PHYS 1403 Introduction to Astronomy Light and Telescope Chapter 6 Todays Topics Astronomical Detectors Radio Telescopes Why we need space telescopes? Hubble Space Telescopes Future Space Telescopes Astronomy at Infrared wavelength Astronomy at X-ray wavelength Major World Telescopes Astronomy at Non-Electromagnetic Wavelengths Astronomical Detectors How to Measure and Record Light The Eye Limited ability The Photographic plate now obsolete Photomultiplier Very limited in capability The CCD (Charge Couple Device) Making Digital Image The Spectrograph Making a Spectrum - Measuring; Chemical Composition Temperature Velocity CCD Camera Makes Digital Images It is a imaging device https://www.youtube.com/watch?v=2vsj7xdec5g 1
How does a CCD work? How does a CCD work? http://astro.unl.edu/classaction/animations/telescopes/buckets.html A CCD Image and Pixel Values Astrophotography Mathworks.com Science from multiple wavelength CCD Images Science from a CCD Image Analyzing a sequence of such image gives us this light curve Brightskies.us 2
Spectrographs/Spectrometer Spectrographs/Spectrometer A CCD spectrometer has a CCD camera and a Spectrometer A CCD image shows the spectrum It is an instrument that allows us to see to colors of white light coming from a star or a hot source Analysis of a Spectrum tells us chemical composition, temperature and velocity Spectra of Some Astronomical Objects Spectra of Chemical Elements Spectra can give us velocity information 3
Radio Astronomy Radio Telescopes Recall: radio waves of ~ 1 cm 1 m also penetrate Earth s atmosphere and can be observed from the ground Large dish focuses the energy of radio waves onto a small receiver (antenna) Amplified signals are stored in computers and converted into images, spectra, etc. Comparing Radio and Optical Images Why are Radio Telescope so Big? Colors in a radio map can indicate different intensities of the radio emission from different locations on the sky Imagine.gsfc.nasa.gov min = 1.22 ( /D) Radio waves are long wavelength waves they give poor resolving power Solution 1: Increase the diameter of the disk But you can make diameter only so big Interference of Light Waves Solution 2: Interferometry Combine the signals from several smaller telescopes to simulate one big mirror. This holds true even if not the entire surface is filled out. This technique also works in optical range min = 1.22 ( /D) https://vimeo.com/60775957 Source: Hewitt 4
Radio Interferometry The Very Large Array (VLA): 27 dishes are combined to simulate a large dish of 36 km in diameter. Science of Radio Astronomy Radio astronomy reveals several features, not visible at other wavelengths: Neutral hydrogen clouds (which don t emit any visible light), containing ~ 90 % of all the atoms in the Universe. Molecules (often located in dense clouds, where visible light is completely absorbed). Radio waves penetrate gas and dust clouds, so we can observe regions from which visible light Even larger arrays consist of dishes spread out over the is heavily absorbed. entire U.S. (VLBA = Very Long Baseline Array) or even the whole Earth (VLBI = Very Long Baseline Interferometry)! Why We Need Space Telescopes? Wavelength Need satellites to observe High flying air planes or satellites Frequency Astronomy at Infrared Wavelength Most infrared radiation is absorbed in the lower atmosphere. However, from high mountain tops or high-flying air planes, some infrared radiation can still be observed. The Stratospheric Observatory for Infrared Astronomy (SOFIA), a joint project of and the German Aerospace Center (DLR), flies at altitudes up to 14 km ( 45,000 ft ). Airborne and Space Telescopes A visual-wavelength image of the planet Jupiter ( left ) compared with a composite infrared image ( right ) using images at wavelengths of 5.4, 24, and 37 microns made during SOFIA s First Light flight in 2010. The white stripe in the infrared image is a region of relatively transparent clouds through which the warm interior of the planet can be seen. Space.com 5
Space Telescopes The Hubble Space Telescope Launched in 1990 Maintained and upgraded by several space shuttle service missions throughout the 1990s and early 2000s Avoids turbulence in Earth s atmosphere Extends imaging and spectroscopy to infrared and ultraviolet The Hubble Space Telescope The Hubble Space Telescope (HST) orbits Earth at an average altitude of 570 km ( 355 mi ) above the surface. In this image, the telescope is viewing toward the upper left. Breath Taking Pics from Hubble 2014: Eagle Nebula and Orion Hubble WFC3/UVIS Breath Taking Pics from Hubble 2017: Supernova 1987A within the Large Magellanic Cloud Breath Taking Pics from Hubble 2003: Mars Approaching Earth European Space Telescopes Herschel Space Observatory Launched in 2009 Carried a 3-m mirror and instruments cooled almost to absolute zero Observes in Infrared wavelength wikipedia 6
Image From Herschel Space Telescopes Future Space Telescope (October 2018?) James Webb Space Telescope (JWST) Expected launch year 2018 Mirror: 6.5 meters Will be in solar orbit ~1 million miles from Earth ESA Comparing HST, James Webb and Herschell Comparing Hubble and James Weeb High Energy Astronomy Telescopes observing gamma-rays, X- rays, and ultraviolet sources must be located high in Earth s atmosphere or in space General-purpose telescopes: e.g., Chandra Single-subject telescopes: e.g., Hindode 7
Chandra X-Ray Observatory Worlds Major Telescpes Non-Electromagnetic Astronomy Radiation from space does not only come in the form of electromagnetic radiation Gravity wave astronomy Gravity waves predicted to be produced by an mass that accelerates, but would be extremely weak and difficult to detect Now gravity waves have been detected LIGO Laser Interferometer Gravitational Wave Observatory (LIGO) Hanford, Washington Livingston, Louisiana Source: wikipedia How LIGO Works Non-Electromagnetic Astronomy Particle astronomy Earth is constantly bombarded cosmic rays highly energetic subatomic particles traveling through space at high velocities Source: wikipedia 8
Acknowledgment The slides in this lecture is for Tarleton: PHYS1411/PHYS1403 class use only Images and text material have been borrowed from various sources with appropriate citations in the slides, including PowerPoint slides from Seeds/Backman text that has been adopted for class. 9