Studying astronomy is deeply relevant in out everyday lives - think of the energy we get from the sun, the tides and night light from the moon, Jupiter protects us from many asteroid collisions, other stars used to provide navigation tools, many other planets, stars and galaxies out there.







This is a golden age of astronomy. Technology now allows us to look deep into space







Some telescopes even live in space



However, some of the good that happens else where in the Universe is not necessarily good on Earth, such as nuclear reactions.



The moon provides us with light at night, which is vitally important for the survival of some species. It also creates the tides on Earth. It is gradually slowing down the length of a day on Earth as energy is lost as the tides slosh around.



The only other place that humans have managed to visit



We've all seen Armegedon and Deep Impact. Most asteroids are harmlessly rotating around the sun, like the plants, in a place called the asteroid belt.



Comets are the other main type of heavenly body. Composed of ice and rock.



The Solar System. Earth is just one of nine planets orbiting the Sun.



Mars is perhaps the planet we are most familiar with. This is partly because of the obsession we have for finding life elsewhere.



Maybe it was detected?



There are many, many objects out there though. Personally I think the chances of life having formed elsewhere are pretty high. This is the famous Hubble Deep Field







The Universe is big. We use scientific notation to make the numbers easier to cope with. 12000 = 1.2 x10^4 and 0.0012 = 1.2x10^-3 e.g.



We also need to know where things are on the sky. We use angles



Note things that look close together in projection may not be close in full 3D separation



Degrees are not accurate enough to express positions of apparently small stars.



We split 1 degree into 60 minutes and 1 minute into 60 seconds



Examples - the pointer stars of the big dipper are 5 degrees apart. The moon is 0.5 degrees across.



Your hand make a good ruler



The first real formula! The physical diameter of an object, the distance it is away and the angle it appears to subtends are related. The angle has to be in arc seconds. I prefer this formula to be written alpha = 206265 D/d with alpha in arc seconds and D and d in the same units. This formular tells us how large things appear to be, i.e. if you have an object of fixed diameter, it will appear twice as small if you move it twice as far away.







The parsec is the basic distance unit we use in astrophysics



Being happy with the conversion is an important things. If you are not happy with this, ask! Think about whether the answer should be larger or smaller.



So this is how big the Universe is.















The stars appear to move across the night sky. This is not because they move (well they do but really slowly) but because the earth rotates.



At different times of night, we are facing a different part of the sky. This example is from California.







Also the earth rotates around the sun once per year so at a set time of night, the stars we face are different.



A convieniant way of thinking about this motion is to imagine that the earth is fixed but that the star rotate round on a celestial sphere.



Depending where we are on earth, there are some stars that we can always see and some we can never see.



The earth is titled on it's axis by 23.5 degrees. This causes the seasons. In June (summer in the northern hemisphere), the north is tilted towards the sun. In December (winter in the northern hemisphere) the north is titled away from the sun. Vice versa in the southern hemisphere. If the seasons were caused by the sun being closer and further from the sun, they would be the same in the north and south.



When the earth is titled towards the sun, the sun can get high in the sky and the light from the sun hits the earth directly and gives its energy to a small patch of the earth.



In the winter, the sun is low in the sky and the energy has to be shared over a larger area.



The path the sun moves on is called the ecliptic. The ecliptic is inclined at 23.5 degrees cos of the earth's tilt. On the summer solstice (June 21st in the North) it rises high in the sky, at the winter solstice (Dec 21st in the North) is is low on the sky. This leads to special places on the Earth - the tropics an the circles. At the artic and antartic poles it is light for the 6 months you are tilted towards the sun (summer) and dark for the 6 months you are tilted away. At the artic and antartic circles there is one day when the sun never sets and one day when the sun never rises (June and Dec 21st - you can work out which is which). The tropics are special for different reasons. On June 21st, the sun travels directly overhead at the tropic of cancer (Dec 21st at the tropic of capricorn in the south). The final mark is the equator. At the equinox's (Mar 21st and Sep 21st) there are equal days and nights the sun travels directly overhead i.e. somewhere between the two tropics the sun can be found at the Zenith at midday.



The height the sun can get to depends on where you are on earth, as discussed above. In general, the closer you are to the equator, the higher the sun can get in the sky (true on the equinox's, true above and below 23 degrees all year round).



The earth is precessing round it's axis. Currently the north star is Polaris. This star lies above the north pole at the north celestial pole. This will change in time (not in our lives).



The phases of the moon from full to new back to full, the full phases are full, waning gibbeous, last quarter, waning crescent, new, waxing crescent, first quarter, waxing gibbeous, full.



The sun shines on different parts of the moon, different amounts of the moon are illuminated.



The moon is locked in synchronous rotation - moon rotates about its axis but with the same rotation period as it takes to rotate around the earth. Therefore the same side of the moon faces the earth. There is no such thing as the dark side of the moon though - all parts are illuminated at some part of the rotation cycle.



Moon orbits around the earth on a plane that varies in inclination between -5 and 5 degrees.



If the Earth, Moon and Sun are lined up in a special way you see either a Solar or Lunar eclipse.



Sun, earth, moon = lunar eclipse. Can be seen anywhere where it is night. If moon highly inclined to earths plane then there is no eclipse, hence you do not see a lunar eclipse every full moon. The phase of the moon has to be full for a lunar eclipse to occur.



Get different 'darknesses'.



Sun, moon, earth then a solar eclipse. Cannot see if moon inclined too much (as above) but also the path of moons shadow on the earth is very narrow. Can only be seen from certain parts of the earth.



Lunar eclipse makes the moon look red.



A solar eclipse - the only time you can see the corona







Moons shadow on the earth



Sometimes the moon is far from the earth during eclipse as the moon orbits the earth on a slightly elliptical orbit. This means it has a smaller angular size (think small angle formular) and only covers part of the sun - an annular eclipse