Caroline Herschel was a famous astronomer. She discovered eight comets, and made observations of nearby stars and distant galaxies. She did all this 200 years ago, during a time when women didn’t usually have jobs in science, and she was the first woman to be paid for her scientific work.
The planet can be found moving from the centre to the right in the picture...
Analysis and evaluation
Scottish Curriculum Links
Planet Earth - Space
By researching developments used to observe or explore space, I can illustrate how our knowledge of the universe has evolved over time.
New comets are still discovered every year. Although large telescopes owned by huge space agencies - such as NASA - can scan the skies, a surprisingly large number of comets are found by amateur astronomers. These people who enjoy studying astronomy as a hobby use the same technique that Caroline Herschel would have used.
Today, as in the past, amateur astronomers look for a fuzzy patch of light through their telescopes. Once they have found a patch of light, they need to check that it isn't a distant galaxy or cluster of stars that has already been identified - they can check it in a catalogue, like the ones Caroline Herschel created. Then finally, they need to watch it! Comets move across the sky while the stars appear to stay still.
Planets also move across the sky, and William Herschel, Caroline's brother, found Uranus using this technique. In the 1930s, Pluto was discovered using photos of the sky taken at different times.
Professional astronomers are now searching for planets around other stars. They do this by watching the light from a particular star. If there is a very large planet orbiting it, the planet blocks out some of the light and the star appears a little dimmer. Or sometimes the planet's gravity makes the star wobble, and this wobble can be seen by looking at how the colour of the star's light changes. So far, well over one hundred planets have been found outside our solar system.
|Key fact: Studying how objects move across the sky allows astronomers to identify them.|
Planets and comets move while the background stars stay still. Here are two drawings of the night sky. How good are your observational skills? Can you find the planet in these pictures?
You don't even need a telescope to do your own astronomy. You can use the night sky for navigation, and some planets are easy to spot when you know where to look.
When and where?
Looking at the sky is best done on a dark night when the moon isn't full, far away from things like street lights, and when there aren't any clouds. But it doesn't have to be exactly like this. Go somewhere as dark as possible. If you can't avoid street lights, use a piece of paper, card or even your hand to block the light out. Be very careful if you are somewhere dark not to trip up. Remember to keep warm in winter - it can get very cold if you are standing out for a long time. And make sure you are not alone, and people know where you are going to be.
First find the constellation Ursa Major. You've probably seen it before.
This constellation looks like a saucepan. The stars are very bright, so you can see it even if you are in the middle of a city. It can also be seen in the UK all year round.
Find Ursa Major in the sky, and then follow a line up from the 'pan' bit of the saucepan up until you meet the next bright star. This is the North Star. When you face it you are always looking north.
You won't be able to see the Whirlpool Galaxy with your naked eyes, but this was one of the fuzzy patches of light that Caroline Herschel would have been familiar with, when she was searching for comets.
Finding the planets is a little harder, but well worth it. During the day, get used to where the sun rises, the path it traces across the sky, and where it sets. This is called the ecliptic. The Moon and all the planets follow this path, more or less.
To find out what planets are visible where you live have a look at http://www.heavens-above.com/ Choose 'Current observing site from database' and pick out where you live. Select 'Whole sky chart' and then pick the day and time that you want to be out looking for planets. The sky chart is drawn as if you were looking up at the sky.
Planets are bright - brighter than most stars - and they don't tend to twinkle like stars do. So look along the ecliptic and see if you can spot anything bright. As Venus is closer to the sun than the Earth, you can find Venus either following the sun down at sunset, or up just before the sun at sunrise. Mars is slightly red in colour.