries can be totally forgotten. Once you start, you're looking at the universe on this scale, they're quite in insignificant and immaterial.

So, if the galaxies themselves aren't the large scale structures, what are those large scale structures?

Well, the universe is like a gigantic cosmological fruit cake, and these galaxies are like the cherries in the fruitcake, and the texture of the cake is like the space. It's actually expanding. It's space itself that's getting bigger. When you plot where the galaxies are in dimensional space, you find remarkably, that the galaxies tend to clump into… it's almost like a foam-like texture. If you take a bath sponge and you blow it up on a gigantic scale, that same sort of texture seems to be there at the universe, on a very large scale.

But it means you say your bubbles in the bath sponge have grown to be where they are, like a hundred million light years across. It would take light a hundred million years to go across one of these bubbles, and quite often, these bubbles are empty. There're no galaxies in them. The galaxies are around the outside.

So it's a rather strange fabric the cosmos shows us, but is not quite entirely like a bath sponge. You do get this kind of texture, but there's also kind of almost rectangular structures, as if nature has been drawing parallel lines and drawing right angles on a phenomenal scale, approaching a billion light years. There's structures known as great walls, where it seems as though these point-like galaxies are arrayed in a big flattened slab. There's a thickness to the slab, there's a texture within it, but these are truly gigantic, colossal things, or literally the largest things we know of in the universe. And, I think the largest things we're ever going to discover.

As an amateur, I've had a look at the Virgo cluster of galaxies. Do these have any bearing tothe structure that you're alluding to?

Uh, the Virgo cluster. We live, in case you are not sure of your address, we live on the fringe of the Virgo super cluster. I, in turn, actually would like to claim that the Virgo super cluster and all us are actually part of a thing called the Centauri Great Wall. A great wall-like structure, which we are actually able to see now, and it extends through much of the southern skies. The interesting thing is we're not in the center of this sort of conglomeration, and you and I are at this moment falling towards it at 600 kilometres a second. We're never going to get there. It's moving away from us much faster than that, but it's nevertheless pulling us in to what we believe it's a gigantic concentration of galaxies. Part of it is actually hidden by the Southern Milky Way and my research, and my collaborators overseas, we've been looking to try and find structures behind the Milky Way, but uh, compared to the absolute rest, yes, we're moving. When you look in the sky and you see the Southern Cross, those stars of course are in the foreground, but it's in the same general direction as we're being pulled, presumably by this great mass of galaxies out there. It's trying to understand that structure and how we're moving, that's what it's all about.

So Tony, just to digress slightly, I believe that at the planetarium, you've put together your first show in Xhosa.

Yes. We had. The first time I think there has ever been a planetarium show with a pre-recorded soundtrack in Xhosa, and it opened just recently at our planetarium. Minister, Ben Ngubane, was there. He put for the opening, and, it seems to have been received well. This is important to us because although English is often seen as the medium for education, for children, particularly from disadvantaged black communities, who will be intimidated by being brought to place and put inside a planetarium here, to have it in their home language, is something more comfortable and acceptable.

And, we've also tried to take things they're familiar with, like taking a soccer ball, and then saying, well the earth is also a ball, the moon is a ball, and using that as a common theme, to do it there. So we're very excited, yes, that we've got this at long last in our planetarium.

 

In its astronomical heyday, Bloemfontein boasted not only one, but two observatories. Near the city, on Naval Hill, the Lamont-Hussey Observatory functioned from 1927 until 1962. It belonged to Michigan University, who also withdrew their support and gave this building to the city council. They converted it into a theatre where the recent conference of the Astronomical Society was held. Here, Dr Robert Stobie delivered the keynote address.

Dr Stobie, can you tell me about the future of astronomy, as you see it, here in South Africa at the present time?

I think, astronomy is really something that South Africa has to address, and in a way, as to why should a country like South Africa be involved in something like astronomy, a subject like astronomy, how does it benefit the person in the street? How does it benefit the country itself? And, I believe that there are very good answers to these questions, but it needs to be much wider known as to what benefits astronomy brings. Astronomy, I think, to me seems a very esoteric subject to some people, but it has got, I think, an important contribution to the future of South Africa, especially if you're thinking about school children where we know that if you catch them at an early enough age, they get very excited by a subject like astronomy. And, we know from studies done in other countries, that it actually encourages them, as a catalyst, to take thinking of careers in science and technology, which is what the country does need.

We don't necessarily need lots of astronomers, but we want to get people excited about science and astronomy, as a very good subject. And, the last point I would make is, I think, in connection with public awareness of the importance of science and technology, that, again, astronomy is a very accessible subject. We know that during the Jupiter impact, the comment last year that, the TV ratings went up by a factor of two just during that week because of intense public interests. So I think for all these reasons, it's really, astronomy, that has a lot to offer South Africa.

 

You know, I couldn't resist taking a short journey outside of the city of Bloemfontein, to this lovely spot where the night sky is really so dark, and it's been a most rewarding journey for me. The sky is so crystal clear, the planets are shining brightly. You know, that brings me to the point where I'd like to actually talk to you a little bit about the formation of the solar system itself.

The sun formed in a cloud of chemical elements drawing more and more matter into itself. As its mass increased, it began to spin on its axis, which resulted in the flattening of the gas cloud into a disk-like structure. In the disc, dust particles stuck together, which in turn clumped together to form asteroid size objects. These in turn formed the protoplanets. These bodies orbited the young sun in this disc-like structure.

When the sun itself actually accumulated enough mass, a nuclear reaction began way down in the depths of the sun, and it caused the sun to illuminate. And, as the sun illuminated, it then gave off its heat, its radiation, which blew the remainder of this gas away, leaving the solid planets in their place. That gas has been blown right out beyond the, the orbit of Pluto, and it lies there, with just enough attraction of the sun to pull it back in. But not enough effort of the solar wind to push it out into space, to disperse forever, and it's in that region of the solar system, a place that we call the Oort Cloud, where the comets are formed.

The planets themselves are quite interesting, and the motion of the planets are all governed by three of the laws that were propounded by Kepler, and another three of the laws that were propounded by Newton. Kepler's three laws, first of all said, his first law was his law of ellipses. It says that the planets do not orbit around the sun in a circle, but rather they orbit around the sun in an ellipse. Now, as you may know, an ellipse has two focal points, and the sun would be at one focal point, and the other focal point would be somewhere out in space. The planets themselves simply revolving or rotating or orbiting around the sun in this elliptical pattern.

Kepler's second law is quite an interesting one as well. It says that if you took a line and drew it from the planet to the sun, then that line would sweep out an equal distance, an equal area, in equal time. What does that really mean to you and me as amateurs? It basically means is that the planets themselves travel rather slowly the further away from the sun they are, and as they come back towards the sun, the gravitational attraction of the sun speeds them up in their orbit. They catapult around the back of the sun and go back out into their orbit.

Kepler's third law is his law of harmonics. It says that the planet's orbital speed and distance from the sun are related. The further the planet is from the sun, the weaker the sun's effect on it.

Also governing the motion of the planets are Newton's three laws: He has a law of inertia, a law of force, and a reactive law. His law of inertia, very simply put, says that… let me give an example: It says, that if I take a tennis ball, and I'm an astronaut, and I'm way out in space, and there's no gravitational effect, no clouds, or anything to slow that ball down, if I throw that ball, the ball will continue in space forever. It'll not change its direction, nor will it change its speed unless of course it bumps into something or something crashes into it and moves it off its course, or if it goes through some kind of cloud, which would slow the ball down.

Newton's second law says, the rate of change of an object's motion is proportional to the applied force in the same direction. The story goes that he discovered this as he watched earth's gravity accelerate an apple's fall from a tree.

The reactive force is quite different. The reactive force says that for every force, there's an opposite and equal reaction. So take a spacecraft that is out in space, if it fires one of its rockets, it's got no air to push against. Most people think that it, pushes against the air, and that makes the rocket go forward in its direction. That's not true. The rocket goes forward because of Newton's third law because Newton's third law says, for every action there's an opposite and equal reaction.

Now, I'll tell you this because these laws, both Kepler's and Newton's laws are the laws that govern the motion of the planets around the sun. Basically, the planets stay around the sun, almost like a stone on an end of a piece of string, that if you whirl it around above your head, that stone couldn't escape. It would want to escape, but it couldn't because the string is holding it back. So in essence, the planets stay revolving around the sun, or orbiting around the sun, because of the gravitational pull that the sun has on the planets, but the planets themselves, because of Kepler's and Newton's laws, would want to escape off into space, and that delicate balance, is what keeps our solar system together.

I often get asked if our solar system is unique, say in our galaxy or beyond in the universe itself? I don't really believe that is the the case. There are so many stars that are very similar to our star the Sun, that it is most probable that other kinds of planetary systems must exist. Astronomers are on the search for likely stars that would be able to support such a planetary system. They look for stars, telltale signs in those stars, maybe a dipping of the star's, brightness or luminosity, that may in fact be a result of a planet moving in front of it or a star that has a already formed ring system around it. So, the astronomers are looking, but my personal belief is that yes, there is going to be another star, or many other stars out there, supporting a solar system, perhaps very similar to our own.

 

Welcome to Sky Watch.

In this section of the program, I will explain to you how to find the planets, and will also tell you of interesting things you should look out for in the coming month.

Why do I look at the night sky? You may say, once one has seen the basic movements of the celestial canvas, monitored the phases of the moon, and seen some of the planets through binoculars, that is enough. If this program tempted you to take only one such hard look heavenward, I think that I would have succeeded in my mission. However, looking at the sky can be likened to a visit to the Kruger National Park. Some visitors have a checklist of the big five animals they wish to find. Once they have seen them, they feel satisfied and return home with enthusiasm. Others become obsessed, not so much with the big five, but with all the little animals, birds and indigenous flora. They go back time and time again. Amateur astronomers are much the same. Some are fascinated armchair astronomers, others casual observers who have a limited knowledge that can impress their guests at an evening braai, while others scan the night sky with binoculars, looking forward to the time that they see the sky through their very own telescope.

The sky's full of different and interesting celestial objects. At first glance, you might think that there are only millions upon millions of stars, but this is not true. Besides the stars, there are the planets of our solar system. They are much, much closer than the stars. The stars themselves vary in distance from the earth. The nearest, Proxima Centauri, is about 450 trillion kilometres away. In the depths of space, we find galaxies, star clusters, black holes and thin veils of gas that we call nebula. This month I'd like to focus primarily on the planets.

Do you remember the rule of thumb that I gave you last month? It'll certainly help you with your planetary observations. The outstretched hand at arm's length covers approximately 20 degrees. The clenched fist, knuckle to knuckle, 10 degrees. The width of your index finger, one degree, and then the joints on your index finger at outstretched arm, two, four, and six degrees respectively.

The planets were called wandering stars because they continually change their position relative to the background stars. Because of this constant movement, it is almost impossible for me to give you fixed locations where you can find them. Sometimes the planets appear to move rather rapidly, and at other times, they appear to move rather slowly. The movement of these celestial objects is attributed to their orbit about the sun, but it is also accentuated by our own orbit as we overtake them. On occasions, they even appear to move backwards, a phenomenon we call retrograde motion.

Earlier in the program I discussed the formation of the solar system, and you may recall that the sun formed from a cloud of gas, which flattened into a disk-like structure. When the sun began to spin, the planets grew within this disc, and all, with the exception of Pluto, orbit on the same plane. Imagine for a moment you are in a swimming pool with your eyes at water level. If you wish to look for several balls floating on the surface of the water, you wouldn't look down into the pool, nor would you look up into the sky, you would simply look turning around, looking along the surface of the water.

When you are looking for the planets, you would need only scan along the orbital plane. The sun appears to move across the sky from the east to the west during the day, and, if you plotted its position every hour, you would've marked out that orbital plane, a line we call the ecliptic. Look no further than just a few degrees either side of the ecliptic to find the planets.

Mercury, Uranus, Neptune, and Pluto, are either too small, or so far away, that you won't be able to see them unless you have a reasonable telescope and some experience finding them. In fact, you'd need to use the Hubble Space Telescope in order to see Pluto. That's because it's so small.

Venus is generally easy to locate. It orbits between the earth and the sun and never appears to stray too far away from the sun. Depending where it is in its orbit, it may appear as the morning, or the evening star, rising before or setting after the sun. Because the orbits of Mars, Jupiter Saturn lie beyond the Earth's orbit, they can be seen anywhere along the ecliptic. Remember that the planets move along the ecliptic, and are sometimes near or even behind the sun, obscuring them for a while in November.

Venus, Mars and Jupiter will be very easy to find as they will be grouped together along the ecliptic. Saturn is also visible along the ecliptic at night, and appears as a bright star-like object in Aquarius. Follow the line of the ecliptic up from the eastern horizon, some 65 degrees, where you should find it. You'll need a small telescope to see its moons and its ring system. If you would like to see Saturn, and don't own a telescope of your own, contact your local center of the astronomical society via their head office in Cape Town, or via one of the two planetaria. These numbers will be listed at the end of tonight's show.

Even if observing is not entirely your cup of tea, why not glance skyward a few times next month when Venus, Mars and Jupiter put on an excellent display? They will appear very close to each other in the night sky in the early evening, and will be visible with the naked eye. The grouping of the planets along the ecliptic is a term that we call a conjunction. The conjunctions of Mars, Venus and Jupiter will begin around about the 15th of November, and look out for them around seven in the evening, some 18 or 20 degrees above the western horizon, along the ecliptic.

Luckily for us, the moon will be in its new moon phase on the 22nd of November, which means that it won't shine brightly enough to spoil our view. Planet's movement along the ecliptic seems to be more noticeable during a conjunction because we are able to compare the planet's relative movements with respect to each other.

You may wish to sketch the positions for about 10 nights, starting on the 15th of November, to appreciate the speed and direction of both Venus, Mars and Jupiter. Although they appear to be very close to one another, in reality they are very, very far apart. Venus lies in the foreground. It's white clouds and proximity make it appear very bright, in fact, bright enough for it to actually shine during the day as well. Mars can also look extremely bright when it is close to the earth, but it is unfortunately about to pass behind the sun. Being so far away, it appears very faint. By far, the furthest away, is Jupiter, but due to its enormous size, it nevertheless appears very bright.

This conjunction can be simulated using computer software that is readily available, or in the planetarium with its sophisticated projector equipment. Pay the planetarium a visit if you would like to know more about this conjunction and the summer night sky.

I trust that you'll have a very exciting month's viewing.

Until next month when we talk about the sun, wishing you clear night skies.



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