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400 400 YearsYears of of AstrometryAstrometry ::From Tycho Brahe to From Tycho Brahe to HipparcosHipparcos
A A technicaltechnical and and scientificscientific developmentdevelopment
Introduction of the telescopeIntroduction of the telescopeMicrometers, divided circles, clocksMicrometers, divided circles, clocksSpace techniquesSpace techniques
Erik Høg, Niels Bohr Institute, Copenhagen University
Updated 17 August 2009 Erik HøgUpdated 17 August 2009 Erik Høg 22
Quadrant 1570 Sighting the star
Tycho Brahe’snew
instruments
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Tycho Braheon Hven1576-97
A barrel of gold
Sextant 1580
1000 stars measuredcelestial reference framefor measurement of planets
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Tycho BraheTycho Brahemural quadrantmural quadrant
One observer for the star,One observer for the star,two assistants for clocks, two assistants for clocks, circle and protocolcircle and protocol
Diagonal division linesDiagonal division lines
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Some results from astrometry 1600Some results from astrometry 1600--17001700
16021602--1619 : Laws of planet orbits by Johannes Kepler 1619 : Laws of planet orbits by Johannes Kepler based on Tycho Brahe’s observationsbased on Tycho Brahe’s observations
1611 : Orbits of the Jupiter satellites by Galileo Galilei1611 : Orbits of the Jupiter satellites by Galileo Galilei
1687 : Laws of dynamics and gravitation by Isaac Newton1687 : Laws of dynamics and gravitation by Isaac Newton
1659 : Planet diameters measured by Christiaan Huygens1659 : Planet diameters measured by Christiaan Huygens
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Two telescopesTwo telescopes
The Dutch The Dutch telescopetelescopeHans Hans LipperheyLipperhey 16081608MicrometerMicrometer not not possiblepossiblesmall small fieldfield, small , small magnificationsmagnifications
The The KeplerKepler telescopetelescopeJohannes Johannes KeplerKepler 16111611MicrometerMicrometer possiblepossible: wires at (5): wires at (5)
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Sextant and quadrantSextant and quadrantWith With nakednaked eyeeye openopen sightsight pinnulespinnules
untiluntil 1679, Johannes 1679, Johannes HeveliusHevelius
TelescopicTelescopicsightsight onon quadrquadr. and . and sextsext..1640 by William 1640 by William GascoigneGascoigne16651665--, Robert , Robert HookeHooke a.oa.o..
MuralMural ””quadrantquadrant” of 140 ” of 140 degdeg..16891689--, John , John FlamsteedFlamsteed
1658 : 1658 : PendulumPendulum clockclock by by ChristiaanChristiaanHuygensHuygens
1659 : 1659 : Wire Wire micrometermicrometer by by HuygensHuygensGascoigneGascoigne 1641, but 1641, but knownknown onlyonly laterlater
Hevelius, brass sextant
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Divided scales and circlesDivided scales and circles
1674 Hevelius : 1674 Hevelius : Scale with vernierScale with vernierand diagonalsand diagonals
The high art of The high art of
of dividing the circleof dividing the circle(1990 book by Allan Chapman)(1990 book by Allan Chapman)
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Some results from astrometry 1700Some results from astrometry 1700--18001800
1725 : The ’Great 1725 : The ’Great CatalogueCatalogue’, 3000 stars, ’, 3000 stars, errorerror 12”, by 12”, by John John FlamsteedFlamsteed usingusing a a muralmural ””quadrantquadrant” of 140 ” of 140 degdeg..1728 : Aberration 20” and 1728 : Aberration 20” and nutationnutation 9” 9” discovereddiscovered by by James James BradleyBradley usingusing a a zenithzenith sectorsector withwith precisionprecision 1” 1”
1737 : 1737 : FlatteningFlattening of the of the EarthEarth measuredmeasured, P.L.M. , P.L.M. MaupertuisMaupertuis
1767 : 1767 : BinariesBinaries predictedpredicted statisticallystatistically by John Michell; by John Michell; 1779… : 1779… : SystematicSystematic observations by W. observations by W. HerschelHerschel; ; 1827 : 1827 : FirstFirst orbitorbit by Felix by Felix SavarySavary1781 : Uranus 1781 : Uranus discovereddiscovered by William by William HerschelHerschel
1783 : William 1783 : William HerschelHerschel: motion of Sun : motion of Sun towardstowards HerculesHercules1010
Transit instrument by Ole RømerTransit instrument by Ole Rømer
1675 1675 -- Transit instrumentTransit instrumentin Copenhagenin Copenhagen
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Meridian circle by Ole RømerMeridian circle by Ole Rømer
1705 1705 -- Meridian circleMeridian circlefull circle and microscopesfull circle and microscopesOnly after 1800 were quadrants Only after 1800 were quadrants out of businessout of business
Hevelius
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Mural quadrant Mural quadrant –– John Bird John Bird -- 17731773
Critical issues :Critical issues :DivisionsDivisionsPlanarity of circlePlanarity of circle
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Jesse RamsdenJesse Ramsden
Dividing machinesDividing machines
Lathes to make roundLathes to make roundmechanical parts, screwsmechanical parts, screws
AltAlt--azimuth circle 1789 for azimuth circle 1789 for Piazzi’s Palermo ObservatoryPiazzi’s Palermo Observatory
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Some results from astrometry 1800Some results from astrometry 1800--19001900
1801 : 1801 : FirstFirst asteroidasteroid, Ceres, , Ceres, discovdiscov. by . by GuiseppeGuiseppe PiazziPiazzi1838 : 1838 : ParallaxParallax of stars by of stars by BesselBessel, Henderson, Struve, Henderson, Struve1850 : 20 1850 : 20 parallaxesparallaxes in a in a cataloguecatalogue by Petersby Peters
1837 : From 390 proper motions 1837 : From 390 proper motions ArgelanderArgelander : solar : solar apexapex1846 : 1846 : NeptuneNeptune predictedpredicted and and discovereddiscoveredCelestialCelestial mechanicsmechanics flourishesflourishes
1860 1860 -- : : BonnerBonner + Cordoba + Cordoba SurveysSurveys 1,000,000 stars1,000,000 stars1890 1890 -- : : PhotographyPhotography : : parallaxesparallaxes and sky and sky surveyssurveys
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Astrometry of small angles 1/2Astrometry of small angles 1/2i.e. within the telescope field of viewi.e. within the telescope field of view
1611 1611 –– 1660 : 1660 : Estimation:Estimation: diameters, relative positions, diameters, relative positions, Galilei et al. Galilei et al. 1659 1659 –– 1990 : 1990 : Wire micrometerWire micrometer by Huygens by Huygens Gascoigne 1640, published laterGascoigne 1640, published laterFrom 1750 also From 1750 also heliometer =heliometer =divideddivided--lens micrometerlens micrometerfor the same purposesfor the same purposes
Science :Science :Diameters of planetsDiameters of planetsRelative positionsRelative positionsDouble stars : stellar massesDouble stars : stellar massesRelative parallaxes 1838Relative parallaxes 1838--19001900
Principle of the wire micrometer
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A
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A B
C. .
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Astrometry of small angles 2/2Astrometry of small angles 2/2i.e. within the telescope field of viewi.e. within the telescope field of view
1890 1890 -- 1990 : 1990 : Photography :Photography : same science as micrometer :same science as micrometer :Diameters of planetsDiameters of planetsRelative positions of stars and solar system objectsRelative positions of stars and solar system objectsDouble stars : stellar massesDouble stars : stellar massesRelative parallaxesRelative parallaxes1990 1990 -- : 1,000,000,000 stars, e.g. US Naval Observatory Catalogues : 1,000,000,000 stars, e.g. US Naval Observatory Catalogues
1920 1920 -- : : Interferometry : Interferometry : stellar diameters, double starsstellar diameters, double stars1990 1990 -- : : Space astrometry :Space astrometry : Hipparcos, HubbleHipparcos, Hubble
1980 1980 -- : : CCD astrometry :CCD astrometry :on ground : 100,000,000on ground : 100,000,000 stars to 17th mag + solar systemstars to 17th mag + solar systemfrom space : from space : Hubble relative parallaxes 0.001”Hubble relative parallaxes 0.001”
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Some results from astrometry 1900Some results from astrometry 1900--20002000By 1900 : 539 stars 0.01”/a motions Decl. > By 1900 : 539 stars 0.01”/a motions Decl. > --10 deg10 deg
1905 : Hertzsprung discovers dwarfs/giants using motions for distances1905 : Hertzsprung discovers dwarfs/giants using motions for distances
100 stars 100 stars 0.04”0.04” relative parallaxesrelative parallaxesBy 1950 : 33,342 stars 0.01”/a motions, By 1950 : 33,342 stars 0.01”/a motions,
5822 stars 5822 stars 0.01”0.01” relative parallaxesrelative parallaxes500 stars with <10%500 stars with <10% error on distanceserror on distances
�� 1970 1970 -- : : Radio astrometry :Radio astrometry : accurate absolute positions, accurate absolute positions, reference system by quasars, Earth rotationreference system by quasars, Earth rotation
1996 : 1996 : Hipparcos satellite : Hipparcos satellite : accurate large accurate large && small anglessmall angles120,000 stars 0.001”/a motions (N 120,000 stars 0.001”/a motions (N && S) S) 120,000 stars 120,000 stars 0.001”0.001” absolute parallaxesabsolute parallaxes22,000 stars with <10%22,000 stars with <10% error on distanceserror on distances
2000 : 2000 : TychoTycho--2 :2 : 2.500,000 stars 0.002”/a motions2.500,000 stars 0.002”/a motionsUSNO : USNO : 1,000,000,000 stars to 20th mag1,000,000,000 stars to 20th mag 1818
Copenhagen meridian Copenhagen meridian circlecirclePhotoelectricPhotoelectric astrometryastrometry beginsbegins in 1925in 1925
Bengt Bengt StrömgrenStrömgren 1925 and 19331925 and 1933ExperimentsExperiments withwithphotoelectricphotoelectric recordingrecording of transitsof transitsCourtesy: Steno Museum, AarhusCourtesy: Steno Museum, Aarhus
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1919
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x ~ timex ~ time
starstartt11 tt22
Ideas 1960Ideas 1960
P. Lacroute 1967: Go to space!P. Lacroute 1967: Go to space!E. Høg 1975: Design of HipparcosE. Høg 1975: Design of Hipparcos
+ switching mirror+ switching mirrorB. B. StrömgrenStrömgren 1933: 1933: slitsslits + + switchingswitching mirrormirrorAtomicAtomic bombsbombs 1957 : 1957 : CountingCounting techniquestechniquesE. Høg 1960 : E. Høg 1960 : SlitsSlits + + countingcounting >>> >>> implementationimplementation onon meridian meridian circlescircles
Light intensityLight intensity= Photons= Photonsper secondper second
Slits + Photon counting vs. TimeSlits + Photon counting vs. Time=> Astrometry + Photometry=> Astrometry + Photometry
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x1 x2 xx1 x2 x
t1 t2 timet1 t2 time
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Carlsberg automatic meridian circleCarlsberg automatic meridian circleon La Palma from 1984on La Palma from 1984
PhotoelectricPhotoelectricduringduring 14 14 yearsyears
ThenThen from 1998from 1998CCD CCD micrometermicrometer ::20,000,000 star20,000,000 starobservationsobservationsper per yearyear0.1” per obs.0.1” per obs.
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Hipparcos and Tycho 1975Hipparcos and Tycho 1975--20002000
FocalFocal plane of plane of HipparcosHipparcos ––TychoTycho
Mission Mission conceptconcept 19751975Mission Mission approvalapproval Feb. 1980Feb. 1980Tycho Tycho proposalproposal April 1981April 1981ObservingObserving 1989 1989 -- 9393CataloguesCatalogues 19961996TychoTycho--2 2 CatalogueCatalogue in 2000in 20002.500,000 stars2.500,000 stars500 citations 500 citations untiluntil 20082008
Modulating gridModulating grid
Star mapperStar mappergridgrid
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TelescopeTelescope of of HipparcosHipparcosSchmidt type Schmidt type system system
D = 0D = 0..29 m29 mF = 1.4 mF = 1.4 m
Two fields on the skyTwo fields on the sky
Observing 1989 Observing 1989 -- 9393
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TelescopeTelescope andand payloadpayload of Gaiaof GaiaLaunchLaunch 20122012
Two SiC primary mirrorsTwo SiC primary mirrors
1.45 1.45 ×× 0.50 m0.50 m22 at 106.5at 106.5°°
Basic angleBasic anglemonitoring systemmonitoring system
CombinedCombinedfocal planefocal plane
(CCDs)(CCDs)F = 35 mF = 35 m
Rotation axis (6 h)Rotation axis (6 h)
Figure courtesy EADSFigure courtesy EADS--AstriumAstrium
Superposition of Superposition of two Fields of View two Fields of View
SiC toroidalSiC toroidalstructurestructure
(optical bench)(optical bench)
Two anastigmatic offTwo anastigmatic off--axis telescopesaxis telescopes
AstrometricAstrometricAstrometricAstrometricAstrometricAstrometricAstrometricAstrometric AccuracyAccuracyAccuracyAccuracyAccuracyAccuracyAccuracyAccuracy versus Timeversus Timeversus Timeversus Timeversus Timeversus Timeversus Timeversus Time
Hipparchus/Ptolemy Hipparchus/Ptolemy Hipparchus/Ptolemy Hipparchus/Ptolemy ---- 1000 stars1000 stars1000 stars1000 stars
1000100010001000
100100100100
10101010
arcsec 1arcsec 1arcsec 1arcsec 1
0.10.10.10.1
0.010.010.010.01
0.0010.0010.0010.001
0.00010.00010.00010.0001
0.000010.000010.000010.00001
Erik Høg
1995/2008 150 BC … 1600 1800 2000 Year150 BC … 1600 1800 2000 Year150 BC … 1600 1800 2000 Year150 BC … 1600 1800 2000 Year
The Landgrave of Hesse The Landgrave of Hesse The Landgrave of Hesse The Landgrave of Hesse ---- 1000 stars1000 stars1000 stars1000 stars
FK5 FK5 FK5 FK5 ---- 1500150015001500
PositionsPositionsPositionsPositions
ParallaxesParallaxesParallaxesParallaxes = = = =
Small anglesSmall anglesSmall anglesSmall angles
All parametersAll parametersAll parametersAll parameters
TychoTychoTychoTycho----2222---- 2.5 million2.5 million2.5 million2.5 million
Hipparcos Hipparcos Hipparcos Hipparcos ---- 120,000120,000120,000120,000
Bessel Bessel Bessel Bessel ---- 1 star1 star1 star1 star
Jenkins Jenkins Jenkins Jenkins ---- 6000600060006000
Gaia 23 millionGaia 23 millionGaia 23 millionGaia 23 millionSIM SIM SIM SIM ---- 10,00010,00010,00010,000
USNO USNO USNO USNO ---- 360360360360
ROEMER ROEMER ROEMER ROEMER ---- 45 million45 million45 million45 millionProposal 1992Proposal 1992Proposal 1992Proposal 1992
Flamsteed Flamsteed Flamsteed Flamsteed ---- 3000300030003000
Tycho Brahe Tycho Brahe Tycho Brahe Tycho Brahe ---- 1000 1000 1000 1000
Argelander Argelander Argelander Argelander ---- 34,00034,00034,00034,000Bradley Bradley Bradley Bradley ---- aberrationaberrationaberrationaberration
PPM PPM PPM PPM ---- 379,000379,000379,000379,000
GaiaGaiaGaiaGaia---- 1200 million1200 million1200 million1200 million
Lalande Lalande Lalande Lalande ---- 50,00050,00050,00050,000