Transcript Alanna Connors, for the AstroStatistics Working Group at Harvard

Astronomy Instruments from the
Quantum Age:
Do New Instruments, or New
Ideas, Drive New Science?
Alanna Connors, for the AstroStatistics Working
Group at Harvard Smithsonian Center for
Astrophysics
“Processing of some sophistication is needed, rather
than being just a fixup at the end.” Tim Cornwell
OUTLINE
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All Optical:
 Eye and Hand
 Telescope and Hand
 Photography
New Science: Equations for fun!
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New Instruments: Seeing the Invisible
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Mathematics of Invariance: Relativity+ QM
Bohr Atom
Below the Visible: Radio, Infrared (skip)
** Above the visible: Ionizing Radiation
Background or signal: Cosmic rays
Old Instruments, New Instruments:
Chandra has it easy, but illustrates main principles
Tougher Instruments; still, “Do It Right”
Early Observations: Eye, Hand
Crab Supernova July 1054 AD
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Anasazi
Japan
Chinese
guest
star
“seen in
the day
like
Venus”
Armillary Sphere
Grand Sweep of Stars and Planets:
How to Infer 3D from meticulous 2D:
Ptolemy, Hypatia, …
Telescope: Galileo and onwards
Allows more meticulous
precision
Planetary Motions: 3D from 2D:
Kepler, Brahe, Hooke, Newton…
Statistics:
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Least-Squares Fitting (LaPlace)
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Periodic Motion (Fourier)
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SKIPPING many interesting math
techniques for orbits, etc.
Quantum Mechanics & Relativity:
Oh, Equations! Fun!
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QUANTUM MECHANICS
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Comes in lumps:
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E = h n ( Energy = Planck constant * frequency )
n = c / l (frequency = light-speed / wavelength)
Wave properties for light AND matter!
Particle properties for matter AND light!
RELATIVITY:
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E = m c^2
Electron ~ 0.5 MeV, Proton and neutron ~ 1 GeV
Potential
Energy
balanced by
angular
momentum
* Angular
momentum
quantized =
nh
* Result:
Constructive
interference:
Integer l’s in
each orbit
Energy levels
~ 1/n^2
Stellar Spectra: Annie Jump Cannon
Women of Harvard College Observatory
Cecelia Payne-Gaposchkin:
Old Astronomy + New QM for 1st Time
Huge amount of careful
observations of spectra
QM tells ionization balance
Startling thesis result:
Most of the visible universe
made of Hydrogen!
New Instruments:
Seeing the Invisible
Jumping Over Whole Story of Radio:
G. Reber, 1932 backyard;
Present VLA
(But Interferometry - very intersting!)
Ionizing Radiation from the Sky
Victor Hess
flies with a
gold-leaf
electroscope
like one at left;
Measures
decreasing
discharge time
as altitude
increases
Radio-Chemistry Skill of Curie Family:
Supply Standards of Radioactive Materials
Radium, purified
New Instruments
•Scintillators (right; also
reading)
•Cloud chamber DEMO
(tracing tracks by hand from
photographs!)
•Geiger Counter DEMO
•Photographic / emulsion
•Basics same as many
modern ones
Take a minute to think about
Statistics, I
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Historical notes on watching for
scintillations in a dark room
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Tracks: tracing by hand (!) until very
recently (some HEP still do!)
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Historical note: for some reason, most technicians who do
this are women -- Claudia Brevard and CGRO EGRET
Any thoughts on statistics?
Take a minute to think about
Statistics, II
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Optical “culture”: What can I see?
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Invisible light “culture”:
m = e * R
*
i
+
b
<counts>=Eff. Area*Inst.Redist.*Source intensity +Sky+Inst. Bkg
Measured counts = Y ~ Poisson (m)
Poisson(m) ~ Normal(m,sqrt(m))
Least-squares, c^2 minimization, CC w/ R
Pre-1975:
Early X-Ray Telescopes:
Bin size>PSF; Many counts/bin; NO processing
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SKYLAB: Solar – very large bright source
Copernicus, ANS; sky, but only point
sources
Pre-1975: Early G-Ray “Telescopes”
Bin size>PSF; fewer counts; “Bin them up”
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SAS-2 satellite:
> 100 MeV G-ray
charged particle shield
profile of Galactic plane covers spark chamberS
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1975-1990's: COS-B Gamma-Ray
Satellite
Preliminary imaging; Simple Gauss-Normal
“fix it up at the end”
Galactic Anti-center region: COS-B satellite (Aug
Crab and Geminga pulsars '75 - Apr '82; 2 keV –
5GeV) Cutaway of spark+ Diffuse emission
chambers, shielding
1975-1990s: Einstein X-Ray Observatory
(HEAO2)
First medium energy X-ray point sources+diffuse
imaging; G-N approximation; “fix it up at the end”
Tycho Supernova Remnant
(1572)
Einstein Observatory (Nov.
'78-April '81; 0.15-3 keV)
Mirror assembly
1990's and Beyond: Great
Observatories
need to do it right; no longer can “fix it up at the
end”
Compton Gamma-Ray
Chandra X-Ray Observatory Jul
Observatory (Apr '91 – Jun '00;
COMPTEL: 0.8-30 MeV; EGRET
20 MeV-100 GeV)
SvOutPlaceObject
1999 and beyond; 0.1-10 keV)
CGRO/EGRET All-Sky Map
diffuse glow; significantly non-Gaussian
statistics
Log Counts per time per 05 degree pixel:
Four years of data
(ranges from zero to thousands per pixel)
SvOutPlaceObject
CGRO/EGRET All-Sky Map
Log Inferred flux per 0.5 degree pixel: Four years of data
(known point and diffuse sources modelled out)
Haar wavelet basis: Dixon, Hartman, Kolaczyk et al
CGRO/COMPTEL All-Sky 1.8MeV
(Knödelseder, Dixon, Diehl, Strong, et al 1998)
very non-diagonal instrument response; horrid background
Mkn 501 at TeV: Whipple Observatory
(Quinn et al. for Whipple collaboration, 1996, ApJL, 456,
p83)
1st AGN DISCOVERED at TeV; horrid background,
response
Chandra has it “easy” …
BUT illustrates main principles
CHANDRA Image of Tycho Supernova
CHANDRA PSF on-axis: varies with energy
CHANDRA
PSF:
spreads off-axi
5 arcmin off-axis
CHANDRA
PSF offaxis
10 arcmin
CHANDRA ACIS BACKGROUND
FI CCD
BI CCD
Effect of a Charged Particle
Event
Higher Energy: More Extreme!
Dim, BKG,
Rate…
Hurley et al GRB940210:
“The diffuse background in this
direction results in about one
photon above 30 MeV detected by
EGRET in 7 minutes. On the
subsequent Compton Observatory
orbit, 1.5 hours later, EGRET had
20 minutes of livetime, and 10
gamma rays were detected from
the region around the annulus, one
with energy 26 GeV.”
* ABOUT 2 DOZEN PAPERS on 1!
Pathway for Future:
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Other instruments: Ground-based TeV
GLAST, Swift, …
CON-X, etc
“Doing it right” in one area helps
many overlapping areas