1

Transits of Venus: the history

Luxembourg, January 2004Jean-Eudes Arlot

IMCCE/observatoire de Paris-CNRS

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The transit of June 8, 2004The transit of June 8, 2004

On June 8, 2004, the planet Venus will pass in front of the Sun. Nobody alive today has seen such an event. Why this event retained the attention of the astronomers in the past?

5h40 UTC

11h05 UTC

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The transit of VenusThe transit of Venus

In the history of humanity, the observation of the transits of Venus was one of the most important mean to measure the universe.

This explains all the efforts made in the past to observe this event, even in the difficulties.

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Looking at the universeLooking at the universe

Look at the sky? Is is possible, just looking at the stars, to know their distances to the Earth?

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Measuring distancesMeasuring distances

Parallax or triangulation or how to measure a distance to somewhere without going there?

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Measuring a distance with angles : the parallaxMeasuring a distance with angles : the parallax

the triangulation

a b

A ?B ?

c?

A

a

B

b

C

c

bac

bac

sinsinsin

180

A

a

B

b

C

c

bac

bac

sinsinsin

180

ca’ C

Base

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The parallax of the SunThe parallax of the Sun

To measure the distance from the Earth to another body of the solar system, we will use the parallax effect from two different sites on Earth

aR

Terre solaireparallaxea

R

• One measure and R to calculate a• R = 6400 km and a ~ 150x106 km• Then ~ 10" ==> difficult to measure

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Measuring distancesMeasuring distances

Measure of the distance Earth-Sun or measure of the radius of the Earth?

This shows the necessity to have a good model before measuring anything

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The parallaxThe parallax

The parallax method allows to measure only distance to close bodies to the Earth since the base of the triangle may not be larger than the Earth.

The Sun is too far: only the Moon, Mars and Venus are accessible.

The Earth and the Moon at the relative scale.

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The parallax of Mars (1672)The parallax of Mars (1672)

Cayenne

Paris

R

D

DR

2sin2

Mars

First measures of distance using parallax:

Cassini and Richer s = 9.5" ( a = 138x 106 km)

Flamsteed s = 10" ( a = 130x 106 km)

First measures of distance using parallax:

Cassini and Richer s = 9.5" ( a = 138x 106 km)

Flamsteed s = 10" ( a = 130x 106 km)

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The parallax of Venus : Halley’s methodThe parallax of Venus : Halley’s method

•a a

•b

b

•c

c

• The relative positions of the chords provide the parallax of Venus.

• The solar disc is used as a reference frame.

• The measure of the length of the chords is replaced by the measure of the duration of the transits.

• The measure of a duration is more accurate.

• But remember that the Sun itself has also a parallax.

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Kepler’s first lawKepler’s first law

Kepler (1571-1630)

• Each planet describes an ellipse of which the Sun is at one of the focus (1605).

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Deuxième loi de KéplerDeuxième loi de Képler

• The surfaces described by the radius-vector planet-Sun, are proportional to the time used to make them (Astronomia Nova, 1609);

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Kepler’s third lawKepler’s third law

• The semi_major axis a and the period of revolution T are linked by a3/T2=constant for all the planets (1618).

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The astronomical unitThe astronomical unit

The third law of Kepler implies that it is sufficient to measure only one distance in the solar system to know all the distances between the planets and the Sun, especially the distance Earth-Sun, known as astronomical unit.

Let us measure the distance from Earth to: Mars, Venus or … Eros.

The astronomical unit will allow us to measure the distance from Earth to the nearest stars.

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Measuring distancesMeasuring distances

The distance to stars: The base of the triangle will be 300 millions kilometers: the

diameter of the orbit of the Earth thanks to two observations made after a 6 months interval.

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The transit of Venus: a rare eventThe transit of Venus: a rare event

Three conditions :Three conditions :Three conditions :Three conditions :

• The Earth and Venus should have the same heliocentric longitudeThe Earth and Venus should have the same heliocentric longitude•The frequency of this configuration is the synodic revolution of The frequency of this configuration is the synodic revolution of Venus (RS).Venus (RS).

• The Earth, Venus and the Sun should be on a same line (Venus should not The Earth, Venus and the Sun should be on a same line (Venus should not be above or below the Sun as seen from the Earth.be above or below the Sun as seen from the Earth.• The frequency of this configurartion is the draconitic revolution The frequency of this configurartion is the draconitic revolution of Venus (RD).of Venus (RD).

• due to the size of the Sun, the Earth and Venus, the event due to the size of the Sun, the Earth and Venus, the event occurs even the two conditions are not completely satisfied.occurs even the two conditions are not completely satisfied.

1 1

2 2

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+ these two conditions may not be satisfied very often+ these two conditions may not be satisfied very often

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A transit as seen from spaceA transit as seen from space

SunSun

planetplanet

Below the Below the shadow coneshadow cone

Axis of the shadow coneAxis of the shadow cone

Shadow coneShadow cone

Penumbra conePenumbra conesummit of the conesummit of the cone of penumbraof penumbra

summit of the summit of the shadow coneshadow cone

Pla

ne o

f Besse

lPla

ne o

f Besse

l

SunSun

(1) Central (1) Central transittransit

(1)

(2) Non-(2) Non-central central transittransit

(3) Partial (3) Partial transittransit

(2)(3) (4)

(4) No (4) No transittransit

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Observation of a transit: what we seeObservation of a transit: what we see

• Duration of a transit of Venus 5 to 8h• Duration of a transit of Mercury 3 to 8 h

t1, t4 : external contacts

t2, t3 : internal contacts

The external contacts are very difficult to observeThe external contacts are very difficult to observe

t1

t1 : 1e contact

t2

t2 : 2e contact

t3t3 : 3e contact

t4

t4 : 4e contact

t1 - t2 : entrance of the planet

t3 - t4 : exit of the planet

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Who, first, has the idea to observe the transits ?Who, first, has the idea to observe the transits ?

• Ptolemeus noted this possibility in his system

• A transit of Mercury is mentionned in 807

– but no transit occurs at that time !

– nearest dates : 23/04/806 and 24/10/809

• Copernic tells that transits are possible

– but invisible because of the size of the planet

• Kepler predicts a transit of Mercury for May 29 1607

– he observed on May 28.

– he noted a black spot on the Sun and announced an

observation

– in fact no transit occurs at that date

– nearest dates : 01/11/1605 and 03/05/1615

• The spots of the Sun were observed by projection after 1610

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First observation of a transit: Gassendi in ParisFirst observation of a transit: Gassendi in Paris

• First observation of a transit

• Use of a darkroom ( and may be a lens )

• Observation from Nov 5 (bad weather on 5 and 6)

• Starting from the sunrise on Nov 7, Gassendi saw a black spot

– Measured diameter of Mercury : 20" (true value : 10")

• Error of 5h from Kepler’s predictions

• Three other observations in Europe

Transit of Mercury on Nov 7, 1631

Calculation for Paris hour Sun

(true solar time)

2e contact 5h 06 -21°3e contact 10h28 +22°

"Le rusé Mercure voulait passer sans être aperçu, il était entré plus tôt

qu'on ne s'y attendait, mais il n'a pu s'échapper sans être découvert "

Mercurius in sole visus et venus invisa Parissiis anno 1631.

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Visibility of the Mercury transit of 1631Visibility of the Mercury transit of 1631

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First observations of a transit of Venus: J. HorrocksFirst observations of a transit of Venus: J. Horrocks

• First observation of a transit of Venus

• Use of a darkroom with a refractor

• Observations on Saturday 3 nothing visible

• On Sunday 4 he observed from the morning, through clouds

• He stopped observing for religious obligations

• At 3h15 he continues his observations and the weather became fair

Transit of Venus on Dec 4. 1639

local time Sun2e contact 15h15 + 4°3e contact 21h30 - 47°sunset 15h50

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Observation of J. Horrocks (Observation of J. Horrocks (Venus in Sole VisaVenus in Sole Visa))

• He made three measures in a hurry before the sunset

t distance (")

3h15 864

3h35 810

3h45 780

3h50 sunset

Diameter of Venus: 1' 16"

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Latin text from HorrocksLatin text from Horrocks

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Observations of W. CrabtreeObservations of W. Crabtree

• Observations made at Manchester

• Cloudy until 3h35 10 min of observation possible only !

• Amazed by the transit, he made no measure !

Painting of F. M. Brown, visible at the City Hall of Manchester

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Visibility of the Venus transit of 1639Visibility of the Venus transit of 1639

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Transits during the XVIIIth centuryTransits during the XVIIIth century

• Longitudes are not yet well known.• Clocks are not good time keepers.• Traveling is slow (sailing).• Voyages are very expensive. • Nobody has never observed a transit of Venus.

Two methods of measure of the parallax :Two methods of measure of the parallax :Method of Halley : Method of Halley : The durations of the transits are compared => no problem with longitude.The durations of the transits are compared => no problem with longitude.Method of Delisle :Method of Delisle :The times of contacts are compared => more observations but The times of contacts are compared => more observations but longitudes have to be known.longitudes have to be known.

Two methods of measure of the parallax :Two methods of measure of the parallax :Method of Halley : Method of Halley : The durations of the transits are compared => no problem with longitude.The durations of the transits are compared => no problem with longitude.Method of Delisle :Method of Delisle :The times of contacts are compared => more observations but The times of contacts are compared => more observations but longitudes have to be known.longitudes have to be known.

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The transit of June 6, 1761The transit of June 6, 1761

• for this first transit, all the astronomical communiuty was ready to observe. for this first transit, all the astronomical communiuty was ready to observe. • voyages were difficult and the 7-years war (a world war) set ablaze seas voyages were difficult and the 7-years war (a world war) set ablaze seas and colonies.and colonies.• the coordination of all the astronomers was made by the french astronomer the coordination of all the astronomers was made by the french astronomer Joseph-Nicolas Delisle (1688-1768) who sent his mappemonde to more than Joseph-Nicolas Delisle (1688-1768) who sent his mappemonde to more than 100 astronomers in the world.100 astronomers in the world.

General circonstancesfirst contact of the penumbra : 1h 55m 17.1s first contact of the shadow : 2h 13m 9.7s

Maximum of the transit : 5h 19m 16.1s Last contact of the shadow : 8h 25m 20.1sLast contact of the penumbra : 8h 43m 12.6s

General circonstancesfirst contact of the penumbra : 1h 55m 17.1s first contact of the shadow : 2h 13m 9.7s

Maximum of the transit : 5h 19m 16.1s Last contact of the shadow : 8h 25m 20.1sLast contact of the penumbra : 8h 43m 12.6s

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Le passage du 6 juin 1761Le passage du 6 juin 1761

Projection de HammerProjection de Hammer

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The transit of June 6, 1761The transit of June 6, 1761

• the Académie Royale des sciences organized the Académie Royale des sciences organized three campaignsthree campaigns of observation. of observation. Two of these voyages took oplace in countries allied of France.Two of these voyages took oplace in countries allied of France.

• the one of the one of César-François Cassini de ThuryCésar-François Cassini de Thury (1714-1784) in (1714-1784) in Vienna Vienna who observed who observed the transit with the archduke Joseph (successful observation).the transit with the archduke Joseph (successful observation).

• the one of the one of the Abbot Jean-Batiste Chappe d'Auterochethe Abbot Jean-Batiste Chappe d'Auteroche (1728-1769) to (1728-1769) to Tobolsk in Tobolsk in SiberiaSiberia invited by the empress Elisabeth I (successful observation). invited by the empress Elisabeth I (successful observation).

• the one of the one of Alexandre Guy PingréAlexandre Guy Pingré who went to who went to Rodrigues Island Rodrigues Island (north of (north of Madagascar), Thanks to the compagnie des Indes (observation partially successful). Madagascar), Thanks to the compagnie des Indes (observation partially successful).

• a fourth astronomer, a fourth astronomer, Guillaume Joseph Hyacinthe Jean-Batiste Le Gentil de Guillaume Joseph Hyacinthe Jean-Batiste Le Gentil de La GalaisièreLa Galaisière (1725-1792), left by sea in order to observe the transit (1725-1792), left by sea in order to observe the transit in Indies at in Indies at PondichéryPondichéry. Unfortunately the city of Pondichéry was taken by the English and he . Unfortunately the city of Pondichéry was taken by the English and he Saw the transit from the ship, unable to make a measurement; he decided to wait Saw the transit from the ship, unable to make a measurement; he decided to wait until the next transit in 1769until the next transit in 1769

At last At last Joseph-Jérôme Lefrançois de LalandeJoseph-Jérôme Lefrançois de Lalande (1732-1807 (1732-1807) ) observed observed fromfrom Luxembourg Palace in Paris Luxembourg Palace in Paris..

The FrenchThe French

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The voyage of Chappe d’AuterocheThe voyage of Chappe d’Auteroche

The travel of Chappe d’Auteroche to Tobol’skThe travel of Chappe d’Auteroche to Tobol’sk

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Relation of the voyage of Le GentilRelation of the voyage of Le Gentil

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The transit of June 6, 1761The transit of June 6, 1761

The EnglishThe English

The english astronomers organized The english astronomers organized two campaignstwo campaigns far from far from England to observe the event.England to observe the event.

• Nevil MaskelyneNevil Maskelyne (1732-1811) went to (1732-1811) went to Sainte-HélèneSainte-Hélène where he where he was not able to observe because of clouds. was not able to observe because of clouds.

•Charles MasonCharles Mason (1728-1786), (1728-1786), James BradleyJames Bradley and and Jeremiah DixonJeremiah Dixon (1733-1779) was supposed to observe from (1733-1779) was supposed to observe from BencoolenBencoolen (Sumatra). (Sumatra). They were not able to make the observation because the French They were not able to make the observation because the French took the city. They observed then at Capetown.took the city. They observed then at Capetown.

•John WinthropJohn Winthrop, professor in Harvard went to , professor in Harvard went to St-John (Terre-Neuve)St-John (Terre-Neuve) where « surrounded by billions of insects " he succeeded to where « surrounded by billions of insects " he succeeded to observe the last contact of the transit.observe the last contact of the transit.

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Voyages organized for the transit of 1761Voyages organized for the transit of 1761

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Results from the transit of 1761Results from the transit of 1761

• The number of observers was The number of observers was 120120, on , on 62 sites62 sites (S. Newcomb, 1959). (S. Newcomb, 1959).

• Note that some sites of observations were previously selected Note that some sites of observations were previously selected (Bencoolen, Pondichéry, Batavia) by Halley in 1716.(Bencoolen, Pondichéry, Batavia) by Halley in 1716.

The large error is due to:The large error is due to:- a bad knowledge of the longitudes- a bad knowledge of the longitudes of the sites of observation of the sites of observation - the black drop effect- the black drop effect which decreases the precision of the measurement which decreases the precision of the measurement of the time of the contacts.of the time of the contacts.

8.5" < 8.5" < < 10.5" < 10.5"

Disappointing results : no improvement of the measures Disappointing results : no improvement of the measures from Mars.from Mars.

Disappointing results : no improvement of the measures Disappointing results : no improvement of the measures from Mars.from Mars.

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The transit of Venus of June 3-4, 1769The transit of Venus of June 3-4, 1769

• The organization of the observations for 1769 were made by The organization of the observations for 1769 were made by Lalande in France and Thomas Hornsby in England. Lalande in France and Thomas Hornsby in England. • They took benefit from the observations of the transit of 1761.They took benefit from the observations of the transit of 1761.

•27 refractors were used, only 3 were used in 1761.27 refractors were used, only 3 were used in 1761.

General circonstancesGeneral circonstancesFirst contact with penumbra : le 3 à 19h 8m 31.2s First contact with penumbra : le 3 à 19h 8m 31.2s First contact with shadow : le 3 à 19h 27m 6.7s First contact with shadow : le 3 à 19h 27m 6.7s Maximum of the transit : le 3 à 22h 25m 20.3sMaximum of the transit : le 3 à 22h 25m 20.3sLast contact with shadow : le 4 à 1h 23m 35.7s Last contact with shadow : le 4 à 1h 23m 35.7s Last contact with penumbra : le 4 à 1h 42m 11.2sLast contact with penumbra : le 4 à 1h 42m 11.2s

General circonstancesGeneral circonstancesFirst contact with penumbra : le 3 à 19h 8m 31.2s First contact with penumbra : le 3 à 19h 8m 31.2s First contact with shadow : le 3 à 19h 27m 6.7s First contact with shadow : le 3 à 19h 27m 6.7s Maximum of the transit : le 3 à 22h 25m 20.3sMaximum of the transit : le 3 à 22h 25m 20.3sLast contact with shadow : le 4 à 1h 23m 35.7s Last contact with shadow : le 4 à 1h 23m 35.7s Last contact with penumbra : le 4 à 1h 42m 11.2sLast contact with penumbra : le 4 à 1h 42m 11.2s

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Visibility of the transit of 1769Visibility of the transit of 1769

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The transit of 1769The transit of 1769

The FrenchThe French•PingréPingré studied the best sites of observation studied the best sites of observation

• Le GentilLe Gentil still in Madagascar, went to Manila, then still in Madagascar, went to Manila, then PondichéryPondichéry where a cloud prevents the observationwhere a cloud prevents the observation

• ChappeChappe accompanied by Pauly, Noël and Dubois and by two accompanied by Pauly, Noël and Dubois and by two spanish astronomers Vicente de Doz et Salvador de Medina went spanish astronomers Vicente de Doz et Salvador de Medina went to California on the to California on the west coast of Mexicowest coast of Mexico, near Cape Lucas today , near Cape Lucas today named San José del Cabo. named San José del Cabo.

• the observation by Chappe was successful the observation by Chappe was successful

• they observed also the lunar eclipse on June 18 1769 to they observed also the lunar eclipse on June 18 1769 to measure the longitude. Unfortunately theu died from an epidemic measure the longitude. Unfortunately theu died from an epidemic of typhus except Pauly by looking after the inhabitantsof typhus except Pauly by looking after the inhabitants

•Pingré and the Comte de FleurieuPingré and the Comte de Fleurieu, observed the event from, observed the event from Cape Cape François in Saint-DomingueFrançois in Saint-Domingue..

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The transit of 1769The transit of 1769

The EnglishThe English

• Dymond et Wales Dymond et Wales went to Fort Churchill in the Hudson bay. went to Fort Churchill in the Hudson bay.

• Father Father Maximilen HellMaximilen Hell, with the danish astronomer C. , with the danish astronomer C. HorrebowHorrebow and a young botanistand a young botanist Borgrewing Borgrewing, went to , went to VardöVardö, an island north to , an island north to Scandinavia.Scandinavia.• A third group went to the islands of the southern seas as A third group went to the islands of the southern seas as proposed by Thomas Hornsby. This voyage was conducted by a proposed by Thomas Hornsby. This voyage was conducted by a young lieutenant, young lieutenant, James CookJames Cook, and the observation of the transit , and the observation of the transit was made in was made in TahitiTahiti, -an island discovered two years earlier by , -an island discovered two years earlier by Samuel Wallis-, by Charles Green and James Cook.Samuel Wallis-, by Charles Green and James Cook.

• A fourth group, A fourth group, Bayley and Dixon, went to Scandinavia; BayleyBayley and Dixon, went to Scandinavia; Bayley observed the transit at observed the transit at Cape NorthCape North and and J. DixonJ. Dixon made the made the observation on the island of observation on the island of HammerfestHammerfest. .

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The voyage of Cook to TahitiThe voyage of Cook to Tahiti

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The voyage of Cook to TahitiThe voyage of Cook to Tahiti

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The voyage of Cook to TahitiThe voyage of Cook to Tahiti

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The transit of 1769The transit of 1769

The RussianThe Russian

• The imperial academy of Russia, thanks to the tzarina Catherine II, The imperial academy of Russia, thanks to the tzarina Catherine II, invited foreign astronomers to observe the transit in Russiainvited foreign astronomers to observe the transit in RussiaThe german jesuit The german jesuit C. MayerC. Mayer, the swiss astronomers , the swiss astronomers MalletMallet and and PictetPictet and the swedish and the swedish J. LexellJ. Lexell, , L. EulerL. Euler went in Russia. went in Russia.

• Observers went also to Yakutsk, Orks and Orenbourg in the south Observers went also to Yakutsk, Orks and Orenbourg in the south of Oural, to Kola peninsula, and to St Petersbourg.of Oural, to Kola peninsula, and to St Petersbourg.

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Voyages organized in 1769Voyages organized in 1769

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The results from the transit of 1769The results from the transit of 1769

• The English made 69 observations and the French 34. The English made 69 observations and the French 34.

• Finally Finally 151 observations151 observations, were made from , were made from 77 sites77 sites. .

• Four observations of the complete transit were made : Finland, Hudson Four observations of the complete transit were made : Finland, Hudson Bay, California and Tahiti.Bay, California and Tahiti.

Author(s) ValuesAuthor(s) ValuesWilliam Smith 8,6045" (1770) William Smith 8,6045" (1770) Thomas Hornsby 8,78" (1770) Thomas Hornsby 8,78" (1770) Pingré et Lalande 9,2" et 8,88" (1770) Pingré et Lalande 9,2" et 8,88" (1770) Pingré 8,80 (1772) Pingré 8,80 (1772) Lalande 8,55"< P < 8,63" (1771) Lalande 8,55"< P < 8,63" (1771) Planmann 8,43 (1772) Planmann 8,43 (1772) Hell 8,70" (1773/1774) Hell 8,70" (1773/1774) Lexell 8.68" (1771) et 8,63" (1772) Lexell 8.68" (1771) et 8,63" (1772)

Author(s) ValuesAuthor(s) ValuesWilliam Smith 8,6045" (1770) William Smith 8,6045" (1770) Thomas Hornsby 8,78" (1770) Thomas Hornsby 8,78" (1770) Pingré et Lalande 9,2" et 8,88" (1770) Pingré et Lalande 9,2" et 8,88" (1770) Pingré 8,80 (1772) Pingré 8,80 (1772) Lalande 8,55"< P < 8,63" (1771) Lalande 8,55"< P < 8,63" (1771) Planmann 8,43 (1772) Planmann 8,43 (1772) Hell 8,70" (1773/1774) Hell 8,70" (1773/1774) Lexell 8.68" (1771) et 8,63" (1772) Lexell 8.68" (1771) et 8,63" (1772)

The conclusion was that the parallax was from 8,43" to 8,80 The conclusion was that the parallax was from 8,43" to 8,80 "" . This . This was a real improvement regarding the result of 1761 providing a was a real improvement regarding the result of 1761 providing a parallax from 8,28 to 10,60".parallax from 8,28 to 10,60".

The conclusion was that the parallax was from 8,43" to 8,80 The conclusion was that the parallax was from 8,43" to 8,80 "" . This . This was a real improvement regarding the result of 1761 providing a was a real improvement regarding the result of 1761 providing a parallax from 8,28 to 10,60".parallax from 8,28 to 10,60".

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The transits of the XIXth centuryThe transits of the XIXth century

• The longitudes are now well determined (telegraph).

• The clocks are good time keepers.

• The travels are faster (steam, Suez channel).

• The travels are still expensive

• The photographs appeared (Daguerréotype)

• The experiences of the XVIIIth century are profitable.

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The transit of December 9, 1874The transit of December 9, 1874

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An example: the observation at St-PaulAn example: the observation at St-Paul

•July 1874 : departure from Paris.July 1874 : departure from Paris.•August 9: Suez channel.August 9: Suez channel.•August 30: arrival in Réunion IslandAugust 30: arrival in Réunion Island•September 22: arrival in Saint-Paul island in a tempestSeptember 22: arrival in Saint-Paul island in a tempest

The probability of fair weather was only 8 to 10%The probability of fair weather was only 8 to 10%

In spite of tempest and bad weather, the observation was a In spite of tempest and bad weather, the observation was a success: 500 exposures of the transit were madesuccess: 500 exposures of the transit were made

The voyage of Commandant Mouchez at Saint-Paul.The voyage of Commandant Mouchez at Saint-Paul.

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The voyage to Saint-PaulThe voyage to Saint-Paul

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The observation at Saint-PaulThe observation at Saint-Paul

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The transit of December 6, 1882The transit of December 6, 1882

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Reduction of photographsReduction of photographs

The measures on the plates were made through macro-The measures on the plates were made through macro-micrometers with an accuracy of one micrometer.micrometers with an accuracy of one micrometer.In France, 1019 plates were taken. All the measurements were In France, 1019 plates were taken. All the measurements were made two times by two different persons.made two times by two different persons.In fact more than 500 000 measurements were made.In fact more than 500 000 measurements were made.

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Recapitulation of the measures of the Earth-Sun distanceRecapitulation of the measures of the Earth-Sun distance

Method date parallax distance " millions km

Mars 1672 9.5 - 10 130 -140

Venus 1761 8.3 - 10.6 125 - 160Venus 1769 8.5 - 8.9 145 - 155

Mars 1862 8.84 149

Flora 1875 8.87 148

Mars 1885 8.78 150

Venus 1874 - 82 8.790-8.880 148.1 - 149.7

Eros 1900 8.806 149.4Eros 1930 8.790 149.7

radar 1970 8.79415 149.5978

Viking+radar 2000 149.597870691

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The recent transits of MercuryThe recent transits of Mercury

The observation of the transits of

Mercury provide us some excperience.Here, the transit of May 9, 1970 at the

Solar Tower in Meudon observatory.

12arcseconds

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Past transits of VenusPast transits of Venus

• The fac-simile of the reports of the observations and voyages made during the past centuries are available on a CD-Rom.

• More than 10 000 pages of rare books were scanned.

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Art and the transit of VenusArt and the transit of Venus

The ceiling The ceiling of the council room of the council room of Paris observatoryof Paris observatory

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Passage de Vénus (Paris observatory, Prouha, 1878)Passage de Vénus (Paris observatory, Prouha, 1878)

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Transit of Mercury (Balla, 1914)Transit of Mercury (Balla, 1914)

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Comic strip: the transit of VenusComic strip: the transit of Venus

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