VENUS in

transit

Robert Wielinga

Venus

Evening star

Goddess of love and beauty

planet

Utrecht, june 8th 2004, 05 h 20 m : sunrise

Utrecht, june 8th 2004, 07 h 19 m : a black dot passes in front of the sun

I : first contact at 07 h 19 mII: seccond contact at 07 h 39 m

III: third contact at 13 h 03 mIV : fourth contact at 13 h 23 m

A transit of Venus: a mini solar eclipse

16311639

17611769

18741882

20042012

21172125

8 8 8 8 8121 ½ 121 ½ 105 ½ 105 ½

Regularity in the occurance of transits of Venus

months00 03 06 09

12 15 18 19

19

When Venus meets the earth

Every the earth is overtaken by Venus

No transit

Transit!

But the orbit of Venus is tilted slightly with respect to orbit of the earth around the sun (3,4o).

Usually when Venus overtakes the earth there is no exact alignment

Exact alignment: very rare!

When Venus meets the earth

jandec

feb

mar

apr

mayjun

jul

aug

sep

oct

nov

1996

1998

19992001

2002

1996 2004 2012

Jeremiah Horrocks observes the transit of 1639

William Crabtree (friend of Horrocks) is the seccond person to observe the 1639 transit

“I beseech you, therefore, with all my strength, to attend to it diligently with a telescope and to make whatever observation

you can….” Horrocks, in a letter to Crabtree

A

A

BB

The path of Venus acros the sun by observers A and B as seen from the earth

Halley (1656-1742) proposed a method to measure the ‘immense distance to the sun’ by international coordinated observations during the transit of 1761.

Voyage with the Endeavour

Captain James Cook

1769: Tahiti

                                 

Captain James Cook

1769: Tahiti

The unfortunate adventures of Guillaume-Joseph-Hyacinthe-Jean-Baptiste Gentil de la Galaisière (Le Gentil)

maart 1760

juli 1760

mei 1761

6 juni 1761

mrt 1768

mrt 1770

okt 1771

aug 1766

The unfortunate adventures of Guillaume-Joseph-Hyacinthe-Jean-Baptiste Gentil de la Galaisière (Le Gentil)

Problems in 1761 / 1769:

- Weather (Le Gentil)

- Longitude

- The BLACK DROP effect

Cairo Rodriguez Is. Mauritius New Zealand

1874 / 1882

New hope:

- Photography

- Parallax of stars

Members of the Dutch expedition in 1874 in front of their accommodation in St. Denis, Réunion

Observation camp of the Dutch expedition

1874: Dutch participation !

Exhibition in Museum Observatory Sonnenborh

VENUS

Distance to the sun: 108 million km 0,72 AU

Diameter: 12.104 km (0,95 x earth)

Massa: 4,7 x 1024 kg (0,80 x earth)

Temperature (surface): 490 °C

Pressure (surface): 90 atmosphere

The atmosphere is is composed mostly of carbon dioxide. There are several layers of clouds, many kilometers thick, composed of sulfuric acid.

Mikhail Lomonosov, june 5, 1761 discovered, during a transit, that Venus has an atmosphere

Magellan spacecraft

Launched from the Space Shuttle (1989)

Venera 13

A partial solar eclipse:the moon covers the sun

Mercury in transit in may 2003

sunspot

Eclipse glasses

Pinnhole projection

Mirror projection

Projection method: safe and handy!

With binoculars (only use one half)

or telescope

Links:

www.sonnenborgh.nl

www.venusovergang.nl (nog niet aktief)

home.hetnet.nl/~smvanroode/venustransit

www.venusovergang.be

www.vt-2004.org