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Exploring the Universe: Visible Light Telescopes and More

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  1. Review • When is Orion visible in Arizona? • What is a circumpolar star or constellation? • When are circumpolar stars or constellations visible in Arizona? • What is the order from least to most complex of galaxy planet, universe, solar system? • Explain gravity.

  2. Studying space from Earth • Tele = distance • Scopos = to watch • Light and radiation (energy in the form of waves that travel through empty space) • How astronomers gather info about space

  3. Light and Other Forms of Radiations • Visible light is a form of electromagnetic radiation which is energy that travels across the distances of different types of waves. • Examples of electromagnetic radiation that you can’t see are radio waves and x-ray. Scientists have developed instruments that can detect these types. • Electromagnetic radiation travels in all directions throughout space. Astronomers determine the size, distance and movement of space objects by studying its radiation. • Radiation can reveal what an object is made of and how it has changed.

  4. Spectrum • White light separated into a range of colors is called a spectrum. • In a spectrum, the colors of visible light differ and appear in the order of their wavelengths. • Wavelength is the distance between one wave peak and the next wave peak. Red light has the longest wavelength and purple the shortest. • Visible light is a small fraction of the Electromagnetic Spectrum

  5. Frequency Frequency is the number of cycles per unit of time. Most often measured in cycles per second

  6. Telescopes • A telescope is a device that gathers electromagnetic radiation (light). • Telescopes provide images that are much clearer than what is seen with the naked eye because telescopes show radiation that eyes can’t detect. • Most telescopes gather radiation with a glass lens or a reflecting surface such as a mirror. Larger lenses and reflecting surfaces produce brighter and more detailed images.

  7. Visible-light Telescopes • Reflecting Telescope – This type of telescope has curved mirrors that gather and focus light. The image comes into focus in front of the mirror. Many reflecting telescopes have a second mirror that reflects the image to recording equipment or to a lens called an eyepiece. • Remember: Reflecting because mirrors reflect an image!

  8. Reflecting Telescope • Eyepiece • Primary mirror • Secondary mirror • Light

  9. Visible-light Telescopes 2. Refracting Telescope – This type of telescope has an objective lens, or curved piece of glass, at one end of a long tube. The lens gathers light and focuses it to form an image near the other end of the tube. An eye piece magnifies this image. • Remember: Refracting because the curved lens changes, bends or deflects light!

  10. Objective lens • Eyepiece

  11. Most powerful visible light telescopes are built on mountain tops or in rural areas to avoid city lights. • The atmosphere interferes with light coming in from space. • The movement of the air in the atmosphere is what makes stars seem to twinkle

  12. Mauna Kea Observatory Hawaii Griffith Observatory Los Angeles European Southern Observatory Chile

  13. Radio Telescopes • Radio telescopes show where radio waves are being emitted by objects in space. Radio telescopes have a large, curved metal surface called a dish. (Parabola) • They are often found in groups with all dishes aimed the same way to gather waves to improve the quality of the image. • Because radio waves are so large they can penetrate the Earth’s atmosphere. What does this mean? • What is one difference between a radio telescope and a visible light telescope?

  14. Space Telescopes • The Hubble telescope is a reflecting telescope that was placed into orbit in 1990. • Because it’s in space, the atmosphere does not interfere with imaging. • The lack of atmospheric interference allows the Hubble to produce very clear images. • Atmosphere blocks most x-rays and gamma rays

  15. Closure • In ISN Answer: • What is radiation? • How are visible light, radio waves, and other forms of electromagnetic radiation different from each other? • What function do mirrors serve in reflecting telescopes? • Why are some telescopes placed high on mountains or in orbit around Earth?

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