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Brocchi's Cluster
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Brocchi's Cluster
Brocchi's Cluster (also known as Collinder 399, Cr 399 or Al Sufi's Cluster) is an asterism of 10 stars. Six of the stars appear in a row, across 1.3° of the night sky. The cluster is in the south of the constellation Vulpecula, near the border with Sagitta. Its nickname is the Coathanger. None of these ten stars are believed to be gravitationally bound to each other, thus they are not a star cluster, a fact established by measurements taken by the Hipparcos satellite in 1997. An additional 30 or so much fainter stars are considered by some to be part of the asterism.
It was first described by the Persian astronomer Al Sufi in his Book of Fixed Stars in 964.
In the 17th century, it was independently rediscovered by the Italian astronomer G. B. Hodierna.
In the 1920s, Dalmero Francis Brocchi, an amateur astronomer and chart maker for the American Association of Variable Star Observers (AAVSO), created a map of the stars for use in calibrating photometers.
In 1931, Swedish astronomer Per Collinder listed it in his catalogue of open clusters.
The status of this group as a star cluster has changed in recent years. The group was considered to be a cluster for most of the 20th century. Looking at better, albeit imprecise metrics, a study in 1970 said that six of the brightest stars formed a cluster; the fainter four did not. Several independent studies since 1998 have determined that the stars are not a true cluster at all, but rather relatively near Milky Way stars with a close angular alignment. These recent studies are based on improved measurements of parallax and proper motion of the stars, taken by the Hipparcos satellite. Hipparcos detected up minute changes in parallax against other stars. This data was first published in 1997 and has been enhanced by subsequent orbits and cross-referencing with other readings.
The asterism is made up of 10 stars ranging from 5th to 7th magnitude which form the conspicuous "coathanger", a straight line of 6 stars with a "hook" of 4 stars on the south side. An additional 30 or so much fainter stars to terrestrial observers are sometimes considered to be associated.
Under a dark sky, the coathanger can be seen with the naked eye as an unresolved patch of light; binoculars, zoom cameras, or a telescope at very low power are usually needed to view this asterism. It can be found by slowly sweeping across the Milky Way along an imaginary line from the bright star Altair toward the even brighter star Vega. About one third of the way, the coathanger should be spotted easily against a darker region of the Milky Way. The asterism is best seen in July–August and north of +20° latitude. As compared to the closest horizon it will be upside-down (as in the picture top right of this page) when at its highest point. South of this latitude it is upright as the 'hanger' is south of the line of 6 stars.
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Brocchi's Cluster
Brocchi's Cluster (also known as Collinder 399, Cr 399 or Al Sufi's Cluster) is an asterism of 10 stars. Six of the stars appear in a row, across 1.3° of the night sky. The cluster is in the south of the constellation Vulpecula, near the border with Sagitta. Its nickname is the Coathanger. None of these ten stars are believed to be gravitationally bound to each other, thus they are not a star cluster, a fact established by measurements taken by the Hipparcos satellite in 1997. An additional 30 or so much fainter stars are considered by some to be part of the asterism.
It was first described by the Persian astronomer Al Sufi in his Book of Fixed Stars in 964.
In the 17th century, it was independently rediscovered by the Italian astronomer G. B. Hodierna.
In the 1920s, Dalmero Francis Brocchi, an amateur astronomer and chart maker for the American Association of Variable Star Observers (AAVSO), created a map of the stars for use in calibrating photometers.
In 1931, Swedish astronomer Per Collinder listed it in his catalogue of open clusters.
The status of this group as a star cluster has changed in recent years. The group was considered to be a cluster for most of the 20th century. Looking at better, albeit imprecise metrics, a study in 1970 said that six of the brightest stars formed a cluster; the fainter four did not. Several independent studies since 1998 have determined that the stars are not a true cluster at all, but rather relatively near Milky Way stars with a close angular alignment. These recent studies are based on improved measurements of parallax and proper motion of the stars, taken by the Hipparcos satellite. Hipparcos detected up minute changes in parallax against other stars. This data was first published in 1997 and has been enhanced by subsequent orbits and cross-referencing with other readings.
The asterism is made up of 10 stars ranging from 5th to 7th magnitude which form the conspicuous "coathanger", a straight line of 6 stars with a "hook" of 4 stars on the south side. An additional 30 or so much fainter stars to terrestrial observers are sometimes considered to be associated.
Under a dark sky, the coathanger can be seen with the naked eye as an unresolved patch of light; binoculars, zoom cameras, or a telescope at very low power are usually needed to view this asterism. It can be found by slowly sweeping across the Milky Way along an imaginary line from the bright star Altair toward the even brighter star Vega. About one third of the way, the coathanger should be spotted easily against a darker region of the Milky Way. The asterism is best seen in July–August and north of +20° latitude. As compared to the closest horizon it will be upside-down (as in the picture top right of this page) when at its highest point. South of this latitude it is upright as the 'hanger' is south of the line of 6 stars.
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