Starship Asterisk*

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Open star clusters like the one seen here are not just perfect subjects for pretty pictures. Most stars form within clusters and these clusters can be used by astronomers as laboratories to study how stars evolve and die. The cluster captured here by the Wide Field Imager (WFI) at ESO’s La Silla Observatory is known as IC 4651, and the stars born within it now display a wide variety of characteristics.

The loose speckling of stars in this new ESO image is the open star cluster IC 4651, located within the Milky Way, in the constellation of Ara (The Altar), about 3000 light-years away. The cluster is around 1.7 billion years old — making it middle-aged by open cluster standards. IC 4651 was discovered by Solon Bailey, who pioneered the establishment of observatories in the high dry sites of the Andes, and it was catalogued in 1896 by the Danish–Irish astronomer John Louis Emil Dreyer.

The Milky Way is known to contain over a thousand of these open clusters, with more thought to exist, and many have been studied in great depth. Observations of star clusters like these have furthered our knowledge of the formation and evolution of the Milky Way and the individual stars within it. They also allow astronomers to test their models of how stars evolve. ...

[img3="Credit: ESO/Alexandre Santerne"]http://cdn.eso.org/images/screen/potw1534a.jpg[/img3][hr][/hr]

This image, taken by ESO Photo Ambassador Alexandre Santerne, is more than a little disorientating at first glance! Resembling an optical illusion or an abstract painting, the starry circles arc around the south celestial pole, seen overhead at ESO's La Silla Observatory in Chile.

Each circular streak represents an individual star, imaged over a long period of time to capture the motion of the stars across the sky caused by the Earth’s rotation. La Silla is based in the outskirts of Chile’s Atacama Desert at some 2400 metres above sea level, and offers perfect observing conditions for long-exposure shots like this; the site experiences over 300 clear nights a year!

The site is host to many of ESO’s telescopes and to national projects run by the ESO Member States. Some of these telescopes can be seen towards the bottom of the image. The ESO 3.6-metre telescope stands tall on the left peak, now home to the world's foremost extrasolar planet hunter: the High Accuracy Radial velocity Planet Searcher (HARPS).

Other telescopes at La Silla include the New Technology Telescope, which partly masks the ESO 3.6-metre telescope, Swiss 1.2-metre Leonhard Euler Telescope, ESO 1-metre Schmidt, the silver-domed MPG/ESO 2.2-metre, Danish 1.54-metre, and ESO 1.52-metre telescopes, which are visible here.

Taking all these facilities together, La Silla is one of the most scientifically productive ground-based facilities in the world after ESO’s Very Large Telescope (VLT) observatory. With almost 300 refereed publications attributable to the work of the observatory per year, La Silla remains at the forefront of astronomy (ann15014).

[img3="Credit: ESA/Hubble & NASA; Acknowledgement: Judy Schmidt "]http://cdn.spacetelescope.org/archives/ ... w1534a.jpg[/img3]

Shown here in a new image taken with the Advanced Camera for Surveys (ACS) on board the NASA/ESA Hubble Space Telescope, is the globular cluster NGC 1783. This is one of the biggest globular clusters in the Large Magellanic Cloud, a satellite galaxy of our own galaxy, the Milky Way, in the southern hemisphere constellation of Dorado.

First observed by John Herschel in 1835, NGC 1783 is nearly 160 000 light-years from Earth, and has a mass around 170 000 times that of the Sun.

Globular clusters are dense collections of stars held together by their own gravity, which orbit around galaxies like satellites. The image clearly shows the symmetrical shape of NGC 1783 and the concentration of stars towards the centre, both typical features of globular clusters.

By measuring the colour and brightness of individual stars, astronomers can deduce an overall age for a cluster and a picture of its star formation history. NGC 1783 is thought to be under one and a half billion years old — which is very young for globular clusters, which are typically several billion years old. During that time, it is thought to have undergone at least two periods of star formation, separated by 50 to 100 million years.

This ebb and flow of star-forming activity is an indicator of how much gas is available for star formation at any one time. When the most massive stars created in the first burst of formation explode as supernovae they blow away the gas needed to form further stars, but the gas reservoir can later be replenished by less massive stars which last longer and shed their gas less violently. After this gas flows to the dense central regions of the star cluster, a second phase of star formation can take place and once again the short-lived massive stars blow away any leftover gas. This cycle can continue a few times, at which time the remaining gas reservoir is thought to be too small to form any new stars. ...

New Hubble Image of the Twin Jet Nebula

[img3="Image Credit: ESA/Hubble & NASA; Acknowledgement: Judy Schmidt"]http://cdn.spacetelescope.org/archives/ ... c1518a.jpg[/img3][hr][/hr]

The shimmering colours visible in this NASA/ESA Hubble Space Telescope image show off the remarkable complexity of the Twin Jet Nebula. The new image highlights the nebula’s shells and its knots of expanding gas in striking detail. Two iridescent lobes of material stretch outwards from a central star system. Within these lobes two huge jets of gas are streaming from the star system at speeds in excess of one million kilometres per hour.

The cosmic butterfly pictured in this NASA/ESA Hubble Space Telescope image goes by many names. It is called the Twin Jet Nebula as well as answering to the slightly less poetic name of PN M2-9.

The M in this name refers to Rudolph Minkowski, a German-American astronomer who discovered the nebula in 1947. The PN, meanwhile, refers to the fact that M2-9 is a planetary nebula. The glowing and expanding shells of gas clearly visible in this image represent the final stages of life for an old star of low to intermediate mass. The star has not only ejected its outer layers, but the exposed remnant core is now illuminating these layers — resulting in a spectacular light show like the one seen here. However, the Twin Jet Nebula is not just any planetary nebula, it is a bipolar nebula.

Ordinary planetary nebulae have one star at their centre, bipolar nebulae have two, in a binary star system. Astronomers have found that the two stars in this pair each have around the same mass as the Sun, ranging from 0.6 to 1.0 solar masses for the smaller star, and from 1.0 to 1.4 solar masses for its larger companion. The larger star is approaching the end of its days and has already ejected its outer layers of gas into space, whereas its partner is further evolved, and is a small white dwarf. ...

bystander wrote:The Wings of the Butterfly (PN M2-9)
ESA Hubble Photo Release | 2015 Aug 26

New Hubble Image of the Twin Jet Nebula

[img3="Image Credit: ESA/Hubble & NASA; Acknowledgement: Judy Schmidt"]http://cdn.spacetelescope.org/archives/ ... c1518a.jpg[/img3][hr][/hr]

The shimmering colours visible in this NASA/ESA Hubble Space Telescope image show off the remarkable complexity of the Twin Jet Nebula. The new image highlights the nebula’s shells and its knots of expanding gas in striking detail. Two iridescent lobes of material stretch outwards from a central star system. Within these lobes two huge jets of gas are streaming from the star system at speeds in excess of one million kilometres per hour.

The cosmic butterfly pictured in this NASA/ESA Hubble Space Telescope image goes by many names. It is called the Twin Jet Nebula as well as answering to the slightly less poetic name of PN M2-9.

The M in this name refers to Rudolph Minkowski, a German-American astronomer who discovered the nebula in 1947. The PN, meanwhile, refers to the fact that M2-9 is a planetary nebula. The glowing and expanding shells of gas clearly visible in this image represent the final stages of life for an old star of low to intermediate mass. The star has not only ejected its outer layers, but the exposed remnant core is now illuminating these layers — resulting in a spectacular light show like the one seen here. However, the Twin Jet Nebula is not just any planetary nebula, it is a bipolar nebula.

Ordinary planetary nebulae have one star at their centre, bipolar nebulae have two, in a binary star system. Astronomers have found that the two stars in this pair each have around the same mass as the Sun, ranging from 0.6 to 1.0 solar masses for the smaller star, and from 1.0 to 1.4 solar masses for its larger companion. The larger star is approaching the end of its days and has already ejected its outer layers of gas into space, whereas its partner is further evolved, and is a small white dwarf. ...

[img3="Credit: ESA/Hubble & NASA and the LEGUS Team
Acknowledgement: Robert Gendler"]http://cdn.spacetelescope.org/archives/ ... w1535a.jpg[/img3][hr][/hr]

This new NASA/ESA Hubble Space Telescope shows Messier 96, a spiral galaxy just over 35 million light-years away in the constellation of Leo (The Lion). It is of about the same mass and size as the Milky Way. It was first discovered by astronomer Pierre Méchain in 1781, and added to Charles Messier’s famous catalogue of astronomical objects just four days later.

The galaxy resembles a giant maelstrom of glowing gas, rippled with dark dust that swirls inwards towards the nucleus. Messier 96 is a very asymmetric galaxy; its dust and gas is unevenly spread throughout its weak spiral arms, and its core is not exactly at the galactic centre. Its arms are also asymmetrical, thought to have been influenced by the gravitational pull of other galaxies within the same group as Messier 96.

This group, named the M96 Group, also includes the bright galaxies Messier 105 and Messier 95, as well as a number of smaller and fainter galaxies. It is the nearest group containing both bright spirals and a bright elliptical galaxy (Messier 105).

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Dominating this image is part of the gigantic nebula Gum 56, illuminated by the hot bright young stars that were born within it. For millions of years stars have been created out of the gas in this nebula, material which is later returned to the stellar nursery when the aging stars either expel their material gently into space or eject it more dramatically as supernova explosions. This image was taken with the MPG/ESO 2.2-metre telescope (using the Wide Field Imager) at the La Silla Observatory in Chile as part of ESO’s Cosmic Gems programme.

Deeply immersed in this huge stellar nursery are three clusters of hot young stars — only a few million years old — which glow brightly in ultraviolet light. It is the light from these stars that causes the nebula’s gas clouds to glow. The radiation strips electrons from atoms — a process known as ionisation — and when they recombine they release energy in the form of light. Each chemical element emits light in characteristic colours and the large clouds of hydrogen in the nebula are the cause of its rich red glow.

Gum 56 — also known as IC 4628 or by its nickname, the Prawn Nebula — is named after the Australian astronomer Colin Stanley Gum, who, in 1955, published a catalogue of H II regions. H II regions such as Gum 56 are huge, low density clouds containing a large amount of ionised hydrogen.

A large portion of the ionisation in Gum 56 is done by two O-type stars, which are hot blue–white stars, also known as blue giants because of their colour. This type of star is rare in the Universe as the very large mass of blue giants means that they do not live for long. After only roughly a million years these stars will collapse in on themselves and end their lives as supernovae, as will many of the other massive stars within the nebula. ...

bystander wrote:Cosmic Recycling
ESO Photo Release | 2015 Sep 02

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Dominating this image is part of the gigantic nebula Gum 56, illuminated by the hot bright young stars that were born within it. For millions of years stars have been created out of the gas in this nebula, material which is later returned to the stellar nursery when the aging stars either expel their material gently into space or eject it more dramatically as supernova explosions. This image was taken with the MPG/ESO 2.2-metre telescope (using the Wide Field Imager) at the La Silla Observatory in Chile as part of ESO’s Cosmic Gems programme.

Deeply immersed in this huge stellar nursery are three clusters of hot young stars — only a few million years old — which glow brightly in ultraviolet light. It is the light from these stars that causes the nebula’s gas clouds to glow. The radiation strips electrons from atoms — a process known as ionisation — and when they recombine they release energy in the form of light. Each chemical element emits light in characteristic colours and the large clouds of hydrogen in the nebula are the cause of its rich red glow.

Gum 56 — also known as IC 4628 or by its nickname, the Prawn Nebula — is named after the Australian astronomer Colin Stanley Gum, who, in 1955, published a catalogue of H II regions. H II regions such as Gum 56 are huge, low density clouds containing a large amount of ionised hydrogen.

A large portion of the ionisation in Gum 56 is done by two O-type stars, which are hot blue–white stars, also known as blue giants because of their colour. This type of star is rare in the Universe as the very large mass of blue giants means that they do not live for long. After only roughly a million years these stars will collapse in on themselves and end their lives as supernovae, as will many of the other massive stars within the nebula. ...