39. DARK MATTER PROOF

Hubble sees the graceful dance of two interacting galaxies
30-October-2007 Two galaxies perform an intricate dance in this new Hubble Space Telescope image. The galaxies, containing a vast number of stars, swing past each other in a graceful performance choreographed by gravity.A pair of galaxies, known collectively as Arp 87, is one of hundreds of interacting and merging galaxies known in our nearby Universe.
The resolution in the Hubble image shows exquisite detail and fine structure that was not observable when Arp 87 was first catalogued in the 1960ís.
The two main players comprising Arp 87 are NGC 3808 on the right (the larger of the two galaxies) and its companion NGC 3808A on the left. NGC 3808 is a nearly face-on spiral galaxy with a bright ring of star formation and several prominent dust arms. Stars, gas, and dust flow
from NGC 3808, forming an enveloping arm around its companion. NGC 3808A is a spiral galaxy seen edge-on and is surrounded by a rotating ring that contains stars and interstellar gas clouds. The ring is situated perpendicular to the plane of the host galaxy disk and is called a
ìpolar ring.îAs seen in other mergers similar to Arp 87, the corkscrew shape of the tidal material or bridge of shared matter between the two galaxies suggests that some stars and gas drawn from the larger galaxy have been caught in the gravitational pull of the smaller one.
The shapes of both galaxies have been distorted by their gravitational interaction with one another.
(News Release Number: STScl - 2007-36
Image credit: NASA, ESA, and The Hubble Heritage Team (STScI/AURA))

Such collisions gives us the possibility to study the famous, but mysterious "Dark Matter".

Is dark matter really existing?
Yes,it is!
This composite image shows the galaxy cluster 1E 0657-56, also known as the "bullet cluster." This cluster was formed after the collision of two large clusters of galaxies, the most energetic event known in the universe since the Big Bang.

These observations provide the strongest evidence yet that most of the matter in the universe is dark.
In galaxy clusters, the normal matter, like the atoms that make up the stars, planets, and everything on Earth, is primarily in the form of hot gas and stars. The mass of the hot gas between the galaxies is far greater than the mass of the stars in all of the galaxies. This normal matter is bound in the cluster by the gravity of an even greater mass of dark matter. Without dark matter, which is invisible and can only be detected through its gravity, the fast-moving galaxies and the hot gas would quickly fly apart.

This image is not a real photo, it is a computer simulation. The blue areas in this image show where astronomers find most of the mass in the clusters (mostly dark matter!!). The concentration of mass is determined using the effect of so-called gravitational lensing, where light from the distant objects is distorted by intervening matter. Most of the matter in the clusters (blue) is clearly separate from the normal matter and gaseous clouds (pink), giving direct evidence that nearly all of the matter in the clusters is dark.
The hot gas (pink) in this collision was slowed by a drag force, similar to air resistance. In contrast, the dark matter was not slowed by the impact, because it does not interact directly with itself or the gas except through gravity. This produced the separation of the dark and normal matter seen in the data. If hot gas was the most massive component in the clusters, as proposed by alternative gravity theories, such a separation would not have been seen. Instead, dark matter is required.
This really is a beautiful proof of the existance of DARK MATTER !!

38. STARDUST 2

Undersea corral? Enchanted castles? Space serpents? These eerie, dark pillar-like structures are actually columns of cool interstellar hydrogen gas and dust that are also incubators for new stars. The pillars protrude from the interior wall of a dark molecular cloud like stalagmites from the floor of a cavern. They are part of the "Eagle Nebula" a nearby star-forming region 7,000 light-years away in the constellation Serpens. The pillars are in some ways akin to buttes in the desert, where basalt and other dense rock have protected a region from erosion, while the surrounding landscape has been worn away over millennia. In this celestial case, it is especially dense clouds of molecular hydrogen gas (two atoms of hydrogen in each molecule) and dust that have survived longer than their surroundings in the face of a flood of ultraviolet
light from hot, massive newborn stars (off the top edge of the picture). The tallest pillar (left) is about a light-year long from base to tip. As the pillars themselves are slowly eroded away by the ultraviolet light, small globules of even denser gas buried within the pillars are uncovered.
The picture was taken on April 1, 1995 with the Hubble Space Telescope Wide Field and Planetary Camera 2. The color image is constructed from three separate images taken in the light of emission from different types of atoms. Red shows emission from singly-ionized sulfur atoms. Green shows emission from hydrogen. Blue shows light emitted by doubly- ionized oxygen atoms.
But don't think it is just a little "object", actually it is a very, very little part of an immense composition of clouds! See the picture below!

This majestic view taken by NASA's Spitzer Space Telescope tells an untold story of life and death in the above mentioned Eagle nebula, an industrious star-making factory located 7,000 light-years away. The image shows the region's entire network of turbulent clouds and newborn stars in infrared light. The color green denotes cooler towers and fields of dust, including the three famous space pillars, dubbed the "Pillars of Creation," which were photographed by NASA's Hubble Space Telescope in 1995 (right of center).
But it is the color red that speaks of the drama taking place in this region. Red represents hotter dust thought to have been warmed by the explosion of a massive star about 8,000 to 9,000 years ago. Since light from the Eagle nebula takes 7,000 years to reach us, this "supernova" explosion would have appeared as an oddly bright star in our skies about 1,000 to 2,000 years ago.
According to astronomers' estimations, the explosion's blast wave would have spread outward and toppled the three pillars about 6,000 years ago (which means we wouldn't witness the destruction for another 1,000 years or so). The blast wave would have crumbled the mighty towers, exposing newborn stars that were buried inside, and triggering the birth of new ones.


This photo shows the famous "Horsehead Nebula", which is situated in the Orion molecular cloud complex. The distance to the region is about 1400 light-years (430 pc).
This beautiful colour image was produced from three images.
There is obviously a wealth of detail, and scientific information can be derived from the colours shown in this photo. Three predominant colours are seen in the image: red from the hydrogen (H-alpha) emission from the HII region; brown for the foreground obscuring dust; and blue-green for scattered starlight.
The blue-green regions of the Horsehead Nebula correspond to regions not shadowed from the light from the stars in the H II region to the top of the picture and scatter stellar radiation towards the observer; these are thus `mountains' of dust. The Horse's `mane' is an area in which there is less dust along the line-of-sight and the background (H-alpha) emission from ionized hydrogen atoms can be seen through the foreground dust.
At this high resolution image the Horsehead appears very chaotic with many wisps and filaments and diffuse dust. At the top of the figure there is a bright rim separating the dust from the HII region. This is an `ionization front' where the ionizing photons from the HII region are moving into the cloud, destroying the dust and the molecules and heating and ionizing the gas.
Such structures are only temporary as they are being constantly eroded by the expanding region of ionized gas and are destroyed on timescales of typically a few thousand years. The Horsehead as we see it today will therefore not last forever and minute changes will become observable as the time passes.

37. STARDUST

It is true that looking to the Milky Way on a cloudness night you still will see black smudges, as if there are many interruptions. But that is the result of a lot of dust clouds, “stardust” as it is named, filling the emptiness a bit.
What’s that: stardust?
We should distinguish between gasses, stardust and dark matter if speaking of clouds in space.
Gasses consists of atoms and/or molecules.
Stardust consists of very small molecular structures of the order of 1 to .001 micron.
Dark matter enclose matter particles not radiating light or very little particles as neutrino’s but also minor black holes, but for the main part perhaps unknown exotic particles. So in fact all what has a certain mass but always extreme dim. The most important feature of dark matter is that it must necessarily contribute to the gravitation but without any mutual attraction what means no pressure effects as in a gas. The reason for supposing such matter is that e.g. movements of stars in galaxies can not be explained by gravitation from centres of mass or other visible objects, so other sources of gravitation are necessary.

Eta Carinae, located 10,000 light-years from Earth, was once the second brightest star in the sky. It is so massive, more than 100 times the mass of our Sun, it can barely hold itself together. Over the years, it has brightened and faded as material has shot away from its surface. Some astronomers think Eta Carinae might die in a supernova blast within our lifetime.
Eta Carinae's home, the Carina Nebula, is also quite big, stretching across 200 light-years of space. This colossal cloud of gas and dust not only gave birth to Eta Carinae, but also to a handful of slightly less massive sibling stars. When massive stars like these are born, they rapidly begin to shred to pieces the very cloud that nurtured them, forcing gas and dust to clump together and collapse into new stars. The process continues to spread outward, triggering successive generations of fewer and fewer stars. Our own Sun may have grown up in a similar environment.

36. SOMBRERO GALAXY

Our own galaxy should have been formed like this magnificent edge-on picture of the Sombrero Galaxy, having the size of the Milky Way. At a distance of 28 million ly and 82.000 ly wide it can be found in the constellation VIRGO. It is one of the larges Hubble mosaics ever assembled, the team took six pictures of the galaxy and then stitched them together to create the final composite image.The photo reveales a myriad of stars in a pancake-shaped disk as wel as a glowing central bulge of stars.

35. DISTRIBUTION OF GALAXIES

We know that the universe is filled up with clusters and superclusters like that of our own galaxy, the Milky Way, and its companions, containing billions and billions and billions of stars and much more!! Nevertheless here again: here is emptiness as well! It is estimated that the intergalactic distances in a cluster of galaxies is of the order of 10^24 cm = 10^6 lightyear!
Michael Strauss of the Princeton University constructed a map of far remote galaxies and it appeared that they were distributed in a very homogeneous way The whole projected surface of the sky has been covered with it, an effect of the two-dimensional reproduction, in reality the mutual distances were on average a million lightyear.

Space is really unimaginable empty, albeit that we have to be cautious with such statements: astronomers responsible for tthe Hubble-telescope just took it as read because of Christmas and oriented their telescope to an according to their opinion empty part of space and let it gone its way, all measuring. On New Years day, after 240 hours measuring, they went to the telescope interested in the results. It appeared that the picture was filled completely with more than thousand galaxies. If that would be valid for the whole universe, there should be more than 50 billion galaxies! Hubble had proved that the boundary of the universe lies very much farther than previously assumed and such a statement is still valid.

An empty universum it seems, but it does not mean that there is no mutual contact, for as already said about our Milky Way, starsystems can absorb other systems, being fully integrated. Collisions between galaxies occur continuously, of which the image above is a nice example. What happens then is giantic, an enormous intensive integration process characterized by the creation of many new stars, Such a process takes billions of years before finally one single, more massive, galaxy results.
The image shows two colliding galaxies in the constellation CANIS MAJOR at a distance of 140 million ly being completely integrated within a 500 million years.

Below a picture of one of the largest galaxies in the universum: the SPIDERWEB GALAXY (constellation HYDRA) on a distance of 10,6 billion ly from earth. In the middle of the "web" there is a very large black hole that captures its victims - smaller galaxies of the size of our Milky Way - in an inescapable net of gravitation. Hundreds of galaxies in this cluster at distances of hundredthousands ly and speeds up to hundreds km/sec. are absorbed by this "black widow".

34. A CHOICE OF ASTRONOMIES

The introduction showed the possibilities we have to get information about the stars and galaxies by observing objects at wavelengths other than those of visible light. Here follows another example:
Four views of the Andromeda Galaxy M31, at different wavelengths give an impression of he power of "multispectral astronomy". By visible light (4) the galaxy appears as a spiral, disk-like aggregation of stars with as bright central bulge.
Infra-red rays (5) come from the galaxy's dust clouds and cool stars, and the rings colour-coded yellow may show where new stars are forming. In radio emissions at 21 centimeters (6) the central bulge disappears. Instead what we see is the galaxy's outlying stock of hydrogen gas, which approaches us (blue) or recedes (red) as the whole galaxy rotates in a clockwise fashion. The fourth view is a close-up of the central region of the galaxy as seen by X - rays (7). Two of the scattered sources registered by the European EXOSAT satellite have flared up since the same region was observed by the American EINSTEIN satellite a few years arlier.

33. THE LOCAL GROUP

The Local Group is the group of galaxies that includes our galaxy, the Milky Way. The group comprises over 30 galaxies, with its gravitational center located somewhere between the Milky Way and the Andromeda Galaxy
The two closest galaxies to the Milky Way are called the Magellanic Clouds, which may be viewed as satellite galaxies to the Milky Way at a distance of a little less than 200,000 light years.
They are only visible in the Southern Hemisphere, but can easily be seen by the naked-eye and their brightest stars can be seen with binoculars. They are irregular galaxies and are much smaller than the Milky Way. Below the Large Cloud and a more accurate detail of it showing that is not exactly a "cloud".




Two galaxies are visible to the naked-eye in the Northern Hemisphere. The Andromeda Galaxy (M31) is a great spiral galaxy much like our own at a distance of about 3 million light years. This galaxy and the Milky Way are approaching each other with a speed of 119 km/sec and will collide with each other within 6.3 billion years.


The other galaxy of the local group that is visible to the naked eye is the spiral M33 in Triangulum at a distance comparable to that of Andromeda. It too is a spiral galaxy, but it is smaller than Andromeda and therefore is harder to see.


The Local Group moves with a speed of 600 km/sc to a point in space which is called: the"GREAT ATTRACTOR" in the constellation "HYDRA"

32. CONSTELLATIONS

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.

31. WHIRLPOOL GALAXY

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

30. BLACK HOLES

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.

29. MILKY WAY

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.