Above: The Large Magellanic Cloud, a satellite galaxy of the Milky Way, is located nearly 200 000 light years from Earth. Photographed by the Hubble Space Telescope (NASA)
Did you know? Images from the Hubble Space Telescope have helped determine the age of the universe.Photographers have been capturing the beauty of nature since the mid 1800s. Over the decades, they have provided stunning images from mountain peaks to ocean depths. However, only recently has it become possible to photograph much of the heavens. Newer, more powerful telescopes can capture images of objects millions of light years away, giving us a glimpse into strange new worlds: fiery ribbons of interstellar dust and gas, cloud-like nebulas, and glowing galaxies!
There's more to photographing outer space than simply taking a snapshot. To create full-colour images of space using astronomical data takes a lot of work. Although telescopes allow stargazers to view things they could never hope to see with the naked eye, most of what is seen through a telescope can still only be perceived in black and white.
Did you know? Your eyes are better at distinguishing between different colour hues than between shades of grey. As a result, colour images of space often appear more detailed than black and white ones.This is because your eyes use two different types of light sensitive cells. Rod cells allow you to see in dim light, like at night. Cone cells allow you to see colours, but they require more light. Even with the help of a telescope, light coming from far-away nebulas is simply too faint for the cone cells in your retinas to distinguish much colour. Instead, you see these objects using our dim-light receptors – the rod cells – and colourful clouds of dust and gas appear in shades of grey.
So how do space photographers produce true-to-life colour images if pictures taken with a telescope are in black and white? Space photographers usually take many different pictures of the same object using different colour filters. Imaging specialists can then use these black and white images to create beautiful colour pictures of space.
First, the image-processing team considers the colour filters through which the images were taken. The colours we see in everyday life are actually caused by wavelengths of light. Different wavelengths allow us to see different colours, but a filter only lets through a certain wavelength of light (and thus a certain colour). Thus, colour images can be created based on the colour of filter used, even if the original image is in black and white.
To view some amazing images of space, visit the Hubble Space Telescope gallery:
http://hubblesite.org/gallery/ The team then considers how an object emits or reflects light. For example, Mars is red because of iron oxides that absorb green wavelengths of light. The final product is an informative picture of faraway stars and galaxies.
The Hubble Space Telescope is one of the most famous telescopes. To create beautiful, colourful images of space, the Hubble team uses a version of Adobe Photoshop – a program you may use at home! In fact, team members say that creating these images is as much an art as it is a science. It sounds like the perfect job for someone who is artistic and also passionate about science!
Ask a Biologist: Seeing Color (Kim Cooper and CJ Kazilek, Arizona State University) Creating Hubble's Technicolor Universe (Ray Villard and Zoltan Levay, Sky & Telescope) Hubble Essentials (HubbleSite) The Meaning of Color in Hubble Images (HubbleSite) What Wavelength Goes With a Color? (NASA)