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Visible light is only part of what astronomers study. They use different types of telescopes to study the entire electromagnetic spectrum.
When you hear the word astronomy, what do you think of? Most people think of stars. But when you study stars, you’re really studying light. Whether you’re doing research, exploring the night sky, or even just looking up, everything that you observe comes from the light. In a dark sky away from the city, on a clear and moonless night, there's a lot to see!
But there’s also a lot out there you can’t see - at least, not with your naked eye. For these things, astronomers turn to telescopes. Using different types of telescopes, astronomers scan not just visible light but the whole electromagnetic spectrum as they gather information about the universe.
What is the electromagnetic spectrum?
The electromagnetic spectrum is the entire possible range of electromagnetic radiation. We can break up the spectrum into different ranges. These ranges include visible light.
Light is made up of electromagnetic radiation waves. Ranges are measured based on their wavelength. Think of the shape of a wave. Each wave has a crest. The wavelength is the distance from crest to crest.
Here are the ranges of the electromagnetic spectrum from longest wavelength to shortest:
- Visible light
- Gamma rays
Why do colours matter?
Colours are important because different colours represent different wavelengths of light.
In general, visible light is the range of colours that humans can see. The spectrum of visible light spans from red to violet. But that isn't the entire picture! Light can have wavelengths much, much longer than red. It can also have wavelengths much, much shorter than violet. In fact, humans can only see a tiny fraction of all light!
What does the electromagnetic spectrum have to do with astronomy?
Everything! Humans can only see visible light. But that doesn't mean the rest of the universe operates in visible light. Some events and objects can only be detected in different ranges of the spectrum. Sometimes, even details on visible objects can only be detected at these other wavelengths.
So what do astronomers do? They build telescopes that can see these wavelengths.
Radio waves have the longest wavelengths. That means radio telescopes need to be huge in order to collect them. Radio telescopes are the giant dishes you may have seen in movies. Canada has radio telescopes in Ontario and British Columbia.
Recently, radio observatories have actually been able to network different dishes together. This way, they can all work together as if they were one giant dish. This process is called interferometry.
Did you know?
Some of the most distant objects in the universe give us light in radio waves.
There are other telescopes that study phenomena in other wavelengths.
- Microwave observatories have given astronomers insight into the cosmic microwave background. That is a radiation field that permeates the entire universe. The cosmic microwave background was created shortly after the Big Bang.
- Infrared telescopes are good for peering through the dust in our galaxy that blocks visible light. They allow astronomers to see things that might otherwise have been invisible.
- Ultraviolet telescopes have helped astronomers understand the chemical composition of our galaxy. This helps scientists understand how our galaxy evolves with time.
- X-ray and gamma ray telescopes can detect highly energetic particles from some of the most exotic objects in the universe. These telescopes give us plenty of data to study things like neutron stars and black holes.
It takes many different telescopes observing many different wavelengths to get a complete picture of our universe. But no matter what part of the spectrum you observe, there's always something to look at and study. Whether it's online images from NASA or your friend's backyard telescope, new sights are only a peep away!