2003 Transit of Mercury        The Live Show

This event will be visible only using a  telescope (small will do). With a regular pair of binoculars the tiny dot of mercury cannot be traced. 


An important warning here : when looking at the sun through a telescope, take the appropriate precautions! Observing the sun without protection, whether it is with the naked eye, binoculars or a telescope, will lead to permanent eye damage, possibly even total blindness! An eyepiece filter in a telescope is not safe, the heat of the concentrated solar radiation can crack such a filter!

So be careful! Only projecting the sun's image on a white screen, or using a Herschel-wedge or objective-filter are safe - prepare yourself fully before observing the sun.

The Transit 

Astronomically, "transit" occurs when the inner planets to earth ( Mercury or Venus), passes across the Sun's disk.   Transit of Mercury occurs when Earth observers see the planet passes across the Sun. When heavenly bodies cross celestial meridian  that is also called "transit". Because of a great distance involved between the mercury and observers on Earth, and also Mercury is so tiny (40% larger than the Moon size - 91.7 Million Km any from Earth), a telescope is needed for observation of this phenomena. On other hand, the transit of Venus is easier to view without any telescope, because of the size,  but proper filter is still required, because of intense sun light. 

Unlike solar eclipses that occur every year, transit is a very rare happening. Transit  takes place when the Earth, planet, and Sun line up at a narrow zone around the line of node on the planet's orbit. There is  absolutely no chance for both the inner planets  i.e.  Mercury and Venus at the same day.  

Kepler had predicted a transit of Mercury would occur in 1631. The first person to observe a transit of Mercury was Pierre Gassendi who watched the event of November 7th, 1631 from Paris. Gassendi  wrote on astronomy, his own astronomical observations and on falling bodies. 

Transits of Mercury occur in pairs about three years apart and always in the months of May and November. In any given century, there are 13 or 14 transits of Mercury. In comparison, transits of Venus occur in pairs with more than a century separating each pair.  



The Importance of  Transit 

Until the end of the 17th Century, there was never a mechanism for calculating  the distance from the Earth to the Sun. It  was a great unknown for many centuries. Estimates had been made, but they were all  far off the mark. Copernicus and Tycho estimated the distance at 1500 earth-radii, and Kepler at 3500 earth-radii. The relative distances between the planets were quite well known (for instance, it was known that Jupiter was about 5 times further from the Sun than the Earth), but the absolute distances were not.

During a stay on the island of Saint-Helena, Sir Edmund Halley (1656-1742) observed a Mercury transit in 1677 and made careful note of the times of entry and exit of Mercury over the Solar Disk. He realised that if a transit would be observed from different latitudes on Earth, the different observers would see Mercury cross the Sun along at a different angle. This effect is known as parallax (this is even more noticeable for Venus transits, since Venus is closer to us than Mercury, which increases the difference in angles) and could be used to determine an accurate Earth-Sun distance. That way the transit acquired its  importance.

Planet Mercury

Mercury is only about one-third the size of the Earth. It is the second smallest planet in the solar system (it was believed to be the smallest until the discovery of  Pluto). The planet Mercury has a diameter of  4,880 km.  Mercury  diameter is 40% smaller than Earth and 40% larger than the Moon. It is even smaller than Jupiter's moon Ganymede and Saturn's moon Titan. Mercury is very close to the Sun. At a distance of 57.9 million Kms from sun, it takes 88 Earth days to circle the Sun and  one mercury day is equivalent to 59 Earth days. Earth is the 3rd planet from the Sun at a distance of about 150 million kilometers.  Mercury apppears  in the daytime sky every day round the year, but because of its close distance to the sun,  it is usually washed out in the solar glow, it is one of the most difficult planets to observe. It may come as a surprise, but many modern astronomers have never seen Mercury.  


However, Mercury plays a practical joke on astronomers. Several factors caused earthbound astronomers to always see the same features over and over. There is a tidal connection between Mercury and the Sun. But it is not 1:1 but a 1.5:1. Mercury actually rotates 1 and a half times for every "year" of Mercury; Mercury's day equals about every 58.6 Earth days. And there is a "synchronicity" factor with Earth's orbital period, and the earth's axis tilt doesn't help either.

Visual Appearance

Mercury orbits the sun in about 3 months. Hence, it will never get farer away of our central star than 25 and always stays in bright twilight. This makes Mercury to a difficult object, although it shines as bright as Sirius.

Similar to our Moon, the Mercury shows us different phases during its orbit around the Sun. Using a telescope, it is possible to distinguish the phases as they change during the view days of visibility.

The following images span the time from superior conjunction (i.e. Mercury is closest to the line of sight from Earth to the Sun, but behind the Sun) to greatest elongation, to the inferior conjunction with the Sun.

Even at elongation, it is never more than 28 degrees from the Sun in our sky.  and also the fastest in its orbit since it is the innermost planet. In fact, the name Mercury derives from its speed in moving around its orbit. It's speed is approximately 158,000 Km/Hour(45 Km per sec).






57,910,000 Km from Sun   

149,600,000 Km from Sun

Orbital Period   

 87.969 Days   

365.26 days1 Earth day)

Length of Day   

58.6 Earth days   

23 hours 57 min 


4,880 Km   

Earth 12,756 Km


3.30 x 10 23 kg   

Earth 6x1024 kg

Maximum surface temperature   



Minimum surface temperature   





Helium    42%   

Sodium    42% 

Oxygen    15% 

Other    1%

Oxygen    21%
Nitrogen    78%

Other    1%

Mercury has no substantial atmosphere. These factors contribute to the fact that the surface of Mercury has the greatest temperature range of any planet or natural satellite in our solar system. The surface temperature on the side of Mercury closest to the Sun reaches 427 degrees Celsius, a temperature hot enough to melt tin. On the side facing away from the Sun, or the night side, the temperature drops to -183 degrees Celsius. 

Scientists have detected a magnetic field surrounding Mercury, though it is not as strong as the field around the Earth. Scientists theorize that Mercury's field is due to an iron-bearing core or possibly to the solar winds. Mercury's atmosphere is very thin and is composed of helium and sodium. The surface of Mercury has been shaped by three processes: impact cratering where large objects struck the surface resulting in crater formation, volcanism where lava flooded the surface, and tectonic activity where the planet's crust moved in order to adjust to the planetary cooling and contracting. Mercury does not have any naturally occurring satellites

We began to learn more about Mercury with radar imaging from the Earth in the 1960s, and obtained most of what we know about the planet from the Mariner 10 space probe was placed into a complicated orbit involving Venus and Mercury and which passed close to Mercury and sent back information three times in the period 1974-1976.  

 Mercury Observation

Mercury can never get more than 28 degrees or two hours from the sun. It is small in angular size, shows no detail in an amateur telescope, and can be conveniently seen only within an hour after sunset or just before sunrise, depending on its position in its orbit around the sun. The best times to view Mercury are in the evening sky around the spring equinox, or in the morning sky, around the autumn equinox.   

Mercury is brightest between greatest elongation and superior conjunction. It should be viewed at greatest elongation in order to obtain a high sky position. Even so, it is hard to see, since it is easily lost behind trees and rooftops which surround the average backyard telescope.

Age of Mercury

Mercury's history of formation is similar to that of Earth's. About 4.5 billion years ago the planets formed. This was a time of intense bombardment for the planets as they scooped up matter and debris left around from the nebula that formed them. Early during this formation, Mercury probably differentiated into a dense metallic core, and a silicate crust. After the intense bombardment period, lava flowed across the surface and covered the older crust. By this time much of the debris had been swept up and Mercury entered a lighter bombardment period. During this period the intercrater plains formed. Then Mercury cooled. Its core contracted which in turn broke the crust and produced the prominent lobate scarps. During the third stage, lava flooded the lowlands and produced the smooth plains. During the fourth stage micrometeorite bombardment created a dusty surface also known as regolith. A few larger meteorites impacted the surface and left bright rayed craters. Other than the occasional collisions of a meteorites, Mercury's surface is no longer active and remains the same as it has for millions of years.

 Could water exist on Mercury?

It would appear that Mercury could not support water in any form. It has very little atmosphere and is blazing hot during the day, but in 1991 scientists at Caltech bounced radio waves off Mercury and found an unusual bright return from the north pole. The apparent brightening at the north pole could be explained by ice on or just under the surface. But is it possible for Mercury to have ice? Because Mercury's rotation is almost perpendicular to its orbital plain, th north pole always sees the sun just above the horizon. The insides of craters would never be exposed to the Sun and scientists suspect that they would remain colder than -161 C. These freezing temperatures could trap water outgassed from the planet, or ices brought to the planet from cometary impacts. These ice deposits might be covered with a layer of dust and would still show bright radar returns.


Recorded evidence of mercury observation: Johann Hieronymus Schroeter observed the planet Mercury and record detailed drawings of Mercury's surface features. Schroeter lived from 1745 to 1816. Unfortunately, his sketches were not very accurate. Streaks similar to the so-called "Martian Canals" were also seen on Mercury by Schiaparellit and Percival Lowell (1855-1916). An astronomer by the name of Eugenios Antoniadi (1870-1944) charted the surface of Mercury in great detail. His maps were used for almost 50 years. He used one of the stronger telescopes of his time and found the canals to be optical illusions.  

Occasional truncations were observed by others but little surface detail was recorded until the 1880's, by Denning in England and Schiaparelli at Milan. Schiaparelli published no individual drawings to this writer's knowledge but did publish the first planisphere (single hemisphere) of Mercury's surface (1889). He believed the planet to rotate synchronously with a period equal to its orbital period, namely 87.969 days. This opinion was not at first universally accepted. Schroter's assistant, Harding, and the astronomer Prince concluded that the Mercurian day was approximately that of the Earth's (Sandner, 1963). Leo Brenner (1896) concluded that it was actually 33 to 35 hours. These opinions lapsed after various observers would observe a feature as motionless over a period of several hours (of date-time observing)(see, for example, McEwen, 1909).

The most important work of the period is that of Antoniadi (1934). Working at Meudon, Antoniadi observed Mercury from 1924 to 1929, firmly established (as he thought) an 88--day rotation period, and gave nomenclature to the various bright and dark areas. Although not the first to do so, he had truly mastered the art of daylight observations. The drawings, being so excellent, if small in number, firmly entrenched various markings into Mercury observation lore, so much so that observational bias imitative of Antoniadi is quite strong in many later drawings.

Mariner 10 provided a close look at Mercury which redrew earlier telescope charts and maps.

Mariner 10 Observations

Obtaining the first close-up views of Mercury was the primary objective of the Mariner 10 spacecraft, launched on November 3, 1973, from Kennedy Space Center in Florida. After a journey of nearly five months, including a flyby of Venus, the spacecraft passed within 703 kilometers (437 miles) of the solar system's innermost planet on March 29, 1974.

Until Mariner 10, little was known about Mercury. Even the best telescopic views from Earth showed Mercury as an indistinct object lacking any surface detail. The planet is so close to the Sun that it is usually lost in solar glare. When the planet is visible on Earth's horizon just after sunset or before dawn, it is obscured by the haze and dust in our atmosphere. Only radar telescopes gave any hint of Mercury's surface conditions prior to the voyage of Mariner 10.

The photographs Mariner 10 radioed back to Earth revealed an ancient, heavily cratered surface, closely resembling our own Moon. The pictures also showed huge cliffs crisscrossing the planet. These apparently were created when Mercury's interior cooled and shrank, buckling the planet's crust. The cliffs are as high as 3 kilometers (2 miles) and as long as 500 kilometers (310 miles).

Instruments on Mariner 10 discovered that Mercury has a weak magnetic field and a trace of atmosphere - a trillionth the density of Earth's atmosphere and composed chiefly of argon, neon and helium. When the planet's orbit takes it closest to the Sun, surface temperatures range from 467 degrees Celsius (872 degrees Fahrenheit) on Mercury's sunlit side to -183 degrees Celsius (-298 degrees Fahrenheit) on the dark side. This range in surface temperature - 650 degrees Celsius (1,170 degrees Fahrenheit) - is the largest for a single body in the solar system. Mercury literally bakes and freezes at the same time.

Days and nights are long on Mercury. The combination of a slow rotation relative to the stars (59 Earth days) and a rapid revolution around the Sun (88 Earth days) means that one Mercury solar day takes 176 Earth days or two Mercury years - the time it takes the innermost planet to complete two orbits around the Sun!

Mercury appears to have a crust of light silicate rock like that of Earth. Scientists believe Mercury has a heavy iron rich core making up slightly less than half of its volume. That would make Mercury's core larger, proportionally, than the Moon's core or those of any of the planets.

After the initial Mercury encounter, Mariner 10 made two additional flybys - on September 21, 1974, and March 16, 1975 - before control gas used to orient the spacecraft was exhausted and the mission was concluded. Each flyby took place at the same local Mercury time when the identical half of the planet was illuminated; as a result, we stlll have not seen one-half of the planet's surface.

The majority of Mercury's surface is covered by plains. Much of it is old and heavily cratered, but some of the plains are less heavily cratered. Scientists have classified these plains as intercrater plains and smooth plains. Intercrater plains are less saturated with craters and the craters are less than 15 kilometers in diameter. These plains were probably formed as lava flows buried the older terrain. The smooth plains are younger still with fewer craters. Smooth plains can be found around the Caloris basin. In some areas patches of smooth lava can be seen filling craters.

Further Facts about Mercury

(Bevan M. French and Stephen P. Maran, eds., "A Meeting with the Universe," NASA EP-177, U.S. Government Printing Office, 1981.)

* The mass of Mercury was accurately determined.

* Any residual atmosphere has less than a million- billionths the pressure of the Earth's atmosphere at sea level.   However, a trace of helium, perhaps derived by outgassing from Mercury's interior, was found.

* It was discovered that Mercury has an internal magnetic field, similar to but weaker than that of Earth.

* Mercury's surface is heavily cratered and resembles that of the Moon. 

* A huge circular impact basin (Mare Caloris), about 1300 kilometers (810 miles) in diameter, was discovered.

* A planetary feature unique to Mercury was found, consisting of long scarps, or cliffs, that apparently were   produced by compression in a major shrinkage of the planet.

* Flat plains, perhaps lava flows, were found.

* Mercury was found to be closer to a perfect sphere than is the Earth.

* Mercury resembles the Earth's moon.

* This planet has no moon.

* Mercury's gravity is about one-third of the Earth's gravity.

* Mercury has a weak magnetic field and a trace of atmosphere (one-trillionth the density of the Earth and composed chiefly of argon, neon and helium).

* Mercury's orbit is more elliptical than any other planet except Pluto.

* Mercury has a crust of light silicate rock.

* Mercury's iron core is about the size of the Earth's moon.

7th May,2003 Transit of Mercury

The transit or passage of a planet across the face of the Sun is a relatively rare occurrence. As seen from Earth, only transits of Mercury and Venus are possible. On the average, there are 13 transits of Mercury each century.   

On Wednesday, 2003 May 07, Mercury will transit the Sun for the first time since 15th November,1999. The entire event will be widely visible from the Europe, Africa and Asia. Japan Australia, and New Zealand will witness the beginning of the transit but the Sun will set before the event ends. Similarly, observers in western Africa, eastern North America and eastern South America will see the end of the event since the transit will already be in progress at sunrise from those regions.

The principal events occurring during a transit are conveniently characterized by contacts, analogous to the contacts of an annular solar eclipse. The transit begins with contact I which is the instant when the planet's disk is externally tangent with the Sun. Shortly after contact I, the planet can be seen as a small notch along the solar limb. The entire disk of the planet is first seen at contact II when the planet is internally tangent with the Sun. During the next several hours, the silhouetted planet slowly traverses the brilliant solar disk. At contact III, the planet reaches the opposite limb and once again is internally tangent with the Sun. Finally, the transit ends at contact IV when the planet's limb is externally tangent to the Sun. Contacts I and II define the phase called ingress while contacts III and IV are known as egress. Position angles for Mercury at each contact are measured counterclockwise from the north point on the Sun's disk.


Geocentric Phases of the 2003 Transit of Mercury  


Universal  Time   


Contact I   



Contact II   






Contact III   



Contact IV   



The transit times in these tables are based of geocentric calculations. Because of parallax, the observed transit times for any given location may differ by up to 3 minutes. Furthermore, the Sun's actual altitude at a location may differ by up to 1 degree from the tables. Such precision is adequate for many applications especially since the geocentric approximation greatly simplifies the circumstances calculations.

Table above gives the times of major events during the transit. Greatest transit is the instant when Mercury passes closest to the Sun's center (i.e. - minimum separation). During the 2003 transit, Mercury's minimum separation from the Sun is 708 arc-seconds. The position angle is defined as the direction of Mercury with respect to the center of the Sun's disk as measured counterclockwise from the celestial north point on the Sun. Figure  below shows the path of Mercury across the Sun's disk and the scale gives the Universal Time of Mercury's position at any instant during the transit. The celestial coordinates of the Sun and Mercury are provided at greatest transit as well as the times of the major contacts. The world map at the bottom of shows figure shows regions of visibility of the event.  

Note that these times are for an observer at Earth's center. The actual contact times for any given observer may differ by up to several minutes. This is due to effects of parallax since Mercury's 12 arc-second diameter disk may be shifted up to nearly 16 arc-seconds from its geocentric coordinates depending on the observer's exact position on Earth. Indian East and west cities observation will be as follows.  



FOR  7th MAY 2003 (Universal  time)





ExternalIngress   hr:mts:sec   



Sun Altitude Degrees



Internal   Ingress   hr:mts:sec



Sun Altitude Degrees



Greatest   Transit  hr:mt:sec



Sun Altitude Degrees  



Internal  Egress hr:mt:sec   



Sun Altitude Degrees 



External Egress hr:mt:sec



Sun Altitude Degrees 




















Additional Information

All transits of Mercury fall within several days of 8 May and 10 November. Since Mercury's orbit is inclined seven degrees to Earth's, it intersects the ecliptic at two points or nodes which cross the Sun each year on those dates. If Mercury passes through inferior conjunction at that time, a transit will occur. During November transits, Mercury is near perihelion and exhibits a disk only 10 arc-seconds in diameter. By comparison, the planet is near aphelion during May transits and appears 12 arc-seconds across. However, the probability of a May transit is smaller by a factor of almost two. Mercury's slower orbital motion at aphelion makes it less likely to cross the node during the critical period. November transits recur at intervals of 7, 13, or 33 years while May transits recur only over the latter two intervals. 

Table 3 lists all transits of Mercury from 2001 through 2100.

Transits of Mercury: 2001-2100     


Universal   Time


1907 Nov 14   



1914 Nov 07   



1924 May 08   



1927 Nov 10   



1937 May 11   



1940 Nov 11   



1953 Nov 14   



1957 May 06   



1960 Nov 07   



1970 May 09   



1973 Nov 10   



1986 Nov 13   



1993 Nov 06   



1999 Nov 15   



2003 May 07   



2006 Nov 08   



2016 May 09   



2019 Nov 11   



2032 Nov 13   



2039 Nov 07   



2049 May 07   



2052 Nov 09   



2062 May 10   



2065 Nov 11   



2078 Nov 14   



2085 Nov 07   



2095 May 08   



2098 Nov 10   



Requirements for observation  

Since Mercury is only 1/158 of the Sun's apparent diameter, a telescope with a magnification of 50x to 100x is recommended to watch this event. Naturally, the telescope must be suitably equipped with adequate filtration to ensure safe solar viewing. The visual and photographic requirements for observing a transit are identical to those for solar viewing. Amateurs can make a scientific contribution by timing the four contacts at ingress and egress.  Observing techniques and equipment are similar to those used for lunar occultations. Since poor seeing often increases the uncertainty in contact timings, an estimate of the possible error associated with each timing should be included.   












Actually, white light observations of contacts I and IV are not technically possible since Mercury is only visible after contact I and before contact IV. However, if Hydrogen-alpha filtration is available, the planet may be visible

against either prominences or the chromosphere before and after contacts I and IV, respectively. Observations of contacts II and III also require amplification. They're often mistaken for the instant when the planet appears internally tangent to the Sun. However, just before contact II, the so-called black drop effect is seen. At that time, the transiting planet seems to be attached to the Sun's limb by a thin column or thread. When the thread breaks and the planet is completely surrounded by sunlight, this marks the true instant of contact II. Contact III occurs in exactly the reverse order. Atmospheric seeing often makes it difficult to measure contact timings with a precision better than several seconds.  






Mercury of Ancient India  


Indian observation : It is interesting to note that telescopes were used from India in the 17th century itself. The earliest use appears to have been in 1651, barely 40 years after its use by Galileo. Jeremiah Shakerley (1626 - ca1655), known in English astronomical circles5 as one of the earliest followers of Kepler, emigrated to Surat in west India. He observed the 1651 transit of Mercury, but could time neither the ingress nor egress. His

effort thus remains a historical curiosity.

(THE GROWTH OF MODERN ASTRONOMY IN INDIA, 1651-1960 R. K. Kochhar Indian Institute of Astrophysics, Bangalore 560034, India)



Indian Astronomy: In Indian astronomy Mercury is Budha. Prof. N.S. Rajaram, a mathematician who has worked for NASA, comments: fabricating astronomical data going back thousands of years calls for knowledge of Newtons Law of Gravitation and the ability to solve differential equations. Failing this advanced knowledge, the data in the Brahminical tables must be based on actual observation.  Ergo sates, the Sanskrit-speaking Vedic seers were present in person to record astronomical observations and preserve them for a full 6,000 years: The observations on which the astronomy of India is founded, were more than three thousand years before the Christian era.Two other elements of this astronomy, the equation of the suns centre and the obliquity of the ecliptic, seem to point to a period still more remote, and to fix the origin of this astronomy 1000 or 1200 years earlier, that is, 4300 years before the Christian era

Mercury of Indian Astrology: Buddha or Mercury Buddha a member of Nava graha, is represented in yellow colour, clothed in yellow garment, with' three arms bearing 'Khadga', 'Khetaka', and 'Gada' and in Varada pose. The influence of Budha (Mercury) is known to be variable, convertible, neutral and dualistic. That is, it expresses a nature in accordance with the character of the graha which it conjoins or aspects: benefic when with fortunate planets or when in favorable aspect, and malefic otherwise.

Mercury in Roman Mythology

Mercury is the Roman gods' messenger.  It was portrayed as a youth, flying with wings at his heels, bearing a caduceus made of olive wood about which were twined two serpents, the rod being surmounted with a pair of wings. This symbol well represents the essential qualities of the planet - duality, speed and wisdom. Mercury is also known as Alipes ("with the winged feet").

Mercury is god of trade and profit, merchants and travelers, but originally of the trade in corn. In later times he was equated with the Greek Hermes. He had a temple in Rome near the Circus Maximus on the Aventine Hill which dates back to 495 BCE. This temple was connected to some kind of trade fair. His main festival, the Mercuralia, was celebrated on May 15 and on this day the merchants sprinkled their heads and their merchandise with water from his well near the Porta Capena. 

During the time of the Roman Empire the cult of Mercury was widely spread, especially among the Celtic and Germanic peoples. The Celts have their Gaulish Mercury, and the Germans identified him with their Wodan. 

Reference Links