The constellations are totally imaginary things that poets, farmers and astronomers have made up over the past 6,000 years and probably even more! In Mesopotania an inscription of the Assyrians has been found showing about 20 names of constellations, one of it is the name: Ursa Major or the BIG DIPPER. Excavations learn us that there existed more than 30.000 years ago already a real bear cult!
The real purpose of constellations is to help us to tell which stars are where, nothing more. On a really dark night, you can see about 1000 to 1500 stars. Trying to tell which is it, is hard. The constellations help by breaking up the sky into more managable bits. They are used as mnemonics, or memory aids. For example, if you spot three bright stars in a row in the winter evening, you might realize, "Oh! That's part of Orion!" Suddenly, the rest of the constellation falls into place and you can declare: "There's Betelgeuse in Orion's left shoulder and Rigel is his foot." And once you recognize Orion, you can remember that Orion's Hunting Dogs are always nearby.
It seems likely that the Greek constellations originated with the Sumerians and Babylonians. From there, knowledge of the constellations somehow made its way to Egypt (perhaps through the Minoans on Crete who had contact with the Babylonians and settled in Egypt after an explosive volcanic eruption destroyed the original civilization)

The constellation CETAURUS represents Chiron who is frequently mentioned in Greek mythology. Chiron was one of the Centaurs, barbarous beasts which were said to be half-horse and half-human. But unlike the others, Chiron was extremely wise and tutored Hercules and Jason. Unfortunately, Hercules accidentally wounded Chiron. The immortal centaur, in great pain, pleaded with the gods to end his suffering. Zeus mercifully let him die and gave him a place among the stars.
The hoofs indicate two stars, the left one being ALPHA CENTAURI, the most nearest star to the sun at a distance of 4.3 ly.

Traveling to Proxima Centauri:
Proxima Centauri (part of the Alpha Centauri star system) has been suggested as a logical first destination for interstellar travel, although as a flare star it would not be particularly hospitable. The current standard spaceship, the Space Shuttle, travels in orbit at 7.8 km/s. At that speed, it would take 160,000 years to reach Proxima. The fastest man-made spacecraft, the HELIOS II - deep space probe, has set a speed record of 70.2 km/s. Even at that speed, the journey to Proxima Centauri would take 18,000 years. The proposed VASIMIR propulsion system, possibly able to achieve speeds up to 300 km/s, would shorten the journey to a "mere" 4,200 years —still firmly beyond the current lifespan of both man and machine. It follows that interstellar travel would require significant development of radical ideas to become feasible, such as the hypothetical generation of ships: laser-pushed solar sails, nuclear fusion powered Bussard ramjets, nuclear pulse drives or warp drives.

The images shown here above and below give two Greek constellations based on old myths together with their modern indications by just connecting the stars composing them.



This image of a famous galaxy : the Whirpool galaxy, gives us a good idea of how our own galaxy, the Milky Way, is composed.
The graceful, winding arms of the majestic spiral galaxy M51 (NGC 5194) appear like a grand spiral staircase sweeping through space. They are actually long lanes of stars and gas laced with dust.

This sharpest-ever image of the Whirlpool Galaxy, taken in January 2005 with the Advanced Camera for Surveys aboard NASA's Hubble Space Telescope, illustrates a spiral galaxy's grand design, from its curving spiral arms, where young stars reside, to its yellowish central core, a home of older stars. The galaxy is nicknamed the Whirlpool because of its swirling structure.

The Whirlpool's most striking feature is its two curving arms, a hallmark of so-called grand-design spiral galaxies. Many spiral galaxies possess numerous, loosely shaped arms which make their spiral structure less pronounced. These arms serve an important purpose in spiral galaxies. They are star-formation factories, compressing hydrogen gas and creating clusters of new stars. In the Whirlpool, the assembly line begins with the dark clouds of gas on the inner edge, then moves to bright pink star-forming regions, and ends with the brilliant blue star clusters along the outer edge.
Some astronomers believe that the Whirlpool's arms are so prominent because of the effects of a close encounter with NGC 5195, the small, yellowish galaxy at the outermost tip of one of the Whirlpool's arms. At first glance, the compact galaxy appears to be tugging on the arm. Hubble's clear view, however, shows that NGC 5195 is passing behind the Whirlpool. The small galaxy has been gliding past the Whirlpool for hundreds of millions of years.

The Whirlpool is one of astronomy's galactic darlings. Located 31 million light-years away in the constellation Canes Venatici (the Hunting Dogs), the Whirlpool's beautiful face-on view and closeness to Earth allow astronomers to study a classic spiral galaxy's structure and star-forming processes



A black hole is a very high concentration of mass exercizing an enormous strong gravitation force. Even light cannot escape that force.

A supermassive black hole is a black hole with a mass of an order of magnitude between 10^5 and 10^10 (hundreds of thousands and tens of billions) of solar masses. It is currently thought that most, if not all galaxies, including the Milky Way, contain supermassive black holes at their galactic centers. Most smaller black holes are generated from collapsing stars, which range up to perhaps 10 solar masses. The minimal supermassive black hole is in the range of a hundred thousand solar masses. There is a lot of evidence that Sagittarius A* is the supermassive black hole residing at the center of the Milky Way, calculated to have a mass of 3.7 million solar masses.
The hole itself is invisible, you see its surroundings in the galactic centre, to be found in the constellation "Sagittarius".
The first picture shows an artist's conception (top) of a supermassive black hole drawing material from a nearby star. At the bottom: images believed to show a supermassive black hole devouring a star in galaxy RXJ 1242-11, at the left side: X-ray image, at the right side: optical image.

This 400 by 900 lightyear mosaic of several Chandra images of the central region of our Milky Way galaxy reveals hundreds of white stars, neutron stars and small black holes bathed in an incandescent fog of multimillion-degree gas. The supermassive black hole at the center of the galaxy is located inside the bright white patch in the center of the image. The colors indicate X-ray energy bands: red (low) - green (medium) - blue (high).
A still more accurate photo is given in the third picture.
The white spots indicate the real centre.




Here a picture ,which is not simple "artificial", because it is based om an enormous quantity of measurements. So it is very "realistic" in a sense!
Our galaxy, where we live in, is called: the MILKY WAY, but is, like the sun, a good average with its diameter of 100.000 lightyear. It has a flat spiral shape, in the centre spherically thickened to a thickness of 10.000 lightyear, while the region in which our sun is found has a thickness of about 400 ly. The sun's location is at a distance of 28.000 ly from the centre of the Milky Way. The sun is orbiting that centre with a speed of 250 km/sec. Roughly 200 billion stars have been counted in our galaxy, that has also some neighbours, such as the smaller galaxies: the MAGELLANIC CLOUDS, a system that will be merged with ours in the long run and then completely integrated. In the centre of the Milky Way there is a so-called "black hole", with an very strong attractive power pulling all surrounding matter.
It seems to be rather crowded in the galaxy with so many stars, but if we calculated the average distance between two stars then it appears to be of the order of 4.4 lightyear! Accidentally it is about the distance between the sun and its nearest star: Alpha Centauri: 4.3 ly. But was is "nearest"? Flying to that star with a aeroplane, say a "Hunter" with a speed of ~1000 km/h it will take about 4 million years to arrive there!
Anyhow, also our Milky Way is astonishing empty!



28. Introduction GALAXIES

Radiation is the most used tool to get information about phenomena and objects in the universum.
The frequency band comprises frequencies from 50 Herz for household plugs, to low frequencies for telephony - radio and tv - microwaves -infrared light - visible light, up to high frequencies for ultraviolet light - X-rays - gamma rays - cosmic radiation with 10^24 Herz!
Note that scaling in the above given radiation pictures is logarithmic and that the visible light frequencies lie within not more than 3000 Hz!! Indeed our eyes are of a very poor quality!
A disadvantage of radiation is that we never see what is "now": looking into a mirror at a distance of 1 meter means seeing the image of 6 nanoseconds before.
It takes about 8 minutes for sunlight to arrive at the earth.
But yet we can "look" at frequencies over the whole spectrum by translating measured frequencies into visible frequencies:
For example, in the black and white Chandra X-ray image of the supernova remnant Cassiopeia A (Cas A) shown on the left, the darker shades represent the most intense X-ray emissions, the lighter shades of gray represent the areas of less intense emission, and the white areas represent the areas of little to no emission. In the yellow and orange version in the middle, a different "color code" was shown. There, the white and yellow colors represent the areas of highest X-ray intensity, the orange to red areas represent the areas of lower intensity, and the black represents little or no emission. Computerprogrammes translate energy intensities into visible frequencies.
The version of Cas A on the right shows an image constructed by selecting different X-ray energy bands from the data, and using a color code to represent these. This representation can highlight temperature variations in the gas, with higher temperatures associated with higher energy X-rays.

Finally, we will use very often as measure of distances the LIGHTYEAR.
One lightyear or 1 ly = 9,4 x 10^17 cm
= 10 trillion km
= tienduizend billion km
= 10 x million x million km (the simplest way to remember it)

and also:
Maas of the earth = 10^24 kg
Mass of the sun = 10^30 kg, that is one million times mass earth.



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.



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.




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.



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.



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.



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.



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?



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.



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.




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.



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.



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.



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.



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.



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



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.



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.



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.



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.



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



The Victoria Crater on Mars with a diameter of 800 meter, result of a meteorite impact.
The part on the left with the rover: "Opportunity" is enlarged on the second photo.



A lot is known about the planet Mars because of the large number pf spacecrafts and spacesondes visiting the planet. Many more are coming! The distance is 90 million km from the earth and its volume is 1/6 of the earth.
Main question is: is there or was there life on Mars?


5. MISSION to the MOON

This is Buzz Aldrin on the moon d.d 19 July 1969 during the first expedition to the moon by the Apollo 11, the first time since the existence of the human species and since the creation of all life, a living being put his feet on a heavenly body, that is not the earth! A revolutionary step!



This photo had been taken by the Voyager II when just passing Pluto and leaving our solar system at a distance of
6 x 10^9 km and 13 year after launching. You see the planets Saturn, Uranus, Neptune aand Venus, Earth, Jupiter.
Stars in the background are blended.


2. EARTH from the MOON, APOLLO 17 and MARS

The earth seen from the moon, 1968, Apollo 8, the first time a human being saw the earth from another space object than the earth!

This picture at the left has been taken by Apollo 17 shortly after leaving earth for a trip to the moon. You will recognize Africa at the right side and and a part of America at the left.

This picture is taken by a spacecraft orbiting the planet Mars. You see the earth and an artificial impression of what Mars really saw! See also next picture.
This is the original picture of how Mars sees the earth and its moon!

The rotation velocity of the earth is 1700 km/h and its orbital speed around the sun is 35 km/sec.!
It is a sphere with a diameter of about 13.000 km with an extreme thin atmosphere layer, less than ~ 0.1% of its diameter. But there is life on earth, because of its volume, its mass, because of the gravitation binding the atmosphere, because the distance to the sun giving exactly the right temperature and thanks to the composition of the atmosphere there are exactly the right elements (water!) and raw materials to make life possible.
A small ball, so insignificant, so invalid in the gigantic universe that it can oppressing anybody realizing that.



With respect to the photo showing the planets with their sizes on scale, note that the distances are not on scale! The planets Venus, Mercury, Earth and Mars are called "the small planets" or "the planets of the inner solar system", the "large planets" of the" outer solar system" are Jupiter, Saturn, Uranus and Neptune. Pluto is no longer called a "planet" but a "dwarf planet" and perhaps not a real planet at all.
You see in the picture that there are more "dwarf planets".