November 19, 2012
Ask An Expert – What Does Space Really Look Like?
John P. Millis, Ph.D. for redOrbit.com — Your Universe Online
This article is the latest installment in a new series where redOrbit´s in-house experts will answer questions submitted by you, the reader. Got a science or space question that´s stumping you? Each week we´ll select a handful of the wiliest questions you can whip up to tease the brains of our resident gurus (we call them 'geeks').Question:
We have seen numerous pictures of other galaxies and other things out there in space and they are always so beautiful and colorful. Is this what I would see if I could theoretically fly passed them. Or are these colorful pictures from infrared or some other form of photography? - Brad Heckman
This is a great question Brad. The short answer is that, in general, what you see in the beautiful images from the Hubble Space Telescope (and other instruments) is not what you would see with your own eyes.
The Hubble Space Telescope (HST) actually detects an object based on its lightness or darkness, effectively rendering black and white images. However, filters can be used to isolate certain wavelengths of light.
For some applications the HST uses a set of three filters to isolate the observed light into three color-bands, approximating the primary colors we see with our eyes. In this instance the images produced by the HST, post-processing, would look very similar to how we would see them with our own eyes.
These images, known as true color as they would mimic how we would see the objects in space, are rare. The reason is that the HST can detect light that our eyes cannot, such as ultraviolet and infrared. Instead, filters are used that will isolate a certain physical process, to help us better understand the physical mechanisms that create the various wavelengths of light from the object.
In the famous Crab Nebula image from the HST (shown above), the outer orange filaments are the remnants of the star that created the supernova, and are composed mostly of hydrogen gas. While the inner part of the image, that faint blue “fog”, comes from the pulsar wind created by electrons orbiting the powerful magnetic fields of the tiny neutron star spinning furiously in the center.
Since each of these processes will give off different wavelengths of light, they can be individually captured using the appropriate filters. Doing so gives us a complete picture of what physical processes dominate the objects that we detect. These images, called false color images, allow us to learn about the physics of how these astronomical bodies evolve.