Transcript 19.

Transit of Venus 2012
T V VENKATESWARAN
Scientist ‘E’
VIGYAN PRASAR
C-20 Qutab Institutional Area, New Delhi, 110 016
Venus transit over image of the sun
A transit of Venus will occur on June 6, 2012 after 8 years!
Will be visible all over India… provides an unique and rare
opportunity
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•What is Transit
•Venus- The Myths
•Venus- The Veiled planet
•Exploring Venus
•When do Transits occur
•How the Distance to Sun was measured
•Transits in History
•Transits and India
•Do Watch the Transit; but safely
The Solar Corona of Aug 11, 1999
In a total solar eclipse, moon comes in between Earth
and Sun; Further as the apparent size of moon is
equal to that of sun, it obstructs the complete face of
sun
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On the other hand,
when
moon
is
rather farthest to
Earth, it’s apparent
size appears small
and is not able to
obstruct the full
face of sun
And results in as Annular Solar Eclipse
(Jan 15, 2010)
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The rim of sun is visible all around the Face of moon in
such occasions
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Photograph of the Transit of Venus on 2004 June 08
Assume, if the obstructing body between Earth and Sun is even farther
away; then the obstructing body would appear as a small black dot on the
face of Sun.
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What is a transit ?
A transit is the observed passage of Mercury or
Venus across the disk of the sun.
While
‘transiting’, the planet would appear as a black
spot.
The word “transit” means passage or movement
— in this case, across the face of the sun.
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Chance of a Lifetime:
The 2012 Transit of
Venus
U.S. Naval Observatory Library
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Tuesday, June 6, 2012
Delhi India
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At Sunrise in Delhi
05:22am
03:39 am
03:57 am
Venus the Beauty
Venus, second planet from Sun
Considered as beauty by the European culture
Is called as sister planet to Earth
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In Egypt the horoscopus priests of Thebes looked across the
Nile and recognized it as the evil star of Set fleeing upward
before Amun-Ra (Sun God) at dawn to be vanquished and
disappear in the brilliance of the rising sun god.
Roman Myth
Venus was originally the goddess
of ferility, particularly of field and
garden. Venus was a Latin
goddess, and when her worship
was adopted in Rome. Venus was
later honoured as the goddess of
love and beauty, when she had
became identified with Aphrodite.
Indeed, the astronomical symbol of Venus is
adopted as the symbol for Women
Indeed keeping mind the association
of Venus with Women, almost all
the features are named after
women..
The northern highland, Ishtar
Terra, honors the Babylonian
goddess of love (and war).
Fault scarps (rupes) are named Vesta
for the Roman hearth goddess and
Ut for the Siberian goddess of the
hearth fire
The western part of Ishtar Terra is a
high volcanic plateau is named after
Lakshmi too
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Mayan Calendar had a cycle
based
upon
Venus’s
period of rotation – four
division;
morning star
236 day disappearance of
the venus which accounts
for 90 days. evening star
250 days, disappearance
of 8 days.
Considered as a God
instrumental in ‘Creation’
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One of the five planets visible to
naked eye
Shukra In India
Identified as Morning and Evening
Star
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Noted by ancient civilizations
A Babylonian clay tablet said to
have reference to Venus
Venus- The Veiled Planet
The cloud cover had prevented
the direct observation of Venus
surface all along.
Two different perspectives of Venus. On the left is a mosaic of images
acquired by the Mariner 10 spacecraft on February 5, 1974. The image shows the
thick cloud coverage that prevents optical observation of the planet's surface. The
surface of Venus remained hidden until 1978 when the Pioneer Venus 1
spacecraft arrived and went into orbit about the planet on December 4th. The
spacecraft used radar to map planet's surface, revealing a new Venus. Later in
August of 1990 the Magellan spacecraft arrived at Venus and began its extensive
planetary mapping mission. This mission produced radar images up to 300
meters per pixel in resolution. The right image show a rendering of Venus from
the Pioneer Venus and Magellan radar images.
Rotates in the opposite direction- implies sun will
rise in the West !
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Venus Statistics
Mass (kg)
4.869e+24
Mass (Earth = 1)
.81476
Equatorial radius (km)
6,051.8
Equatorial radius (Earth = 1)
.94886
Mean density (gm/cm^3)
Mean distance from the Sun (km)
Mean distance from the Sun (Earth = 1)
Rotational period (days)
Orbital period (days)
Mean orbital velocity (km/sec)
5.25
108,200,000
0.7233
-243.0187
224.701
35.02
Orbital eccentricity
0.0068
Tilt of axis (degrees)
177.36
Orbital inclination (degrees)
Equatorial surface gravity (m/sec^2)
Equatorial escape velocity (km/sec)
Mean surface temperature
Atmospheric pressure (bars)
3.394
8.87
10.36
482°C
92
Atmospheric
composition
Mainly :
Carbon dioxide
96 %
Nitrogen
3+ %
Trace amounts of:
Sulfur dioxide, water
vapour,
carbon monoxide, argon,
helium, neon,
hydrogen chloride, and
hydrogen fluoride.
A cutaway view of the possible internal structure of Venus. The image was
created from Mariner 10 images used for the outer atmospheric layer. The surface
was taken from Magellan radar images. The interior characteristics of Venus are
inferred from gravity field and magnetic field measurements by Magellan and prior
spacecraft. The crust is shown as adark red, the mantle as a lighter orange-red,
and the core yellow
A mosaic of three images acquired by the Mariner 10 spacecraft on
February 5, 1974. It shows the thick cloud coverage that prevents optical
observation of the surface of Venus. Only through radar mapping is the surface
revealed
On February 10, 1990 the Galileo spacecraft acquired this image of Venus.
Only thick cloud cover can be seen.
Hubble Space Telescope ultraviolet-light image of the planet Venus, taken on
January 24, 1995, when Venus was at a distance of 113.6 million kilometers from
Earth. At ultraviolet wavelengths cloud patterns become distinctive. In particular, a
horizontal "Y" shaped cloud feature is visible near the equator. The polar regions are
bright, possibly showing a haze of small particles overlying the main clouds. The dark
regions show the location of enhanced sulfur dioxide near the cloud tops. From
previous missions, astronomers know that such features travel east to west along with
the Venus' prevailing winds, to make a complete circuit around the planet in four days.
A portion of Western Eistla Regio is displayed in this three dimensional
perspective view of the surface of Venus. The viewpoint is located 1,310
kilometers (812 miles) southwest of Gula Mons at an elevation of 0.78 kilometers
(0.48 mile). The view is to the northeast with Gula Mons appearing on the
horizon. Gula Mons, a 3 kilometer (1.86 mile) high volcano, is located at
approximately 22 degrees north latitude, 359 degrees east longitude. The impact
crater Cunitz, named for the astronomer and mathematician Maria Cunitz, is
visible in the center of the image. The crater is 48.5 kilometers (30 miles) in
diameter and is 215 kilometers (133 miles) from the viewer's position
A portion of Western Eistla Regio is displayed in this three dimensional
perspective view of the surface of Venus. The viewpoint is located 725 kilometers
(450 miles) southeast of Gula Mons. A rift valley, shown in the foreground, extends
to the base of Gula Mons, a 3 kilometer (1.86 miles) high volcano. This view is
facing the northwest with Gula Mons appearing at the right on the horizon. Sif
Mons, a volcano with a diameter of 300 kilometers (180 miles) and a height of 2
kilometers (1.2 miles), appears to the left of Gula Mons in the background
The southern scarp and basin province of western Ishtar Terra are portrayed
in this three dimensional perspective view. Western Ishtar Terra is about the size
of Australia and is a major focus of Magellan investigations. The highland terrain is
centered on a 2.5 km to 4 km high (1.5 mi to 2.5 mi high) plateau called Lakshmi
Planum which can be seen in the distance at the right. Here the surface of the
plateau drops precipitously into the bounding lowlands, with steep slopes that
exceed 5% over 50 km (30 mi).
A portion of Alpha Regio is displayed in this three-dimensional perspective view of the
surface of Venus. Alpha Regio, a topographic upland approximately 1300 kilometers
across, is centered on 25 degrees south latitude, 4 degrees east longitude. In 1963,
Alpha Regio was the first feature on Venus to be identified from earth-based radar. The
radar-bright area of Alpha Regio is characterized by multiple sets of intersecting trends
of structural features such as ridges, troughs, and flat-floored fault valleys that, together,
form a polygonal outline. Directly south of the complex ridged terrain is a large ovoidshaped feature named Eve. The radar-bright spot located centrally within Eve marks the
location of the prime meridian of Venus
Arachnoids are one of the more remarkable features found on Venus. They
are seen on radar-dark plains in this Magellan image mosaic of the Fortuna region.
As the name suggests, arachnoids are circular to ovoid features with concentric
rings and a complex network of fractures extending outward. The arachnoids range
in size from approximately 50 kilometers (29.9 miles) to 230 kilometers (137.7
miles) in diameter.
Two groups of parallel features that intersect almost at right angles are visible. The
regularity of this terrain caused scientists to nickname it graph paper terrain. The
fainter lineations are spaced at intervals of about 1 kilometer (.6 miles) and extend
beyond the boundaries of the image. The brighter, more dominant lineations are
less regular and often appear to begin and end where they intersect the fainter
lineations.
Exploring Venus
Was knows as morning star and evening star
Periodicity known to ancient Indian astronomers
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Morning Star
Venus is visible as morning star, at times, visible before sunrise in the
Eastern Sky. Visible in the dawn, progressively the visibility is hampered
by the daylight.
Evening Star
At times, Venus is visible in the evening, after sunset in the western sky,
once the dusk sets in.
Telescope
provided a new
vision of Venus
Phases of Venus
was visible
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Confirmed the
Heliocentric view
Galileo demonstrated that the
Ptolemaic model the solar
system was unable to
account for observations
of Venus phases
• However, the actual
surface was still a
mystery until Radar
and Space probes
uncovered it
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• Soviet Spacecraft
Venera was the first to
reach the planet and
take photographs (first
planet to be reached
by space mission !)
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Venus Surface
Surface as imaged by the Venera- 13 lander
• Mariner Mission provided even more detailed picture
of Venus; through the use of Radar imagery.
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Magellan
Launched 1989. 98% of Venus
mapped from Sept 1992 to October
1994
Radar map and radar altimetry.
Brighter areas have higher radar
reflectivity (rougher)
Resolution about 120-300m
Venus Topography
Venus Global Topography
Red (highest) and
blue (lowest)
Aphrodite Terra:> half size of Africa
Artemis Corona
Centred 90 degrees east
Aino Planitia
Venus showing crescent phase
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Picture of Venus taken by Mariner 10
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Picture taken by Galileo spacecraft
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The idea of conjunction of planet was known to
ancient people, including Indian astronomers
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But in recorded history
‘Transit of Venus or
Mercury’ is said to be
predicted by Kepler
for the first time as a
consequence of the
Heliocentric system
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• The first Transit to be
observed by telescope
was by Gassendi- that
of Mercury
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Celestial clockwork
Every 19 months: Venus
00 03 06 09 overtakes
12 15 18 19 the Earth.
But Venus’s orbit is tilted 3.4o
with respect to Earth’s.
no transit
So usually, when
Venus overtakes
Earth, alignment
is not exact.
3.4o
Exact alignment
is very rare!
transit!
During 1996, Venus was in inferior conjunction (same side of
Sun); but its path due to tilt did not pass across the face of sun.
Hence no Transit.
However during 2004 and 2012, it will cross the face of sun;
resulting in Transit.
Years when transits of Venus
occurred
1631
1639
8
1761
1769
121 ½
8
1874
1882
105 ½
8
2004
2012
121 ½
8
2117
2125
105 ½
8
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Nicolaus
Copernicus
(1473-1543):
Johannes Kepler  (1571-1630):
predicted transit of 1631
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Jeremiah Horrocks (1618-1641)
(one of only two people known to have observed 1639 transit)
“Contemplate this most extraordinary phenomenon, never in our time to
be seen again!”
• Horrocks was the first to observe the Venus Transit in
16 31
• Actually he computed that the Transits of Venus occurs
in pair with a gap of 8 years and thus predicted 1639
Transit of Venus
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In spite of his keen
interest,
Horrocks
was interrupted from
his observation by
more
pressing
duties- my be his
divine duties as a
priest.
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• Horrocks used the
Transit to measure the
absolute distance to
the Sun..relative
distance was evident
from Kepler’s Laws.
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• Halley found that
Transit of Venus could
be used to measure the
distance accurately
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Edmond Halley (1656-1742)
Proposed “a method by which the
immense distance of the Sun may be
truly obtained” from international
observations of the 1761 transit.
http://wwwastronomy.mps.ohiostate.edu/~pogge/Ast16
1/Unit4/venussun.html
http://www-gap.dcs.st-and.ac.uk/~history/PictDisplay/Halley.html
Mt. Wilson Observatory
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The Astronomical Unit (A.U.)
“the noblest, and otherwise most difficult problem” –Edmond Halley
A.U. = avg. distance between Earth and Sun
= 5 million miles? (100 C.E.)
= 14 million miles? (1600 C.E.)
¾ A.U.
1 A.U.
¼ A.U.
= 66 million miles? (1700 C.E.)
To determine absolute scale of
solar system, astronomers
needed to measure the A.U.
Halley’s idea: during 1761 transit,
use parallax to measure distance
from Earth to Venus (~¼ A.U.).
Parallax: a way to measure distances
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Parallax: a way to measure distances
If two observers on Earth measure Venus’s parallax shift against
the Sun, then they can deduce the distance from Earth to Venus –
and from that, the A.U.
a
b
a
d
Practically, each
observer would time
Venus’s moments of
ingress and egress to
the second.
a
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One of the towering
achievement of
18th Century
astronomycomputation of
absolute value of
AU
Observers were
sent to al parts of
the world to take
measurement.
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Using Halley's Method for computing the Solar Parallax; observations
were made from various parts of the World
The calculated solar parallax varied between 8.55" and 8.88".
The modern accepted value is 8.794148".
It can be truly said, that the real distance
from the Earth to the Sun - the 'Astronomical Unit' - was at last
discovered.
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The transits of 1761 and 1769
the first world-wide collaboration in the history of science
England, France, Russia, the
American colonies…
Hundreds of observers…
…in some 150 locations around
the globe.
1761: Charles Mason and
Jeremiah Dixon (England)
and the trials of the Seven Years’ War
• December, 1760: HMS Sea Horse leaves Portsmouth for Sumatra…
…promptly meets French warship…
…and returns to port with 11 dead.
• M&D to London: “We will not proceed thither, let the Consequence be what it will.”
• London to M&D: “Your refusal to proceed… would be a reproach to the Nation in general, to
the Royal Society in particular, and more Especially and fatally to yourselves.”
• M&D to London: “grumble mumble grumble…”
• February, 1761: HMS Sea Horse leaves Portsmouth again.
• April, 1761: HMS Sea Horse reaches Cape of Good Hope, South Africa…
…where they discover the French have taken their destination in Sumatra.
• M&D to London: “We’re staying right here – so nyah!” [paraphrase]
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1769:
Capt. James Cook
and his first voyage on the
Endeavour
The South Seas Project
1761 and 1769:
The Sad Tale of Guillaume-Joseph-Hyacinthe-JeanBaptiste Gentil de la Galaisière (Le Gentil)
Mar 1760
May 1761
Jun 6,
1761
Jul 1760
1761 and 1769:
The Sad Tale of Guillaume-Joseph-Hyacinthe-JeanBaptiste Gentil de la Galaisière (Le Gentil)
Oct 1771
Mar 1768
Mar 1770
Aug 1766
“That is the fate
which often
awaits
astronomers. I
had gone more
than ten thousand
leagues; it seemed
that I had crossed
such a great
expanse of seas,
exiling myself
from my native
land, only to be
the spectator of a
fatal cloud.”
1761 / 1769 A.U.
measurements
• Difficulties:
• weather
• longitude
• Venus has atmosphere!
• “black drop” effect
• 1761 results:
• A.U. = 78-96 million miles
• 1769 results:
• A.U. = 92-96 million miles
1874 / 1882 transits
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•New discoveries in solar system:
• Uranus (1781), asteroids (1801), Neptune
(1846)
a
• New astronomical equipment:
• Photography (Expected to remove black drop;
but could not provided the expected result)
• Spectroscopy
d
• Distances to stars measured
• Stellar parallax
The A.U. sets the scale for the whole cosmos!
2 A.U.
• With a view to overcome the limitation, during the 19th
century astronomers attempted to use the Spectroscope
• La behold! Accidentally they discovered the atmosphere of
Venus
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1874 / 1882 transits
result: A.U. = 92.6-93.0 million miles
U.S. Naval Observatory Library
U.S. Naval Observatory Library
[New ways to measure A.U. were soon found, more precise.
Current value of A.U. (radar): 149597870 kilometers !]
Cairo
Rodriguez Is.
Mauritius
New Zealand
Pathani Samanta
There are indications that the famous Indian
astronomer of Orissa, Pathani Samanta also
observed the Venus transit of 1874.
Pathani Samanta Chandrasekhar, it is said to have
predicted the 1874 Transit working solely within the
Indian Traditional Astronomical system
“Solar eclipse due to Sukra (Venus) – To find the eclipse of the Sun
due to Sukra, their bimba (angular diameter) and size of other tara
graha is stated. In Kali year 4975 (1874 AD) there was a Solar
Eclipse due to Sukra in Vrischika Rasi (Scorpio). Then Sukra bimba
was seen as 1/32 of solar bimba which is equal to 650 yojana. Thus it
is well proved that bimba of Sukra and planets is much smaller than
the Sun.”
• India and Transit had a
long association…
actually first use of
telescope in India is
said to be by Jermiah
Shakerley in 1651 at
Surat to observe the
Transit of Mercury
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• During the 19th century India was a preferred
location for the circumstance for the Transit was
perfect.
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Major J F Tennent
made observations
from Roorkey and
arranged observations
from Lahore during
the 1874 Transit. There
were also observations
made from Danapur in
addition to many
private observations
• Ragoonatha charry
observed the event..
Participated in the
endeavor
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In 1874 he published a pamphlet on the Transit of Venus,
being induced to do so, as he states, by the fact that
“although the class of phenomena to which the Transit of Venus
belongs is mentioned in Hindu treatises on Astronomy, especially of
the Sidhanta Siromani, yet the Sidhantis or Hindu astronomers are
really not familiar with the nature of this particular occurrence, and
cannot predict it with even a rough approach to accuracy, happening
as it does at such strange and rare intervals."
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Another Indian observer to take keen interest was
Ankitam Venkata Narsinga Rao. He along with his
European friends observed the transit of 1874 and
reported the results to Royal Astronomical Society.
His private
observatory at
Daba Gardens,
Vizagapatam
with the Transit
observers
.
The first use of spectroscope to successfully observe the Transit was in
Muddupur, Bengal. A Italian team of Astronomers made the observation.
The telescopes used by them were gifted to Calcutta Observatory.
The Venus Transit party at Muddapur (1874)
First from left sitting is Father Lafont while third is Pietro
Tacchini.
• The Transit has been observed only very few times.. Just
five times till now
• 1639, 1761, 1769, 1874 and 1882
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Venus touching
the inner face –
II Contact
Venus leaving
the sun- III
Contact
Entry of
Venus – I
Contact
End of TOV IV
Contact
It is once in a life time opportunity.. Visible all over India
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How NOT to observe the transit
WARNING: Looking at the Sun without proper
protection can result in eye damage and permanent
blindness.
• Do not look at the Sun with the naked eye
– Not even through haze or clouds, or at sunrise/sunset
• Do not look at the Sun through non-approved
filters
• Never look at the Sun with binoculars or a
telescope without a proper solar filter attached
– Permanent blindness can occur within seconds
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Let’s not miss this unique opportunity; but
observe the Transit safely.. Take
precaution…
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How to SAFELY observe the transit
Eclipse99 Ltd.
wear approved solar filters
pinhole projection / pinhole mirror
(Venus can be seen with naked eye!)
binocular projection
telescopic projection
approved solar filter
on front end of ‘scope
Complied by
Dr T V Venkateswaran
Thanks to:
Dr S. Chatterji, Indian Inst of Astrophysics,
Bangalore
Dr Vivek Monterio- Navnirmithi Mumbai
Dr Arvind Ranade & Amithab Pandey,
Vigyan Prasar
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Acknowledgements
NASA, JPL,
Royal Astronomical Society,
Indian National Science Academy
Dr Hingley,
Dr Ratnashree,
Dr Rajesh Kochjar,
David Sellers,
Fred Espenak
… and many others ….