ESO WFI: Beautiful image of the open Wild Duck Cluster, Messier 11

The Wide Field Imager (WFI) on the MPG/ESO 2.2-meter telescope at the La Silla Observatory in Chile has taken this beautiful image of the open Wild Duck Cluster, Messier 11, or NGC 6705. 

The blue stars in the centre of the image are the young, hot stars of the cluster. 

The surrounding redder stars are older, cooler background stars. 

Credit: ESO

The Wide Field Imager on the MPG/ESO 2.2-meter telescope at ESO's La Silla Observatory in Chile has taken this beautiful image, dappled with blue stars, of one of the most star-rich open clusters currently known, Messier 11, also known as NGC 6705 or the Wild Duck Cluster.

Messier 11 is an open cluster, sometimes referred to as a galactic cluster, located around 6000 light-years away in the constellation of Scutum (The Shield).

It was first discovered by German astronomer Gottfried Kirch in 1681 at the Berlin Observatory, appearing as nothing more than a fuzzy blob through the telescope.

It wasn't until 1733 that the blob was first resolved into separate stars by the Reverend William Derham in England, and Charles Messier added it to his famous catalogue in 1764.

Messier was a comet hunter and the catalogue came into being as he was frustrated by constantly observing fixed, diffuse objects that looked like comets (for example, objects that we now know to be clusters, galaxies and nebulae).

He wanted a record in order to avoid accidentally observing them again and confusing them with possible new comets.

This particular stellar cluster was noted down as the eleventh such object, hence the name of Messier 11.

Open clusters are typically found lying in the arms of spiral galaxies or in the denser regions of irregular galaxies, where star formation is still common.

Messier 11 is one of the most star-rich and compact of the open clusters, being almost 20 light-years across and home to close to 3000 stars.

Open clusters are different to globular clusters, which tend to be very dense, tightly bound by gravity, and contain hundreds of thousands of very old stars, some of which are nearly as old as the Universe itself.

Studying open clusters is great way to test theories of stellar evolution, as the stars form from the same initial cloud of gas and dust and are therefore very similar to one another, they all have roughly the same age, chemical composition, and are all the same distance away from Earth.

However, each star in the cluster has a different mass, with the more massive stars evolving much faster than their lower mass counterparts as they use up all of their hydrogen much sooner.


This video takes you on a journey to the open cluster Messier 11 as seen with the Wide Field Imager (WFI) on the MPG/ESO 2.2-metre telescope at the La Silla Observatory. 

Credit: ESO/N. Risinger (skysurvey.org)/J. Bohanon

In this way, direct comparisons between the different evolutionary stages can be made within the same cluster: for example, does a 10 million year old star with the same mass as the Sun evolve in a different way to another star that is the same age, but half as massive?

In this sense, open clusters are the closest thing astronomers have to "laboratory conditions".

Because the stars within open clusters are very loosely bound to one another, individuals are very susceptible to being ejected from the main group due to the effect of gravity from neighbouring celestial objects.

NGC 6705 is already at least 250 million years old, so in a few more million years it is likely that this Wild Duck formation will disperse, and the cluster will break up and merge into its surroundings.

This image was taken by the Wide Field Imager on the MPG/ESO 2.2-metre telescope at ESO's La Silla Observatory in northern Chile.

More information: 
Research papers on NGC 6705: adsabs.harvard.edu/cgi-bin/bas… h=NGC+6705&version=1

ESO Wide Field Imager: A study in scarlet

This new image from the Wide Field Imager on the MPG /ESO 2.2-metre telescope at the La Silla Observatory in Chile reveals a cloud of hydrogen and newborn stars called Gum 41.

In the middle of this little-known nebula, brilliant hot young stars emit energetic radiation that causes the surrounding hydrogen to glow with a characteristic red hue. 

Credit: ESO

This new image from ESO's La Silla Observatory in Chile reveals a cloud of hydrogen called Gum 41.

In the middle of this little-known nebula, brilliant hot young stars are giving off energetic radiation that causes the surrounding hydrogen to glow with a characteristic red hue.

This area of the southern sky, in the constellation of Centaurus (The Centaur), is home to many bright nebulae, each associated with hot newborn stars that formed out of the clouds of hydrogen gas.

The intense radiation from the stellar newborns excites the remaining hydrogen around them, making the gas glow in the distinctive shade of red typical of star-forming regions.

Another famous example of this phenomenon is the Lagoon Nebula, a vast cloud that glows in similar bright shades of scarlet.

Mount Stromlo Observatory

The nebula in this picture is located some 7300 light-years from Earth. Australian astronomer Colin Gum discovered it on photographs taken at the Mount Stromlo Observatory near Canberra, and included it in his catalogue of 84 emission nebulae, published in 1955.

Gum 41 is actually one small part of a bigger structure called the Lambda Centauri Nebula, also known by the more exotic name of the Running Chicken Nebula. Gum died at a tragically early age in a skiing accident in Switzerland in 1960.

In this picture of Gum 41, the clouds appear to be quite thick and bright, but this is actually misleading.

If a hypothetical human space traveller could pass through this nebula, it is likely that they would not notice it as, even at close quarters, it would be toofaint for the human eye to see.

Lambda Centauri Nebula

This helps to explain why this large object had to wait until the mid-twentieth century to be discovered, its light is spread very thinly and the red glow cannot be well seen visually.

This new portrait of Gum 41, likely one of the best so far of this elusive object, has been created using data from the Wide Field Imager (WFI) on the MPG/ESO 2.2-metre telescope at the La Silla Observatory in Chile.

It is a combination of images taken through blue, green, and red filters, along with an image using a special filter designed to pick out the red glow from hydrogen.

Asteroid Chariklo found to have two rings

Observations at many sites in South America, including ESO's La Silla Observatory, have made the surprise discovery that the remote asteroid Chariklo is surrounded by two dense and narrow rings. 

This is the smallest object by far found to have rings and only the fifth body in the Solar System, after the much larger planets Jupiter, Saturn, Uranus and Neptune, to have this feature. 

The origin of these rings remains a mystery, but they may be the result of a collision that created a disc of debris. 

This artist's impression shows how the rings might look from close to the surface of Chariklo. 

Credit: ESO /L. Calçada /Nick Risinger (skysurvey.org)


Observations at many sites in South America have made the discovery that the asteroid Chariklo is surrounded by two dense and narrow rings.

This is the smallest object by far found to have rings and only the fifth body in the Solar System to have this feature.

The origin of these rings remains a mystery, but they may be the result of a collision that created a disc of debris.

The rings of Saturn are one of the most spectacular sights in the sky, and less prominent rings have also been found around the other giant planets.

Despite many careful searches, no rings had been found around smaller objects orbiting the Sun in the Solar System.

Now observations of the distant minor planet (10199) Chariklo as it passed in front of a star have shown that this object too is surrounded by two fine rings.

"We weren't looking for a ring and didn't think small bodies like Chariklo had them at all, so the discovery, and the amazing amountof detail we saw in the system, came as a complete surprise!" says Felipe Braga-Ribas (Observatório Nacional/MCTI, Rio de Janeiro, Brazil) who planned the observation campaign and is lead author on the new paper.

Chariklo is the largest member of a class known as the Centaurs and it orbits between Saturn and Uranus in the outer Solar System.

Predictions had shown that it would pass in front of the star UCAC4 248-108672 on 3 June 2013, as seen from South America.

Astronomers using telescopes at seven different locations, including the 1.54-metre Danish and TRAPPIST telescopes at ESO's La Silla Observatory in Chile, were able to watch the star apparently vanish for a few seconds as its light was blocked by Chariklo—an occultation.

Chariklo is a comet-like miniature planet located between Saturn and Uranus. 

It has a diameter of 250 km and new observations show that there are two rings of ice particles and pebbles. 

This is the first time such a small celestial body with rings has been observed. 

Credit: Lucie Maquet

But they found much more than they were expecting. A few seconds before, and again a few seconds after the main occultation there were two further very short dips in the star's apparent brightness.

Something around Chariklo was blocking the light! By comparing what was seen from different sites the team could reconstruct not only the shape and size of the object itself but also the shape, width, orientation and other properties of the newly discovered rings.

The team found that the ring system consists of two sharply confined rings only seven and three kilometres wide, separated by a clear gap of nine kilometres—around a small 250-kilometre diameter object orbiting beyond Saturn.

"For me, it was quite amazing to realise that we were able not only to detect a ring system, but also pinpoint that it consists of two clearly distinct rings," adds Uffe Gråe Jørgensen (Niels Bohr Institute, University of Copenhagen, Denmark), one of the team.

"I try to imagine how it would be to stand on the surface of this icy object, small enough that a fast sports car could reach escape velocity and drive off into space, and stare up at a 20-kilometre wide ring system 1000 times closer than the Moon."

The special camera is Irish, and the software programs were specially developed over five years at the Niels Bohr Institute by three astronomers and two Ph.D. students. 

It takes 40 images per second and the resolution is just as fantastic as if it was out in space. 

It is now sitting on the Danish telescope at the La Silla Observatory in Chile. 

The main purpose of the camera is to observe exoplanets, which are planets orbiting a star other than the Sun, but the sensitive camera has also shown its strength for making extremely precise observations of other objects. 

Credit: Jesper Skottfelt, Niels Bohr Institute

Although many questions remain unanswered, astronomers think that this sort of ring is likely to be formed from debris left over after a collision. It must be confined into the two narrow rings by the presence of small putative satellites.

"So, as well as the rings, it's likely that Chariklo has at least one small moon still waiting to be discovered," adds Felipe Braga Ribas.

The rings may prove to be a phenomenon that might in turn later lead to the formation of a small moon. Such a sequence of events, on a much larger scale, may explain the birth of our own Moon in the early days of the Solar System, as well as the origin of many other satellites around planets and asteroids.

The leaders of this project are provisionally calling the rings by the nicknames Oiapoque and Chuí, two rivers near the northern and southern extremes of Brazil.

More information: Paper: dx.doi.org/10.1038/nature13155