ALMA Warms Up the View of the Coldest Place In the Universe

Where is the coldest place in the Universe? Right now, astronomers consider the “Boomerang Nebula” to have the honors. Located about 5,000 light-years away in the constellation Centaurus, this pre-planetary nebula carries a temperature of about one Kelvin – or a brisk, minus 458 degrees Fahrenheit. That makes it even colder than the natural background temperature of space! What makes it more frigid than the elusive afterglow of the Big Bang? Astronomers are employing the powers of the Atacama Large Millimeter/submillimeter Array (ALMA) telescope to tell us more about its chilly properties and unusual shape.

The “Boomerang” is different all the way around. It is not yet a planetary nebula. The fueling light source – the central star – just isn’t hot enough yet to emit the massive amounts of ultra-violet radiation which lights up the structure. Right now it is illuminated by starlight shining off its surrounding dust grains. When it was first observed in optical light by our terrestrial telescopes, the nebula appeared to be shifted to one side and that’s how it got its fanciful name. Subsequent observations with the Hubble Space Telescope revealed an hour-glass structure. Now, enter ALMA. With these new observations, we can see the Hubble images only show part of what’s happening and the dual lobes seen in the older data were probably only a “trick of the light” as presented by optical wavelengths.

“This ultra-cold object is extremely intriguing and we’re learning much more about its true nature with ALMA,” said Raghvendra Sahai, a researcher and principal scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California, and lead author of a paper published in the Astrophysical Journal. “What seemed like a double lobe, or ‘boomerang’ shape, from Earth-based optical telescopes, is actually a much broader structure that is expanding rapidly into space.”

So what is going on out there that makes the Boomerang such a cool customer? It’s the outflow, baby. The central star is expanding at a frenzied pace and it is lowering its own temperature in the process. A prime example of this is an air conditioner. It uses expanding gas to create a colder core and as the breeze blows over it – or in this case, the expanding shell – the environment around it is cooled. Astronomers were able to determine just how cool the gas in the nebula is by noting how it absorbed the constant of the cosmic microwave background radiation: a perfect 2.8 degrees Kelvin (minus 455 degrees Fahrenheit).

Credit: NASA/ESA
Credit: NASA/ESA
“When astronomers looked at this object in 2003 with Hubble, they saw a very classic ‘hourglass’ shape,” commented Sahai. “Many planetary nebulae have this same double-lobe appearance, which is the result of streams of high-speed gas being jettisoned from the star. The jets then excavate holes in a surrounding cloud of gas that was ejected by the star even earlier in its lifetime as a red giant.”

However, the single-dish millimeter wavelength telescopes didn’t see things the same as Hubble. Rather than a skinny waist, they found a fuller figure – a “nearly spherical outflow of material”. According to the news release, ALMA’s unprecedented resolution permitted researchers to determine why there was such a difference in overall appearance. The dual-lobe structure was evident when they focused on the distribution of carbon monoxide molecules as seen at millimeter wavelengths, but only toward the inside of the nebula. The outside was a different story, though. ALMA revealed a stretched, cold gas cloud that was relatively rounded. What’s more, the researchers also pinpointed a thick corridor of millimeter-sized dust grains enveloping the progenitor star – the reason the outer cloud took on the appearance of a bowtie in visible light! These dust grains shielded a portion of the star’s light, allowing just a glimpse in optical wavelengths coming from opposite ends of the cloud.

“This is important for the understanding of how stars die and become planetary nebulae,” said Sahai. “Using ALMA, we were quite literally and figuratively able to shed new light on the death throes of a Sun-like star.”

There’s even more to these new findings. Even though the perimeter of the nebula is beginning to warm up, it’s still just a bit colder than the cosmic microwave background. What could be responsible? Just ask Einstein. He called it the “photoelectric effect”.

Original Story Source: NRAO News Release.

This Planetary Nebula Comes With a Twist

From the Cat’s Eye to the Eskimo, planetary nebulae are arguably among the most dazzling objects in the Universe. These misnamed stellar remnants are created when the outer layers of a dying star blows off and expands into space. However, they can look radically different from one another, revealing complicated histories and structures.

But recently, astronomers have argued that some of the most exotic shapes are the result of not one, but two stars at the center. It is the interaction between the progenitor star and a binary companion that shapes the resulting planetary nebula.

The archetypal planetary nebula is spherical. Most planetary nebulae, however, have been shown to be non-spherical, complex structures.

“LoTr 1 is one such planetary nebula, but with a twist,” Amy Tyndall – a graduate student at the University of Manchester and lead author on the study – told Universe Today. It has not one star at its center but two. The binary central star system consists of a faint, hot white dwarf and a cool companion – a rapidly rotating giant.

LoTr 1 with a binary central star system and two slightly elongated shells, with ages of 17 and 35 thousand years.
LoTr 1 with a binary central star system and two slightly elongated shells, with ages of 17 and 35 thousand years. Credit: Tyndal et al.

LoTr 1 was first discovered by astronomers using the 1.2 meter telescope at the Royal Observatory in Edinburgh, Scotland. At the time it seemed that LoTr 1 was similar to a particular group of 4 planetary nebulae (Abell 35, Abell 70, WeBo 1 and LoTr 5), all of which had a central binary star system.

Another common factor amongst this particular group is that in most cases the companion star seemed to be a barium star – a cool giant that shows relatively large amounts of barium. Before the planetary nebula forms, the progenitor star dredges up an excess amount of Barium on its surface. It then releases a Barium-enriched stellar wind, which falls on its companion star.

“After the stellar envelope is ejected to form the surrounding nebula, the giant star evolves into a white dwarf, while the contaminated star retains the barium from the wind as it continues to evolve to form a Barium star,” explains Tyndall.

Tyndall and her collaborates set out to see if the companion star within LoTr 1 was in fact a Barium star. They acquired data from telescopes in both Chile and Australia and compared their results to the two other elusive planetary nebulae in the group: Abell 70 and WeBo 1.

“If barium is indeed present, it would be a good step further towards our understanding of how mass is transferred between stars in a binary system, and how that subsequently affects the formation and morphology of planetary nebulae,” says Tyndall.

While the results show that LoTr 1 does consist of binary star system, the companion star is not a Barium star. But a null result is still a result. “LoTr 1 remains an interesting object to us as it shows that we still have huge gaps in our knowledge as to how these stunning objects form,” Tyndall told Universe Today.

Without the presence of Barium, it would appear at first that little mass was transferred to the companion star. However, the companion star is rotating rapidly, which is a direct consequence of mass transfer. The most plausible explanation is that the mass was transferred before the barium could be dredged up to the stellar surface.

If the stellar evolution was cut short this way then there will be detectable evidence in the properties of the white dwarf. The next step will be to take another look at this odd planetary nebula in hopes of better understanding the complexities of this system.

The paper has been accepted for publication in the Monthly Notices of the Royal Astronomical Society and is available for download here.

Endings and Beginnings – Magnetic Jets Shape Stellar Transformation

The incredible visual appearance of planetary nebulae are some of the most studied and observed of deep space objects. However, these enigmatic clouds of gas have defied explanation as to their shapes and astronomers are seeking answers. Thanks to a new discovery made by an international team of scientists from Sweden, Germany and Austria, we have now observed a jet of high-energy particles in the process of being ejected from an expiring star.

When a sun-like star reaches the end of its life, it begins to shed itself of its outer layers. These layers blossom into space at speeds of a few kilometers per second, forming a variety of shapes and sizes – yet we know little about what causes their ultimate appearance. Now astronomers are taking a close look at a rather normal star that has reached the end of its life and is beginning to form a planetary nebula. Cataloged as IRAS 15445-5449, this stellar study resides 230,000 light years away in the constellation of Triangulum Australe (the Southern Triangle). Through the use of the CSIRO Australia Telescope Compact Array, a compliment of six 22-meter radio telescopes in New South Wales, Australia, researchers have found what may be the answer to this mystery… high-speed magnetic jets.

“In our data we found the clear signature of a narrow and extremely energetic jet of a type which has never been seen before in an old, Sun-like star,” says Andrés Pérez Sánchez, graduate student in astronomy at Bonn University, who led the study.

How does a radio telescope aid researchers in an optical study? In this case the radio waves emitted by the dying star are compatible with the trademark high-energy particles they are expected to produce. These “spouts” of particles travel at nearly the speed of light and coincident jets are also known to emanate from other astronomical objects that range from newborn stars to supermassive black holes.

“What we’re seeing is a powerful jet of particles spiraling through a strong magnetic field,” says Wouter Vlemmings, astronomer at Onsala Space Observatory, Chalmers. “Its brightness indicates that it’s in the process of creating a symmetric nebula around the star.”

Will these high-energy particles contained within the jet eventually craft the planetary nebula into an ethereal beauty? According to the astronomers, the current state of IRAS 15445-5449 is probably a short-lived phenomenon and nothing more than an intense and dramatic phase in its life… One we’re lucky to have observed.

“The radio signal from the jet varies in a way that means that it may only last a few decades. Over the course of just a few hundred years the jet can determine how the nebula will look when it finally gets lit up by the star,” says team member Jessica Chapman, astronomer at CSIRO in Sydney, Australia.

Will our Sun also follow suit? Right now the answer is unclear. There may be more to this radio picture than meets the ear. However, rest assured that this new information is being heard and might well become the target of additional radio studies. Considering the life of a planetary nebula is generally expected to last few tens of thousands of years, this is a unique opportunity for astronomers to observe what might be a transient occurrence.

“The star may have an unseen companion – another star or large planet — that helps create the jet. With the help of other front-line radio telescopes, like ALMA, and future facilities like the Square Kilometre Array (SKA), we’ll be able to find out just which stars create jets like this one, and how they do it,” says Andrés Pérez Sánchez.

Original Story Source: Royal Astronomical Society News Release.

Hubble and NTT Capture Strange Alignment of Planetary Nebulae

While taking a look at more than a hundred planetary nebulae in our galaxy’s central bulge, astronomers using the NASA/ESA Hubble Space Telescope and ESO’s New Technology Telescope have found something rather incredible. It would appear that butterfly-shaped planetary nebulae – despite their differences – are somehow mysteriously aligned!

We know that stars similar to our Sun end their lives shedding their outer layers into space. Like a reptile’s intact skin casing, this stellar material forms a huge variety of shapes known as planetary nebulae. One of the more common forms is bipolar – which creates a bowtie or butterfly shape around the progenitor star.

Like snowflakes, no two planetary nebulae are exactly alike. They are created in different places, under different circumstances and have very different characteristics. There is no way that any of these nebulae, nor the responsible stars that formed them, could have interacted with other planetary nebulae. However, according to a new study done by astronomers from the University of Manchester, UK, there seems to be a rather incredible coincidence… A surprising number of these stellar shells are lining up the same way from our galactic point of view.

“This really is a surprising find and, if it holds true, a very important one,” explains Bryan Rees of the University of Manchester, one of the paper’s two authors. “Many of these ghostly butterflies appear to have their long axes aligned along the plane of our galaxy. By using images from both Hubble and the NTT we could get a really good view of these objects, so we could study them in great detail.”

According to the news release, the astronomers observed 130 planetary nebulae in the Milky Way’s central bulge. They identified three different types, and closely examined their characteristics and appearance.

“While two of these populations were completely randomly aligned in the sky, as expected, we found that the third — the bipolar nebulae — showed a surprising preference for a particular alignment,” says the paper’s second author Albert Zijlstra, also of the University of Manchester. “While any alignment at all is a surprise, to have it in the crowded central region of the galaxy is even more unexpected.”

What causes a planetary nebula to take on a particular shape? For some time, astronomers figured their appearance may have been affected by the rotation of the star system in which they form. Many factors could contribute, such as whether or not the spawning star is a binary, or if it has a planetary system. Both of these factors could help mold the eventual outcome of the shed stellar material. However, bipolar planetary nebulae are the most extreme. Astronomers theorize their shapes are the product of jets blowing mass from the binary system perpendicular to the orbit.

“The alignment we’re seeing for these bipolar nebulae indicates something bizarre about star systems within the central bulge,” explains Rees. “For them to line up in the way we see, the star systems that formed these nebulae would have to be rotating perpendicular to the interstellar clouds from which they formed, which is very strange.”

We accept the fact that the properties of the parent stars are the biggest contributor to a planetary nebula’s shape, but this new information gives an enigmatic edge to the final outcome. Not only is each unique, but the Milky Way itself adds even more complexity. The entire central bulge rotates around the galactic center, and this bulge may have considerably more influence than we expected… the influence of its magnetic fields. The researchers suggest this “orderly behavior of the planetary nebulae” may have occurred because a strong magnetic field was present when the bulge formed. Since planetary nebulae nearer to us don’t line up in the same orderly fashion, it would be logical to assume these magnetic fields were much stronger when our galaxy first formed.

“We can learn a lot from studying these objects,” concludes Zijlstra. “If they really behave in this unexpected way, it has consequences for not just the past of individual stars, but for the past of our whole galaxy.”

Original Story Source: ESO News Release.

Looking Into The Green Eye Of Planetary Nebula IC 1295

Located on Cerro Paranal in the Atacama Desert of northern Chile, the ESO’s Very Large Telescope was busy using the FORS instrument (FOcal Reducer Spectrograph) to achieve one of the most detailed observations ever taken off a lonely, green planetary nebula – IC 1295. Exposures taken through three different filters which enhanced blue light, visible green light, and red light were melded together to make this 3300 light year distant object come alive.

Located in the constellation of Scutum, this jewel in the “Shield” is a miniscule star that’s at the end of its life. Much like our Sun will eventually become, this white dwarf star is softly shedding its outer layers, like an unfolding flower in space. It will continue this process for a few tens of thousands of years, before it ends, but until then IC 1295 will remain something of an enigma.

“The range of shapes observed up to today has been reproduced by many theoretical works using arguments such as density enhancements, magnetic fields, and binary central systems. Despite this, no complete agreement between models and properties of a given morphological group has been achieved. One of the main reasons for this is selection criteria and completeness of studied samples.” say researchers at Georgia State University. “The samples are usually limited by available images in few bands such as Ha, [NII] and [OIII]. Of course they are also limited by distance, since the further away the object is, the harder it is to resolve its structure. Even with the modern telescopes, obtaining a truly complete sample is far from being achieved.”

Why is this common deep space object like IC 1295 such a mystery? Blame it on its structure. It is comprised of multiple shells.- gaseous layers which once were the star’s atmosphere. As the star aged, its core became unstable and it erupted in unexpected releases of energy – like expansive blisters breaking open. These waves of gas are then illuminated by the ancient star’s ultraviolet radiation, causing it to glow. Each chemical acts as a pigment, resulting in different colors. In the case of IC 1295, the verdant shades are the product of ionised oxygen.

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This video sequence starts with a broad panorama of the Milky Way and closes in on the small constellation of Scutum (The Shield), home to many star clusters. The final detailed view shows the strange green planetary nebula IC 1295 in a new image from ESO’s Very Large Telescope. This faint object lies close to the brighter globular star cluster NGC 6712. Credit: ESO/Nick Risinger (skysurvey.org)/Chuck Kimball. Music: movetwo

However, green isn’t the only color you see here. At the heart of this planetary nebula beats a bright, blue-white stellar core. Over the course of billions of years, it will gently cool – becoming a very faint, white dwarf. It’s just all part of the process. Stars similar to the Sun, and up to eight times as large, are all theorized to form planetary nebulae as they extinguish. How long does a planetary nebula last? According to astronomers, it’s a process that could be around 8 to 10 thousand years.

“Athough planetary nebulae (PNe) have been discovered for over 200 years, it was not until 30 years ago that we arrived at a basic understanding of their origin and evolution.” says Sun Kwok of the Institute of Astronomy and Astrophysics. “Even today, with observations covering the entire electromagnetic spectrum from radio to X-ray, there are still many unanswered questions on their structure and morphology.”

Original Story Source: ESO Photo Release.

Greek Observatory Probes Ancient Star

Some 2,500 years ago, a Greek astronomer named Aristarchus certainly made some very correct assumptions when he postulated the Sun to be at the center of our known Universe and that the Earth revolved around it. Through this, he also knew that the stars were incredibly far away and now his namesake telescope, the new 2.3 meter Aristarchos, is taking that distant look from the Helmos Observatory, high atop the Peloponnese Mountains in Greece. Its purpose is to determine the distance and evolution of a mysterious star system – one which is encased in an ethereal nebula.

While looking at the demise of a possible binary star system, researchers Panos Boumis of the National Observatory of Athens and John Meaburn of the University of Manchester, set out to photograph this enigmatic study with the narrowband imaging camera onboard the Aristarchos telescope. Their target designation is planetary nebula KjPn8, and it was originally discovered during the 1950’s Palomar Sky Survey. What makes it out of the ordinary is two huge lobes, measuring a quarter of a degree across, which surround the system. This artifact was researched by Mexican astronomers at the San Pedro Martir Observatory some four decades after its revelation, but it wasn’t until the year 2000 that the Hubble Space Telescope uncovered its central star.

An image of the giant lobes of the planetary nebula KjPn 8 in the light of the emission lines of hydrogen and singly ionised nitrogen, obtained with the narrowband camera on the new 2.3-m Aristarchos telescope. Detailed measurements of the lobes have allowed the determination of their expansion velocity, distance and ages. The results indicate their origin in a remarkable eruptive binary system. Credit: P. Boumis / J. Meaburn
An image of the giant lobes of the planetary nebula KjPn 8 in the light of the emission lines of hydrogen and singly ionised nitrogen, obtained with the narrowband camera on the new 2.3-m Aristarchos telescope. Detailed measurements of the lobes have allowed the determination of their expansion velocity, distance and ages. The results indicate their origin in a remarkable eruptive binary system. Credit: P. Boumis / J. Meaburn

Dr. Boumis and Prof. Meaburn began to study this ancient cosmic artifact, concentrating on measuring the expansion with utmost accuracy. Through their work, they were unable to uncover the system’s distance and trace the history of the lobes through time. What they discovered was KjPn8 is roughly 6,000 light years away and the lobes of material have three epochs: 3200, 7200 and 50,000 years. According to the research team: “The inner lobe of material is expanding at 334 km per second, suggesting it originates in an Intermediate Luminosity Optical Transient (ILOT) event. ILOTs are caused by the transfer of material from a massive star to its less massive companion, in turn creating jets that flow in different directions. We believe that the core of KjPn8 is therefore a binary system, where every so often ILOT events lead to the ejection of material at high speed.”

It is certainly a triumph for the Aristachos Telescope and the new Greek facility. Dr. Bournis is quite proud of the conclusive results gathered by telescope – especially when the object in question cries out for more research. He comments: “Greece is one of the global birthplaces of astronomy, so it is fitting that research into the wider universe continues in the 21st century. With the new telescope we expect to contribute to that global effort for many years to come.”

Original Story Source: Royal Astronomical Society News Release.

Portrait Of NGC 5189: New Light On An Old Planetary Nebula

Stretching across three light years of space and located about 3,000 light years away in the direction of the constellation of Musca, an incredible and rather understudied planetary nebula awaits a new hand to bring out new light. While most planetary nebula have a rather normal, bloated star look, NGC 5189 shows an extraordinary amount of loops and curls not normally seen in objects of its type. Just what is going on here?

This incredibly detailed image comes from the one and only Robert Gendler and was assembled from three separate data sources. The detail for the nebula is from Hubble Space Telescope data, the background starfield from the Gemini Observatory/AURA and the color data from his own equipment. Here we see fanciful gas clouds with thick clumps decorating them. Intense radiation and gas streams from the central dying star in waves, fashioning out hollows and caves in the enveloping clouds. While these clumps in the clouds may appear as wispy details, each serves as a reminder of just how vast space can be… for each an every one of them is about the same size as our Solar System.

“The complex morphology of this PN is puzzling and has not been studied in detailed so far. Our investigation reveals the presence of a new dense and cold infrared torus (alongside the optical one) which probably generated one of the two optically seen bipolar outflows and which might be responsible for the twisted appearance of the optical torus via an interaction process.” says L. Sabin (et al). ” The high-resolution MES-AAT spectra clearly show the presence of filamentary and knotty structures as well as three expanding bubbles. Our findings therefore suggest that NGC 5189 is a quadrupolar nebula with multiple sets of symmetrical condensations in which the interaction of outflows has determined its complex morphology.”

And just as incredibly large as some things can be – others can be as small. At the heart of NGC 5189 shines the tiny light of its central star… no bigger than Earth. It wobbles its way through time, rotating rapidly and spewing material into space like a runaway fire hydrant. Astronomers speculate there might be a binary star hidden inside, since usually planetary nebulae of this type have them. However, only one star has been found at the nebula’s center and it might be one very big, very bad wolf.

“Around 15% are known or suspected binaries, while the remaining 18% are non-emission line nuclei which require further study. Selecting for LIS (low ionization structures) therefore will give a mix of mostly binary and emission line nuclei which will require further observations to separate.” explains B. Miszalski (et al). “Almost all the [WR] CSPN in the sample belong to the hot [WO] type that have more extreme and chaotic LIS covering their entire nebulae, presumably due to turbulence from the strong [WR] winds disrupting pre-existing LIS.”

Just why is this celestial tapestry so complicated and complex? The answer isn’t a simple one – it’s one that has many plausible theories. We know that when a star similar to the Sun expends its fuel, it will begin to shed its outer layers… layers which normally take on very basic shape. These “normal” shapes are usually a sphere, sometimes a double lobe and at times it can be a ring or helix. However, NGC 5189 just doesn’t follow rules. Over time, researchers have speculated it has given off different outlfows at different stages – one prominent as a very visible torus situated around mid-point in the structure – consistent with the theory of a binary star system with a precessing symmetry axis. Still, there is clearly more research needed.

“Our preliminary results of a comparative spectroscopic study of these two objects shows that the chemical composition of the two nebulae is completely different, even though their morphology is most probably quite similar.” says VF Polcaro (et al). ” In addition, the PN appears much more chemically homogeneous. These features are clearly associated with the evolutionary paths of the stars.”

“The striking broad emission line spectroscopic appearance of Wolf-Rayet (WR) stars has long defied analysis, due to the extreme physical conditions within their line and continuum forming regions.” explains Paul Crowther. “Theoretical and observational evidence that WR winds depend on metallicity is presented, with implications for evolutionary models, ionizing fluxes, and the role of WR stars within the context of core-collapse supernovae and long-duration gamma ray bursts.”

Is NGC 5189 the handiwork of a binary star? Or is it the product of an intensely hot Wolf-Rayet? Like the proverbial Tootsie Pop equation… the world may never know.

Many thanks to Robert Gendler for sharing this incredible image with us.

NGC 1846 – Hubble Reveals Peculiar Life And Death Of A Stellar Population

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About 160,000 light years away in the direction of southern constellation Doradus, sits a globular cluster. It’s not a new target for the Hubble Space Telescope, but it has had a lot to say for itself over the last twelve years. It’s actually part of the Large Magellanic Cloud, but it’s no ordinary ball of stars. When it comes to age, this particular region is mighty complex…

In a 34 minute exposure taken almost a half dozen years ago, the Hubble snapped both life and death combined in an area where all stars were once assumed to be the same age. Globular clusters, as we know, are spherical collections of stars bound by gravity which orbit the halo of many galaxies. At one time, astronomers assumed their member stars were all the same age – forming into their own groups at around the same time the parent galaxy formed. But now, evidence points toward these balls of stars as having their own agenda – and may have evolved independently over the course of several hundreds of million years. What’s more, we’re beginning to learn that globular cluster formation may differ from galaxy to galaxy, too. Why? Chances are they may have encountered additional molecular clouds during their travels which may have triggered another round of star formation.

“An increasing number of photometric observations of multiple stellar populations in Galactic globular clusters is seriously challenging the paradigm of GCs hosting single, simple stellar populations.” says Giampaolo Piotto of the University of Padova, Italy. “These multiple populations manifest themselves in a split of different evolutionary sequences as observed in the cluster color-magnitude diagrams. Multiple stellar populations have been identified in Galactic and Magellanic Cloud clusters.”

However, it’s not the individual stars which make this Hubble image such a curiosity, it’s the revelation of a planetary nebula. This means a huge disparity in the member star’s ages…. one of up to 300 million years. Is it possible that the shell and remains of this dead star is a line-of-sight phenomenon, or is it truly a cluster member?

“We report on Hubble Space Telescope/ACS photometry of the rich intermediate-age star cluster NGC 1846 in the Large Magellanic Cloud, which clearly reveals the presence of a double main-sequence turn-off in this object. Despite this, the main-sequence, subgiant branch and red giant branch are all narrow and well defined, and the red clump is compact.” says A. D. Mackey and P. Broby Nielsen. ” We examine the spatial distribution of turn-off stars and demonstrate that all belong to NGC 1846 rather than to any field star population. In addition, the spatial distributions of the two sets of turn-off stars may exhibit different central concentrations and some asymmetries. By fitting isochrones, we show that the properties of the colour–magnitude diagram can be explained if there are two stellar populations of equivalent metal abundance in NGC 1846, differing in age by around 300 million years.”

So what’s wrong with the picture? Apparently nothing. The findings have been studied and studied again for errors and even “contamination” by field stars in relation to NGC1846’s main sequence turn off. It’s simply a bit of a cosmic riddle just waiting for an explanation.

“We propose that the observed properties of NGC 1846 can be explained if this object originated via the tidal capture of two star clusters formed separately in a star cluster group in a single giant molecular cloud.” concludes Mackey and Nielson. “This scenario accounts naturally for the age difference and uniform metallicity of the two member populations, as well as the differences in their spatial distributions.”

Original Story Source: NASA’s Hubble Finds Stellar Life and Death in a Globular Cluster. For Further Reading: A double main-sequence turn-off in the rich star cluster NGC 1846 in the Large Magellanic Cloud, Population Parameters of Intermediate-Age Star Clusters in the Large Magellanic Cloud. I. NGC 1846 and its Wide Main-Sequence Turnoff and Multiple stellar populations in three rich Large Magellanic Cloud star clusters.

Graphenes In Spaaaaaace!

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And just where have your buckyballs been lately? More technically known as fullerenes, this magnetic form of carbon shows some pretty interesting properties deduced from laboratory work here on Earth. But even more interesting is its cousin – graphene. And guess where it’s been found?!

When you picture a fullerene, you conjure up a mental image of carbon atoms arranged in a three-dimensional configuration with two structures: C60 which patterns out similar to a soccer ball and C70 which more closely resembles a rugby ball. Both of these types of “buckyballs” have been detected in space, but the real kicker is graphene. Its technical name is planar C24 and instead of being geodesic, it’s the thinnest substance known. Just one atom thick, this flat sheet of carbon is a portrait in extraordinary strength, conductivity and elasticity. Graphene was first synthesized in the lab in 2004 and now planar C24 may have been detected in space.

Through the use of the Spitzer Space Telescope, a team of astronomers led by Domingo Aníbal García-Hernández of the Instituto de Astrofísica de Canarias in Spain have not only picked up a C70 fullerene molecule, but may have also detected graphene as well. “If confirmed with laboratory spectroscopy – something that is almost impossible with the present techniques – this would be the first detection of graphene in space” said García-Hernández.

Letizia Stanghellini and Richard Shaw, members of the team at the National Optical Astronomy Observatory in Tucson, Arizona suspect collisional shocks generated in stellar winds of planetary nebulae could be responsible for the presence of fullerenes and graphenes through the destruction of hydrogenated amorphous carbon grains (HACs). “What is particularly surprising is that the existence of these molecules does not depend on the stellar temperature, but on the strength of the wind shocks” says Stanghellini.

So where has this discovery taken place? Try the Magellanic Clouds. In this case, using a planetary nebula “closer to home” is not part of the equation because science needs to be certain the material they are looking at is indeed the by-product of a planetary nebula and not a mix. Fortunately the SMG is known to be metal-poor, which enhances the chances of spotting complex carbon molecules. Right now the challenge has been to pinpoint the evidence for graphene from Spitzer data.

“The Spitzer Space Telescope has been amazingly important for studying complex organic molecules in stellar environments” says Stanghellini. “We are now at the stage of not only detecting fullerenes and other molecules, but starting to understand how they form and evolve in stars.” Shaw adds “We are planning ground-based follow up through the NOAO system of telescopes. We hope to find other molecules in planetary nebulae where fullerene has been detected to test some physical processes that might help us understand the biochemistry of life.”

Original News Source: National Optical Astronomy Observatory News Release.

Just for You: A Necklace from Hubble

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Awww, how nice of the Hubble Space Telescope, providing us all with a little cosmic bling in this great new view of the Necklace Nebula! From the image, it’s quite obvious why this object carries the name it does (and who wants to call it by its technical name PN G054.2-03.4, anyway?). The Necklace Nebula is a recently discovered planetary nebula, the glowing remains of an ordinary, Sun-like star. You’d need to have a fairly large neck to wear this necklace, as the nebula consists of a bright ring measuring 12 trillion miles wide, dotted with dense, bright knots of gas that resemble diamonds in a necklace.

How did this unique nebula originate? A long time ago, (about 10,000 years) in an aging binary star system far away (15,000 light-years from Earth) one of the old stars ballooned to the point where it engulfed its companion star. The smaller star continued orbiting inside its larger companion, increasing the giant’s rotation rate.

The bloated companion star spun so fast that a large part of its gaseous envelope expanded into space. Due to centrifugal force, most of the gas escaped along the star’s equator, producing a ring. The embedded bright knots are dense gas clumps in the ring.

The pair is so close, only a few million miles apart, they appear as one bright dot in the center. The stars are furiously whirling around each other, completing an orbit in a little more than a day.

The Necklace Nebula is located in the constellation Sagitta. In this composite image, taken on July 2, Hubble’s Wide Field Camera 3 captured the glow of hydrogen (blue), oxygen (green), and nitrogen (red).

Thanks Hubble for the new cosmic jewelry!

Want a larger version of this bling? See the HubbleSite for more info.