1. Science 9: Unit E: Space Exploration Topic 4: Bigger and Smarter Telescopes

2. Bigger Telescopes  A limitation of early telescopes was that they were too small to see that far into space.  Beginning in the 1700s bigger and bigger telescopes were built to see more detail in the universe.  Sir Herschel Walker used a huge telescope and used it to discover Uranus, the first planet discovered since the time of the ancient Greeks.  Modern telescopes are often two or more telescopes combined together. The images from the different telescopes are combined into a single image by a super computer.

3. Adaptive Optics  A problem with telescopes on Earth is that the moving atmosphere distorts the image of the stars and planets; that’s why stars twinkle in the sky.  A way around this problem is to build telescopes where the atmosphere is thinner like on mountain tops.  Another method is to have a computer measure the amount of distortion from the atmosphere and change the shape of the mirror or lens to compensate for the effect of the moving atmosphere. This is called adaptive optics and an example of A.O. is the New Technology Telescope (NTT) in Chile.  To avoid the problem of the atmosphere completely is to have a telescope out of the atmosphere completely. This was the reason the Hubble Space Telescope was built. Having no atmosphere has led to much more detailed images.

4. Triangulation  Triangulation is the method of using a triangle’s geometry to calculate the distance to an object you can’t reach, such as a star.

5. Triangulation  Step 1: Create a baseline. Create two points as far away from each other as possible where you can still see the distant object. The longer the distance between the two points, the more accurate the measurement.

6. Triangulation Cont’d  Step 2: Measure the angles from the end of the baseline. Use a protractor to calculate the angle to the distant object. With stars you need an astrolabe and compass to calculate the azimuth-altitude coordinates of the star.

7. Triangulation Cont’d  Step 3: Make a scale drawing of the triangle you made. Use a protractor to draw in the correct angles and a ruler to accurately draw out the scale model baseline. Make sure you choose a suitable scale factor. The altitude of the triangle is the nearest distance to the distant object.

8. Triangulation Cont’d  When triangulating the distance to stars, the largest baseline we can use is the orbit of the Earth. Therefore the two angle measurements must be made six months apart.  Parallax is the apparent change in position of the stars as the Earth moves along in its orbit.  A limitation of triangulating is that it can only be used on nearby stars.

9. Big Distances  An astronomical unit (AU) is a unit of distance. It represents the distance from the sun to the Earth (150 million km).  1 AU = 150 million km.  For example the distance of Pluto to the sun is 40 AU. The distance of the nearest star to the sun is about 271000 AU.  An even bigger unit of distance is the light year. It represents the distance that light covers in one year. Since light travels at 300’000 km/s this is a very large distance, about 63’000 AU or 9.5 trillion km. The North Star is 431 ly away from us.