Page 7 - Curriculum Visions Dynamic Book

Observing stars
During the 1700s, ever more powerful telescopes were built. That allowed people such as the British astronomer William Herschel and his son John to measure enormous numbers of faint stars and to try to find how they are placed in the Universe. Herschel was the first to realize that stars are enormous distances apart.
Later, photographic evidence would show that stars are not truly fixed in position, but move very slowly across the sky. They only appear unmoving because of their enormous distances from us.
The sky at night
One of the problems in understanding how the Universe works is the need to get a clear view of where everything is. Although since earliest times people have been able to look at the sky and see stars and some planets, they have always seen them from the same position. That can produce a distorted view of the real shape and position of objects in space.
For example, we see a band of concentrated stars sweeping over the sky, and we call them the Milky Way. But they
are not a band. Instead, they are the edge of a flattened disk containing countless stars. From Earth we cannot see the true shape of the galaxy of stars in the Milky Way.
Similarly, when we look at our Sun, it is not at all obvious to us that it is just like the stars we see at night. That is because it is so close that we see it as a yellow-white coloured disk. The nearest star is so far away that we cannot see it as a disk at all, but only as a point of light. This is the same effect as we get when we see car headlights far off at night. They seem to be just two points of light; but as the car gets closer, we can see the twin headlights as two yellow-white disks.
Many features of the Universe are like this. For example, many of the largest structures in the observable Universe are so far away that they can only be seen as points or blurs of light. And if they do not shine with their own internal light (which includes X-rays and radio Waves), we do not see (detect) them at all.
atom The smallest particle of an element. galaxy A system of stars and interstellar
matter within the Universe.
hUbble space telescope An orbiting telescope (and so a satellite) that was placed above the Earth’s atmosphere so that it could take images that were far clearer than anything that could be obtained from the surface of the Earth.
laWs of motion Formulated by Sir Isaac Newton, they describe the forces that act on a moving object.
milky Way The spiral galaxy in which our star and Solar System are situated.
radio Waves A form of electromagnetic radiation, like light and heat. Radio waves have a longer wavelength than light waves.
sensor Adeviceusedtodetectsomething. solar system The Sun and the bodies
orbiting around it.
 The Hubble space telescope, which took most of the images in this book, does not “see” space. Its sensors detect a range of wavelengths of radiation other than light. The colours shown
in its images are not always what we would see if we were to go into space. Instead, colours are used to represent temperature, for example, or they can display wavelengths of radiation that we would never see at all.
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