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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

33

Tycho Braheon Hven1576-97

A barrel of gold

Sextant 1580

1000 stars measuredcelestial reference framefor measurement of planets

44

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

55

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

66

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)

2

77

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

88

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)

99

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

1111

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

1212

Mural quadrant Mural quadrant –– John Bird John Bird -- 17731773

Critical issues :Critical issues :DivisionsDivisionsPlanarity of circlePlanarity of circle

3

1313

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

1414

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

1515

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

..

A

.

A B

C. .

.

1616

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”

1717

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

yy

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

yy

x1 x2 xx1 x2 x

t1 t2 timet1 t2 time

2020

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.

2121

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

2222

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

2323

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