Radio Astronomy
Ganesh Sankaranarayanan
Graduate Student
Electrical Engineering
UW Campus Observatory
• Built in 1892
• Located on 4th and
University St
• Moved in 1895 to the
current location
• Second Building on
campus next to denny
hall
Telescope

6-inch Brashear
objective lens
 Warner & Swasey
equatorial mount
 90-inch focal length
 Warner & Swasey
wooden , rests on 3
civil war era cannon
balls!
Visible World
Electromagnetic spectrum

Electromagnetic
radiation
 The visible world (We
see very little!)
 Radio spectrum
 X-ray, UV,IR
spectrum
History of Radio Astronomy
Serendipity?
Karl Jansky –1928
Rotating Telescope
History of Radio Astronomy
Grote Reber -1937
9 meter dish antenna
Image courtesy NRAO
Radio Sources
21-cm Neutral Hydrogen Lines
High Energy State
Low energy state
21-cm photon
Radio Sources
21-cm Neutral Hydrogen lines
Discovery

Harold Irving Ewen 1951
Emission once in few
million years
 80% Hydrogen in
Universe
 21-cm emission not
obstructed by dust
 Used to map galaxies
and ISM
Milky Way in 21cm
Image courtesy of NRAO/AUI
M33 Radio and Optical Composite
Image courtesy of NRAO/AUI and NOAO/AURA/NSF
Orion Nebula M42
Image courtesy of NRAO/AUI
Radio Sources
Pulsars





Image courtesy Jodrell Bank Pulsar Group
Discovered in 1967
Rapidly rotating
neutron star
10-15 km radius
Cosmic clocks in the
sky
First thought to be a
signal from aliens
(“little green men”)
Sounds of Pulsars
PSR B0329+54
47 Tucanae
PSR B1937+21
PSR B0531+21, The
Crab Pulsar
Image and sound courtesy Jodrell Bank Pulsar Group
Pulsar and Supernova Remnant
Image courtesy of NRAO/AUI
Crab Nebula Pulsar
Image Courtesy J. Hester (ASU), CXC, HST, NRAO, NSF, NASA
Radio Sources
Quasars

Quasar : Quasi- stellar
radio source
 Most distant object to emit
radio waves
 Contain super massive
black holes in the center
 Radio emission produced
by synchrotron radiation
 Reflect the stage of
universe billions of years
ago
Quasar
Image courtesy of NRAO/AUI
Radio Sources
MASERS

Dense molecular clouds
with strong emission (T >
106 K)
 MASER action
Microwave Amplification
by Stimulated Emission
of Radiation
 OH,H2O,SiO,
CH3CH2OH and more…
Water MASER
Image courtesy of NRAO/AUI
Radio Sources
Cosmic Microwave Background
Radiation
Arno Penzias and Robert Wilson 1963
Robert Wilson on
cosmic noise
Image and sound courtesy
Lucent Technologies Inc.
Cosmic Microwave Background
Radiation
COBE
The COBE datasets were developed by the NASA Goddard Space Flight
Center under the guidance of the COBE Science Working Group and were
provided by the NSSDC.
Radio Sources Sun
Image courtesy of NRAO/AUI
Radio Sources Planets
Saturn
Jupiter during impact
of comet ShoemakerLevy 9
Image courtesy of NRAO/AUI
Radio Telescopes Arecibo




Located in Puerto
Rico
Operated by
Cornell and NSF
1000 ft (304.8 m)
Used for
Astronomy,
atmospheric and
planetary studies
Radio Telescopes
Green Bank Telescope

Located in Green
bank, West Virginia
 485 feet tall -- taller
than the Statue of
Liberty!
 100 by 110 m width
 World’s Largest
steerable radio
telescope
Image courtesy of NRAO/AUI
Radio Telescopes
VLI (Very Large Array)



Located in Socorro, NM
27 antennas interferometer
Each antenna 25 meters( 82
feet) in diameter
Image courtesy of NRAO/AUI
VLBI (Very Large Baseline Array)
ALMA The Atacama Large
Millimeter Array

Atacama desert,
Chile
 64 radio
telescopes
 12 meter (39 feet)
wide dish antenna
 Expected to
operate in 2011
Image courtesy of NRAO/AUI
Radio Telescopes around the
world

Europe
 Westerbork Synthesis Radio Telescope (WSRT) ,
Netherlands
 The Ryle Telescope, United Kingdom

Australia
 Mopra Observatory

Asia
 Giant Meterwave Radio Telescope(GMRT) , India
 Nobeyama millimeter array ,Japan
Radio Astronomy at UW

UAI established in
1999
 7ft dish
 Currently building
motion control and
receivers for 21cm
hydrogen lines (1420
MHz)
Future of Radio Astronomy

More cost to build radio telescopes
 Consortium among countries to build future telescopes

Major advancements in telescope technologies
 Better design to control noise over effective area

GMRT,ALMA
 Better angular resolution

Encroachment of radio frequencies by ground and
satellite communications
 More power in deciding frequency allocations
 Better modulation techniques to prevent spill over
The End
Questions ?
Thank You