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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 m
II: seccond contact at 07 h 39 m
III: third contact at 13 h 03 m
IV : fourth contact at 13 h 23 m
A transit of Venus: a mini solar eclipse
Regularity in the occurance of transits of Venus
1631
1639
8
1761
1769
121 ½
8
1874
1882
105 ½
8
2004
2012
121 ½
8
2117
2125
105 ½
8
When Venus meets the earth
Every 19 months the earth is overtaken by Venus
00 03 06 09
12 15 18 19
When Venus meets the earth
But the orbit of Venus is tilted slightly
with respect to orbit of the earth
around the sun (3,4o).
No transit
Usually when
Venus overtakes
the earth there
is no exact
alignment
Transit!
Exact alignment:
very rare!
1998
jan
2002
dec
nov
feb
oct
mar
2001
sep
1999
apr
aug
may
jun
1996
jul
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
Halley (1656-1742) proposed a method to measure
the ‘immense distance to the sun’ by international
coordinated observations during the transit of 1761.
A

B
B 
A
The path of Venus acros the sun by
observers A and B as seen from the
earth
Captain James Cook
VoyageTahiti
1769:
with the Endeavour
Captain James Cook
1769: Tahiti
The unfortunate adventures of Guillaume-Joseph-Hyacinthe-JeanBaptiste Gentil de la Galaisière (Le Gentil)
maart 1760
mei 1761
6 juni 1761
juli 1760
The unfortunate adventures of Guillaume-Joseph-Hyacinthe-JeanBaptiste Gentil de la Galaisière (Le Gentil)
okt 1771
mrt 1768
mrt 1770
aug 1766
Problems in 1761 / 1769:
- Weather (Le Gentil)
- Longitude
- The BLACK DROP effect
1874 / 1882
New hope:
- Photography
- Parallax of stars
Cairo
Rodriguez Is.
Mauritius
New Zealand
1874: Dutch participation !
Members of the Dutch expedition in
1874 in front of their accommodation
in St. Denis, Réunion
Observation camp of
the Dutch expedition
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
sunspot
Mercury in
transit in
may 2003
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