Understand the electromagnetic spectrum and how it is organized. Understand what different types of electromagnetic radiation can reveal about astronomical objects. Understand and describe important properties of electromagnetic radiation. Understand how technology is used to collect electromagnetic radiation and turn it into images. Understand what can be learned from analyzing the light from astronomical objects. Understand how different types of lenses and telescopes work Understand and describe the quantization of energy at the atomic level Understand that all objects emit and absorb electromagnetic radiation and distinguish between objects that are blackbody radiators and those that are Qualitatively describe the shift in frequency in sound or electromagnetic waves due to the relative motion of a source or a receiver Please be careful with the lenses at your desks – they are glass and can break if dropped!

Telescopes

Words to know: Objective- larger mirror or lens that collects light Aperture- diameter of the objective Eyepiece- smaller lens, used as a magnifier Focal length- measure (usually in mm) of the path light takes before its focused in the eyepiece

Telescopes Telescopes have 2 purposes. There are 2 kinds of telescopes Collect more light than the eye can To study objects with increased resolution (make them bigger) Of those two functions, the first one - gathering more light - is by far the most important. This comes as a surprise to many people, who think that magnification, or power is the linchpin of telescope functionality. The higher the power, the better, one would think. But this isn’t so There are 2 kinds of telescopes Refracting – lense Reflecting – mirror Telescopes have 2 main elements. Mirror or lens that collects light – OBJECTIVE Smaller lens system that magnifies – EYEPIECE

Calculations for Telescopes Focal ratio (f-ratio) Focal length of objective aperture This is the ‘speed’ of a telescope’s optics, The smaller (faster) the f/number the lower the magnification the wider the field the brighter the image with any given eyepiece or camera. Fast f/4 to f/5 focal ratios are generally best for lower power wide field observing and deep space photography. Slow f/11 to f/15 focal ratios are usually better suited to higher power lunar, planetary, and binary star observing and high power photography.

Calculations for Telescopes Magnification (make bigger) Focal length of telescope Focal length of the eyepiece Calculations for Telescopes More isn’t always better… Doubling the power gives you one-fourth the image brightness and reduces the sharpness by one half.

Refractor – bends light

Refracting (made famous by Galileo)

History Refracting telescopes were first available in the early 1600s. Hans Lippershey (1570-1619) of Holland is often credited with the invention of the telescope. He was the first to make the new device widely known. The telescope was introduced to astronomy in 1609 by Galileo, who became the first man to see sunspots, the four large moons of Jupiter, and the rings of Saturn. Galileo's telescope was similar to a pair of opera glasses in that it used an arrangement of glass lenses to magnify objects. This arrangement provided limited magnification and a narrow field of view; Galileo could see no more than ¼ of the moon without repositioning.

Lenses - make observations Lens name Image when held close to eye Image when held at arms length Double Concave Double Convex Both at the same time! How does the shape of the lenses affect the light? How does one at a time compare to looking through both at the same time?

Reflector– Collects light

Reflecting (made famous by Isaac Newton)

History In 1704, Isaac Newton announced a new concept in telescope design where instead of glass lenses, a curved mirror was used to gather in light and reflect it back to a point of focus. This reflecting mirror acts like a light-collecting “bucket”. The reflector telescope that Newton designed opened the door to magnifying objects millions of times-far beyond what could ever be obtained with a lens.

Famous Telescopes Fermi Compton* Chandra* VLA VLT Arecibo Keck Spitzer* Hubble* NASA's series of Great Observatories satellites are four large, powerful space-based telescopes. Each of the Great Observatories has had a similar size and cost at program outset, and each has made a substantial contribution to astronomy. The four missions each examined a region of the electromagnetic spectrum to which it was particularly suited.

Hubble

Fermi Centaurus A, one of the nearest galaxies to the Milky Way, is the brightest source of radio waves as seen from Earth. If humans could see these wavelengths, then the galaxy would occupy an area of the sky equal to 20 times the apparent size of the full Moon. Fermi found that this area is also emitting more Gamma Rays than ever expected.

Compton – Gamma Rays

Chandra – X-Rays

Spitzer

VLA 50 miles west of Socorro, New Mexico. The VLA has made key observations of black holes and protoplanetary disks around young stars, discovered magnetic filaments and traced complex gas motions at the Milky Way's center, probed the Universe's cosmological parameters, and provided new knowledge about the physical mechanisms that produce radio emission.

Aricebo Puerto Rico. At 1000 feet across, it is the largest dish antenna in the world. The dish, built into a bowl in the landscape, focuses radio waves from the sky on the feed antenna suspended above it on cables. Since the dish itself can't move, the telescope is steered to point at different regions of the sky by moving the feed antenna (dome) along the curving metal track.

Keck The Keck Observatory is a two- telescope astronomical observatory at an elevation of 13,600 ft near the summit of Mauna Kea in Hawai'i. The primary mirrors of each of the two telescopes are 10 meters in diameter, making them the second largest optical telescopes in the world. The telescopes can operate together to form a single astronomical images.

Hale Telescope It was the largest aperture (200-inch) optical telescope in the world from its completion in 1948 until 1976.

VLT – Very large telescope In the Atacama Desert of northern Chile. The VLT consists of four individual telescopes, each with a primary mirror 8.2 m across, which are generally used separately but can be used together. The four separate optical telescopes are known as Antu, Kueyen, Melipal and Yepun, which are all words for astronomical objects in the Mapuche language.  The VLT operates at visible and infrared wavelenths The VLT is the most productive ground-based facility for astronomy, with only the Hubble Space Telescope generating more scientific papers among facilities operating at visible wavelengths. Among the pioneering observations carried out using the VLT are the first direct image of an exoplanet, the tracking of individual stars moving around the supermassive black hole at the center of the Milky Way, and observations of the afterglow of the furthest known gamma-ray burst.

The Crab Nebula, first seen on Earth in the year 1054. x- ray (Chandra), optical (Palomar), infrared (Keck), radio (VLA)

On Google Classroom Due Tomorrow

Things to Study: Electromagnetic Spectrum Types of electromagnetic radiation Electromagnetic Waves Properties of Waves calculating energy, wavelength and frequency Telescopes Spectroscopes and Diffraction Types of Spectrum, identifying elements with spectrum Blackbody Radiation Curves Wein’s Law and the Stefan-Boltzmann Law