The Great January Comet of 1910, formally designated C/1910 A1 and often referred to as the Daylight Comet,. was a

comet A comet is an icy, small Solar System body that warms and begins to release gases when passing close to the Sun, a process called outgassing. This produces an extended, gravitationally unbound atmosphere or Coma (cometary), coma surrounding ...

which appeared in January 1910. It was already visible to the

naked eye Naked eye, also called bare eye or unaided eye, is the practice of engaging in visual perception unaided by a magnification, magnifying, Optical telescope#Light-gathering power, light-collecting optical instrument, such as a telescope or microsc ...

when it was first noticed, and many people independently "discovered" the comet. At its brightest, it outshone the planet

Venus Venus is the second planet from the Sun. It is often called Earth's "twin" or "sister" planet for having almost the same size and mass, and the closest orbit to Earth's. While both are rocky planets, Venus has an atmosphere much thicker ...

, and was possibly the brightest comet of the 20th century.

Observational history

Discovery

The comet came to

solar conjunction Solar conjunction generally occurs when a planet or other Solar System object is on the opposite side of the Sun from the Earth. From an Earth reference, the Sun will pass between the Earth and the object. Communication with any spacecraft in sol ...

about 1 degree from the Sun on 17 December 1909 but was still about 1 AU from the Sun. In January the comet brightened rather suddenly, and was initially visible from the Southern Hemisphere only. A number of individuals claimed "discovery", but the comet is thought to have been first spotted by diamond miners in the

Transvaal Transvaal is a historical geographic term associated with land north of (''i.e.'', beyond) the Vaal River in South Africa. A number of states and administrative divisions have carried the name ''Transvaal''. * South African Republic (1856–1902; ...

before dawn on January 12, 1910, by which time it was already a prominent naked-eye object of

apparent magnitude Apparent magnitude () is a measure of the Irradiance, brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction (astronomy), ...

−1.0 with a

declination In astronomy, declination (abbreviated dec; symbol ''δ'') is one of the two angles that locate a point on the celestial sphere in the equatorial coordinate system, the other being hour angle. The declination angle is measured north (positive) or ...

of −29 (i.e. best seen from the Southern Hemisphere). The first person to study the comet properly was

Scottish Scottish usually refers to something of, from, or related to Scotland, including: *Scottish Gaelic, a Celtic Goidelic language of the Indo-European language family native to Scotland *Scottish English *Scottish national identity, the Scottish ide ...

astronomer

Robert T. A. Innes Robert Thorburn Ayton Innes FRSE FRAS (10 November 1861 – 13 March 1933) was a British-born South African astronomer best known for discovering Proxima Centauri in 1915, and numerous binary stars. He was also the first astronomer to have see ...

at the Transvaal Observatory in

Johannesburg Johannesburg ( , , ; Zulu language, Zulu and Xhosa language, Xhosa: eGoli ) (colloquially known as Jozi, Joburg, Jo'burg or "The City of Gold") is the most populous city in South Africa. With 5,538,596 people in the City of Johannesburg alon ...

on January 17, after having been alerted two days earlier by the editor of a Johannesburg newspaper. The comet reached

perihelion An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides perta ...

on January 17 and was at that time visible in daylight with the unaided eye, having a magnitude of –5.0 due to the

forward scatter Forward scattering is the deflection of waves by small angles so that they continue to move in close to the same direction as before the scattering. It can occur with all types of waves, for instance light, ultraviolet radiation, X-rays as well as ...

ing of light. It came to solar conjunction a second time on 18 January 1910. Following perihelion, it declined in brightness but became a spectacular sight from the

Northern Hemisphere The Northern Hemisphere is the half of Earth that is north of the equator. For other planets in the Solar System, north is defined by humans as being in the same celestial sphere, celestial hemisphere relative to the invariable plane of the Solar ...

in the evening twilight, its noticeably curved tail reaching up to 50 degrees by early February.

Halley's Comet and the Daylight Comet

The year 1910 saw considerable media interest in the predicted return of

Halley's Comet Halley's Comet is the only known List of periodic comets, short-period comet that is consistently visible to the naked eye from Earth, appearing every 72–80 years, though with the majority of recorded apparitions (25 of 30) occurring after ...

, which reached perihelion on April 20. The appearance of the Daylight Comet several months earlier therefore came as something of a surprise, and made an extremely strong impression on an expectant public; when Halley's Comet returned again in

1986 The year 1986 was designated as the International Year of Peace by the United Nations. Events January * January 1 ** Aruba gains increased autonomy from the Netherlands by separating from the Netherlands Antilles. ** Spain and Portugal en ...

, many older people's accounts of having seen it in 1910 clearly referred to the Daylight Comet instead.. Owing to a "telephonic error", the comet was initially reported as being named Drake's Comet, though once the error was realised the press afterwards referred to it as the Daylight Comet or Sunset Comet, as no single individual was credited with its discovery.

Panic

Newspapers in various cities reported people having been scared by the appearance of the comet. The Morning Post of Camden, New Jersey reported that similar scares happened in past years when comets had been seen. In Korea many thought the comet would kill them all off. Some stopped going to work, just ate and drank and waited for the world to end.

References

Notes

Citations

External links

Donald Yeomans, "Great Comets in History". (Accessed 5/6/08)The Great Daylight Comet of 1910
by John W. Bortle, Sky and Telescope * {{DEFAULTSORT:1910 A1 Non-periodic comets Sungrazing comets Great comets

Great January Comet Of 1910 The Great January Comet of 1910, formally designated C/1910 A1 and often referred to as the Daylight Comet,. was a comet which appeared in January 1910. It was already visible to the naked eye when it was first noticed, and many people independent ...

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