3.3.1 Objects at different wavelengths
The Orion nebula is full of stars – but many of them are hidden from us. This is because their light is prevented from reaching us by dust, which absorbs the light. However, we can see the stars if we look at them at a different wavelength.
What extra information can scientists get by looking at the radiation of different wavelengths that comes from astronomical objects? The answer is simple: objects like planets, stars and galaxies can look very different when observed in different parts of the electromagnetic spectrum.
Figure 13 shows the Orion Nebula – an object that you have seen several times already! But this picture is very different from the one you saw last week. This image, taken by the Chandra Orbiting Observatory, shows radiation from the X-ray part of the spectrum, not the visible part. The very bright stars in the centre of the image are those of the Trapezium Cluster.
Figure 14 and 15 show more images of the Orion Nebula, again with the bright Trapezium cluster in the centre. The first image is taken by NASA’s WISE observatory, of the infrared radiation emitted.
In all the images, the bright stars of the Trapezium cluster can be located, but each image picks up something different. The X-ray image no longer shows the ‘whispy’ part of the nebula – as there are only isolated sources of X-rays. Clearly, whatever is emitting this high-energy radiation is not directly related to the dust that is visible at other wavelengths.
In the next section, you’ll find out more about where telescopes might be located for their most effective use.