Seeing beyond the rainbow
Introduction
We think of a rainbow going from red to violet because that is what our eyes can see, but there are colours beyond the rainbow that can be seen with special telescopes!
Beyond red there is infrared light and beyond that, microwaves and radio waves.
Beyond violet there is ultraviolet light, X-rays and gamma rays.
We learn a lot of new information about objects in space by looking at them in all these different types of light.
The nearby Andromeda galaxy looks very different when seen through telescopes that detect different types of light. The image below shows the galaxy taken with different telescopes that "see" in different types of light.
Credit: infrared: ESA/Herschel/PACS/SPIRE/J. Fritz, U. Gent; X-ray: ESA/XMM-Newton/EPIC/W. Pietsch, MPE; optical: R. Gendler
Basic Instructions for Visitors
Press the buttons to see the mysterious patch of sky called Barnard 68 in different colours. Even in colours we cannot see with our eyes!
You can carefully move the camera to look up at yourself, or at the Barnard 68 model on the table!
Detailed Instructions for Visitors
On the front-left of the desk there is a large rectangular board, which is coated in plastic, and has five circular buttons towards the front. These buttons control a camera that is towards the centre-front of the desk and has the shape of an irregular tower about 50 cm tall. The buttons select different type of light (wavelength) that the camera will see with. The top of this camera can be rotated gently with the ball-shaped handles. Allowing the camera to point either towards the desk or towards yourself. The camera is attached to one of the monitors at the back of the table. This monitor shows what the camera is seeing. There is also a second monitor which displays some information about each type of light (provided below).
On the front right of the desk is angled box. This top of this box has a plastic top which has a picture of a patch of sky on it. The camera points towards this picture when orientated towards the desk. This is a tactile and heated model that you can explore with your hands. An explanation is given here to what is going on in the image.
This image looks like a field of stars (points of light) of different colours (blue, red, and yellow-green). In the centre there is a large black splodge where only black can be seen. The model is also tactile so you can feel where some of the stars are located. Interestingly, whilst the eyes can not see any stars in the central black splodge, there are stars there - they are just hidden by dust and can not been seen in visible light!
When you select the left-most button on the board, the camera is seeing in blue-light. The bluest stars appear most bright in this image. Blue stars are the hottest stars, reaching 10s of thousands of Kelvin.
When you select the next button (working to the right), the camera is seeing in green-yellow light. The yellow-green stars appear brightest in this image. The Sun is this type of colour and they are "middle" temperature stars (around 5000-6000 degrees).
The next button (the third from the left) selects the camera to see in red light. The reddest stars are brightest in this image. Red stars are cooler, with temperaturs of a couple of thousand degrees.
Moving to the fourth button from the left, things become interesting! We have now moved to colours beyond red, into the near-infrared. Our eyes can not see infrared light, so we need special camera for this. Now in the image, we can see that there are stars hiding behing the black patch. They can been seen in the near-infrared, but not with visible light. If you feel the model image you will feel the circles where these stars are in the central part. Many ground-based telescopes can see in near-infrared, including the Very Large Telescope.
The final button (the right-most) selects far-infrared light for the camera. Now we are seeing colours way beyond what we can see with our eyes. The image no longer shows any stars, but a glowing splodge in the centre. This glowing splodge is exactly where the black splodge is in the visible light. This is because there is dust in this region which is giving out some heat. This heat produces a glow in the far infrared. If you touch the model you will be able to feel the heat in this region. The Herschel Space Observatory is an example space-based telescope that could see in the far-infrared.
There we have it! Our eyes can only see a tiny part of what is going on in the Universe. Some of the Universe only becomes apparent to us if we use special cameras that use colours beyond red.