APA
National Aeronautics and Space Administration, Science Mission Directorate. (2010). X-Rays. Retrieved March 31, 2011, fromhttp://missionscience.nasa.gov/ems/11_xrays.html
May 06, 2011
X-Rays
http://missionscience.nasa.gov/ems/11_xrays.html
May 04, 2011
Visualization: From Energy to Image
APA
National Aeronautics and Space Administration, Science Mission Directorate. (2010). Visualization: From Energy to Image. Retrieved March 31, 2011, fromhttp://missionscience.nasa.gov/ems/04_energytoimage.html
MLA
ScienceHOW DO WE VISIUALIZE LIGHT WE CAN'T SEE?
False color, or representative color, is used to help scientists visualize data from wavelengths beyond the visible spectrum. Scientific instruments onboard NASA spacecraft sense regions within the electromagnetic spectrum—spectral bands. The instruments direct the electromagnetic energy onto a detector, where individual photons yield electrons related to the amount of incoming energy. The energy is now in the form of "data," which can be transmitted to Earth and processed into images.Infrared Waves
APA
National Aeronautics and Space Administration, Science Mission Directorate. (2010). Infrared Waves. Retrieved March 31, 2011, fromhttp://missionscience.nasa.gov/ems/07_infraredwaves.html
MLA
Science
INFRARED ENERGY
A remote control uses light waves just beyond the visible spectrum of light—infrared light waves—to change channels on your TV. This region of the spectrum is divided into near-, mid-, and far-infrared. The region from 8 to 15 microns (µm) is referred to by Earth scientists as thermal infrared since these wavelengths are best for studying the longwave thermal energy radiating from our planet.A typical television remote control uses infrared energy at a wavelength around 940 nanometers. While you cannot "see" the light emitting from a remote, some digital and cell phone cameras are sensitive to that wavelength of radiation. Try it out!
Infrared lamps heat lamps often emit both visible and infrared energy at wavelengths between 500nm to 3000nm in length. They can be used to heat bathrooms or keep food warm. Heat lamps can also keep small animals and reptiles warm or even to keep eggs warm so they can hatch.
DISCOVERY OF INFRARED
In 1800, William Herschel conducted an experiment measuring the difference in temperature between the colors in the visible spectrum. He placed thermometers within each color of the visible spectrum. The results showed an increase in temperature from blue to red. When he noticed an even warmer temperature measurement just beyond the red end of the visible spectrum, Herschel had discovered infrared light!THERMAL IMAGING
We can sense some infrared energy as heat. Some objects are so hot they also emit visible light—such as a fire does. Other objects, such as humans, are not as hot and only emit only infrared waves. Our eyes cannot see these infrared waves but instruments that can sense infrared energy—such as night-vision goggles or infrared cameras–allow us to "see" the infrared waves emitting from warm objects such as humans and animals. The temperatures for the images below are in degrees Fahrenheit.COOL ASTRONOMY
Many objects in the universe are too cool and faint to be detected in visible light but can be detected in the infrared. Scientists are beginning to unlock the mysteries of cooler objects across the universe such as planets, cool stars, nebulae, and many more, by studying the infrared waves they emit.The Cassini spacecraft captured this image of Saturn's aurora using infrared waves. The aurora is shown in blue, and the underlying clouds are shown in red. These aurorae are unique because they can cover the entire pole, whereas aurorae around Earth and Jupiter are typically confined by magnetic fields to rings surrounding the magnetic poles. The large and variable nature of these aurorae indicates that charged particles streaming in from the Sun are experiencing some type of magnetism above Saturn that was previously unexpected.
SEEING THROUGH DUST
Infrared waves have longer wavelengths than visible light and can pass through dense regions of gas and dust in space with less scattering and absorption. Thus, infrared energy can also reveal objects in the universe that cannot be seen in visible light using optical telescopes. The James Webb Space Telescope (JWST) has three infrared instruments to help study the origins of the universe and the formation of galaxies, stars, and planets.When we look up at the constellation Orion, we see only the visible light. But NASA's Spitzer space telescope was able to detect nearly 2,300 planet-forming disks in the Orion nebula by sensing the infrared glow of their warm dust. Each disk has the potential to form planets and its own solar system. Credit: Thomas Megeath (Univ.
A pillar composed of gas and dust in the Carina Nebula is illuminated by the glow from nearby massive stars shown below in the visible light image from the Hubble Space Telescope. Intense radiation and fast streams of charged particles from these stars are causing new stars to form within the pillar. Most of the new stars cannot be seen in the visible-light image (left) because dense gas clouds block their light. However, when the pillar is viewed using the infrared portion of the spectrum (right), it practically disappears, revealing the baby stars behind the column of gas and dust.
MONITORING THE EARTH
To astrophysicists studying the universe, infrared sources such as planets are relatively cool compared to the energy emitted from hot stars and other celestial objects. Earth scientists study infrared as the thermal emission (or heat) from our planet. As incident solar radiation hits Earth, some of this energy is absorbed by the atmosphere and the surface, thereby warming the planet. This heat is emitted from Earth in the form of infrared radiation. Instruments onboard Earth observing satellites can sense this emitted infrared radiation and use the resulting measurements to study changes in land and sea surface temperatures.There are other sources of heat on the Earth's surface, such as lava flows and forest fires. The Moderate Resolution Imaging Spectroradiometer (MODIS) instrument onboard the Aqua and Terra satellites uses infrared data to monitor smoke and pinpoint sources of forest fires. This information can be essential to firefighting efforts when fire reconnaissance planes are unable to fly through the thick smoke. Infrared data can also enable scientists to distinguish flaming fires from still-smoldering burn scars.
Credit: Space Science and
The global image on the right is an infrared image of the Earth taken by the GOES 6 satellite in 1986. A scientist used temperatures to determine which parts of the image were from clouds and which were land and sea. Based on these temperature differences, he colored each separately using 256 colors, giving the image a realistic appearance.
Why use the infrared to image the Earth? While it is easier to distinguish clouds from land in the visible range, there is more detail in the clouds in the infrared. This is great for studying cloud structure. For instance, note that darker clouds are warmer, while lighter clouds are cooler. Southeast of the Galapagos, just west of the coast of
We know, from looking at an infrared image of a cat, that many things emit infrared light. But many things also reflect infrared light, particularly near infrared light. Learn more about
REFLECTED Near-infrared radiation.
ELECTROMAGNETIC ENERGY
When you tune your radio, watch TV, send a text message, or pop popcorn in a microwave oven, you are using electromagnetic energy. You depend on this energy every hour of every day. Without it, the world you know could not exist.
Electromagnetic energy travels in waves and spans a broad spectrum from very long radio waves to very short gamma rays. The human eye can only detect only a small portion of this spectrum called visible light. A radio detects a different portion of the spectrum, and an x-ray machine uses yet another portion. NASA's scientific instruments use the full range of the electromagnetic spectrum to study the Earth, the solar system, and the universe beyond.
Electromagnetic radiation is reflected or absorbed mainly by several gases in the Earth's atmosphere, among the most important being water vapor, carbon dioxide, and ozone. Some radiation, such as visible light, largely passes (is transmitted) through the atmosphere. These regions of the spectrum with wavelengths that can pass through the atmosphere are referred to as "atmospheric windows." Some microwaves can even pass through clouds, which make them the best wavelength for transmitting satellite communication signals.
While our atmosphere is essential to protecting life on Earth and keeping the planet habitable, it is not very helpful when it comes to studying sources of high-energy radiation in space. Instruments have to be positioned above Earth's energy-absorbing atmosphere to "see" higher energy and even some lower energy light sources such as quasars.
Leia Mais…
Electromagnetic energy travels in waves and spans a broad spectrum from very long radio waves to very short gamma rays. The human eye can only detect only a small portion of this spectrum called visible light. A radio detects a different portion of the spectrum, and an x-ray machine uses yet another portion. NASA's scientific instruments use the full range of the electromagnetic spectrum to study the Earth, the solar system, and the universe beyond.
OUR PROTECTIVE ATMOSPHERE
Our Sun is a source of energy across the full spectrum, and its electromagnetic radiation bombards our atmosphere constantly. However, the Earth's atmosphere protects us from exposure to a range of higher energy waves that can be harmful to life. Gamma rays, x-rays, and some ultraviolet waves are "ionizing," meaning these waves have such a high energy that they can knock electrons out of atoms. Exposure to these high-energy waves can alter atoms and molecules and cause damage to cells in organic matter. These changes to cells can sometimes be helpful, as when radiation is used to kill cancer cells, and other times not, as when we get sunburned.ATMOSPHERIC WINDOWS
Seeing Beyond our Atmosphere
NASA spacecraft, such as RHESSI, provide scientists with a unique vantage point, helping them "see" at higher-energy wavelengths that are blocked by the Earth's protective atmosphere.Electromagnetic radiation is reflected or absorbed mainly by several gases in the Earth's atmosphere, among the most important being water vapor, carbon dioxide, and ozone. Some radiation, such as visible light, largely passes (is transmitted) through the atmosphere. These regions of the spectrum with wavelengths that can pass through the atmosphere are referred to as "atmospheric windows." Some microwaves can even pass through clouds, which make them the best wavelength for transmitting satellite communication signals.
While our atmosphere is essential to protecting life on Earth and keeping the planet habitable, it is not very helpful when it comes to studying sources of high-energy radiation in space. Instruments have to be positioned above Earth's energy-absorbing atmosphere to "see" higher energy and even some lower energy light sources such as quasars.
Anatomy of an Electromagnetic Wave
APA
National Aeronautics and Space Administration, Science Mission Directorate. (2010). Anatomy of an Electromagnetic Wave. Retrieved March 31, 2011, fromhttp://missionscience.nasa.gov
/ems/02_anatomy.html
MLA
Sciencehttp://missionscience.nasa.gov/ems/02_anatomy.html
Energy, a measure of the ability to do work, comes in many forms and can transform from one type to another. Examples of stored or potential energy include batteries and water behind a dam. Objects in motion are examples of kinetic energy. Charged particles—such as electrons and protons—create electromagnetic fields when they move, and these fields transport the type of energy we call electromagnetic radiation, or light.
WHAT ARE WAVES?
Mechanical waves and electromagnetic waves are two important ways that energy is transported in the world around us. Waves in water and sound waves in air are two examples of mechanical waves. Mechanical waves are caused by a disturbance or vibration in matter, whether solid, gas, liquid, or plasma. Matter that waves are traveling through is called a medium. Water waves are formed by vibrations in a liquid and sound waves are formed by vibrations in a gas (air). These mechanical waves travel through a medium by causing the molecules to bump into each other, like falling dominoes transferring energy from one to the next. Sound waves cannot travel in the vacuum of space because there is no medium to transmit these mechanical waves.Classical waves transfer energy without transporting matter through the medium. Waves in a pond do not carry the water molecules from place to place; rather the wave's energy travels through the water, leaving the water molecules in place, much like a bug bobbing on top of ripples in water.
ELECTROMAGNETIC WAVES
Credit: Ginger Butcher
Electricity can be static, like the energy that can make your hair stand on end. Magnetism can also be static, as it is in a refrigerator magnet. A changing magnetic field will induce a changing electric field and vice-versa—the two are linked. These changing fields form electromagnetic waves. Electromagnetic waves differ from mechanical waves in that they do not require a medium to propagate. This means that electromagnetic waves can travel not only through air and solid materials, but also through the vacuum of space.In the 1860's and 1870's, a Scottish scientist named James Clerk Maxwell developed a scientific theory to explain electromagnetic waves. He noticed that electrical fields and magnetic fields can couple together to form electromagnetic waves. He summarized this relationship between electricity and magnetism into what are now referred to as "Maxwell's Equations."
Heinrich Hertz, a German physicist, applied Maxwell's theories to the production and reception of radio waves. The unit of frequency of a radio wave -- one cycle per second -- is named the hertz, in honor of Heinrich Hertz.
His experiment with radio waves solved two problems. First, he had demonstrated in the concrete, what Maxwell had only theorized — that the velocity of radio waves was equal to the velocity of light! This proved that radio waves were a form of light! Second, Hertz found out how to make the electric and magnetic fields detach themselves from wires and go free as Maxwell's waves — electromagnetic waves.Electromagnetic waves are formed by the vibrations of electric and magnetic fields. These fields are perpendicular to one another in the direction the wave is traveling. Once formed, this energy travels at the speed of light until further interaction with matter.
WAVES OR PARTICLES? YES!
Light is made of discrete packets of energy called photons. Photons carry momentum, have no mass, and travel at the speed of light. All light has both particle-like and wave-like properties. How an instrument is designed to sense the light influences which of these properties are observed. An instrument that diffracts light into a spectrum for analysis is an example of observing the wave-like property of light. The particle-like nature of light is observed by detectors used in digital cameras—individual photons liberate electrons that are used for the detection and storage of the image data.POLARIZATION
One of the physical properties of light is that it can be polarized. Polarization is a measurement of the electromagnetic field's alignment. In the figure above, the electric field (in red) is vertically polarized. Think of a throwing a Frisbee at a picket fence. In one orientation it will pass through, in another it will be rejected. This is similar to how sunglasses are able to eliminate glare by absorbing the polarized portion of the light.DESCRIBING ELECTROMAGNETIC ENERGY
The terms light, electromagnetic waves, and radiation all refer to the same physical phenomenon: electromagnetic energy. This energy can be described by frequency, wavelength, or energy. All three are related mathematically such that if you know one, you can calculate the other two. Radio and microwaves are usually described in terms of frequency (Hertz), infrared and visible light in terms of wavelength (meters), and x-rays and gamma rays in terms of energy (electron volts). This is a scientific convention that allows the convenient use of units that have numbers that are neither too large nor too small.FREQUENCY
The number of crests that pass a given point within one second is described as the frequency of the wave. One wave—or cycle—per second is called a Hertz (Hz), after Heinrich Hertz who established the existence of radio waves. A wave with two cycles that pass a point in one second has a frequency of 2 Hz.WAVELENGTH
Electromagnetic waves have crests and troughs similar to those of ocean waves. The distance between crests is the wavelength. The shortest wavelengths are just fractions of the size of an atom, while the longest wavelengths scientists currently study can be larger than the diameter of our planet!ENERGY
An electromagnetic wave can also be described in terms of its energy—in units of measure called electron volts (eV). An electron volt is the amount of kinetic energy needed to move an electron through one volt potential. Moving along the spectrum from long to short wavelengths, energy increases as the wavelength shortens. Consider a jump rope with its ends being pulled up and down. More energy is needed to make the rope have more waves.
Subscribe to:
Posts (Atom)
