27. SUN

Before leaving our solar system we should first start discussing the most nearest star in our galaxy: the SUN.
Nearest, but that is relatively: a sun with the size of 1 meter should show the earth as a marble at 100 meter distance! The sun is as star a quite common star, a dull mediocrity in all aspects, in size, in mass, in spectrum, in brightness, in temperature, etc.etc. Lucky for us, we would not be there, were all these aspects a little bit different.
Its energy is delivered by nuclear fusion processes in the core, where hydrogen is converted into helium under tremendous pressure and at very high temperatures. Its radiation stretches to outside the planetsystem, in particular the fatal very strong gammaradiation, X - ray radiation and ultraviolet radiation and, don't forget, the SOLAR WIND, consisting of particles of helium, hydrogen, protons, electrons, ions, etc. fired with very high speed (500 km/sec) and in large numbers into space. A non-protected man on the moon would disappear completely in a second! We, on earth, are protected by the VAN ALLEN BELTS, magnetic fields created by the core of the earth and bending the wind to the earthpoles ( Polarlight!).
The sun is still under investigation in particular by the SOHO-sonde, fixed at a location at ~1% (!) of the distance to the sun, the so-called "Lagrange point" where the gravitational attraction of earth and sun are equal. So we really don't need a solar-eclipse, no more endless waiting for such a show, we can do it now 24 hours per day!
What is the future of the sun? Well, say after a billion years the sun will become considerable brighter than today, he will become "a red giant", causing fast increasing temperatures, evaporating oceans on earth. It is for sure that then life on earth will become quickly impossible. Looking another 5-6 billion years further, the sunlight will be hundred times stronger than today and the sun start to shrink into a compact, white-hot core, a "white dwarf", the beginning of the end, dying, but that will take another trillion of years.

26. IMPACT on COMET TEMPEL.1

It is really possible to approach a comet, touching him and even analyse its inner part. This is done in 2005, by sending a spacecraft, which shoot a probe to the comet and measured the dustcloud after impact. The size of he comet is 14 x 4 km, the distance: 130x 10^6 km and it took roughly 5 months to arrive there.

25. COMET HALE-BOPP

It is not true that comets are always coming from the Kuiperbelt or the Oortcloud. There is a wellknown comet not of that origine and which is "long-periodic": Comet Hale-Bopp. A comet with a very long-stretched elliptical orbit in a plane perpendicular to the plane of the planets and with a period of 4200 years. Its "perihelion" (closest position near the sun and the reversal point) is 138 million km, so nearer to the sun than to the earth. He passed the earth on 200 million km on 23 March 1997, leading to a very impressive appearance on the firmament during the years 1995-1998. According to the measurements he will never touch the earth. The comet has a diameter 40 km, being a very rough estimate.

24. COMETS

Sofar 34 comets hav been found. In the upper photo the orbits of the comets Shoemaker-Levy and the Great Comet of 1680 is shown.The lower photo shows the comets Shoemaker-Levy (rests), Hale Bopp and Halley's. The last one, visible in 1986, will appear again in 2062.

23. KUIPER and OORT BELT

Space explorations leads us to the conclusion that space in our solarsystem is awesome empty. Distances to the sun vary from 50 million to 6 billion km, that means that in a ball volume with radius of 6 billion km the planets are completely negligible with respect to their part of the content, neither have asteroids any significance, their mutual distances are millions of kilometers.
Thus empty, nasty empty!
But still there are the KUIPERBELT and the OORTCLOUD, comprising numerous comets. Are they filling up space perhaps a bit more? Let's have a look.
Kuiper has calculated that between about 50 AU and 500 AU ( "Astronomical Unit" with 1 AU = 150 million km) there is a belt with a very large quantity of ice bodies. That belt is considered as to be the birthplace of "short-periodic comets". It is estimated that there are 35.000 of such comets larger than 100 km, the rest, a 100 to 200 million comets, are all smaller or very small. Neptune has a strong influence on all those smaller ones if coming in its neighbourhood, which then are swung into far space or are found back in orbits between the other planets, even inside the inner part of our solarsystem. A rough calculation tells us that all those comets still have on average mutual distances of billions of kilometers.
The OORTCLOUD is also result of very accurate calculations, based on the orbits of 19 comets, by another famous Dutch astronomer: van Oort. It concerns a spherical cloud around the whole planetsystem on a distance of a bit less than a trillion km (= 10^12 km) up to more than about one lightyear ( = 10^13 km). He estimated the content of that cloud on a trillion comets, but that means that the distance between the comets are billions of kilometers on average if you confine the comets into a shell of 10^11 to10^13 kilometers thick.
Conclusion: we cannot deny that space in our planet system is empty, it remains an unbelievable "nothing"!
The difference with the Kuiperbelt is the orbit of an object: these orbits lay in completely ad random planes not making small angles with the plane of the planets, as do orbits in the Kuiperbelt.
The OORT cloud is considered to be the source of long-periodic comets. It is unknown how these clouds have been created, but it is for sure that they are remnants of the original nebula from which the solar system evolved.

22. ASTEROID on MARS

Not only the earth is "attractive" for asteroids, also other planets have got their portion! Here an asteroid, called "Phobos", with a diameter of 25 km, circulating around Mars at a height of 5800 km! It will smash on Mars probably in blocks after 1 million years.

21. CRATER in ARIZONA USA

The large crater in North-Arizona USA, one and a half kilometer wide and 200 m deep is result of a metallic meteorite with 30 m diameter, crashing about 50.000 years ago. Of the near-earth asteroids, the 1000 to 2000 medium-size objects with nearly one kilometer diameter, of which one in 300.000 years crashed the earth on average, are a much more extensive threat. It can happen to morrow, after tenth of years or after a million years, the past does not say anything about the future! The still larger asteroids, roughly ten kilometer in diameter, of which there are only a few (perhaps 10 pieces), have hit the earth on average once in hundred million years. Something like that should have taken place some 65 million years ago causing three quarter of all living species on earth to die out. The crater formed by that object with a diameter of 170 km has been found near the peninsula of Mexico. The size of the object is estimated to be 10 - 20 km in diameter.
Can we do something against it? In a sense, yes. There exist "space-watch" - observatories, engaged in identifying number, size and orbit of asteroids, some nights observing 600 asteroids, but nearly all of them are smaller than 10 m. Are they much larger then we have to reckon with 10 to 100 years preparation to cause a change in the orbit of a dangerous one. It requires extremely accurate calculations and very complex spacecrafts to reach the asteroid with its enormous speed in an orbit influenced by many other celestial objects. A small chemical explosion will already be sufficient to push them out of their orbit, but you should know beforehand very precisely what the new orbit will be!!
We certainly will be able in the near future to divert such threads, the question is yet: always?

20. PASSING ASTEROID

This an example of a passing asteroid, see the trail in the upright corner. It's in the constellation Centaurus. Such a trail makes it possible to measure the speed and to calculate the orbit of the object.

19. ASTEROIDS and COMETS

Between MARS and JUPITER there is an immense belt of asteroids, still wider than the distance between earth and sun. The sizes of those asteroids differ from sandgrains to hundreds of meters. There are thousands of them and they create a great risk during space-missions beyond Mars: one single, small stone and it would be the end of the sonde because the speed of a spacecraft is of the order of 40.000 km/h and moreover the average speed of an asteroid is 5 km/s = 18000 km/h!
But nothing happened sofar, the probability is very low indeed.
There have been many impacts on earth during the past, where they are called: "meteorites". On Friday 9. October 1992 a meteorite destroyed the backbunker of a 1980 Chevrolet Malibu in New York, see picture. The stone was saled for $ 59.000 and the car inclusive the damage went for $ 10.000!
More serious are the larger ones: in 1908 a meteorite with a diameter of 60 m smashed into the Tunguska Valley in Siberia, an xplosion heard in London.
September 2002 a meteorite came down 1100 km north of the city Irkoetsk in East Siberia. At least 60 km^2 has been devastated, fortunately an inhabitated area, but Amsterdam would have been wiped out if that piece of stone has been turned up there, an effect corresponding to a strong atomic bomb. It is supposed that this cosmic object is exploded in the air.
Finally on 14. June 2002 a small asteroid, a hundred meter diameter, passed by the earth on 120.000 km, that is less than 1/3 of the distance earth - moon!
There are hundred thousands of such "near-earth asteroids" and it can happen once in a century, but three quarter of the earth is water and there are plenty of regions with little or no population, so the chance is large that no critical area is hit.
The graph in the center of the picture shows that the number of asteroids with large diameter is very low. The majority of the small-sized asteroids will evaporate in the atmosphere.

18. PLUTO

PLUTO, discriminated, a bastard, if you want. Is it a planet or not? Not, in fact, by decision at the International Astronomical Conference in August 2006. It has a diameter of only 2300 km, one sixth of the earth diameter, in volume not yet 0,02 part of the earth. The excentricity of the orbit and slope of the plane deviates highly of those of the other planets, the ellipse crosses the ellipses of the other ones. Perhaps just an object from the Kuiperbelt (discussed later) ? Officially it is now a "dwarf-planet".
Pluto has relatively a very large "moon" on a distance of only 20.000 km, therefore he is often indicated as a "double planet".
Distance to earth: 6 x 10^9 km.

17. NEPTUNE

This is NEPTUNE. Distance to earth: 4.5 x 10^9 km or 4.5 billion km, but in spite of that, one succeeded to manage the VOYAGER with an accuracy of 40 km along the planet after a journey of 12 years. That led the American projectleader to the statement:" That is the heavenly equivalence of a golfball smashed in one blow into a hole in London!" Don't forget that it takes 4 hours for a lightsignal to arrive at the spacecraft and another 4 hours to get an answer!
Moreover, the Voyager is now, 2006, outside our solarsystem, arriving in the area called the "heliopause" where the solarwind is confronted with the interstellar dust, between 12 x 10^9 - 26 x 10^9 km.

16. URANUS

In January 1986 the VOYAGER II arrived at Uranus after a flight of about 10 years. Its speed was then 40.000 km/h. Uranus , at a distance of 2.7 million km and only one third of Jupiter, deviates considerably in composition and atmosphere from that of Jupiter or Saturn: no bands, no patches, no spiral or gasmixtures and a strange, weak magnetic field. Uranus has 27 moons of which the largest ones are given in the second picture. Uranus orbits the sun in 84 year, during that time the position of its rings is variing as seen from the earth: see the third picture. Next year: 2007, the rings will appear edge-on.

15. TITAN MOON of SATURNUS

Saturn has many moons (34!) of which one: TITAN has a thick cloud cover of specifically nitrogen and a little bit of methane. A very interesting and rare moon. Therefore it was decided to send a probe. A probe is a small, light and good manageable craft with little apparatus which makes it easier to let it down to the surface of a moon or planet, in contradiction to normal, large spacecrafts which have all things on board to perform the most diverse measurements, therefore often as large as a single-family dwelling. In 1997 the Huygensprobe has been launched as part of the spacecraft Cassini intended to investigate Titan. In spite of its speed:~ 40.000km/h it took seven years to arrive in January 2005, then the probe was disconnected and landed on Titan, that took 2.5 hours. The situation on Titan is comparable with the situation on earth before the evolution process started and radically changed the atmosphere. It is expected that the observations and analyses by this probe will learn us how the process on earth took place.
This picture gives an impression of the surface of the moon.

14. SATURNUS

After Jupiter comes Saturn, once more 600 million km from Jupiter and three quarter of the volume of Jupiter, Sometimes called "the most beautiful star" in the sky, because of its fascinating and astonishing system of rings. Obviously all other gasplanets (the large ones) appear to have rings as well, but they are very dim. The rings are very thin, consisting of various elements and some are even intertwined. For the rest Saturn resembles at most his big brother Jupiter.
The second photo shows two moons passing through the rings, giving the possiblity for additional and interesting information.

13. COMET FRAGMENTS IMPACT JUPITER

This picture shows the fragments of the comet that smashed into Jupiter and was disrupted by gravitation.

12. COMET IMPACT JUPITER

Everyone will remember the impressive pictures of the impact of the socalled comet Shoemaker-Levy 9 of which 21 fragments plunged into the atmosphere of Jupiter with a speed of 216.000 km/h. See the comet fragments on their way to Jupiter in the next photo. It shows clearly how "tidal forces", result of the enormous gravitationstrength splitting up the comet and stretching the lumps, reducing their dimenions down to a few kilometers at the moment of impact.

11. JUPITER

Jupiter can quite well harbor thirty earths. Its distance is 0,8 billion km from earth and its temperature is about 150° C.
Jupiter is famous for its red spot, where two earths can fit in. His 10 moons are perhaps still more interesting than the planet itself. They are very different, from completely bald, pockmarked boulder to a fire breathng ball, covered with a very thick cloud layer.

10. PLANET ORBITS

Here you see the orbits of the planets, all more or less in the same plane, except Pluto. Note also the large difference in orbit diameter of Mars and Jupiter. Between these orbits there is een enormous belt of asteroids! Tell you later about these asteroids.

9. WATER on MARS

This photo shows that there must have been water on Mars. Most up to date information confirms this supposition. Warm, wet conditions may have prevailed on the planet for long periods during the early history. If the eras of Earth - like conditions were frequent and long, life would have had a better chance of evolving.

8. MARS ROVER

The "rovers" as they are called are all of this type. The length is about 2 meter .