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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

Gemini (x2)

VLT (x4)

MagellanSALT

LBT (x2)

Spitzer

Ground-based Space-based

• 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

Courtesy J. Nelson

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.

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.

Basic Telescope Design

• Refracting: lenses

• Limited by chromaticaberration and sagging

Refracting telescopeYerkes 1-m refractor

Basic Telescope Design

• Reflecting: mirrors

• Most research telescopestoday are reflecting designs

Reflecting telescope Gemini North 8-m

Keck I and Keck II, Mauna Kea, Hawaii

Limitations

Observing problems due to Earth environment

1. Light Pollution

8.4-m LSST 2018

6x8.4-m GMT 2019

Major Observatory Sites

Star imaged with a 2m

ground-based telescope

2. Turbulence causes twinkling blurs images.

A CCD image from the

Hubble Space Telescope

3. Atmosphere absorbs most of EM spectrum, including

all the UV and X-ray, and most infrared wavelengths

0 1.0 2.0

log TELESCOPE DIAMETER (m)

SCALING LAW DATA

OPTICAL ENDOSTRUCTURES

OPTICAL

HALES UB

(MAG)MMT-2

T E L E S C

C O S T ( M $ , 1 9

9 9 $ )

E X O S T R U

C T U R E S

NANJING

100 M$

ENDOSTRUCTURE

TELESCOPES

4 10 20 100

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.

Solutions

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

Steward Observatory Mirror Lab

MMT 6.5 m telescope

Mt. Hopkins, Arizona

Magellan 6.5 m telescopes

Las Campanas, Chile

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

Bird’s Eye View of LBT

This is the largest

mirror ever made. So is this.

Giant Magellan Telescope

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.

Loading Glass

Close furnace, prepareto melt and spin.

Inspect, weigh, and load

18 tons of borosilicate

glass in ~5 kg blocks.

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.

First GMT segment. The others are off-axis parabaloids (challenging!)

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.

Second LBT mirror on

its way up Mt. Graham

Mirror being installed in

support cell at the telescope

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

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.

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.

Binary Star: AO on (left), and off (right), where

the active control gives more than an order of

magnitude improvement in angular resolution.

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

The Sharpest Image Ever Made

Interferometers

Interferometry

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

Radio Interferometer

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

Optical Interferometer

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

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

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.

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

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

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

CCD Data Issues

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!

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

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

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

NASA Great Observatories WMAP LISA

Gamma X-Ray Optical IR Microwaves Gravity Waves

Across the EM Spectrum

far-IR mid-IR near-IR opt UV far-UV X-ray gamma

Spitzer

Hubble

Chandra and XMM

FUSE INTEGRAL

Planck

Herschel

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

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

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 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

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

HST Overview

• 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

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.

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

•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.

Grunsfeld from orbit

T 10 S i I t

Top 10: Science Impact

Dark energy

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

• 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

Making Color Images

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.

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.

Next geometric distortions in the camera are mapped and removed

(left), and the seams between the different images are eradicated.

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)

3/19/2013 83

3/19/2013 84

3/19/2013 85

3/19/2013 86

3/19/2013 87

3/19/2013 89

Big Glass

JWST6.5m

GCT10.4m

GMT 21.5m

TMT 30m

30m Plus Adaptive Optics

OWL 100m

Invisible Waves

Arecibo 300m

Square Kilometer Array

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

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

Due to shallow angle of collecting the radiation, X-ray telescopes

need more mirror area and are more complex/expensive to build.

Beyond Vision

Ways of Seeing the Universe

The Universe as a Telescope

Gravity Waves

In General Relativity, any time a mass distribution changes

it creates ripples in space-time that propagate in 3D at the

pp p p p g

speed of light. The blue lines connect red markers of space

LIGO Livingston Observatory

LIGO Hanford Observatory

LIGO Layout

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)

Beam Pipe and Enclosure

• 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

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

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

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:

LIGO and LISA

Frontiers

Big Bang + 700,000,000 years

First Light and Beyond

Big Bang + 100,000,000 years

Big Bang + 300,000 years

Big Bang + 10-35 seconds

Beyond Einstein

• New probes of the inflationary epoch• The possibility of hidden dimensions

• Observational tests of the multiverse

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