P.V.V. Jayaweera Institute of Fundamental Studies Hantana Road, Kandy.

Sir Frederick William Herschel ( ) musician and an astronomer famous for his discovery of the planet Uranus in 1781 Discover “calorific rays” in 1800 later renamed as “Infrared rays” Discovery of Infrared

What is Infrared (IR) ? (the prefix infra means `below‘) The electromagnetic spectrum includes gamma rays, X-rays, ultraviolet, visible, infrared, microwaves, and radio waves. The only difference between these different types of radiation is their wavelength or frequency.

Visible Micro wave near-IRmid-IRFar-IR = 0.75  m Cannot see (human eye) Infrared is usually divided into 3 spectral regions 0.8–5  m 5-40  m  m Some animals can "see" in the infrared. For example, snakes in the pit viper family (e.g. rattlesnakes) have sensory "pits," which are used to detect infrared light. This allows the snake to find warm-blooded animals.

The primary source of infrared radiation is heat or thermal radiation. This is the radiation produced by the motion of atoms and molecules in an object. Any object which has a temperature above absolute zero (0 K) radiates in the infrared. Landing space shuttle person holding burning match Cat Infrared image of Orion

Human & vehicle at total darkness thermal image in white=hot mode same image in Black=hot mode Human Suspect climbing over fence at 2:49 AM in total darkness Suspect attempting to burglarize vehicle at 1:47 AM in total darkness.

IR Astronomy Infrared Astronomy is the detection and study of the infrared radiation (heat energy) emitted from objects in the Universe. Viewing the Invisible Exploring the Hidden Universe Detecting Cool Objects Exploring the Early Universe Adding To Our Knowledge of Visible Objects

Infrared Windows Object in the Universe sends us light at all wavelengths of the electromagnetic spectrum. However, most of this light does not reach us at ground level.

Spectral Region Wavelength Range (Microns) Temperature Range (Degrees Kelvin) What We See Near-Infrared(0.7-1) to to (3,000- 5,200) Cooler red stars Red giants Dust is transparent Mid-Infrared5 to (25-40)( ) to 740 Planets, comets and asteroids Dust warmed by starlight Protoplanetary disks Far-Infrared (25-40) to ( ) ( ) to ( ) Emission from cold dust Central regions of galaxies Very cold molecular clouds

Viewing the Invisible The Universe sends us a tremendous amount of information in the form of electromagnetic radiation (or light). Much of this information is in the infrared, which we cannot see with our eyes or with visible light telescopes. Only a small amount of this infrared information reaches the Earth's surface, yet by studying this small range of infrared wavelengths, astronomers have uncovered a wealth of new information

Central region of Milky Way Galaxy Exploring the Hidden Universe In space, there are many regions which are hidden from optical telescopes because they are embedded in dense regions of gas and dust. However, infrared radiation can pass through dusty regions of space without being scattered. This means that we can study objects hidden by gas and dust such as the center of our galaxy.

Detecting Cool Objects Many objects in the universe which are much too cool and faint to be detected in visible light, can be detected in the infrared. These include cool stars, infrared galaxies, clouds of particles around stars, nebulae, interstellar molecules, brown dwarfs and planets. For example, the visible light from a planet is hidden by the brightness of the star that it orbits.

Exploring the Early Universe As a result of the Big Bang, the universe is expanding and most of the galaxies within it are moving away from each other. Astronomers have discovered that all distant galaxies are moving away from us and that the farther away they are, the faster they are moving. This recession of galaxies away from us has an interesting effect on the light emitted from these galaxies. When an object is moving away from us, the light that it emits is "redshifted". This means that the wavelengths get longer and thereby shifted towards the red part of the spectrum.

Adding to Our Knowledge of Visible Objects Objects which can be seen in visible light can also be studied in the infrared. Infrared astronomy can not only allow us to discover new objects and view previously unseen areas of the universe, but it can add to what we already know about visible objects. To get a complete picture of any object in the Universe we need to study all of the radiation that it emits. Infrared Astronomy has, and will continue to, add a great deal to our knowledge about the Universe and the origins of our Solar System.

Manufacturer/typesize (pixel)technologypixel pitch Hawaii1k x 1kHgCdTe18.5 u m Aladdin1k x 1kInSb27 u m Hawaii2k x 2kHgCdTe18.0 Infrared array detectors HgCdTe (Mercury-Cadmium-Telluride) InSb (Indium Antimonide)