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Radio astronomy from your backyard

Radio astronomy from your backyard. An introduction to radio astronomy for optical amateur astronomers. Ciprian “Chip” Sufitchi N2YO NOVAC Meeting - Sep 14, 2014. Solar flare X1.6 – Sep 10, 1745Z. Thomas Ashcraft, New Mexico: Stereo recording 22/23 MHz. What is radio astronomy?.

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Radio astronomy from your backyard

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  1. Radio astronomy from your backyard An introduction to radio astronomy for optical amateur astronomers Ciprian “Chip” Sufitchi N2YO NOVAC Meeting - Sep 14, 2014

  2. Solar flare X1.6 – Sep 10, 1745Z Thomas Ashcraft, New Mexico: Stereo recording 22/23 MHz

  3. What is radio astronomy? • Radio astronomy is a subfield of astronomy that studies celestial objects at radio frequencies. • Radio astronomy covers 6 decades in frequency across the e-m spectrum • Meter (1 cm – 30 m) • Millimeter (1 mm to 10 mm) • Sub-millimeter (< 1 mm, up to 0.4 mm) • e.g. FM radio and TV stations (~ 3 meters); wireless internet (wi-fi), microwave ovens/mobile phones (10-15 cm).

  4. A little history Karl Jansky - 1932 Discovery of cosmic radio waves

  5. A little history Grote Reber (1911-2002) – The first radio astronomer (W9GFZ) Built the first parabolic radio telescope (9 m diameter) Detected Milky Way, Sun, Cas-A, Cyg-A, Cyg-X @ 160 & 480 MHz (ca. 1939-1947)

  6. A little history • 1944: The 1420 MHz (21 cm) HI emission line is predicted) • 1951: The 21 cm emission line detected • 1955: Discovery of Jovian emission Historical marker: Seneca, MD in Montgomery County (32 miles away) IN 1955 SCIENTISTS BERNARD BURKE AND KENNETH FRANKLIN FROM THE CARNEGIE INSTITUTION OF WASHINGTON ACCIDENTALLY DISCOVERED NATURALLY-GENERATED RADIO WAVES FROM JUPITER USING A 96-ACRE ANTENNA ARRAY. THIS DISCOVERY LED TO GREATER UNDERSTANDING OF PLANETARY MAGNETIC FIELDS AND PLASMAS AND OPENED A NEW WINDOW IN OUR EXPLORATION OF THE SOLAR SYSTEM.

  7. A little history • 1963: Discovery of Quasars (3C273) • 1965: Cosmic Microwave Background detected (Penzias & Wilson) • 1967: Discovery of Pulsars (Jocelyn Bell-Burnell and Anthony Hewish)

  8. Society of Amateur Radio Astronomers (SARA) • 1981 SARA is founded: a scientific, non-profit group created for the sole purpose of supporting amateur radio astronomy • The group consists of optical astronomers, ham radio operators, engineers, teachers and non-technical persons. • Bi-Monthly electronic Radio Astronomy Journal • Membership $20/year

  9. Society of Amateur Radio Astronomers (SARA) • Grant program: over $6,000 in support of student projects in the 2013-2014 fiscal year • Manufactures and distributes RA project kits: SuperSID, RASDR (soon) • Once a year, SARA meets for a three-day conference at the National Radio Astronomy Observatory, located in Green Bank, West Virginia • http://www.radio-astronomy.org

  10. Earth’s atmosphere is transparent to radio waves

  11. What makes radio astronomy special? The radio sky is generally quite different from the optical sky. Most of the radio sources are located at cosmological distances! The NRAO 5 GHz sky survey projected on the sky around Green Bank, WV

  12. What else makes radio astronomy special? Radio polarization measurements are just about the only way astronomers have of measuring magnetic fields in galaxies. Non-thermal nature of radio emission: probes the violent, high energy, Universe.

  13. What else makes radio astronomy special? Radio waves (including sub-mm) are largely unaffected by dust - can detect highly obscured star-forming systems at high red shift.

  14. What else makes radio astronomy special? Radio waves at mm wavelengths measure fluctuations in the temperature of the photons that escaped from the last scattering surface (z ~ 1000), when the Universe became neutral. The power spectrum of the CMB signal can be used to determine the main cosmological parameters.

  15. What else makes radio astronomy special? The neutral hydrogen 21 cm emission line

  16. What else makes radio astronomy special? SETI... future radio telescopes may at last provide the answer to the ultimate question... “Are we alone?” The Wow! signal was a strong narrowband radio signal detected by Jerry R. Ehman on August 15, 1977, while he was working on a SETI project at the Big Ear radio telescope of The Ohio State University

  17. Cosmic Radio Sources - emission mechanisms Black body radiation (thermal emission) Units of spectral energy density are Watts per Hz per sq meter per steradian h: Plank constant = 6.62E-34 m2 kg/s k: Boltzmann constant = 1.38E-23 m2 kg s-2 K-1 The Raleigh-Jeans law: at low frequencies the intensity increases with the square of the frequency

  18. Cosmic Radio Sources - emission mechanisms Black body radiation (thermal emission) “Brightness temperature” Active galaxy ~ 1E12 K Blank sky = 2.73 K Sun@300 MHz = 500000 K Orion nebula = 10-100 K Quasars at 5 GHz ~ 1E12 K

  19. Cosmic Radio Sources - emission mechanisms Black body radiation (thermal emission) The Flux density (S), is the power received (P) within a certain frequency band (dν), via a certain effective collecting area (A) with efficiency η The unit of Flux density is the Jansky (Jy): 1Jy = 10-26 W m-2 Hz-1

  20. Cosmic Radio Sources - emission mechanisms • Produced when charged particles (usually electrons) spiral around magnetic field lines • Strong magnetic fields are required • Pulsars, magnetic stars • Sun, Jupiter, Saturn: low frequencies Cyclotron radiation Synchrotron radiation • Synchrotron emission is associated with the acceleration of relativistic and ultra-relativistic electrons in a weak magnetic field • Observed in supernova remnants, galaxies, interstellar medium • Helps to map magnetic fields of galaxies

  21. Cosmic Radio Sources - emission mechanisms • Interstellar molecules (H2, CO, CN) emit radiation by rotation rather than direct transition of their electrons • The radiation emitted tends to be in the microwave region (hundreds of GHz) Spectral line radio emission: Interstellar molecules

  22. Cosmic Radio Sources - emission mechanisms • The 21 cm HI line is produced by magnetic hyperfine splitting in the electronic ground state of the H atom • The very small energy difference between the 2 states (dE ~ 6 μ eV) corresponds to 21 cm line ν =1420.40575 MHz) Neutral hydrogen: 21 cm line

  23. Cosmic Radio Sources - emission mechanisms • A spontaneous spin-flip from the one state to another is highly forbidden with an extremely small probability (once every 11 million years) • When collisions between H atoms occur, a random spin-flip transition may happen (typically every 200 years) • … but there is a lot of hydrogen in ISM and galaxies! Neutral hydrogen: 21 cm line

  24. Cosmic Radio Sources - emission mechanisms Cosmic Microwave Background (CMB) The CMB is well explained as radiation left over from an early stage in the development of the universe Measurements of the CMB show that it is almost a perfect black-body

  25. Radio telescopes (Antennas) Dipoles

  26. Radio telescopes (Antennas) Parabolic dishes Az/El mount Equatorial (polar) mount

  27. Radio telescopes (Antennas) Reflector types

  28. Radio telescopes (Antennas) Reflector types

  29. Radio telescopes (Antennas) Appreciating the scale of large radio telescopes....

  30. Radio telescopes (Antennas) • The largest fully steerable dishes have D~ 100 m • Problem: θ ~ λ/D; impossible to achieve sub-arcsecond resolution • Weight and size: pointing accuracy and tracking are affected Interferometers

  31. Radio telescopes (Antennas) Interferometers

  32. Radio telescopes (Antennas) Interferometers The Very Large Array (VLA): 27 x 25 m telescopes up to 36 km in New Mexico The Very Long Base Array (VLBA): 10 x 25 m telescopes on a 8000 km baseline

  33. Radio astronomy: books The “blue book”: John D. Kraus – “Radio astronomy”

  34. Radio astronomy: books Burke & Graham-Smith: “An introduction to radio astronomy”

  35. Radio astronomy: books Steven Arnold: “Getting started in radio astronomy”

  36. Radio astronomy: books Jeff Lashey: “The radio sky and how to observe it”

  37. Radio astronomy: books William Lanc: “Radio astronomy projects”

  38. Optical vs amateur radio astronomy Seeing is believing!

  39. Optical vs amateur radio astronomy Equipment – simple/inexpensive or complex/expensive

  40. Optical vs amateur radio astronomy

  41. Optical vs amateur radio astronomy SKYNET: remote control telescopes. Contact Tom Finkenbinder for access PROMPT robotic telescopes in Chile 20 meter Green Bank radio telescope

  42. Projects: Pulsar detection Joe Taylor: “Detecting pulsars with amateur equipment” Nobel Laureate Joe Taylor, K1JT at SARA conference 2014 – Green Bank WV

  43. Projects: Pulsar detection • Pulsars are rapidly rotating neutron stars which sweep out a beam of electromagnetic radiation like a light house. PSR 0329+54 Period: 0.71 s Frequency: 410 MHz PSR 0833 (Vela pulsar) Period: 0.089 s Frequency: 410 MHz PSR B0531 (Crab pulsar) Period: 0.033045 s Frequency: 410 MHz

  44. Projects: Pulsar detection

  45. Projects: Pulsar detection

  46. Projects: Pulsar detection

  47. Projects: Pulsar detection

  48. Projects: Pulsar detection http://www.k5so.com/

  49. Project: Radio Jove • Cyclotron and synchrotron emissions from Jupiter • Natural satellite Io plays an important role • The most intense source is the Io-dependent Io-B • Decametric emission (4 – 39.5 MHz)

  50. Project: Radio Jove

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