Transit of Venus 2012

T V VENKATESWARAN Scientist ‘E’

VIGYAN PRASARC-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

•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

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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

The Solar Corona of Aug 11, 1999

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And results in as Annular Solar Eclipse (Jan 15, 2010)

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

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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 08Assume, 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, 2012Delhi India

05:22am03:57 am03:39 am

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At Sunrise in Delhi

Venus the Beauty

Is called as sister planet to Earth

Venus, second planet from Sun

Considered as beauty by the European culture

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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 western part of Ishtar Terra is a high volcanic plateau is named after Lakshmi too

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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

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

The cloud cover had prevented the direct observation of Venus surface all along.

Venus- The Veiled Planet

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) 5.25

Mean distance from the Sun (km) 108,200,000

Mean distance from the Sun (Earth = 1) 0.7233

Rotational period (days) -243.0187

Orbital period (days) 224.701

Mean orbital velocity (km/sec) 35.02

Orbital eccentricity 0.0068

Tilt of axis (degrees) 177.36

Orbital inclination (degrees) 3.394

Equatorial surface gravity (m/sec^2) 8.87

Equatorial escape velocity (km/sec) 10.36

Mean surface temperature 482°C

Atmospheric pressure (bars) 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 ovoid-shaped 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.

Was knows as morning star and evening star

Periodicity known to ancient Indian astronomers

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Exploring Venus

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.

Morning Star

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 SurfaceSurface 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

Red (highest) andblue (lowest)

Centred 90 degrees east

Aphrodite Terra:> half size of Africa

Aino Planitia

Artemis Corona

Venus Global Topography

Venus showing crescent phaseMain Menu

Picture of Venus taken by Mariner 10Main Menu

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 clockworkmonths:

00 03 06 0912 15 18 19

19Every Venus overtakes the Earth.

no transit

transit!

But Venus’s orbit is tilted 3.4o with respect to Earth’s.

So usually, when Venus overtakes Earth, alignment is not exact.

Exact alignment is very rare!

3.4o

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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

16311639

17611769

18741882

20042012

21172125

8 8 8 8 8121 ½ 121 ½ 105 ½ 105 ½

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Johannes Kepler (1571-1630):

predicted transit of 1631

Nicolaus Copernicus (1473-1543):

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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!”

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• 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)

Mt. Wilson Observatory

http://ww

w-gap.dcs.st-and.ac.uk/~history/P

ictDisplay/H

alley.html

Proposed “a method by which the immense distance of the Sun may be truly obtained” from international observations of the 1761 transit.

http://ww

w-

astronomy.m

ps.ohio-state.edu/~pogge/A

st161/Unit4/

venussun.html

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The Astronomical Unit (A.U.)“the noblest, and otherwise most difficult problem” –Edmond Halley

4/10 A.U.

¾ A.U.

1 A.U.

A.U. = avg. distance between Earth and Sun

= 5 million miles? (100 C.E.)

= 14 million miles? (1600 C.E.)

= 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.).

¼ A.U.

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Parallax: a way to measure distances

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Parallax: a way to measure distances

d

b

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.

Practically, each observer would time Venus’s moments of ingress and egress to the second.

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One of the towering achievement of 18th Century astronomy- computation 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 distancefrom the Earth to the Sun - the 'Astronomical Unit' - was at last

discovered.

The transits of 1761 and 1769the 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.

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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: “We’re staying right here – so nyah!” [paraphrase]

• 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: “grumble mumble grumble…”

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The South Seas Project

1769: Capt. James Cook

and his first voyage on the Endeavour

1761 and 1769: The Sad Tale of Guillaume-Joseph-Hyacinthe-Jean-

Baptiste Gentil de la Galaisière (Le Gentil)Mar 1760

Jul 1760

May 1761

Jun 6, 1761

Aug 1766Mar 1768

Mar 1770

Oct 1771

“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 and 1769: The Sad Tale of Guillaume-Joseph-Hyacinthe-Jean-

Baptiste Gentil de la Galaisière (Le Gentil)

1761 / 1769 A.U. measurements• Difficulties:

• weather

• longitude

• 1761 results:

• A.U. = 78-96 million miles

• 1769 results:

• A.U. = 92-96 million miles

• Venus has atmosphere!

• “black drop” effect

1874 / 1882 transits•New discoveries in solar system:

• Uranus (1781), asteroids (1801), Neptune (1846)

• New astronomical equipment:

• Photography (Expected to remove black drop; but could not provided the expected result)

• Spectroscopy

• Distances to stars measured

• Stellar parallax

The A.U. sets the scale for the whole cosmos!

d

2 A.U.

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• 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

Cairo Rodriguez Is. Mauritius New Zealand

U.S. Naval Observatory LibraryU.S. Naval Observatory Library

result: A.U. = 92.6-93.0 million miles

[New ways to measure A.U. were soon found, more precise.

Current value of A.U. (radar): 149597870 kilometers !]

Pathani Samanta

There are indications that the famous Indian astronomer of Orissa, Pathani Samanta also observed the Venus transit of 1874.

“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.”

Pathani Samanta Chandrasekhar, it is said to have predicted the 1874 Transit working solely within the

Indian Traditional Astronomical system

• 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

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“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."

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.

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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.

First from left sitting is Father Lafont while third is Pietro Tacchini.

The Venus Transit party at Muddapur (1874)

• The Transit has been observed only very few times.. Just five times till now• 1639, 1761, 1769, 1874 and 1882

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It is once in a life time opportunity.. Visible all over India

Entry of Venus – I Contact

Venus touching the inner face –II Contact

Venus leaving the sun- III Contact

End of TOV IV Contact

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 transitEclipse99 Ltd.

wear approved solar filters (Venus can be seen with naked eye!)

pinhole projection / pinhole mirror

binocular projection telescopic projectionapproved solar filter on front end of ‘scope

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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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AcknowledgementsNASA, JPL, Royal Astronomical Society, Indian National Science Academy

Dr Hingley, Dr Ratnashree, Dr Rajesh Kochjar, David Sellers, Fred Espenak… and many others ….