Astronomy for Beginners – Northern Lights

Written by Marko on September 16, 2007

I have been thinking what to write to this “astronomy for beginners” topic series. Should I start from the beginning as it is in astronomy books or should I immediately start writing about telescopes and how to use them? Well, I’m not sure. That’s why I decided to write just random posts, whatever happens to come to my mind. Later on I can reorganize the posts into categories such as “telescopes”, “nebulae”, “stars”, etc.

I come from northern Finland, from Lappland. Over there the night sky is very dark due to lack of artificial lights and temperature can also go below -40 celsius degrees. The conditions are pretty much the same as in northern Alaska. Northern lights can be very, very impressive and stunning. Few times I have seen absolutely awesome northern lights and it is sad that I haven’t been able to catch them with a camera. Next we’ll talk about these northern lights.

Where can they be seen?

Northern lights are a spectacular formation of colorful lights on night sky. Its red, green, blue and blue-red colors become visible on the sky close to the poles. They are difficult to predict but it has been noticed that they exist once a month on average on both hemispheres. On northern hemisphere they are called as Aurora Borealis and on southern hemisphere as Aurora Australis. Aurora Borealis can be seen on the northern side of 50 degrees northern latitude. Aurora Australis can be seen on the southern side of 50 degrees southern latitude. Countries where they can be seen well are Alaska, Canada, Scotland, Norway, Sweden, Finland and Russia (mainly Siberia) on northern side. On southern side the countries are South-America, Tasmania, New Zealand and Southern Australia. The most impressive lights can be seen close to the poles, in places like Cape Evans in Antarctis.

Where do they come from?

Solar wind brings charged particles to the upper levels of Earth’s atmosphere. They move towards northern and southern poles, and while the particles collide with the gas of the atmosphere colorful formations of light can be seen. A typical formation of northern lights looks like a moving belt in which the brightness of colors varies. The colors of northern lights depend on the altitude and the consistence of the atmosphere.

Green-yellow light is caused by oxygen in the altitude of 90-150 kilometers. Red light is caused by oxygen above 150 kilometers and hydrogen around 100 kilometers. A crown is a rear formation of northern lights. It is the most impressive and very bright phenomenon. A crown is a northern light that begins from a spot in the middle of the sky and has very bright rays covering the horizon.

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