Antique Stars Could Help Solve Mysteries Of Early Milky Way

The Milky Way is like NGC 4594 (pictured), a disc shaped spiral galaxy with around 200 billion stars. The three main features are the central bulge, the disk, and the halo. Credit: ESO
The Milky Way is like NGC 4594 (pictured), a disc shaped spiral galaxy with around 200 billion stars. The three main features are the central bulge, the disk, and the halo. Credit: ESO

[/caption]

Utilizing ESO’s giant telescopes located in Chile, researchers at the Niels Bohr Institute have been examining “antique” stars. Located at the outer reaches of the Milky Way, these superannuated stellar specimens are unusual in the fact that they contain an over-abundance of gold, platinum and uranium. How they became heavy metal stars has always been a puzzle, but now astronomers are tracing their origins back to our galaxy’s beginning.

It is theorized that soon after the Big Bang event, the Universe was filled with hydrogen, helium and… dark matter. When the trio began compressing upon themselves, the very first stars were born. At the core of these neophyte suns, heavy elements such as carbon, nitrogen and oxygen were then created. A few hundred million years later? Hey! All of the elements are now accounted for. It’s a tidy solution, but there’s just one problem. It would appear the very first stars only had about 1/1000th of the heavy-elements found in sun-like stars of the present.

How does it happen? Each time a massive star reaches the end of its lifetime, it will either create a planetary nebula – where layers of elements gradually peel away from the core – or it will go supernova – and blast the freshly created elements out in a violent explosion. In this scenario, the clouds of material once again coalesce… collapse again and form more new stars. It’s just this pattern which gives birth to stars that become more and more “elementally” concentrated. It’s an accepted conjecture – and that’s what makes discovering heavy metal stars in the early Universe a surprise. And even more surprising…

Right here in the Milky Way.

“In the outer parts of the Milky Way there are old ‘stellar fossils’ from our own galaxy’s childhood. These old stars lie in a halo above and below the galaxy’s flat disc. In a small percentage – approximately one to two percent of these primitive stars, you find abnormal quantities of the heaviest elements relative to iron and other ‘normal’ heavy elements”, explains Terese Hansen, who is an astrophysicist in the research group Astrophysics and Planetary Science at the Niels Bohr Institute at the University of Copenhagen.

The 17 observed stars are all located in the northern sky and could therefore be observed with the Nordic Optical Telescope, NOT on La Palma. NOT is 2.5 meter telescope that is well suited for just this kind of observations, where continuous precise observations of stellar motions over several years can reveal what stars belong to binary star systems.
But the study of these antique stars just didn’t happen overnight. By employing ESO’s large telescopes based in Chile, the team took several years to come to their conclusions. It was based on the findings of 17 “abnormal” stars which appeared to have elemental concentrations – and then another four years of study using the Nordic Optical Telescope on La Palma. Terese Hansen used her master’s thesis to analyse the observations.

“After slaving away on these very difficult observations for a few years I suddenly realised that three of the stars had clear orbital motions that we could define, while the rest didn’t budge out of place and this was an important clue to explaining what kind of mechanism must have created the elements in the stars”, explains Terese Hansen, who calculated the velocities along with researchers from the Niels Bohr Institute and Michigan State University, USA.

What exactly accounts for these types of concentrations? Hansen explains their are two popular theories. The first places the origin as a close binary star system where one goes supernova, inundating its companion with layers of heavier elements. The second is a massive star also goes supernova, but spews the elements out in dispersing streams, impregnating gas clouds which then formed into the halo stars.

The research group has analysed 17 stellar fossils from the Milky Way’s childhood. The stars are small light stars and they live longer than large massive stars. They do not burn hydrogen longer, but swell up into red giants that will later cool and become white dwarves. The image shows the most famous of the stars CS31082-001, which was the first star that uranium was found in.
“My observations of the motions of the stars showed that the great majority of the 17 heavy-element rich stars are in fact single. Only three (20 percent) belong to binary star systems – this is completely normal, 20 percent of all stars belong to binary star systems. So the theory of the gold-plated neighbouring star cannot be the general explanation. The reason why some of the old stars became abnormally rich in heavy elements must therefore be that exploding supernovae sent jets out into space. In the supernova explosion the heavy elements like gold, platinum and uranium are formed and when the jets hit the surrounding gas clouds, they will be enriched with the elements and form stars that are incredibly rich in heavy elements”, says Terese Hansen, who immediately after her groundbreaking results was offered a PhD grant by one of the leading European research groups in astrophysics at the University of Heidelberg.

May all heavy metal stars go gold!

Original Story Source: Niels Bohr Institute News Release. For Further Reading: The Binary Frequency of r-Process-element-enhanced Metal-poor Stars and Its Implications: Chemical Tagging in the Primitive Halo of the Milky Way.

Asteroid Lutetia… A Piece Of Earth?

This image of the unusual asteroid Lutetia was taken by ESA’s Rosetta probe during its closest approach in July 2010. Lutetia, which is about 100 kilometres across, seems to be a leftover fragment of the same original material that formed the Earth, Venus and Mercury. It is now part of the main asteroid belt, between the orbits of Mars and Jupiter, but its composition suggests that it was originally much closer to the Sun. Credit: ESA 2010 MPS for OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA

[/caption]

According to data received from ESA’s Rosetta spacecraft, ESO’s New Technology Telescope, and NASA telescopes, strange asteroid Lutetia could be a real piece of the rock… the original material that formed the Earth, Venus and Mercury! By examining precious meteors which may have formed at the time of the inner Solar System, scientists have found matching properties which indicate a relationship. Independent Lutetia must have just moved its way out to join in the main asteroid belt…

A team of astronomers from French and North American universities have been hard at work studying asteroid Lutetia spectroscopically. Data sets from the OSIRIS camera on ESA’s Rosetta spacecraft, ESO’s New Technology Telescope (NTT) at the La Silla Observatory in Chile, and NASA’s Infrared Telescope Facility in Hawaii and Spitzer Space Telescope have been combined to give us a multi-wavelength look at this very different space rock. What they found was a very specific type of meteorite called an enstatite chondrite displayed similar content which matched Lutetia… and what is theorized as the material which dates back to the early Solar System. Chances are very good that enstatite chondrites are the same “stuff” which formed the rocky planets – Earth, Mars and Venus.

“But how did Lutetia escape from the inner Solar System and reach the main asteroid belt?” asks Pierre Vernazza (ESO), the lead author of the paper.

It’s a very good question considering that an estimated less than 2% of the material which formed in the same region of Earth migrated to the main asteroid belt. Within a few million years of formation, this type of “debris” had either been incorporated into the gelling planets or else larger pieces had escaped to a safer, more distant orbit from the Sun. At about 100 kilometers across, Lutetia may have been gravitationally influenced by a close pass to the rocky planets and then further affected by a young Jupiter.

“We think that such an ejection must have happened to Lutetia. It ended up as an interloper in the main asteroid belt and it has been preserved there for four billion years,” continues Pierre Vernazza.

Asteroid Lutetia is a “real looker” and has long been a source of speculation due to its unusual color and surface properties. Only 1% of the asteroids located in the main belt share its rare characteristics.

“Lutetia seems to be the largest, and one of the very few, remnants of such material in the main asteroid belt. For this reason, asteroids like Lutetia represent ideal targets for future sample return missions. We could then study in detail the origin of the rocky planets, including our Earth,” concludes Pierre Vernazza.

Original Story Source: ESO News Release.

Are Pluto and Eris Twins?

Artist's rendering of the distant dwarf planet Eris. New suggests that Eris is almost exactly the same diameter as Pluto. Eris is very reflective - possibly due to the frozen remains of its atmosphere. Image Credit: ESO/L. Calçada

[/caption]

Back a couple of weeks ago, I wrote an article highlighting the debate between scientists on which dwarf planet is bigger, Pluto or Eris. During a planetary science conference earlier this month in France, word “leaked” out that Eris was still more massive, but likely smaller in diameter.

Today, the latest findings were published in Nature, and as such are now “official”. There’s also some additional information, so I’d like to revisit this topic and include some new details which may help answer the question:

Could Eris and Pluto actually be twins?

Before we answer the pressing question, let’s revisit my prior post at: http://www.universetoday.com/89901/pluto-or-eris-which-is-bigger/.

Bruno Sicardy of the Paris Observatory and his team calculated the diameter of Eris in 2010. The technique they used took advantage of an occultation between Eris and a faint background star. Sicardy’s results provided a diameter of 2,326 kilometers for Eris, slightly less than his 2009 estimate of Pluto’s diameter at 2,338 kilometers.

Combining the diameter estimate with mass estimates yielded a density estimate for Eris which suggests, and is supported by its extra mass, that its composition is far more rocky than Pluto, with Eris being only 10-15% ice by mass.

In this week’s announcement by the European Southern Observatory, additional information was presented which sheds new light on cold, distant Eris.

Regarding the new density estimates, Emmanuel Jehin, one of Sicardy’s team members mentions, “This density means that Eris is probably a large rocky body covered in a relatively thin mantle of ice”.

Further supporting Jehin’s assertion, The surface of Eris was found to be extremely reflective, (96% of the light that falls on Eris is reflected, making it nearly as reflective as a backyard telescope mirror). Based on the current estimate, Eris is more reflective than freshly fallen snow on Earth. Based on spectral analysis of Eris, its surface reflectivity is most likely due to a surface of nitrogen-rich ice and frozen methane. Some estimates place the thickness of this layer at less than one millimeter.

Jehin also added, “This layer of ice could result from the dwarf planet’s nitrogen or methane atmosphere condensing as frost onto its surface as it moves away from the Sun in its elongated orbit and into an increasingly cold environment. The ice could then turn back to gas as Eris approaches its closest point to the Sun, at a distance of about 5.7 billion kilometers.”

Based on the new information on surface composition and surface reflectivity, Sicardy and his team were able to make temperature estimates for Eris. The team estimates daytime temperatures on Eris of -238 C, and that temperatures on the night side of Eris would be much lower.

Sicardy concluded with, “It is extraordinary how much we can find out about a small and distant object such as Eris by watching it pass in front of a faint star, using relatively small telescopes. Five years after the creation of the new class of dwarf planets, we are finally really getting to know one of its founding members.”

Source(s): ESO Press Release , Universe Today

Two New Globular Star Clusters Discovered By VISTA

This image from VISTA is a tiny part of the VISTA Variables in the Via Lactea (VVV) survey that is systematically studying the central parts of the Milky Way in infrared light. On the right lies the globular star cluster UKS 1 and on the left lies a much less conspicuous new discovery, VVV CL001 — a previously unknown globular, one of just 160 known globular clusters in the Milky Way at the time of writing. The new globular appears as a faint grouping of stars about 25% of the width of the image from the left edge, and about 60% of the way from bottom to top. Credit: ESO/D. Minniti/VVV Team

[/caption]

Where there once was 158, there is now more… Globular clusters, that is. Thanks to ESO’s VISTA survey telescope at the Paranal Observatory in Chile, the Via Lactea (VVV) survey has cut through the gas and dust of the Milky Way to reveal the first star cluster that is far beyond our center. But keep your eyes on the prize, because as dazzling as the cluster called UKS 1 is on the right is, the one named VVV CL001 on the left isn’t as easy to spot.

Need more? Then keep on looking, because VVV CL001 isn’t alone. The next victory for VISTA is VVV CL002, which is shown in the image below. What makes it special? It’s quite possible that VVV CL002 is the closest of its type to the center of our galaxy. While you might think discoveries of this type are commonplace, they are actually out of the ordinary. The last was documented in 2010 and it’s only through systematically studying the central parts of the Milky Way in infrared light that new ones turn up. To add even more excitement to the discovery, there is a possibility that VVV CL001 is gravitationally bound to UKS 1, making it a binary pair! However, without further study, this remains unverified.

This image from VISTA is a tiny part of the VISTA Variables in the Via Lactea (VVV) survey that is systematically studying the central parts of the Milky Way in infrared light. In the centre lies the faint newly found globular star cluster, VVV CL002. This previously unknown globular, which appears as an inconspicuous concentration of faint stars near the centre of the picture, lies close to the centre of the Milky Way. Credit: ESO/D. Minniti/VVV Team

Thanks to the hard work of the VVV team led by Dante Minniti (Pontificia Universidad Catolica de Chile) and Philip Lucas (Centre for Astrophysics Research, University of Hertfordshire, UK) we’re able to feast our eyes on even more. About 15,000 light years away on the other side of the Milky Way, they’ve turned up VVV CL003 – an open cluster. Due the intristic faintness of these new objects, it’s a wonder we can see them at all… In any light!

Original Story Source: ESO Press Release.

Early Galaxies – Clearing The “Cosmic Fog”

Scientists have used ESO’s Very Large Telescope to probe the early Universe at several different times as it was becoming transparent to ultraviolet light. This brief but dramatic phase in cosmic history — known as reionisation — occurred around 13 billion years ago. By carefully studying some of the most distant galaxies ever detected, the team has been able to establish a timeline for reionisation for the first time. They have also demonstrated that this phase must have happened quicker than astronomers previously thought.

[/caption]

The seasons are changing for both hemispheres and it’s not uncommon to wake up to wonderful, mysterious swirls of fog. What we experience here on Earth is water vapor, but the Universe was once filled with a fog of hydrogen gas. As the hours progress, the Sun slowly burns it off – quietly revealing trees, houses and the road ahead. In time after expansion began, the electrically neutral hydrogen gas was slowly swept away by the light of ultraviolet radiation from early galaxies…

Using the Very Large Telescope (VLT) like a “time machine”, a team of astronomers cut through the cosmic cloud layer to view some of the most distant galaxies recorded so far – a look back between 780 million and a billion years after the Big Bang. These antediluvian galaxies excited the gas, making it electrically charged (ionised), it gradually became transparent to ultraviolet light. While you may argue this process is technically known as reionization, there is theorized to be a brief timeline when hydrogen was also ionised.

“Archaeologists can reconstruct a timeline of the past from the artifacts they find in different layers of soil. Astronomers can go one better: we can look directly into the remote past and observe the faint light from different galaxies at different stages in cosmic evolution,” explains Adriano Fontana, of INAF Rome Astronomical Observatory who led this project. “The differences between the galaxies tell us about the changing conditions in the Universe over this important period, and how quickly these changes were occurring.”

As we know from spectroscopy, each element has its own signature – the emission lines – and the strongest in ultraviolet is the Lyman-alpha line generated from hydrogen. This bold spectral signature is easily recognizable – even at a vast distance. By observing the Lyman-alpha line for five very remote galaxies, the team was able to establish two critical factors: their distance through redshift and how soon they could be detected. Through this process, the astronomers were then able to establish how much the Lyman-alpha emission was reabsorbed by the neutral hydrogen fog and create a timeline… A whole lot like recording what minute each landmark reappears when terrestrial fog clears and seeing the long road ahead.

“We see a dramatic difference in the amount of ultraviolet light that was blocked between the earliest and latest galaxies in our sample,” says lead author Laura Pentericci of INAF Rome Astronomical Observatory. “When the Universe was only 780 million years old this neutral hydrogen was quite abundant, filling from 10 to 50% of the Universe’ volume. But only 200 million years later the amount of neutral hydrogen had dropped to a very low level, similar to what we see today. It seems that reionization must have happened quicker than astronomers previously thought.”

As always, there’s a bit more to the story. In this case, by understanding the rate at which the ancient absorbent obstruction began fading, scientists could also deduce the source of the powerful ultraviolet radiation. Could it be first generation stars – or even the work of primeval black holes?

“The detailed analysis of the faint light from two of the most distant galaxies we found suggests that the very first generation of stars may have contributed to the energy output observed,” says Eros Vanzella of the INAF Trieste Observatory, a member of the research team. “These would have been very young and massive stars, about five thousand times younger and one hundred times more massive than the Sun, and they may have been able to dissolve the primordial fog and make it transparent.”

To prove anything, it’s going to take a lot more research and some very accurate measurements – ones that are already in the planning stage for the future ESO European Extremely Large Telescope. But, in the meantime, the team used the great light-gathering power of the 8.2-metre VLT to carry out spectroscopic observations, targeting galaxies first identified by the NASA/ESA Hubble Space Telescope and in deep images from the VLT.

Original Story Source: ESO Press Release. For Further Reading: Probing The Earliest Galaxies And The Epoch Of Reionization.

Sunny Side Up: New Image of the Fried Egg Nebula Reveals a Rare Yellow Hypergiant Star

An image from the Very Large Telescope of IRAS 17163-3907, which has a huge dusty double shell surrounding the central hypergiant star. The star and its shells resemble an egg white around a yolky centre, leading astronomers to nickname the object the Fried Egg Nebula. Credit: ESO/E. Lagadec

[/caption]

A new look at the Fried Egg Nebula has revealed one of the rarest classes of stars in the Universe, a yellow hypergiant. This “sunny-side-up” view shows for the first time a huge dusty double shell surrounding this huge star.

“This object was known to glow brightly in the infrared but, surprisingly, nobody had identified it as a yellow hypergiant before,” said Eric Lagadec from the European Southern Observatory, who led the team that produced the new images.

And there’s good reason to keep an eye on this star: it will likely soon die an explosive death, and will be one of the next supernova explosions in our galaxy.

The monster star, IRAS 17163-3907 has a diameter about a thousand times bigger than our Sun. At a distance of about 13,000 light-years from Earth, it is the closest yellow hypergiant found to date and new observations show it shines some 500,000 times more brightly than the Sun. The total mass of this star is estimated to be roughly twenty times that of the Sun.

The star and its shells resemble an egg white around a yolky center, hence, the nickname of the Fried Egg Nebula – which is much easier to say than IRAS 17163-3907.

The observations of the star and the discovery of its surrounding shells were made using the VISIR infrared camera on the VLT. The pictures are the first of this object to clearly show the material around it and reveal two almost perfectly spherical shells.

Astronomers say that if the Fried Egg Nebula were placed in the center of the Solar System, Earth would lie deep within the star itself and the planet Jupiter would be orbiting just above its surface. The much larger surrounding nebula would engulf all the planets and dwarf planets and even some of the comets that orbit far beyond the orbit of Neptune. The outer shell has a radius of 10,000 times the distance from the Earth to the Sun.

Yellow hypergiants are in an extremely active phase of their evolution, undergoing a series of explosive events — this star has ejected four times the mass of the Sun in just a few hundred years. The material flung out during these bursts has formed the extensive double shell of the nebula, which is made of dust rich in silicates and mixed with gas.

Source: ESO

Can You Spot the Running Chicken in this Nebula?

The Running Chicken Nebula, a cloud of gas and newborn stars that lies around 6500 light-years away from us in the constellation of Centaurus (The Centaur). It’s official name is IC 2944, or the Lambda Centauri Nebula. Credit:ESO

[/caption]

A brand new image from the Wide Field Imager on the MPG/ESO 2.2-meter telescope reveals the Lambda Centauri Nebula, a cloud of glowing hydrogen and newborn stars in the constellation of Centaurus. The nebula is also known as IC 2944. But it also has one of the most unique nicknames of any other nebula: The Running Chicken Nebula. Can you see a chicken shape in pictures of this red star-forming region? There is some disagreement over exactly which part of the nebula is chicken shaped, with various bird-like features showing up across the picture.

The Running Chicken lies around 6,500 light-years from Earth, and hot newborn stars that formed from clouds of hydrogen gas shine brightly with ultraviolet light. This intense radiation in turn excites the surrounding hydrogen cloud, making it glow a distinctive shade of red.

The other features in this image that stand are the opaque black clumps silhouetted against the red background in part of this image. These are examples of a type of object called Bok globules. They appear dark as they absorb the light from the luminous background. However, observations of these dark clouds using infrared telescopes, which are able to see through the dust that normally blocks visible light, have revealed that stars are forming within many of them.

ESO is having a contest on their Flickr page where you can submit your views of where the chicken outline lies on this, and in participating, you can win some prizes from ESO.

Source: ESO

Colorful Cluster of Stars Competes with the Tarantula Nebula

The star cluster NGC 2100 in the Large Magellanic Cloud. Credit: ESO

[/caption]

Who can shine the brightest in the Large Magellanic Cloud? A brilliant cluster of stars, open cluster NGC 2100 shines brightly, competing with the nearby Tarantula Nebula for bragging rights in this image from ESO’s New Technology Telescope (NTT).

Observers perhaps often overlook NGC 2100 because of its close proximity to the impressive Tarantula. The glowing gas of the Tarantula Nebula even tries to steal the limelight in this image — the bright colors here are from the nebula’s outer regions, and is lit up by the hot young stars that lie within the nebula itself.

But back to the star cluster — this brilliant star cluster is around 15 million years old, and located in the Large Magellanic Cloud, a nearby satellite galaxy of the Milky Way. An open cluster has stars that are relatively loosely bound by gravity. These clusters have a lifespan measured in tens or hundreds of millions of years, as they eventually disperse through gravitational interaction with other bodies.

This new picture was created from exposures through several different color filters.The stars are shown in their natural colors, while light from glowing ionized hydrogen (shown here in red) and oxygen (shown in blue) is overlaid.

See more info at the ESO website.

Astrophoto: Laser Lightning!

Lightning strikes during a test of a new laser guide star at the Allgäu Public Observatory in Ottobeuren, Germany. Credit: Martin Kornmesser, ESO

[/caption]

Yikes! This science-fiction-like scene was captured by Martin Kornmesser, a visual artist for the European Southern Observatory. Just as the ESO was testing a new laser guide star unit at the Allgäu Public Observatory in Ottobeuren, Germany, a thunderstorm erupted, throwing down bolts of lightning. The folks at ESO say this is a “very visual demonstration of why ESO’s telescopes are in Chile, and not in Germany.” Although the storm was still far from the observatory, the lightning appears to clash with the laser beam in the sky.

Laser guide stars are one type of adaptive optics astronomers use to correct for the blurring effect of the atmosphere in astronomical observations. The laser creates an artificial guide star 90 kilometers up in the Earth’s atmosphere. The laser in this photograph is a powerful one, with a 20-watt beam, but the power in a bolt of lightning peaks at a trillion watts — although it lasts for just a fraction of a second. Shortly after this picture was taken the storm reached the observatory, forcing operations to close for the night.

See more info at the ESO website.

Looking Into a Pair of Cosmic Eyes

A beautiful yet peculiar pair of galaxies, NGC 4438 and NGC 4435, nicknamed The Eyes. Credit: ESO/Gems project

[/caption]

Have you ever looked through your telescope and felt like you were being watched? These two galaxies in the Virgo cluster form a pair of cosmic eyes that stare right back at you! These two oval-shaped galaxies, NGC 4438 (left) and NGC 4435, are nicknamed “The Eyes” since they resemble a pair of eyes glowing in the dark when seen in a moderate-sized telescope. This image was taken by the Very Large Telescope at Paranal in Chile, using the FORS2, a visual and near ultraviolet FOcal Reducer and low dispersion Spectrograph for the VLT.

These eyes have likely changed in shape over time, and astronomers can see evidence that the pair probably both were spiral galaxies in the past. The contents of NGC 4438 have been stripped out by a violent process: a collision with another galaxy. This clash has distorted the galaxy’s spiral shape, much as could happen to the Milky Way when it collides with its neighboring galaxy Andromeda in three or four billion years.

Although the two eyes look similar at their centers, their outskirts could not be more different. NGC 4435 is compact and seems to be almost devoid of gas and dust. In contrast, NGC 4438 has a lane of obscuring dust just below its nucleus, with young stars visible just left of its center, and gas extends at least up to the edges of the image.

ESO, the European Southern Observatory, is a collaboration between 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious program focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organizing cooperation in astronomical research.

See more about this image at the ESO website.