Radio waves are also emitted by stars and gases in space. Microwave: Microwave radiation will cook your popcorn in just a few minutes, but is also used by astronomers to learn about the structure of nearby galaxies. Infrared: Night vision goggles pick up the infrared light emitted by our skin and objects with heat.
In space, infrared light helps us map the dust between stars. Visible: Our eyes detect visible light. Fireflies, light bulbs, and stars all emit visible light. Ultraviolet: Ultraviolet radiation is emitted by the Sun and are the reason skin tans and burns. X-ray: A dentist uses X-rays to image your teeth, and airport security uses them to see through your bag. Hot gases in the Universe also emit X-rays.
Gamma ray: Doctors use gamma-ray imaging to see inside your body. The biggest gamma-ray generator of all is the Universe. Are radio waves completely different physical objects than gamma-rays? They are produced in different processes and are detected in different ways, but they are not fundamentally different. Radio waves, gamma-rays, visible light, and all the other parts of the electromagnetic spectrum are electromagnetic radiation. Electromagnetic radiation can be described in terms of a stream of mass-less particles, called photons , each traveling in a wave-like pattern at the speed of light.
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.
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. 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.
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. This information can be essential to firefighting efforts when fire reconnaissance planes are unable to fly through the thick smoke.
What we usually measure from a large object like a star is the energy flux , the power emitted per square meter. It turns out that the energy flux from a blackbody at temperature T is proportional to the fourth power of its absolute temperature. This relationship is known as the Stefan-Boltzmann law and can be written in the form of an equation as. Notice how impressive this result is. Increasing the temperature of a star would have a tremendous effect on the power it radiates.
If the Sun, for example, were twice as hot—that is, if it had a temperature of 11, K—it would radiate 2 4 , or 16 times more power than it does now. Tripling the temperature would raise the power output 81 times. Hot stars really shine away a tremendous amount of energy. While energy flux tells us how much power a star emits per square meter, we would often like to know how much total power is emitted by the star. We can determine that by multiplying the energy flux by the number of square meters on the surface of the star.
Two stars have the same size and are the same distance from us. Star A has a surface temperature of K, and star B has a surface temperature twice as high, 12, K. How much more luminous is star B compared to star A?
Two stars with identical diameters are the same distance away. One has a temperature of K and the other has a temperature of K. Which is brighter? How much brighter is it? The electromagnetic spectrum consists of gamma rays, X-rays, ultraviolet radiation, visible light, infrared, and radio radiation.
The emission of electromagnetic radiation is intimately connected to the temperature of the source. The higher the temperature of an idealized emitter of electromagnetic radiation, the shorter is the wavelength at which the maximum amount of radiation is emitted.
The total power emitted per square meter increases with increasing temperature. X-rays: electromagnetic radiation with wavelengths between 0. Skip to main content. Radiation and Spectra. Search for:. Example 2: Calculating the Power of a Star While energy flux tells us how much power a star emits per square meter, we would often like to know how much total power is emitted by the star.
Key Concepts and Summary The electromagnetic spectrum consists of gamma rays, X-rays, ultraviolet radiation, visible light, infrared, and radio radiation. Licenses and Attributions. CC licensed content, Shared previously. Produced in nuclear reactions; require very high-energy processes. Gas in clusters of galaxies, supernova remnants, solar corona. They are defined as such because no single primary colour can be created from the other two, but all other colours can be formed by combining blue, green, and red in various proportions.
Although we see sunlight as a uniform or homogeneous colour, it is actually composed of various wavelengths of radiation in primarily the ultraviolet, visible and infrared portions of the spectrum.
The visible portion of this radiation can be shown in its component colours when sunlight is passed through a prism , which bends the light in differing amounts according to wavelength. The next portion of the spectrum of interest is the infrared IR region which covers the wavelength range from approximately 0. The infrared region can be divided into two categories based on their radiation properties - the reflected IR , and the emitted or thermal IR. Radiation in the reflected IR region is used for remote sensing purposes in ways very similar to radiation in the visible portion.
The reflected IR covers wavelengths from approximately 0. The thermal IR region is quite different than the visible and reflected IR portions, as this energy is essentially the radiation that is emitted from the Earth's surface in the form of heat.
The thermal IR covers wavelengths from approximately 3. The portion of the spectrum of more recent interest to remote sensing is the microwave region from about 1 mm to 1 m. This covers the longest wavelengths used for remote sensing.
The shorter wavelengths have properties similar to the thermal infrared region while the longer wavelengths approach the wavelengths used for radio broadcasts.
0コメント