The latest ESO (European Southern Observatory) report:

Cosmic Recycling

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 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.

This video sequence starts with a view of the rich central parts of the Milky Way and then closes in on a spectacular region of star formation known as the Prawn Nebula (also known as Gum 56 and IC 4628) in the constellation of Scorpius (The Scorpion). The final close up view is a very sharp image taken using the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile. Credit: ESO/Nick Risinger (skysurvey.org). Music: Johan B Monell

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 [1]. 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.

Besides the many newborn stars nestled in the nebula, this large region is still filled with enough dust and gas to create an even newer generation of stars. The regions of the nebula giving birth to new stars are visible in the image as dense clouds. The material forming these new stars includes the remains of the most massive stars from an older generation that have already ended their lives and ejected their material in violent supernova explosions. Thus the cycle of stellar life and death continues.

Given the two very unusual blue giants in this area and the prominence of the nebula at infrared and radio wavelengths, it is perhaps surprising that this region has been comparatively little studied as yet by professional astronomers. Gum 56 has a diameter of around 250 light-years, but despite its huge size it has also often been overlooked by visual observers due to its faintness, and because most of the light it emits is at wavelengths not visible to the human eye.

The nebula is at a distance of about 6000 light-years from Earth. In the sky it can be found in the constellation Scorpius (The Scorpion) where it has a projected size which is four times the size of the full Moon [2].

This image, which only captures a part of the nebula, was taken with the 2.2-metre MPG/ESO telescope using the Wide Field Imager (WFI) camera as part of the ESO Cosmic Gems programme. The programme makes use of telescope time that cannot be used for science observations to produce images of interesting, intriguing or visually attractive objects. All data collected may also be suitable for scientific purposes, and are made available to astronomers through ESO’s science archive.

Notes

[1] Note that these stars fall outside the field of view of this particular image and do not appear in the picture.

[2] A wide-angle view of the Prawn Nebula taken by the VLT Survey Telescope was published earlier (eso1340a).

Here’s the NASA JPL preview of the night sky for September:

And TMRO.tv offers a Space Pod about the coming month’s cosmic highlights:

Astronomer of TMRO, Jared Head takes a look at what is in the sky for September, 2015. Don’t forget to look up!

TMRO Space Pods are crowd funded shows. If you like this episode consider contributing to help us to continue to improve. Head over tohttp://www.patreon.com/spacepod for information, goals and reward levels. Don’t forget to check out our weekly live show campaign as well over at http://www.patreon.com/tmro

A release today from the Hubble Space Telescope team:

The wings of the butterfly

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.

The characteristic shape of the wings of the Twin Jet Nebula is most likely caused by the motion of the two central stars around each other. It is believed that a white dwarf orbits its partner star and thus the ejected gas from the dying star is pulled into two lobes rather than expanding as a uniform sphere. However, astronomers are still debating whether all bipolar nebulae are created by binary stars. Meanwhile the nebula’s wings are still growing and, by measuring their expansion, astronomers have calculated that the nebula was created only 1200 years ago.

Within the wings, starting from the star system and extending horizontally outwards like veins are two faint blue patches. Although these may seem subtle in comparison to the nebula’s rainbow colours, these are actually violent twin jets streaming out into space, at speeds in excess of one million kilometres per hour. This is a phenomenon that is another consequence of the binary system at the heart of the nebula. These jets slowly change their orientation, precessing across the lobes as they are pulled by the wayward gravity of the binary system.

The two stars at the heart of the nebula circle one another roughly every 100 years. This rotation not only creates the wings of the butterfly and the two jets, it also allows the white dwarf to strip gas from its larger companion, which then forms a large disc of material around the stars, extending out as far as 15 times the orbit of Pluto! Even though this disc is of incredible size, it is much too small to be seen on the image taken by Hubble.

An earlier image of the Twin Jet Nebula using data gathered by Hubble’s Wide Field Planetary Camera 2 was released in 1997. This newer version incorporates more recent observations from the telescope’s Space Telescope Imaging Spectrograph (STIS).

A version of this image was entered into the Hubble’s Hidden Treasures image processing competition, submitted by contestant Judy Schmidt.

The latest report from ESO (European Southern Observatory):

Sibling Stars

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.

The stars in IC 4651 all formed around the same time out of the same cloud of gas [1]. These sibling stars are only bound together very loosely by their attraction to one another and also by the gas between them. As the stars within the cluster interact with other clusters and clouds of gas in the galaxy around them, and as the gas between the stars is either used up to form new stars or blown away from the cluster, the cluster’s structure begins to change. Eventually, the remaining mass in the cluster becomes small enough that even the stars can escape. Recent observations of IC 4651 showed that the cluster contains a mass of 630 times the mass of the Sun [2] and yet it is thought that it initially contained at least 8300 stars, with a total mass 5300 times that of the Sun.

As this cluster is relatively old, a part of this lost mass will be due to the most massive stars in the cluster having already reached the ends of their lives and exploded as supernovae. However, the majority of the stars that have been lost will not have died, but merely moved on. They will have been stripped from the cluster as it passed by a giant gas cloud or had a close encounter with a neighbouring cluster, or even simply drifted away.

This video starts with a view of the southern Milky Way and takes us on a journey towards the open star cluster IC 4651, in the constellation of Ara (The Altar). The MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile captured the final rich and colourful close-up view. Credit: ESO/Digitized Sky Survey 2/N. Risinger (skysurvey.org)

A fraction of these lost stars may still be gravitationally bound to the cluster and surround it at a great distance. The remaining lost stars will have migrated away from the cluster to join others, or have settled elsewhere in the busy Milky Way. The Sun was probably once part of a cluster like IC 4651, until it and all its siblings were gradually separated and spread across the Milky Way.

This image was taken using the Wide Field Imager. This camera is permanently mounted at the MPG/ESO 2.2-metre telescope at the La Silla Observatory. It consists of several CCD detectors with a total of 67 million pixels and can observe an area as large as the full Moon. The instrument allows observations from visible light to the near infrared, with more than 40 filters available. For this image, only three of these filters were used.

This pan video gives a close-up view of a rich array of colourful stars known as IC 4651. It was captured by the Wide Field Imager (WFI) camera, on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile. Credit: ESO

Notes

[1] Although many of the stars captured here belong to IC 4651, most of the very brightest in the picture actually lie between us and the cluster and most of the faintest ones are more distant.

[2] This quantity is in fact much larger than the numbers quoted by previous studies which surveyed smaller regions, leaving out many of the cluster’s stars that lie further from its core.