Introduction of radio astronomy
Download as PPTX, PDF8 likes3,540 views
This document provides an introduction to radio astronomy, including its history and key discoveries. It discusses how radio astronomy works and some of the tools used, such as radio telescopes, receivers, and interferometers. Important figures who contributed to the field are also mentioned, such as Maxwell, Jansky, and Reber. Current large radio astronomy projects and arrays are summarized. In conclusion, radio astronomy is used to learn about the universe through radio wave observations and produce images where light cannot be seen.
Introduction of radio astronomy
- 1. INTRODUCTION OF RADIOASTRONOMY By MANHAR 15AE6018 Dept of Aerospace
- 3. The Discovery of Radio Waves Maxwell, Hertz and Marconi The Birth of Radio Astronomy Jansky and Reber Tools of Radio Astronomy What we use to detect radio Radio Astronomy Instruments What is Radio Astronomy? Content.. How it works ? Radio AstronomyToday RadioTelescope Arrays History of Radio Astronomy The Ideal RadioTelescope
- 4. Astronomy at wavelengths from a few mm to tens of meters Visible light has wavelengths in the region of 500nm, that is, 5 x10-7 meters From a physics standpoint, there's no difference between visible light, and microwave/radio-wave “light”. Living things have receptors for only a tiny part of the EM spectrum What is Radio Astronomy?
- 5. History of Radio Astronomy Like much in science, it was discovered accidentally Karl Jansky, 1933, working on sources of static on international radio-telephone circuits at wavelengths of 10-20m. Discovered that static rose and fell with a period of 23 hours, 56 minutes. Must be of celestial origin Built directional antenna Pinpointed source at galactic centre, in Sagittarius
- 6. James Clerk Maxwell Tied together theories of electricity and magnetism (Maxwell’s equations) to derive the electromagnetic theory of light
- 7. Electric and magnetic fields oscillate together with the same frequency and period Electromagnetic waves do not require a medium! The velocity and wavelength spectrum are define c = f
- 8. Karl Guthe Jansky Founder of Radio Astronomy Hired by Bell Labs in the late 1920’s, Jansky’s mission was to find sources of radio interference
- 9. Jansky constructed a directional 20.5 MHz antenna on a turntable to locate radio noise source positions Sources of noise Nearby storms Distant storms A faint hiss that returned every 23 hours 56 minutes
- 10. Grote Reber Radio Astronomy Pioneer After Jansky’s project ended, Bell Labs was not interested in studying radio astronomy Reber continued Jansky’s original work, by constructing his own radio telescope in 1937 Provided the first maps of the radio sky at 160 and 480 MHz
- 11. Radio AstronomyToday Radio Astronomy at the cutting-edge of astrophysical research Roughly 70% of what we know today about the universe and its dynamics is due to radio astronomy observations, rather than optical observations Big projects all over the world VLA, New Mexico Arecibo, Puerto Rico GBT, Green Bank,WestVirginia Westerbork, Jodrell Bank, ALMA, Hat Creek, SKA, etc Scientists named the basic flux unit after Karl Jansky 1 Jansky == 10-26 watts/hz/meter2
- 12. Colors of light we can’t see… Ionizing Radiation UV X-Rays Gamma Rays Non-Ionizing Radiation IR Microwave Radio
- 13. Receiver Feed Horn Amplifier Mixer Spectrometer Antenna Control Control Computer Example signal path of a radio telescope
- 14. Radio waves areVERY weak! Radio brightness measured in units of Janskys 1 Jansky (Jy) = 10-26 W/m2/Hz Typical sources: Sun: 10,000’s of Jy Brightest Supernova Remnant: 1000’s of Jy Active Galactic Nuclei: 10-100
- 15. Now a days, there are more similarities between optical and radio telescopes than ever before Optical TelescopeRadio Telescope
- 17. Astronomy expands to the entire spectrum
- 18. The Ideal RadioTelescope Directional antennae, such as those with reflectors, isolate the radio power from single sources to reduce confusing radiation from others Low temperature receivers are more sensitive Large collecting areas increase gain and resolution Resolution: roughly 57.3 /D degrees (: observing wavelength, D: diameter of aperture)
- 19. Optical telescopes have an advantage on radio telescopes in angular resolution A one meter optical telescope has a resolution of 0.1 seconds of arc. Since radio telescopes cannot be built large enough to match optical resolution, they can be combined as an interferometer to emulate a large single dish
- 20. Radio Telescope parabolic reflector control room receiver The 140 FootTelescope Green Bank, WV
- 22. TheVLA: An array of 27 antennas with 25 meter apertures maximum baseline: 36 km 75 Mhz to 43 GHz RadioTelescope Arrays
- 23. Very Large Array radio telescope (near Socorro NM) Very Large Array, resolution – 1.4 arc seconds
- 24. ALMA: An array of 64 antennas with 12 meter apertures maximum baseline: 10 km 35 GHz to 850 GHz RadioTelescope Arrays
- 25. At 21-cm wavelengths, PARI’s 26-m and Smiley (4.6 m) have resolutions of 0.5 and 2.5 degrees respectively
- 26. Greenbank (WV) 100-m telescope in has a resolution of 7 arc-minutes
- 27. 300-m telescope inArecibo, Puerto Rico (resolution – 2.4 arcminutes)
- 28. VLBA 10 Antennas of theVery Long Baseline Array (resolution – 5 milli-arcseconds)
- 29. Tools of Radio Astronomy Your FM radio is an example of a simple antenna and receiver Radio waves actually cause free electrons in metals to oscillate! Radio receivers amplify these oscillations, so, radio telescopes measure the voltage on the sky
- 30. Radio Astronomy Instruments Parabolic reflector From a few meters to over 300m! Focal-plane antenna at focus of reflector Waveguide Dipole Various One or more Low Noise Amplifiers Professional instruments chill the amplifiers in liquid Helium to reduce inherent electronic noise Amateurs don't (usually) have that option Use the best amplifiers they can afford Sometimes chill with dry ice
- 31. Receiver chain Spectral Total-power Pulsar Back-end data processing Pulsar processing can require enormous computer power Total-power and spectral can require large amounts of storage space Radio Astronomy instruments cont...
- 32. Cosmic Microwave Background Theorized by George Gamow, in 1948 Would have to be present if Big Bang theory correct Penzias and Wilson at Bell Laboratories discovered it while calibrating sensitive satellite communications experiment in 1965. Found 2.7K excess system noise--why? Received Nobel Prize in Physics for this work in 1978 In 2006, George Smoot received Nobel Prize for mapping the so- called anisotropy (tiny variations) in the CMB, using a satellite to produce map.
- 33. Solar system objects Sun Very strong microwave emitter Makes daytime observing of weaker objects impossible Upper solar atmosphere strong black-body emitter Moon Black-body radiation with surface temperature around 200K NOT reflection of solar microwave radiation! Jupiter/Io Io plasma torus interacts with Jupiters magnetic field Synchrotron emission peaked at 20-30MHz
- 34. Many “big science” RA projects underway SKA Square KilometerArray Goal is to build a multi-dish telescope with an effective collecting area of 1km2 or more! ALMA Atacama Large MillimeterArray 80 dish array, movable dishes Located 5km up on the Atacama plain, Chile Allows observing millimeter and submillimeter wavelengths New CMB satellites:WMAP, PLANCK More detailed maps of the CMB anisotropy New Radio Astronomy science
- 35. CONCLUSION The radio astronomy is use to information of universe and capture the image when he light has came or not seen A radio telescope uses a large concave dish at reflect radio wave to a focal point Radio telescope record signal from the sky A clever technology enables radio astronomers to produce resolution radio image the idea behind interferometry is to combine the data receiver simultaneously by two or more telescope
- 36. Abstract High angular resolution images of extragalactic radio sources are being made with the Highly Advanced Laboratory for Communications and Astronomy (HALCA) satellite and ground- based radio telescopes as part of theVery Long Baseline Interferometry (VLBI) Space Observatory Programme (VSOP). VSOP observations at 1.6 and 5 gigahertz of the milli–arc-second– scale structure of radio quasars enable the quasar core size and the corresponding brightness temperature to be determined, and they enable the motions of jet components that are close to the core to be studied. Here,VSOP images of the gamma-ray source 1156+295, the quasar 1548+056, the ultraluminous quasar 0014+813, and the superluminal quasar 0212+735 are presented and discussed.
- 37. http/www.google search wikipedia.org/wiki/Radio Astronomy Society of Amateur Radio Astronomer http://www.radio-astronomy.org “Radio Astronomy Projects, 3rd ed”, http://www.radiosky.com http://www.atnf.csiro.au/outreach/education/everyone/radio-astronomy National Radio Astronomy Observatory http://www.nrao.edu http://www.cv.nrao.edu/course/astr534/ERA.shtm • www.astro.yale.edu/workshop/.../JeffreyKenney_RadioInterferometry • www.physics.gmu.edu References: