What are the wavelength and frequency of light?

Light travels in waves. The wavelength of a light wave is the distance between successive peaks or troughs of a wave. Wavelength is a measurement of the energy of electromagnetic radiation. Every spectral region has a wavelength associated with it. Scientists often characterize light in terms of its wavelength. For example, light with a wavelength range from 1 millimeter to 10 meters is part of the radio spectrum.
The frequency of a light wave is the number of wave crests that pass by you every second. The frequency of a light wave, f, multiplied by the wavelength of light, w, is equal to the speed of light, c. c is always 300,000,000 meters per second or about 186,000 miles per second. (c=fw). Note: the greek letter Lamda is often used to designate wavelength.

Does light have energy?

Yes! Light travels in waves. Waves transmit energy from one place to another. Every wavelength of light has a different energy. Long wavelength light such as radio and infrared light have a much lower energy than ultraviolet or X-ray light. The energy of a light wave is directly related to the frequency of light. The higher the light's frequency, the higher the energy of the light.

What is a spectral filter?

A spectral filter is a device on the telescope that blocks specific wavelengths of light. The device is often made from clear glass or plastic that is coated with special chemicals that are opaque to certain wavelengths and transparent to others. Spectral filters are used when astronomers want to observe an object in one part of the electromagnetic spectrum. For example, if an astronomer wants to observe a star in the infrared, he uses an infrared filter on the telescope that blocks all wavelengths except infrared light.

What is a spectral scanner?

A spectral scanner is a computer program that scans an observed image or object and provides valuable information about the astronomical source. The spectral scanner creates a spectral intensity plot of the image.

What is a spectral intensity plot?

A spectral intensity plot is a graph of intensity versus wavelength for a given image. Objects such as stars and galaxies emit light in all wavelengths. However, some objects emit more light in one wavelength than in others. The spectral intensity plot can show you in which parts of the electromagnetic spectrum the object shines the brightest and in which part the object shines the faintest. In the below example, the astronomical source was observed in infrared and ultraviolet light. The spectral intensity plot of the infrared image shows a high intensity at infrared wavelengths. The spectral intensity plot of the ultraviolet image shows a much lower intensity of light at ultraviolet wavelengths. With this information, you might conclude that the object is brighter in the infrared than it is in the ultraviolet.

How can one tell what elements make up an object?

Matter is made up of atoms. If atoms are energized by starlight they can give off light of their own. Every element gives off light in a specific part of the electromagnetic spectrum. The light the atom gives off is unique to that particular element, kind of like a fingerprint or DNA is unique to every person. By studying the electromagnetic spectrum of an object you can take the objects "fingerprint" and find out what it's made of. The elemental spectrometer (Spectral Scanner) does this analysis for you.

What is an elemental spectrometer?

An elemental spectrometer (Spectral Scanner) is a tool that can determine what elements are contained in an object. It analyses the spectrum of a source and outputs the elements to the telescope control panel. In The Galaxy Experiment, the elemental spectrometer is referred to as a Spectral Scanner.

What kinds of telescopes do astronomers use to make observations?

Astronomers need different types of equipment to observe objects in different parts of the electromagnetic spectrum. Just like our eye, some types of instruments can "see" visible light, while others can only "see" infrared light or ultraviolet light. Here are some notes about various telescopes:

• Radio telescopes. Radio radiation is the lowest energy region of the electromagnetic spectrum. The long wavelengths associated with radio waves allow most radio radiation to pass through the Earth's atmosphere. Radio telescopes are different from visible or infrared telescopes in that they do not need reflective mirrors to focus the light. Radio waves are so long that they can be harnessed with large plastic or metal dishes. Radio observations have helped astronomers study the big bang and the chemistry of space.
• Infrared telescopes. Most infrared radiation is blocked out by the Earth's atmosphere. However, a few narrow bands of infrared light can pass through the atmosphere and be observed using ground based telescopes. In order to observe the rest of the infrared sky we have to observe from space. Infrared radiation is mostly heat radiation that is emitted by warm stars and interstellar dust. Infrared observations have helped astronomers learn about the formation of stars and galaxies.
• Visible Light telescopes. Long before telescopes were invented, astronomers used their eyes to make observations of the night sky. Since eyes can only light in the visible part of the spectrum, they could only observe a small part of the electromagnetic spectrum. Visible light passes easily through the Earth's atmosphere and can be observed using ground based telescopes. Visible light telscopes use a series of lenses and mirrors to produce an image that can be magnified for closer observations. These telescopes are located in observatories in many countries around the world. Observatories are usually located at high elevations, away from city lights and above the clouds. Modern technology has allowed us to reduce the blurriness of images and to create very large telescopes, capable of capturing more light from space in a given time. The most advanced visible telescopes have been launched above the Earth's atmosphere to reduce any distortion or interference of light caused by the atmosphere. Some visible telescopes have been launched on space probes providing us with detailed images of planet surfaces.
• Ultraviolet telescopes. Much of the ultraviolet light that reaches the Earth from space is absorbed by our atmosphere. If you spend any time at the beach, you might know that some of the ultraviolet or UV light does get through our atmosphere and can be very harmful to our skin. To prevent skin damage, many of us wear sunblock to finish off the job that the Earth's atmosphere couldn't handle. Astronomers that want to study light in this region of the electromagnetic spectrum, they must use special telescopes that get above most of the Earth's atmosphere. Space observatories and high altitude balloons are the most common ways of making ultraviolet observations.
• X-Rays telescopes. If you think ultraviolet radiation is bad for you skin, continuous exposure to X-ray light would permanently damage our skin in minutes. Luckily for us, the atmosphere blocks out all of the X-rays that reach the Earth from space. This means that in order to study light at X-ray wavelengths, we need to go into space. X-ray light has such high energy that special telescopes with angled mirrors are needed to capture and focus the light. X-ray astronomy has helped us learn about some of the most puzzling objects in our universe like black holes and neutron stars.
• Gamma-rays telescopes. Gamma rays cannot be captured and reflected in mirrors (since they pass right through). Gamma-ray telescopes, therefore, are different than regular telescopes and use a process called Compton scattering, which actually measures a loss of energy when a gamma-ray strikes an electron, to "view" the rays.