Breaking Light Into Its Components
If you send sunlight through a prism, as Sir Isaac Newton did, you’ll see a rainbow of colors. This visible light is just a small part of the electromagnetic spectrum.
Today, astronomers study all the light streaming from objects in space. Their tools are spectrographs and spectroscopes, which break up light into its component wavelengths.
What a Spectrum Tells Us
A spectrum of the light from an object indicates its temperature and the chemical elements it contains. The way the dark and light bars are arranged in a spectrum can also reveal the speed of an object and the direction in which it is moving. These spectral “fingerprints” help identify many physical characteristics of stars, planets, and galaxies.
Seeing Through Earth’s Turbulent Atmosphere
How Adaptive Optics Systems Work
While Earth’s atmosphere makes life possible, it also gets in the way of astronomers who want to study objects in space. There are two ways to deal with this atmospheric blurring: put observatories in space above the atmosphere or add adaptive optics to telescopes on the ground.
Adaptive optics systems distort mirrors to “correct” for atmospheric effects. This provides sharper images.
The Result of Adaptive Optics
An adaptive optics system shoots a laser beam through the atmosphere. This creates an artificial “guide star” that the system uses to measure the distortion of our atmosphere. Information is then fed to a mechanism that makes constant, tiny adjustments to the mirrors to match the atmospheric distortion. The resulting image looks clearer and sharper, as if the atmosphere weren’t in the way.
Combining the Light
Sometimes a target is too far away or is one of many objects in a crowded field. This makes it difficult to observe. Even a large telescope may not provide a sharp enough view. To get clearer views of objects, astronomers want to build ever-larger telescopes. If this isn’t possible, they combine light from two or more telescopes in a technique called interferometry, as with the Crab Nebula radio image.
Sharpening the View
When multiple telescopes (A and B) are combined in an interferometer, the resulting super-observatory lets astronomers achieve the sharpness of a much larger telescope (C). They can use it to zero in on very small areas of the sky, like individual stars or the centers of galaxies. Interferometry is a technique that is used today with both optical and radio telescopes.