page_title: Open cluster
section_title: Historical observations
hierarchical_section_title: Open cluster / Historical observations
caption_attribution_description: English: A Star Cluster in the Wake of Carina This colourful new image from the MPG/ESO 2.2-metre telescope at ESO's La Silla Observatory in Chile shows the star cluster NGC 3590. These stars shine brightly in front of a dramatic landscape of dark patches of dust and richly hued clouds of glowing gas. This small stellar gathering gives astronomers clues about how these stars form and evolve — as well as giving hints about the structure of our galaxy's pinwheeling arms. NGC 3590 is a small open cluster of stars around 7500 light-years from Earth, in the constellation of Carina (The Keel). It is a gathering of dozens of stars loosely bound together by gravity and is roughly 35 million years old. This cluster is not just pretty; it is very useful to astronomers. By studying this particular cluster — and others nearby — astronomers can explore the properties of the spiral disc of our galaxy, the Milky Way. NGC 3590 is located in the largest single segment of a spiral arm that can be seen from our position in the galaxy: the Carina spiral feature. The Milky Way has multiple spiral arms, long curved streams of gas and stars stretching out from the galactic centre. These arms — two major star-filled arms, and two less populated minor arms — are each named after the constellations in which they are most prominent [1]. The Carina spiral feature is seen from Earth as a patch of sky heavily populated with stars, in the Carina-Sagittarius minor arm. The name of this arm — Carina, or The Keel — is quite appropriate. These spiral arms are actually waves of piled up gas and stars sweeping through the galactic disc, triggering sparkling bursts of star formation and leaving clusters like NGC 3590 in their wake. By finding and observing young stars like those in NGC 3590, it is possible to determine the distances to the different parts of this spiral arm, telling us more about its structure. Typical open clusters can contain anything from a few tens to a few thousands of stars, and provide astronomers with clues about stellar evolution. The stars in a cluster like NGC 3590 are born at around the same time from the same cloud of gas, making these clusters perfect test sites for theories on how stars form and evolve. This image from the Wide Field Imager (WFI) on the MPG/ESO 2.2-metre telescope at La Silla, shows the cluster and the gas clouds surrounding it, which glow in orange and red hues due to the radiation coming from nearby hot stars. WFI's large field of view also captures a colossal number of background stars. To obtain this image, multiple observations were made using different filters to capture the different colours of the scene. This image was created by combining images taken in the visible and infrared parts of the spectrum, and a special filter that collected only light coming from glowing hydrogen. Notes [1] These four arms are named the Carina-Sagittarius, Norma, Scutum-Centaurus, and Perseus arms. About the Object Name:	NGC 3590 Type:	• Milky Way&#160;: Star&#160;: Grouping&#160;: Cluster&#160;: Open • Milky Way&#160;: Nebula&#160;: Appearance&#160;: Emission&#160;: H II Region Colours &amp; filters Band	Telescope Optical B MPG/ESO 2.2-metre telescope WFI Optical H-alpha MPG/ESO 2.2-metre telescope WFI Optical V MPG/ESO 2.2-metre telescope WFI Optical R MPG/ESO 2.2-metre telescope WFI . Deutsch: Ein Sternhaufen im Kielwasser von Carina Diese farbenfrohe neue Aufnahme des MPG/ESO 2,2-Meter-Teleskops am La Silla-Observatorium der ESO in Chile zeigt den Sternhaufen NGC 3590. Diese Sterne leuchten hell vor einem beeindruckenden Hintergrund aus dunklen Flecken von Staub und intensiv gefärbten Wolken aus leuchtendem Gas. Diese kleine Ansammlung von Sternen gibt Astronomen sowohl Hinweise darauf, wie diese Sterne entstanden sind und sich entwickeln, als auch darauf, wie die Struktur der Arme unserer Spiralgalaxie beschaffen ist. NGC 3590 ist ein kleiner offener Sternhaufen, der sich ungefähr 7500 Lichtjahre von der Erde entfernt im Sternbild Carina (der Schiffskiel) befindet. Er besteht aus einer Ansammlung von Dutzenden von Sternen, die durch ihre Eigengravitation schwach gebunden und etwa 35 Millionen Jahre alt ist. Dieser Sternhaufen ist nicht nur schön, er ist auch sehr nützlich für Astronomen. Durch Untersuchungen dieses und anderer nahegelegener Sternhaufen können Astronomen die Eigenschaften der Spiralscheibe unserer Galaxie, der Milchstraße, erforschen. NGC 3590 befindet sich im größten einzelnen Segment eines Spiralarms, der von unserer Position in der Galaxis aus gesehen werden kann: die Spiralstruktur um das Sternbild Carina. Die Milchstraße besitzt mehrere Spiralarme, lange geschwungene Ströme aus Gas und Sternen, die sich vom Zentrum der Galaxis aus erstrecken. Diese Arme, zwei mit Sternen gefüllte Hauptarme und zwei weniger bevölkerte Nebenarme, sind alle nach den Sternbildern benannt, durch die sie hauptsächlich verlaufen [1]. Die Spiralstruktur um das Sternbild Carina wird von der Erde aus als ein Teil des Himmels, der stark mit Sternen bevölkert ist, gesehen. Er liegt im Carina-Sagittarius-Nebenarm. Der Name dieses Armes - Carina, oder auch der Schiffskiel - ist durchaus angemessen. Diese Spiralarme sind eigentlich Wellen von aufgetürmtem Gas und Sternen, die durch die Milchstraßenebene rauschen und dabei schillernde Ausbrüche von Sternentstehung verursachen, die Sternhaufen wie NGC 3590 zurücklassen. Durch das Aufsuchen und Beobachten junger Sterne, wie jene in NGC 3590, ist es möglich die Entfernung der unterschiedlichen Teile des Spiralarms zu bestimmen und so mehr über dessen Struktur zu erfahren. Typische offene Sternhaufen beherbergen jegliche Anzahl zwischen einigen zehn bis mehreren tausenden von Sternen und liefern Astronomen Hinweise auf die Entwicklung von Sternen. Die Sterne in einem Sternhaufen wie NGC 3590 werden ungefähr zur gleichen Zeit aus derselben Gaswolke gebildet, wodurch diese Gebiete zum perfekten Versuchsort für die Überprüfung von Theorien zur Sternentstehung und Entwicklung werden. Diese Aufnahme des Wide Field Imager (WFI) am MPG/ESO 2,2-Meter-Teleskop am La Silla-Observatorium zeigt den Sternhaufen und die Gaswolken, die ihn umgeben. Durch die Strahlung von nahen heißen Sternen leuchten die Wolken orange und rot. Das große Sichtfeld des WFI fängt außerdem eine riesige Anzahl von Hintergrundsternen ein. Für diese Aufnahme wurden mehrere Beobachtungen mit verschiedenen Filtern durchgeführt, um die verschiedenen Farben der Szenerie einzufangen. Das Bild wurde mittels Kombination mehrerer Einzelaufnahmen angefertigt, die im sichtbaren und infraroten Spektralbereich aufgenommen wurden sowie mit einem speziellen Filter, der nur die Strahlung von leuchtendem Wasserstoff sammelt. Endnoten [1] Diese vier Arme tragen die Namen Carina-Sagittarius, Norma, Scutum-Centaurus und Perseus.
context_page_description: An open cluster is a group of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way Galaxy, and many more are thought to exist. They are loosely bound by mutual gravitational attraction and become disrupted by close encounters with other clusters and clouds of gas as they orbit the galactic center. This can result in a migration to the main body of the galaxy and a loss of cluster members through internal close encounters. Open clusters generally survive for a few hundred million years, with the most massive ones surviving for a few billion years. In contrast, the more massive globular clusters of stars exert a stronger gravitational attraction on their members, and can survive for longer. Open clusters have been found only in spiral and irregular galaxies, in which active star formation is occurring.
  Young open clusters may be contained within the molecular cloud from which they formed, illuminating it to create an H II region. Over time, radiation pressure from the cluster will disperse the molecular cloud.
context_section_description: The prominent open cluster the Pleiades has been recognized as a group of stars since antiquity, while the Hyades forms part of Taurus, one of the oldest constellations. Other open clusters were noted by early astronomers as unresolved fuzzy patches of light. In his Almagest, the Roman astronomer Ptolemy mentions the Praesepe cluster, the Double Cluster in Perseus, the Coma Star Cluster, and the Ptolemy Cluster, while the Persian astronomer Al-Sufi wrote of the Omicron Velorum cluster. However, it would require the invention of the telescope to resolve these "nebulae" into their constituent stars. Indeed, in 1603 Johann Bayer gave three of these clusters designations as if they were single stars.
  The first person to use a telescope to observe the night sky and record his observations was the Italian scientist Galileo Galilei in 1609. When he turned the telescope toward some of the nebulous patches recorded by Ptolemy, he found they were not a single star, but groupings of many stars. For Praesepe, he found more than 40 stars. Where previously observers had noted only 6–7 stars in the Pleiades, he found almost 50. In his 1610 treatise Sidereus Nuncius, Galileo Galilei wrote, "the galaxy is nothing else but a mass of innumerable stars planted together in clusters." Influenced by Galileo's work, the Sicilian astronomer Giovanni Hodierna became possibly the first astronomer to use a telescope to find previously undiscovered open clusters. In 1654, he identified the objects now designated Messier 41, Messier 47, NGC 2362 and NGC 2451.
  It was realised as early as 1767 that the stars in a cluster were physically related, when the English naturalist Reverend John Michell calculated that the probability of even just one group of stars like the Pleiades being the result of a chance alignment as seen from Earth was just 1 in 496,000. Between 1774–1781, French astronomer Charles Messier published a catalogue of celestial objects that had a nebulous appearance similar to comets. This catalogue included 26 open clusters. In the 1790s, English astronomer William Herschel began an extensive study of nebulous celestial objects. He discovered that many of these features could be resolved into groupings of individual stars. Herschel conceived the idea that stars were initially scattered across space, but later became clustered together as star systems because of gravitational attraction. He divided the nebulae into eight classes, with classes VI through VIII being used to classify clusters of stars.
  The number of clusters known continued to increase under the efforts of astronomers. Hundreds of open clusters were listed in the New General Catalogue, first published in 1888 by the Danish-Irish astronomer J. L. E. Dreyer, and the two supplemental Index Catalogues, published in 1896 and 1905. Telescopic observations revealed two distinct types of clusters, one of which contained thousands of stars in a regular spherical distribution and was found all across the sky but preferentially towards the centre of the Milky Way. The other type consisted of a generally sparser population of stars in a more irregular shape. These were generally found in or near the galactic plane of the Milky Way. Astronomers dubbed the former globular clusters, and the latter open clusters. Because of their location, open clusters are occasionally referred to as galactic clusters, a term that was introduced in 1925 by the Swiss-American astronomer Robert Julius Trumpler.
  Micrometer measurements of the positions of stars in clusters were made as early as 1877 by the German astronomer E. Schönfeld and further pursued by the American astronomer E. E. Barnard prior to his death in 1923. No indication of stellar motion was detected by these efforts. However, in 1918 the Dutch-American astronomer Adriaan van Maanen was able to measure the proper motion of stars in part of the Pleiades cluster by comparing photographic plates taken at different times. As astrometry became more accurate, cluster stars were found to share a common proper motion through space. By comparing the p
caption: The colorful star cluster NGC 3590.[10]
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