1 slides observing
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How do telescopes help us learn about the universe?
• Telescopes collect vastly more light flux than our eyes
light-collecting area, proportional to D2
• Telescopes can see much more detail than our eyes
angular resolution, proportional to 1/D
• Telescopes/instruments can detect radiation that is
invisible to our eyes (e.g., infrared, ultraviolet)
• Bigger is better! More light collected and the imagesare sharper with larger telescopes, but subject to the
limitation imposed by the atmosphere for telescopes
at high-altitude ground-based observing sites.
A telescope is characterized by its diameter, D
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Hale
Keck1
Keck2
MMT
HET
Gemini (x2)
VLT (x4)
MagellanSALT
LBT (x2)
GTC
LSST
GMT
CELT
E-ELT
HST
Spitzer
JWST
1949
1990
1995
2000
2005
2010
2015
2020
Ground-based Space-based
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• Plot of largest optical/infrared
telescope size vs. time reveals
an exponential growth rate.
– Remarkable given all the
various social, economic,
and technical factors.
• Extrapolating from Keck 10 m:
• 10 m 1993
• 25 m 2034
• 50 m 2065
•
100 m 2097 – History doesn’t explain how
future gains will be made.
Technical innovation is still
essential for progress.
L o g 1 0 c o l l e c t i n g a r e a ( m e t e r s
2 )
Courtesy J. Nelson
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Angular Resolution
•
This is the minimum angular separationthat the telescopecan distinguish.
• For the naked eye it
is about 1 minute ofarc, 1/60 of degree.
• The normal limit dueto turbulence in the
atmosphere is 0.5-1seconds of arc.
• Diffraction limit isn’trealized for D > 0.3m.
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Telescope Resolution
Resolution is improved with a
larger mirror (up to the limit
imposed by the atmosphere)
and also by observing shorter
wavelengths of light/radiation.
Rule of Thumb:
Imaging angular resolution of 0.1“
Diffraction limit of 1.3m telescope
Can resolve size of 100 AU at 10 l.y.
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Basic Telescope Design
• Refracting: lenses
• Limited by chromaticaberration and sagging
Refracting telescopeYerkes 1-m refractor
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Basic Telescope Design
• Reflecting: mirrors
• Most research telescopestoday are reflecting designs
Reflecting telescope Gemini North 8-m
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Keck I and Keck II, Mauna Kea, Hawaii
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Limitations
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Observing problems due to Earth environment
1. Light Pollution
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8.4-m LSST 2018
6x8.4-m GMT 2019
Major Observatory Sites
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Star imaged with a 2m
ground-based telescope
2. Turbulence causes twinkling blurs images.
A CCD image from the
Hubble Space Telescope
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3. Atmosphere absorbs most of EM spectrum, including
all the UV and X-ray, and most infrared wavelengths
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0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
0 1.0 2.0
log TELESCOPE DIAMETER (m)
SCALING LAW DATA
OPTICAL ENDOSTRUCTURES
RADIO
OPTICAL
HE T
HALES UB
KECK
V L
T
NTT
MMT-1
GE M
(COL)
(MAG)MMT-2
R A D
I O
BONN
DS N
l o g
T E L E S C
O P E
C O S T ( M $ , 1 9
9 9 $ )
SMT
E X O S T R U
C T U R E S
NANJING
100 M$
ENDOSTRUCTURE
TELESCOPES
4 10 20 100
2.4
30
TELESCOPE DIAMETER (m)
Telescopes also follow
a cost “scaling law”
Recent history: Cost ~ D2.3
This is because a mirror
scales according to areaor D2 while the building
scales as volume or D3.
Other complex issuesare vibrations, flexure,
and the increasing size
and cost of instruments.
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Solutions
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Frontier Technology
The data rate for the Large Synoptic
Survey Telescope is 1 Gb/s, or 20 Tb
a night, all of which will be reduced
in real time and put out on the Web
The spun-cast 8.4m LSSTmirror is so accurate that
if it were the size of the
US the biggest bumps on
it would be one inch high
S d Ob i L b
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Steward Observatory Mirror Lab
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MMT 6.5 m telescope
Mt. Hopkins, Arizona
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Magellan 6.5 m telescopes
Las Campanas, Chile
l l
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Large Binocular Telescope
Mt. Graham, Arizona
Currently this is the world’s most powerful telescope;
two 8.4 meter mirrors, equivalent to a 12 m telescope
Bi d’ E Vi f LBT
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Bird’s Eye View of LBT
This is the largest
mirror ever made. So is this.
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Giant Magellan Telescope
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Honeycomb Sandwich Mirrors
top view
side view
(section)
Honeycomb sandwich structure makes the mirror stiff yet
light, and it can follow changing night-time air temperature.
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Loading Glass
Close furnace, prepareto melt and spin.
Inspect, weigh, and load
18 tons of borosilicate
glass in ~5 kg blocks.
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UV cameras mounted in
the furnace lid monitor thecasting.
Glass Melting
Heat to 1160˚C, spin at 4.9 rpm, hold four hours toallow glass to fill mold. Cool rapidly to 900˚C then
slowly for 3 months, 2.4˚C/day through annealing.
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First GMT segment. The others are off-axis parabaloids (challenging!)
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The stress-lap polishing of the surface is accurate to one millionth of an inch.
The mirror forms images so sharp you could read a newspaper from 5 miles.
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Second LBT mirror on
its way up Mt. Graham
Mirror being installed in
support cell at the telescope
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Adaptive Optics
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Adaptive Optics
• Rapid changes in mirror shape compensate for atmospheric
turbulence and allow telescopes to approach diffraction limit.
How is technology revolutionizing astronomy?
Without adaptive optics With adaptive optics
T i th diff ti li it d i i t ti l f l t l
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View of convex rear surface of the first LBT secondary shell, showing
aluminum coating for capacitive sensors and magnets for actuators.
To gain the diffraction-limited imaging potential of a large telescope
a light secondary mirror must have its shape adjusted at 50-100 Hz
to take out wave-front variations caused by atmospheric turbulence.
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Figuring of the Optical Surface
Figuring is done with a 30 cm diameter stressed lap. Stressed lap bends
actively to follow curvature variations over aspheric surface. A stiff lap
smoothes out small-scale surface errors as if the mirror were spherical.
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Binary Star: AO on (left), and off (right), where
the active control gives more than an order of
magnitude improvement in angular resolution.
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M92: HST (left) and AO on the ground (right),
with exposure times scaled to control for the
larger telescope used for ground-based data.
The Sharpest Image E er Made
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The Sharpest Image Ever Made
f
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Interferometers
Interferometry
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Interferometers give big gains in
resolution more than sensitivity.
Signals have to be combined in
phase, or coherently, requiringregistration to a fraction of the
wavelength. This is much harder
for light than for radio waves.
Interferometry
• Coherently combine waves from separate telescopes to
reach the resolution equivalent to the largest separation.
R di I f
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Radio Interferometer
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Atacama Large
Millimeter Array
Completion due
in 2016, with 66
antennas of 12m
and 7m diameterat an altitude of
5000m in Chile’s
Atacama Desert.
O ti l I t f t
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Optical Interferometer
D t t
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DetectorsIn the late 1970’s Charge-Coupled Detectors (CCDs) began
to be used in astronomy, taking over from photographicplates and image tubes. By the 1990’s, all major research
telescopes in the world were using nitrogen-cooled CCDs.
How a CCD Works
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How a CCD Works
Like a “bucket brigade,”
a CCD collects light like
rain then passes it along
each row where is gets
measured, then along
the columns. But CCDsactually turn incoming
light into electrons and
store electrical charge
in “wells” that are readout in two dimensions
and then converted into
a digital signal.
CCDs Large and Small
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CCDs Large and Small
2 million pixels 3 billion pixels
Research-grade CCDs have more pixels than digital camerasand are operated at liquid nitrogen temperatures. They’re
virtually perfect, with (1) almost no blemishes, (2) nearly
100% quantum efficiency, (3) large dynamic range, and (4)
a few electrons read noise.
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The camera on the LSST will enable “celestial cinematography,” taking
an image of the entire northern sky every three days to Hubble depth.
The Ubiquitous CCD
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The Ubiquitous CCD
In 1969, Willard Boyle and George
Smith were facing the closure of
their Bell Labs operation, so they
came up with the idea in one hour.
Now, there are 200mdigital cameras and
500m cellphones with
CCDs sold every year.
CCD Data Issues
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Experiments &Instruments
Simulations
answers
questions
•
Data ingest (1 GB per second)• Managing a petabyte
• Common data schemas
• How to organize it?
• How to mine/explore it?
•How to coexist with others
• Query and Visualization tools• Support and Training
• Real-Time Performance – Execute queries in a minute
– Batch query scheduling
?
A Big Data Problem
Literature
Other Archives facts
facts
CCD Data Issues
S A t
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Space Astronomy
Space Astronomy
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Space Astronomy
• Highly successful NASA “Great Observatories” and planetary
probes have revolutionized our view of the universe, although
they cost 10-20x more than same size telescope on the ground.
Note: This timeline from
6 years ago shows some
missions that are slipping
at a rate of ~1 year/year!
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The Moon would be a great spot for an observatory (but at
what price?) Hubble has cost about $8 billion, and counting.
The Electromagnetic Spectrum
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The Electromagnetic Spectrum
NASA Great Observatories
Gamma X-Ray Optical IR
NASA’s flagships are the
“Great Observatories,”
which are all currently in
operation, though Spitzeris in “warm mode” after
exhausting its helium. All
of them can make images
and do spectroscopy, and
are used to study planets,
stars and galaxies. They’re
all $1 billion plus missions
The Electromagnetic Spectrum
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The Electromagnetic Spectrum
NASA Great Observatories WMAP
Gamma X-Ray Optical IR Microwaves
Special purpose
missions such as
WMAP cost less
(about $300m),which is 5 to 6x
less than a Great
Observatory and
can also answermajor scientific
questions.
The Electromagnetic Spectrum and Beyond
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The Electromagnetic Spectrum and Beyond
NASA Great Observatories WMAP LISA
Gamma X-Ray Optical IR Microwaves Gravity Waves
Across the EM Spectrum
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far-IR mid-IR near-IR opt UV far-UV X-ray gamma
Spitzer
Hubble
Chandra and XMM
GALEX
FUSE INTEGRAL
Planck
Herschel
Swift
SIM,
TPF?
JWST
SOFIA
Galileo Updated
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Galileo Updated
The International Year of Astronomy saw
the launch of the “Galileoscope,” a version
of his best instrument made with modern
materials. Only $25, including the tripod!
History of Optical Telescopes
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108
1600 1700 1800 1900 2000
G a l i l e o
Sensitivity
Improvement
over the Eye
Year of Observation
Telescopes alone
Photographic & electronic detection
106
104
102
H u y g e n s
e y e p i e c e
S l o w
f r a t i o
s
S h o r t ’ s 2 1
. 5 ”
H e r s c h e l l ’ s 4 8 ”
R o s s e ’ s 7 2 ”
P h o t o
g r a p h y
M o u n t W i l s
o n 1 0 0 ”
M o u n t P a l o
m a r 2 0 0 ”
S o v i e t 6 - m
1010
E l e c t r o n i c
H u b b l e S p a c e T e l e s c o p e
History of Optical Telescopes
On the Earth:13 of 8 metersor over sincethe mid 90s
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Hubble Space Telescope
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Hubble Space Telescope
HST Overview
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• An orbiting telescope that collects lightfrom celestial objects at visible, UV, and
near-infrared wavelengths• Launched 24 April, 1990, aboard the
Space Shuttle Discovery
• Dimensions: Cylindrical 24,500 lb(11,110-kg), 43 ft long (13.1 m ) and 14.1ft (4.3m) wide
• Orbital period: 96 minutes
• Primarily powered by the sunlightcollected by its two solar arrays
• The telescope’s primary mirror is 2.4 m(8 ft) in diameter
• Was created by NASA with substantialand continuing participation by ESA
• Operated by the Space Telescope ScienceInstitute (STSI) in Baltimore
• Named for Edwin Powell Hubble
"The Hubble Space Telescope is the most
productive telescope since Galileo's"
- Robert Kirshner, President of the
American Astronomical Society
HST Overview
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Guy at Sears told us it would work.
“Top 10 excuses for the HST”
Some kid on Earth is playing
with the garage door opener.
Whatchamacallit is jammed against the
doohickey that looks like a cowboy hat.
See if you can think straight after
12 straight days of drinking Tang.
Bum with squeegee smeared lens
at traffic light.
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Blueprints drawn up by that
“Hey Vern” guy.
“Top 10 excuses for the HST”
Those darn raccoons.
Should not have used GE parts.
Ran out of quarters.
Race of super-evolved galactic
beings is screwing with us.
COSTAR
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•Corrective Optics Space Telescope Axial Replacement (COSTAR).
• Designed to correct spherical aberration due to mis-calibrationof primary mirror before launch.
• Added as part of another instrument and inserted into the lightpath of all instruments during the 1st Shuttle servicing mission.
COS
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Grunsfeld from orbit
T 10 S i I t
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Top 10: Science Impact
Dark energy
Eg
First stars
• Creation of galaxies (HDF, UDF)
• Acceleration of the universe: SN Ia
• Distance scale of the universe: H0
• Giant black holes in galaxies
• Emission lines in active galaxies
• Intergalactic medium (QAL)• Interstellar medium chemistry
• Gamma Ray Burst sources
• Protoplanetary disks
• Extrasolar planets
Mplanet
Young planetary
systemsAurorae on Jupiter
Astronomical Telescope: Astronomical Price Tag
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• Original budget: $475 million
• OTA: $69.4 million
• Actual cost: In 1986, when itwas first assembled for launch,it cost $1.6 billion, and hadseveral technical problems.Four years of tinkering andimprovements later, it finally
launched – at $2.2 billion (notcounting $0.5 billion launch!)
• Percentage overrun: 460%
• Mirror had spherical aberration
– only seeing ~20% of the light.
• SM-1: repaired faulty optics,
next 4 rejuvenated the facility.
• Price, after 21 years: $6 billion.
Hubble Images
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Hubble Images
Making Color Images
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g g
The final color image on the left is the result of extensive processing.
There are four individual images (the top right quadrant at a higher
resolution) and separate images taken through different color filters.
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Each color filter has two equal exposures taken (left and right); the
streaks are cosmic ray hits in the CCD silicon. They arrive randomly
and can be removed very efficiently by combining the two images.
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Next geometric distortions in the camera are mapped and removed
(left), and the seams between the different images are eradicated.
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Blue is assigned to the oxygen filter image, green to the hydrogenfilter image, and red to the sulfur filter image. They are combined.
Courtesy: Jeff Hester (ASU)
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Big Glass
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Big Glass
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JWST
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JWST6.5m
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GCT10.4m
GMT 21.5m
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TMT 30m
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30m Plus Adaptive Optics
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OWL 100m
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Invisible Waves
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Arecibo 300m
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Square Kilometer Array
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The Square Kilometer Array is being built by 18 countries. It will
have 8000 antennas spread over 3000 kilometers, with a central
filled region, and sensitivity 100 x any existing radio telescope
The Cool Universe
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For thermal wavelengths, space is the ideal environment. It’s
almost as good at high altitudes in a plane. The Stratospheric
Observatory for Infrared Astronomy saw first “heat” in 2010.
SOFIA is a 747-SP with
a 2.5m telescope, and
it replaces the 1m KAO
X-ray telescope: “grazing incidence” optics
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Due to shallow angle of collecting the radiation, X-ray telescopes
need more mirror area and are more complex/expensive to build.
Beyond Vision
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Ways of Seeing the Universe
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The Universe as a Telescope
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Gravity Waves
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In General Relativity, any time a mass distribution changes
it creates ripples in space-time that propagate in 3D at the
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pp p p p g
speed of light. The blue lines connect red markers of space
LIGO Livingston Observatory
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LIGO Hanford Observatory
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LIGO Layout
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Power-recycled, cavity-enhancedMichelson Interferometer
Arm Cavities:• Livingston: 4km long
• Hanford: 4km and 2km long
TITM = 2.7%, Finesse ~ 115
Power Recycling mirror:TPR = 2.7%, Gain ~ 50
Mirrors:• Material: Fused Silica
• 25 cm diameter
• 10 cm thick
• Wedged (~2deg)
225W
15kW
5W
Beam Pipe and Enclosure
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• Minimal Enclosure (no services)
• Beam Pipe
– 1.2m diam; 3 mm stainless
– 65 ft spiral weld sections
– 50 km of weld (NO LEAKS!)
Suspension and Optics
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Single suspension 0.31mm music wire
Fused Silica
Surface figure = /6000
• surface uniformity < 1nm rms
• scatter < 50 ppm
• absorption < 2 ppm
• internal Q’s > 2 x 106
Signal Sources
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BANG!
Binary systems» Neutron star – Neutron star
» Black hole – Neutron star
» Black hole – Black hole
Periodic Sources
» Rotating pulsars
“Burst” Sources
» Supernovae
» Gamma ray bursters
» ?????
Stochastic» Big Bang Background
» Cosmic Strings
LIGO is a laser
interferometer
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interferometer
that can detect
motions belowthe size of one
proton over a
span of 5km;
it’s by far the
most accurateexperiment in
physics ever, a
precision of:
10-22
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LIGO and LISA
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Frontiers
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Big Bang + 700,000,000 years
First Light and Beyond
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Big Bang + 100,000,000 years
First Light and Beyond
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Big Bang + 300,000 years
First Light and Beyond
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Big Bang + 10-35 seconds
Beyond Einstein
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• New probes of the inflationary epoch• The possibility of hidden dimensions
• Observational tests of the multiverse
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