Small Magellanic Cloud

	Email		Print
	Bookmark		Link

Small Magellanic Cloud

The Small Magellanic Cloud (SMC) is a dwarf galaxy

Dwarf galaxy

A dwarf galaxy is a small galaxy composed of up to several billion stars, a small number compared to our own Milky Way's 200-400 billion stars....
. It contains several hundred million stars.

Some speculate that the SMC was once a barred spiral galaxy

Barred spiral galaxy

A barred spiral galaxy is a spiral galaxy with a central bar-shaped structure composed of stars. Bars are found in approximately half of all spiral galaxies....
that was disrupted by the Milky Way to become somewhat irregular

Irregular galaxy

Some galaxies do not have a regular shape, like a spiral galaxy or an elliptical galaxy. Those galaxies are known as irregular galaxies. Their shape is uncommon....
. It still contains a central bar structure.

At a distance of about 200,000 light-year

Light-year

A light-year or light year is a Units of measurement of length, equal to just under ten orders_of_magnitude_%28numbers%29#1012 kilometres....
s, it is one of the Milky Way's nearest neighbors. It is also one of the most distant objects that can be seen with the naked eye.

With a mean declination

Declination

In astronomy, declination is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle....
of approximately -73 degrees, it can only be viewed from the Southern Hemisphere and the lower latitudes of the Northern Hemisphere.

Discussion

Ask a question about 'Small Magellanic Cloud'

Start a new discussion about 'Small Magellanic Cloud'

Answer questions from other users

Full Discussion Forum

Encyclopedia

The Small Magellanic Cloud (SMC) is a dwarf galaxy

Dwarf galaxy

Barred spiral galaxy

Irregular galaxy

Light-year

Declination

Constellation

A constellation is a group of stars that appear to have a physical proximity in the sky. The stars in a constellation are often vastly distant from each other, but they appear close to each other from the perspective of Earth....
of Tucana

Tucana

Tucana...
and appears as a hazy, light patch in the night sky about 3 degrees across. It looks like a detached piece of the Milky Way. Since it has a very low surface brightness

Surface brightness

Surface brightness is a concept used in astronomy when describing extended astronomical objects such as galaxy and nebulae....
, it is best viewed from a dark site away from city lights.

It forms a pair with the Large Magellanic Cloud

Large Magellanic Cloud

The Large Magellanic Cloud is a nearby galaxy, one thought to be a satellite galaxy of our own. At a distance of slightly less than 50 kiloparsecs , the LMC is the third closest galaxy to the Milky Way, with the Sagittarius Dwarf Spheroidal and Canis Major Dwarf Galaxy lying closer to the center of the Milky Way....
(LMC), which lies a further 20 degrees to the east. The Small Magellanic Cloud is a member of the Local Group

Local Group

The Local Group is the galaxy groups and clusters of galaxy that includes our galaxy, the Milky Way. The group comprises over 50 galaxies , with its gravitational center located somewhere between the Milky Way and the Andromeda Galaxy....
.

Observation history

In the southern hemisphere, the Magellanic clouds have long been included in the lore of native inhabitants, including south sea

Pacific Ocean

The Pacific Ocean is the largest of the Earth's oceanic divisions. Its name is derived from the Latin name Mare Pacificum, "peaceful sea", bestowed upon it by the Portugal explorer Ferdinand Magellan....
islanders and indigenous Australians

Indigenous Australians

Indigenous Australians are the first human inhabitants of the Australian continent and its nearby islands and their descendants. Indigenous Australians are distinguished as either Australian Aborigines or Torres Strait Islanders, who currently together make up about 2.6% of Australia's population....
. Persian astronomer Al Sufi

Abd Al-Rahman Al Sufi

Abd al-Rahman al-Sufi was a Persians Islamic astronomy also known as Abd ar-Rahman as-Sufi, or Abd al-Rahman Abu al-Husayn, Abdul Rahman Sufi, Abdurrahman Sufi and known in the west as Azophi; the Azophi and the minor planet 12621 Alsufi are named after him....
labelled the larger of the two clouds as Al Bakr, the White Ox. Europe

Europe

Europe is, conventionally, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally divided from Asia to its east by the water divide of the Ural Mountains, the Ural , the Caspian Sea, and by the Caucasus Mountains to the southeast....
an sailors may have first noticed the clouds during the Middle Ages

Middle Ages

File:Karl 1 mit papst gelasius gregor1 sacramentar v karl d kahlen.jpgThe Middle Ages of European history are a period in history which lasted for roughly a millennium, commonly dated from the fall of the Roman Empire in the 5th century to the beginning of the Early Modern Period in the 16th century, marked by the division of Western Christi...
when they were used for navigation. Portuguese

Portugal

Portugal , officially the Portuguese Republic , is a country on the Iberian Peninsula. Located in southwestern Europe, Portugal is the westernmost country of mainland Europe and is bordered by the Atlantic Ocean to the west and south and by Spain to the north and east....
and Dutch

Holland

Holland is a name in common usage given to two regions in the western part of Netherlands. The name 'Holland' is also often mistakenly used to refer to the whole of The Netherlands....
sailors called them the Cape Clouds, a name that was retained for several centuries. During the circumnavigation of the Earth by Ferdinand Magellan

Ferdinand Magellan

Ferdinand Magellan was a Portuguese people List of maritime explorers who, while in the service of the Spanish Crown, tried to find a westward route to the Spice Islands of Indonesia....
in 1519–22, they were described by Antonio Pigafetta

Antonio Pigafetta

Antonio Pigafetta , was a Republic of Venice scholar born in Vicenza. He was engaged to accompany and assist the Portugal captain Ferdinand Magellan and his Spanish crew on their trip to the Maluku Islands....
as dim clusters of stars. In Johann Bayer

Johann Bayer

Johann Bayer was a Germany lawyer and Star cartographyer . He was born in Rain, Bavaria in 1572. He began his study of philosophy in Ingolstadt in 1592, and moved later to Augsburg to begin work as a lawyer....
's celestial atlas Uranometria

Uranometria

Uranometria is the short title of a Star_atlas produced by Johann Bayer.It was published in Augsburg, Germany, in 1603 by Christophorus Mangus under the full title Uranometria : omnium asterismorum continens schemata, nova methodo delineata, aereis laminis expressa. This translates to "Uranometria, containing charts of all the con...
, published in 1603, he named the smaller cloud, Nubecula Minor. In Latin

Latin

Latin is an Italic language, historically spoken in Latium and Ancient Rome. Through the Military history of the Roman Empire, Latin spread throughout the Mediterranean and a large part of Europe....
, Nubecula means a little cloud.

Between 1834 and 1838, John Frederick William Herschel made observations of the southern skies with his reflector from the Royal Observatory at the Cape of Good Hope

Cape of Good Hope

The Cape of Good Hope is a rocky headlands and bays on the Atlantic Ocean coast of South Africa. There is a very common misconception that the Cape of Good Hope is the southern tip of Africa and the dividing point between the Atlantic Ocean and Indian Oceans, but in fact the southernmost point is Cape Agulhas, about 150 kilometres t...
. While observing the Nubecula Minor, he described it as a cloudy mass of light with an oval shape and a bright center. Within the area of this cloud he catalogued a concentration of 37 nebulae and clusters.

In 1891, Harvard College Observatory

Harvard College Observatory

Arequipa Region

Arequipa is a region in southwestern Peru. It is bordered by the Ica Region, Ayacucho Region, Apur?mac Region and Cusco Region regions on the north; the Puno Region on the east; the Moquegua Region on the south; and the Pacific Ocean on the west....
. From 1893 and 1906, under the direction of Solon Bailey

Solon Irving Bailey

Solon Irving Bailey was an American astronomer.He joined the staff of Harvard College Observatory in 1887.After the observatory received the "Boyden Fund" bequest from the will of Uriah A....
, the telescope at this site was used to survey photographically both the Large and Small Magellanic Clouds. Henrietta Swan Leavitt

Henrietta Swan Leavitt

Henrietta Swan Leavitt was an United States astronomer, and the deaf daughter of a Congregational church minister. A graduate of Radcliffe College, Leavitt went to work in 1893 at the Harvard College Observatory in a menial capacity as a human computer, assigned to count images on photographic plates....
, an astronomer at the Harvard College Observatory

Harvard College Observatory

The Harvard College Observatory is an institution managing a complex of buildings and multiple instruments used for astronomy research by the Harvard University Department of Astronomy....
, used the plates from Arequipa to study the variations in relative luminosity of stars in the SMC. In 1908, the results of her study were published, which showed that a type of variable star

Variable star

A star is classified as variable if its apparent magnitude as seen from Earth changes over time, whether the changes are due to variations in the star's actual luminosity, or to variations in the amount of the star's light that is blocked from reaching Earth....
called a "cluster variable", later called a Cepheid variable

Cepheid variable

A Cepheid variable or Cepheid is a member of a particular class of variable stars, notable for a fairly tight correlation between their period of Radial pulsations and absolute luminosity....
after the prototype star Delta Cephei

Delta Cephei

Delta Cephei is a binary star system approximately 891 light-years away in the constellation of Cepheus . The names Alrediph, Al Radif or variants are derived from the Arabic "??????" , or "the Follower"....
, showed a definite relationship between the variability period and the star's luminosity. This important period-luminosity relation allowed the distance to any other cepheid variable to be estimated in terms of the distance to the SMC. Hence, once the distance to the SMC was known with greater accuracy, Cepheid variables could be used as a standard candle for measuring the distances to other galaxies.

Using this period-luminosity relation, in 1913 the distance to the SMC was first estimated by Ejnar Hertzsprung

Ejnar Hertzsprung

Ejnar Hertzsprung was a Denmark chemistry and astronomy.In the period 1911-1913 with Henry Norris Russell, he developed the Hertzsprung-Russell diagram....
. First he measured thirteen nearby cepheid variables to find the absolute magnitude

Absolute magnitude

In astronomy, absolute magnitude measures a celestial object's intrinsic brightness. To derive the absolute magnitude from the observed apparent magnitude of a celestial object its value is corrected for distance to the observer....
of a variable with a period of one day. By comparing this to the periodicity of the variables as measured by Leavitt, he was able to estimate a distance of 10,000 parsecs (30,000 light years) between the Sun and the SMC. This later proved to be a gross underestimate of the true distance, but it did demonstrate the potential usefulness of this technique.

Small Magellanic Cloud

Observation history

See also

External links