A total
solar eclipse
A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby obscuring the view of the Sun from a small part of Earth, totally or partially. Such an alignment occurs approximately every six months, during the eclipse season i ...
occurred at the Moon's
ascending node of orbit on Tuesday, August 18, 1868 (also known as "The King of Siam's eclipse"), with a
magnitude of 1.0756. A
solar eclipse
A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby obscuring the view of the Sun from a small part of Earth, totally or partially. Such an alignment occurs approximately every six months, during the eclipse season i ...
occurs when the
Moon
The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...
passes between
Earth
Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...
and the
Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. A total solar eclipse occurs when the Moon's
apparent diameter is larger than the Sun's, blocking all direct sunlight, turning day into darkness. Totality occurs in a narrow path across Earth's surface, with the partial solar eclipse visible over a surrounding region thousands of kilometres wide. Occurring about 6.5 days after
perigee (on August 17, 1868, at 22:35 UTC), the Moon's apparent diameter was larger.
The path of totality was visible from parts of modern-day
Ethiopia
Ethiopia, officially the Federal Democratic Republic of Ethiopia, is a landlocked country located in the Horn of Africa region of East Africa. It shares borders with Eritrea to the north, Djibouti to the northeast, Somalia to the east, Ken ...
,
Eritrea
Eritrea, officially the State of Eritrea, is a country in the Horn of Africa region of East Africa, with its capital and largest city being Asmara. It is bordered by Ethiopia in the Eritrea–Ethiopia border, south, Sudan in the west, and Dj ...
,
Djibouti
Djibouti, officially the Republic of Djibouti, is a country in the Horn of Africa, bordered by Somalia to the south, Ethiopia to the southwest, Eritrea in the north, and the Red Sea and the Gulf of Aden to the east. The country has an area ...
,
Yemen
Yemen, officially the Republic of Yemen, is a country in West Asia. Located in South Arabia, southern Arabia, it borders Saudi Arabia to Saudi Arabia–Yemen border, the north, Oman to Oman–Yemen border, the northeast, the south-eastern part ...
,
India
India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...
, the
Andaman and Nicobar Islands
The Andaman and Nicobar Islands is a union territory of India comprising 572 islands, of which only 38 are inhabited. The islands are grouped into two main clusters: the northern Andaman Islands and the southern Nicobar Islands, separated by a ...
,
Myanmar
Myanmar, officially the Republic of the Union of Myanmar; and also referred to as Burma (the official English name until 1989), is a country in northwest Southeast Asia. It is the largest country by area in Mainland Southeast Asia and has ...
,
Thailand
Thailand, officially the Kingdom of Thailand and historically known as Siam (the official name until 1939), is a country in Southeast Asia on the Mainland Southeast Asia, Indochinese Peninsula. With a population of almost 66 million, it spa ...
,
Cambodia
Cambodia, officially the Kingdom of Cambodia, is a country in Southeast Asia on the Mainland Southeast Asia, Indochinese Peninsula. It is bordered by Thailand to the northwest, Laos to the north, and Vietnam to the east, and has a coastline ...
,
Vietnam
Vietnam, officially the Socialist Republic of Vietnam (SRV), is a country at the eastern edge of mainland Southeast Asia, with an area of about and a population of over 100 million, making it the world's List of countries and depende ...
,
Malaysia
Malaysia is a country in Southeast Asia. Featuring the Tanjung Piai, southernmost point of continental Eurasia, it is a federation, federal constitutional monarchy consisting of States and federal territories of Malaysia, 13 states and thre ...
,
Brunei
Brunei, officially Brunei Darussalam, is a country in Southeast Asia, situated on the northern coast of the island of Borneo. Apart from its coastline on the South China Sea, it is completely surrounded by the Malaysian state of Sarawak, with ...
,
Indonesia
Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania, between the Indian Ocean, Indian and Pacific Ocean, Pacific oceans. Comprising over List of islands of Indonesia, 17,000 islands, including Sumatra, ...
, and
Papua New Guinea
Papua New Guinea, officially the Independent State of Papua New Guinea, is an island country in Oceania that comprises the eastern half of the island of New Guinea and offshore islands in Melanesia, a region of the southwestern Pacific Ocean n ...
. A partial solar eclipse was also visible for parts of
East Africa
East Africa, also known as Eastern Africa or the East of Africa, is a region at the eastern edge of the Africa, African continent, distinguished by its unique geographical, historical, and cultural landscape. Defined in varying scopes, the regi ...
, the
Middle East
The Middle East (term originally coined in English language) is a geopolitical region encompassing the Arabian Peninsula, the Levant, Turkey, Egypt, Iran, and Iraq.
The term came into widespread usage by the United Kingdom and western Eur ...
,
Central Asia
Central Asia is a region of Asia consisting of Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, and Uzbekistan. The countries as a group are also colloquially referred to as the "-stans" as all have names ending with the Persian language, Pers ...
,
South Asia
South Asia is the southern Subregion#Asia, subregion of Asia that is defined in both geographical and Ethnicity, ethnic-Culture, cultural terms. South Asia, with a population of 2.04 billion, contains a quarter (25%) of the world's populatio ...
,
Southeast Asia
Southeast Asia is the geographical United Nations geoscheme for Asia#South-eastern Asia, southeastern region of Asia, consisting of the regions that are situated south of China, east of the Indian subcontinent, and northwest of the Mainland Au ...
,
Australia
Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...
, and western
Oceania
Oceania ( , ) is a region, geographical region including Australasia, Melanesia, Micronesia, and Polynesia. Outside of the English-speaking world, Oceania is generally considered a continent, while Mainland Australia is regarded as its co ...
.
The eclipse was predicted more precisely by
King Mongkut of
Thailand
Thailand, officially the Kingdom of Thailand and historically known as Siam (the official name until 1939), is a country in Southeast Asia on the Mainland Southeast Asia, Indochinese Peninsula. With a population of almost 66 million, it spa ...
than it was by French astronomers. The eclipse allowed for the discovery of
helium
Helium (from ) is a chemical element; it has chemical symbol, symbol He and atomic number 2. It is a colorless, odorless, non-toxic, inert gas, inert, monatomic gas and the first in the noble gas group in the periodic table. Its boiling point is ...
by both
Pierre Janssen and
Norman Lockyer, who observed
Solar prominences with
spectroscopes.
Observations
Solar eclipse 1868Aug18-Bullock.png, Bullock sketch of the eclipse, ''Total Eclipses of the Sun'', 1900.
Sketches of the total solar eclipse, 1868 (19745966082).jpg, M. Stephan sketches of the eclipse, ''Archives des missions scientifiques et littéraires'', 1868.
Map of the solar eclipse of August 18, 1868 (19757912091).jpg, Map of the forecast path of the total eclipse, ''Archives des missions scientifiques et littéraires'', 1868.
Several expeditions were sent to observe the eclipse.
* One of two expeditions from Germany was sent to Aden. The expedition was led by
Gustav Spörer.
* The second expedition was sent to the west coast of India. The expedition was led by
Friedrich Tietjen.
*Captain Bullock observed from the
Celebes sea, sketching the appearance of the corona, while
Gustav Fritsch
Gustav Theodor Fritsch (5 March 1838 – 12 June 1927) was a German anatomist, anthropologist, traveller and physiologist from Cottbus.
Fritsch studied natural science and medicine in Berlin, Breslau and Heidelberg. In 1874 he became an asso ...
accompanied an expedition to
Aden
Aden () is a port city located in Yemen in the southern part of the Arabian peninsula, on the north coast of the Gulf of Aden, positioned near the eastern approach to the Red Sea. It is situated approximately 170 km (110 mi) east of ...
.
Discovery of helium
French astronomer
Pierre Janssen observed the eclipse from
Guntur
Guntur (), natively spelt as Gunturu, is a city in the States and union territories of India, Indian state of Andhra Pradesh and the administrative headquarters of Guntur district. The city is part of the Andhra Pradesh Capital Region and is lo ...
in
Madras State,
British India
The provinces of India, earlier presidencies of British India and still earlier, presidency towns, were the administrative divisions of British governance in South Asia. Collectively, they have been called British India. In one form or another ...
. It was the first total eclipse since
Gustav Kirchhoff's
1859 theory that the
Fraunhofer lines in the solar spectrum correspond to the emission line of the different chemical elements present in the Sun. Correspondingly, Janssen observed the eclipse with the aid of a
spectroscope. He noticed a bright yellow line (
''λ'' = 587.49 nm) in the spectra of the
solar prominences that could not be due to sodium as had previously been assumed, and was subsequently able to observe the same line even without the need for an eclipse. The same result was found independently by British astronomer
Norman Lockyer, and both Janssen's and Lockyer's communications were presented to the
French Academy of Sciences
The French Academy of Sciences (, ) is a learned society, founded in 1666 by Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French Scientific method, scientific research. It was at the forefron ...
on October 26, 1868.
King Mongkut's calculation
King Mongkut, also known as Rama IV of
Siam, was able to calculate and predict the solar eclipse two years earlier.
The calculations were correct as to the place, the time and the type of the solar eclipse that would happen. The eclipse took place precisely as the king had predicted, the total phase lasting six minutes and 46 seconds. In fact, his calculations were better — by about two seconds — than those of the French astronomers, who acknowledged his accuracy. Mongkut was exposed to
malaria
Malaria is a Mosquito-borne disease, mosquito-borne infectious disease that affects vertebrates and ''Anopheles'' mosquitoes. Human malaria causes Signs and symptoms, symptoms that typically include fever, Fatigue (medical), fatigue, vomitin ...
, then developed chills and fever. He died on October 1, 1868.
According to the Thai Astronomical Society and NASA, this eclipse is known as "The King of Siam's eclipse".
[๒๐๐ ปี พระบาทสมเด็จพระจอมเกล้าเจ้าอยู่หัว พระบิดาแห่งวิทยาศาสตร์ไทย](_blank)
Eclipse details
Shown below are two tables displaying details about this particular solar eclipse. The first table outlines times at which the moon's penumbra or umbra attains the specific parameter, and the second table describes various other parameters pertaining to this eclipse.
Eclipse season
This eclipse is part of an
eclipse season, a period, roughly every six months, when eclipses occur. Only two (or occasionally three) eclipse seasons occur each year, and each season lasts about 35 days and repeats just short of six months (173 days) later; thus two full eclipse seasons always occur each year. Either two or three eclipses happen each eclipse season. In the sequence below, each eclipse is separated by a
fortnight.
Related eclipses
Eclipses in 1868
*
A penumbral lunar eclipse on February 8.
*
An annular solar eclipse on February 23.
*
A penumbral lunar eclipse on March 8.
*
A penumbral lunar eclipse on August 3.
* A total solar eclipse on August 18.
*
A penumbral lunar eclipse on September 2.
Metonic
* Preceded by:
Solar eclipse of October 30, 1864
* Followed by:
Solar eclipse of June 6, 1872
Tzolkinex
* Preceded by:
Solar eclipse of July 8, 1861
* Followed by:
Solar eclipse of September 29, 1875
Half-Saros
* Preceded by:
Lunar eclipse of August 13, 1859
* Followed by:
Lunar eclipse of August 23, 1877
Tritos
* Preceded by:
Solar eclipse of September 18, 1857
* Followed by:
Solar eclipse of July 19, 1879
Solar Saros 133
* Preceded by:
Solar eclipse of August 7, 1850
* Followed by:
Solar eclipse of August 29, 1886
Inex
* Preceded by:
Solar eclipse of September 7, 1839
* Followed by:
Solar eclipse of July 29, 1897
Triad
* Preceded by:
Solar eclipse of October 17, 1781
* Followed by:
Solar eclipse of June 20, 1955
Solar eclipses of 1866–1870
The partial solar eclipses on April 15, 1866 and October 8, 1866 occur in the previous lunar year eclipse set, and the solar eclipses on June 28, 1870 (partial) and
December 22, 1870 (total) occur in the next lunar year eclipse set.
Saros 133
Metonic series
All eclipses in this table occur at the Moon's ascending node.
Tritos series
Inex series
Notes
References
NASA chart graphics*
Googlemap*
NASA Besselian elements
''Observations of the Total Solar Eclipse of August 18, 1868'' by Charles G. PerrinsDrawing of Corona*
{{Commons category, Solar eclipse of 1868 August 18
1868 08 18
1868 in science
1868 08 18
Helium
August 1868
Astronomy in Thailand