1. Types of Astronomy How we use different parts of the EMS to learn about the Universe

2.  The different forms of EM radiation are the same basic kind of energy  They differ by wavelength and frequency  High frequency/short wavelength(gamma)  Low frequency/long wavelength (radio) The Electromagnetic Spectrum Low frequency & Long wavelength High frequency & Short wavelength

3.  We use many different wavelength of EM radiation in our everyday lives  Medical imaging (Xrays)  Sterilization (UV)  Cooking (microwave)  Communications (Radio)  Visual displays (visible light)  We also use various EM radiation to learn about the universe The Electromagnetic Spectrum

4.  Visible light from nearby celestial objects have been observed for millenia  The Sun, planets, stars, comets, meteors, supernovae  Little was known about these objects, so myths grew around them  Basic patterns of motion over time were documented  These studies formed the basis of mathematics and Science The Early Efforts

5.  When lenses were invented, people started using them to improve the view of celestial objects  Galileo used a crude telescope (Looking Glass) to study the sky, and used his observations to differentiate the planets from the stars  He also identified and tracked the motion of sun spots, which allowed him to understand the rotation of the sun  Analyzing their motions led him to understand the Solar System’s true arrangement Early Telescopes

6.  As lenses became better, stronger lenses made larger images of objects in the sky (refracting telescope)  Refraction, however, made the images fuzzy  Newton used mirrors to collect the light (the first reflecting telescope) in late 1600’s  Eliminated the refraction effect and got sharper images  The larger the mirror the more light is collected  Dimmer objects could be seen with larger mirrors… Limits to Lenses

7.  Keck Observatory on Mauna Kea in Hawaii  Elevation 13,796 feet above sea level (2.6 miles!)  Mirror is 10 meters in diameter  Too large to fit into our classroom! Largest Optical Telescope

8.  No loss of energy to Earth’s atmosphere  Outside most of the atmosphere, so no background light to deal with  Mirror is 2.4 meters in diameter  Can observe visible light, near infrared, near UV Hubble Space Telescope

9.  Optical Telescopes can observe  Visible light  Near Infrared  Near Ultraviolet Usable Wavelengths in Astronomy Optical Telescopes

10.  Collects radio waves instead of light  Uses a dish-shaped collector to gather the waves  Receivers then amplify the waves and detect signals  Larger the dish, the more waves collected  Radio waves may be available while light waves are blocked Radio Telescopes

11.  The radio telescopes below are all located at the Haystack Observatory in Westford/Groton/Tyngsboro  They are used for studying the atmosphere, for tracking satellites in Earth orbits, changes in the Earth, and astronomical tasks, too! Haystack Observatory

13. Combining Observations Use multiple modes to Get more complete image  Visible light Radio waves  Infrared  Ultraviolet  X-rays

14.  Radio Telescopes can observe  Most radio waves  Longer microwaves  Very long wavelengths (10 meters +) are blocked by the Ionosphere Usable Wavelengths in Astronomy Optical Telescopes Radio Telescopes

15.  The atmosphere only lets through certain forms of EM radiation  Visible light (obviously)  Radio waves  Microwaves  NOT Infrared  NOT Ultraviolet  NOT X-rays  NOT Gamma rays Limitations from the Atmosphere

17.  Chandra Xray Observatory  Launched July 1999  One of NASA’s four Great Observatories  Uses stacked mirrors and a very slight angle to focus Xrays  Objects not visible can be detected Xray Telescopes

18.  NuStar Xray Observatory  Launched June, 2012  Measures higher-energy X-rays (6-79 KeV) than Chandra or other previous X-ray telescopes  July 27, 2012 – completed post-launch assessment  August 2012 starting to observe Xray Telescopes

19.  Xray Telescopes can observe  Xrays! Usable Wavelengths in Astronomy Optical Telescopes Radio Telescopes Xray Telescopes

20.  Fermi Gamma Ray Space Telescope  Launched June, 2008  One of NASA’s four Great Observatories  Has LAT (Large Area Telescope) and Gamma-ray Burst Monitor Gamma Ray Telescopes

21.  Gamma Ray Telescopes can observe  Gamma Rays! Usable Wavelengths in Astronomy Optical Telescopes Radio Telescopes Xray Telescopes Gamma Ray Telescopes

22.  Using two or more telescopes at the same time to compare signals and get finer data on direction (resolution)  A specialized computer (Correlator) calculates information from the two receivers  Can be used with optical or radio scopes Interferometry

23.  Using two very widely spaced telescopes at the same time to compare signals  Used to measure changes in the Earth (Geodesy)  Can be thousands of miles apart  Must have very accurate timers  Worldwide project being set up to get image of the supermassive black hole at our galaxy’s center VLBI Very Long Baseline Interferometry

24.  Project coordinated by Haystack Observatory using radio telescopes around the world to create a network of sites/radio dishes to be able to resolve the Event Horizon of the supermassive black hole at the center of our galaxy, the Milky Way.  Sagittarius A* (pronounced “A star”) is optically invisible due to clouds of dust around the galactic core  Radio telescopes hope to take the first image of this object around 2016 EHT Event Horizon Telescope

25.  Have used radio telescopes in:  Hawaii  Arizona  California  Demonstrated the capability of the technology  Now adding an additional site  Atacama Desert, Chile (ALMA) EHT Event Horizon Telescope

26. EHT Eventual Sites  Hawaii (Mauna Kea)  California (CARMA Cedar Flat,CA)  Arizona (Mt. Graham, AZ)  Chile (ALMA Atacama, Chile)  Mexico  Spain  France  Antartica  Greenland

27. EHT The Goal