By Winter Sie-Hilland and Kevin Mogk RADIO ASTRONOMY TIMELINE.

By Winter Sie-Hilland and Kevin Mogk

RADIO ASTRONOMY TIMELINE

Image courtesy of NRAO/AUI

MAJOR DISCOVERIES• 1951 the 21 cm line for neutral Hydrogen is first observed (National

Radio Astronomy Observatory. 2011.)

• 1941 First radio map of the sky by Grote Gerber (MITTON 20057 p289)

• 1942 Stanley Hey finds radios bursts from the sun. (Space Academy. 2014; HEY 1973)

• 1955 Burke and Frankelin discover radio noise coming from Jupiter. (Space Academy. 2014 )

• 1961-63 Discovery of quasars (Space Academy. 2014 )

• 1964 Discovery of a uniform e-m radiation that permeates in all directions of the universe, became know as the Cosmic background radiation, or cosmic microwave background at a temperature of 2.73 K (MITTON 2007 p74-5)

• 1967 Jocelyn Bell and Tony Hewish discover the first pulsars. (Space Academy. 2014 )

• 1992 the space telescope COBE (Cosmic Background Explorer) discovers temperature variations in the CMB of 1/1,000,000 of a degree, consistent with the big bang theory (MITTON 2007 p74-5)

JANSKY • Karl Guthe Jansky was born in Norman Oklahoma, October 22, 1905

(d.Feb.14, 1950)• Degree in physics from the University of Wisconsin• Worked for Bell Telephone Laboratories in Holmdel, NJ, beginning in

1928• New York Times of May 5, 1933.

Photo Credit: Bell Labs

THE 21 CM LINE

• In 1944 Desiring to see beyond the dust lanes of the Milky Way, Jan Oort postulates the idea of an immersion line for hydrogen in the electro-magnetic spectrum at a wavelength that could piece the dust of out inner galaxy.

• In 1945 Hulst, one of Oorts students, predicts that neutral hydrogen would be visible at the 21 cm line.

• It is not until 1951 That Harold Ewen and Edward Prucell succeed in the detection of the 21 cm line with their horn shaped antenna at Harvard University.

National Radio Astronomy Observatory 2003 and 2011

REBER AND KRAUS:SURVEYORS OF STATIC

• Grote Reber built a radio telescope in his back yard in 1937

• First systematic survey of radio waves from the sky

• A range of wavelengths

• 3300 MHz

• 900 MHz

• 160 MHz (1.9m wavelength)

• Published the first radio sky survey in the Astrophysical Journal [ApJ 100, 279 (1944)].

NARO; Reber’s Telescope, now at Green Bank WV

• John Kraus, after World War II, started a radio observatory at Ohio State University and wrote a textbook on radio astronomy, which is

still the "bible" for radio astronomers.

OTHER FORMS BESIDES DISHES

• 1951 H1 Horn

• Ewan and Purcell’s H1 galactic emmision detector

• 1.4 GHz, wavelength of 21cm

• 1962 Echo Horn Reflector (Bell Labs horn antenna)

• Penzias and Wilson discovered cosmic background radiation

Horn Antenna — Holmdel, New Jersey.Horn Antenna, circa 1960.(Photo Credit: Bell Labs)

DISHES• 1957 Jodrell Bank Lovell

Telescope

• 76 meter steerable antenna (3rd largest in world now)

• 1962 Arecibo (Upgraded in 1974 and 1996)

• 1000 foot (305 m) diameter spherical surface

• 8GHz max, wavelength of 3.8 cm

• 1972 Effelsberg

• 100 m dish that has flex (Homology)

• 86 GHz max

• NRAO GBT (Pics next slide)

• 100 m aperture

• 290 MHz to 100 GHzArecibo: Image courtesy of the NAIC - Arecibo Observatory, a facility of the NSF

DISH OR NO DISH

At 9:43 p.m. EST on Tuesday the 15th of November 1988, the 300-Foot telescope in Green Bank collapsed

 Green Bank 300 ft telescope: Images courtesy of NRAO/AUI 

INTERFEROMETRY

INTERFEROMETERS

• 1948 Dover Heights Sea Interferometer, Australia

• 1962 Cambridge Interferometer

• 178 MHz

• Produced the 4C Catalog (Ryle and Neville, (MNRAS 125, 39, 1962))

 GBI; Image courtesy of NRAO/AUI 

INTERFEROMETERS

• 1963 Ohio State Big Ear, USA (Kraus design)

• 175ft diameter dish at 1.4 GHz. Wavelength 21 cm (H1)

• 1965 Nancay, France

• 1978 GBI (Green Bank 3-Element Interferometer)

• 300 foot and 140 foot

• Offline 2000, due to funding

VLAVERY LARGE ARRAY

(1980)

• The Very Large Array (VLA) radio telescope is located on the plains of San Agustin, 80 kilometers (50 miles) west of Socorro, New Mexico

• NRAO (National Radio Astronomy Observatory) operated by Associated Universities, Inc. under a cooperative agreement with the National Science Foundation

 Image courtesy of NRAO/AUI

• 27 individual antennas arranged in a "Y" pattern• Each antenna in the

array measures 25 meters (82 feet) in diameter and weighs about 230 tons

• Four times each year, the VLA antennas are moved into new configurations by a transporter that moves along dual sets of railroad tracks

• their closest configuration (about 1 kilometer wide) the VLA is able to image large portions of the sky

• largest configuration is about 36 kilometers wide

ARRAYS, THEN V.S. NOW

• Jansky detected three powerful (~10000 Jy) sources

• The expanded Very Large Array can see 1 μJy • (100000000000 times improvement in resolution from Jansky)

• Part of difference is collecting area. The rest is due to cooled broadband receivers with HEMT amplifiers for cm wavelength and SIS mixers for mm λ’s

* For reference, a cell phone on the Moon would produce a signal at earth of roughly 50,000 Jy

VERY LONG BASELINE ARRAY

Image courtesy of NRAO/AUI and Earth image courtesy of the SeaWiFS Project NASA/GSFC and ORBIMAGE

• 10 radio antennas spread out

• Each antenna is 82 feet (25 meters) in diameter, weighs 240 tons

• data from each of the ten antennas are recorded onto magnetic discs and shipped to the Array Operations Center where they are combined in pairs in a correlator, the specialized supercomputer at the heart of an interferometer (analogous to the VLA)

The VLBA was dedicated in 1993

Composite image credit: Tae-Hyun, Jung (MPIfR, 2004)

ALTACAMA LARGE MILLIMETER/SUBMILLIMITER ARRAY

(ALMA) (2013)

• A giant array of 12-m antennas (the 12-m array)• with baselines up to 16 km

• A compact array of 7-m and 12-m antennas to greatly enhance ALMA's ability to image extended targets

• Located on the Chajnantor plateau at 5000m altitude

• Initially, it will observe at wavelengths in the range 3 mm to 400 μm (84 to 720 GHz)

*antennas can be moved around, in order to form arrays with different distributions of baseline lengths

The design of ALMA is driven by three key science goals:1. The ability to detect spectral

line emission from CO or [CII] in a normal galaxy like the Milky Way at a redshift of z=3, in less than 24 hours

2. The ability to image the gas kinematics in protostars and in protoplanetary disks around young Sun-like stars in the nearest molecular clouds (150 pc)

3. The ability to provide precise high dynamic range images at an angular resolution of 0.1 arcsec

LONG WAVELENGTH ARRAYThe LWA is an effort to advance astronomy by using inexpensive antenna stations to build a very large aperture to probe the depths of space at the

lowest frequencies – between 10 MHz and 88 MHz

LOFAR in Germany will work on the same concept when complete (www.lofar.org)

Image courtesy of The LWA Consortium

2011 construction complete

This first station is referred to as LWA1, and consists of 256,

dual-polarization dipoles (10-88MHz)

built at the VL site next to the VLA site

THE FUTURE OF RADIO:

THE SQUARE KILOMETER ARRAY

“The SQUARE KILOMETRE ARRAY is a global project to design and construct a next generation international radio

telescope. The SKA will detect electromagnetic radiation at wavelengths from meters to

centimetres with a collecting area of one million square meters (one

square kilometre); 100 times larger than our most powerful existing radio

telescope array.” http://www.skatelescope.ca/

SKA IS MADE UP OF The Australian SKA Pathfinder

(ASKAP) telescope

• It is made of 36 identical 12-metre wide dish antennas and will form the basis of a 96-dish survey telescope to be built in SKA's first phase

• Equipped with innovative Phased Array Feed (PAF) receivers designed and built by CSIRO• PAFs provide multi-pixel

images of the sky, allowing it to survey large areas of the sky quickly.

ASKAP antennas (MRO) in Western Australia,

2010. Credit: WA Department

of Commerce

Murchison Widefield Array• (MWA) is a revolutionary low-frequency telescope with no moving

parts.

• By computing the received signals with a supercomputer, radio waves from sections of the sky are isolated making it is possible for the telescope to be shared between observers studying different parts of the sky at once

SKA IS MADE UP OF

Image is one of 128 tiles of the Murchison Widefield Array

(MWA) telescope. Credit: WA Department of

Commerce

NOBEL

• 1974 the Nobel prize for physics was awarded to Sir Martin Ryle and Antony Hewish for their pioneering work in radio astronomy.

• Ryle was recognized for his observations and inventions including the aperature synthesis technique.

• Hewish for his role in discovering pulsars.

• 1978 the novel prize for physics was awarded half to Arno Allan Penzias & Robert Wilson for their work in the discovery of the cosmic microwave background. (the other half to Pyotr Kapista for discoveries in low temperature physics.)

Nobel Prize 2014 A & B

QUESTIONS

• SKA Video if there is time:

http://www.ska.edu.au/downloads/assets/SKA_HD.mp4

ALMA. 2014. General Website. http://www.almaobservatory.org/ BURKE, Bernard; GRAHAM-SMITH, F. 2010. An Introduction to Radio Astronomy. New York: Cambridge

University Press. 444 pp. 3rd ed.COUPER, Heather and HENBEST, Nigel. 1999, The Firefly Space Encyclopaedia, London; DK Publishing.

303pp.FREEDMAN, Roger; KAUFMANN III, William. 2005. Universe. New York: W. H. Freeman Company. 693

pp. 7th ed.HEY, J. S. 1973. An Evolution of Radio Astronomy. New York: Science History Publications. 214 pp.MITTON, Jacqueline. 2007. Cambridge Illustrated Dictionary of Astronomy. New York: Cambridge University

Press. 397 pp.National Radio Astronomy Observatory. 2011. “Doc” Ewen and the discovery of Radio emission from

Hydrogen. http://www.nrao.edu/whatisra/hist_ewenpurcell.shtml National Radio Astronomy Observatory. 2003. Prediction of 21cm Line Radiation.

http://www.nrao.edu/whatisra/hist_oortvandehulst.shtml.National Radio Astronomy Observatory, History of Radio Telescopes, Paul Vanden Bout

http://apps3.aps.org/aps/meetings/april09/presentations/C6-2-VandenBout.pdfNobel Prize. 2014 A. TheNobel prize in Physics 1974.

http://www.nobelprize.org/nobel_prizes/physics/laureates/1974/.Nobel Prize. 2014 B. TheNobel prize in Physics 1974.

http://www.nobelprize.org/nobel_prizes/physics/laureates/1978/ Space Academy. 2014. The First 50 Years of Radio Astronomy.

http://www.spaceacademy.net.au/museum/RA50.htm The Long Wavelength Array, http://www.phys.unm.edu/~lwa/index.htmlThe Square Kilometre Array. 2014 A. The SKA Layout. https://www.skatelescope.org/location/layout/ The Square Kilometre Array. 2014 B. The Project Timeline.

https://www.skatelescope.org/project/projecttimeline/ CSIRO. 2014 A. CSIRO ASKAP Radio Telescope. http://www.atnf.csiro.au/projects/askap/index.html

CSIRO. 2014 B. CSIRO ASKAP Timeline. http://www.atnf.csiro.au/projects/askap/timeline.html

References