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


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!


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


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.

Kepler Drops In On Planetary Nebula


Discovered by amateur Austrian astronomer, Matthias Kronberger, planetary nebula Kn 61 just happens to be in a relatively small piece of celestial real estate being monitored by NASA’s Kepler planet finding mission. Lucky for us, we’re able to take a look at the photographic results of the new nebula obtained with the Gemini Observatory.

“Kn 61 is among a rather small collection of planetary nebulae that are strategically placed within Kepler’s gaze,” said Orsola De Marco of Macquarie University in Sydney, Australia who is the author of a 2009 paper speculating on how companion stars or even planets may influence and shape the intricate structure seen in many planetary nebulae. “Explaining the puffs left behind when medium sized stars like our Sun expel their last-breaths is a source of heated debate among astronomers, especially the part that companions might play,” says De Marco, “it literally keeps us up at night!”

And visions like this keeps the Kepler Mission continually monitoring a 105 square degree area of sky located in Cygnus looking for changes in stellar brightness which could spell a planetary transit, companion star – or something else. “It is a gamble that possible companions, or even planets, can be found due to these usually small light variations,” says George Jacoby of the Giant Magellan Telescope Organization and the Carnegie Observatories (Pasadena). “However, with enough objects it becomes statistically very likely that we will uncover several where the geometries are favorable – we are playing an odds game and it isn’t yet known if Kn 61 will prove to have a companion.” Jacoby also serves as the Principal Investigator for a program to obtain follow-up observations of Kn 61’s central star with Kepler.

To help sift through the huge amount of data provided by Kepler, professional and amateur astronomers are working as partners to help locate objects such as planetary nebula. So far, six have been found in the digital sky survey – including Kn 61. “Without this close collaboration with amateurs, this discovery would probably not have been made before the end of the Kepler mission. Professionals, using precious telescope time, aren’t as flexible as amateurs who did this using existing data and in their spare time. This was a fantastic pro-am collaboration of discovery,” says Jacoby, who serves as the liaison with the Deep Sky Hunters (DSH) and requested their help to survey the Kepler field. Jacoby published a paper with DSH members in 2010 that describes the techniques used.

“Planetary nebulae present a profound mystery,” says De Marco. “Some recent theories suggest that planetary nebulae form only in close binary or even planetary systems – on the other hand, the conventional textbook explanation is that most stars, even solo stars like our sun, will meet this fate. That might just be too simple.” Jacoby also elucidates that terrestrial observations are unable to detect such phenomena with a high rate of regularity “This is quite likely due to our inability to detect these binaries from the ground and if so then Kepler is likely to push the debate strongly in one direction or the other.”

As for our own galaxy, over 3,000 planetary nebulae have been identified and cataloged. We know they are the end product of a dying star, but not what role companions stars (or even planets) may take in their structure. Of these, only 20% have binary central stars – but this low number may be our inability to resolve them. Hopefully the space-based Kepler telescope can one day reveal their mysteries us!

Original News Source: Gemini Observatory Image Release.

WISE Captures a Glowing Cylinder in Space


It’s not like we’ve never seen the planetary nebula NGC 1514 before, but we’ve never seen it though WISE’s infrared eyes, until now. And in a stunning surprise, cylindrical rings appear to be encircling the dying star, like a neon-lit carousel, or perhaps like rolling tire surrounding a glowing blob. “I just happened to look up one of my favorite objects in our WISE catalogue and was shocked to see these odd rings,” said Michael Ressler, a member of the WISE science team at JPL. “This object has been studied for more than 200 years, but WISE shows us it still has surprises.

Space station from the movie 2001: A Space Odyssey.

At first glance the rings look like the double-ringed space station in the movie 2001: A Space Odyssey. (Too bad the Bad Astronomer beat me to that likeness. He also compared it to a tuna can.)

Other people see different things in this image.

“I am reminded of the jellyfish exhibition at the Monterey Bay Aquarium — beautiful things floating in water, except this one is in space,” said Edward (Ned) Wright, the principal investigator of the WISE mission at UCLA, and a co-author of a paper on the findings, reported in the Astronomical Journal.

WISE was able to spot the rings for the first time because their dust is being heated and glows with the infrared light that WISE can detect. In visible-light images, the rings are hidden from view, overwhelmed by the brightly fluorescing clouds of gas.

Here’s what NGC 1514 looks like in visible light from a ground observatory:

NGC1514 in visible light. Image credit: Digitized Sky Survey/STScI

The object is actually a pair of stars, seen as a single dot at the center of the blue orb. One star is a dying giant somewhat heavier and hotter than our sun, and the other was an even larger star that has now contracted into a dense body called a white dwarf. As the giant star ages, it sheds some its outer layers of material. An inner shell of ejected material is seen in bright, light blues. An outer shell can also be seen in more translucent shades of blue.

This planetary nebula is also called the “Crystal Ball” nebula, and Ressler said although NGC 1514’s structure looks unique, is probably similar in overall geometry to other hour-glass nebulae, such as the Engraved Hourglass Nebula.

Planetary Nebula MyCn18: An Hourglass Pattern Around a Dying Star. Credit: Raghvendra Sahai and John Trauger (JPL), the WFPC2 science team, and NASA.

The structure looks different in WISE’s view because the rings are detectable only by their heat; they do not fluoresce at visible wavelengths, as do the rings in the other objects.

The WISE science team says that more oddballs like NGC 1514 are sure to turn up in the plethora of WISE data — the first batch of which will be released to the astronomical community in spring 2011.

Source: JPL

Chinese Dragon in Space!

This new image from the ESO telescope in Chile shows what looks like a Chinese dragon in the sky. But really, it is NGC 5189 an S-shaped planetary nebula adorned with red and green cosmic fireworks. This dragon isn’t breathing fire – the colorful “smoke” is a signal that a star is dying.

At the end of its life, a star with a mass less than eight times that of the Sun will blow its outer layers away, giving rise to a planetary nebula. Some of these stellar puffballs are almost round, resembling huge soap bubbles or giant planets (hence the name), but others, such as NGC 5189 are more intricate.

In particular, this planetary nebula exhibits a curious “S”-shaped profile, with a central bar that is most likely the projection of an inner ring of gas discharged by the star, seen edge on. The details of the physical processes producing such a complex symmetry from a simple, spherical star are still the object of astronomical controversy. One possibility is that the star has a very close (but unseen) companion. Over time the orbits drift due to precession and this could result in the complex curves on the opposite sides of the star visible in this image.

This image has been taken with the New Technology Telescope at ESO’s La Silla Observatory in Chile, using the now decommissioned EMMI instrument. It is a combination of exposures taken through different narrowband filters, each designed to catch only the light coming from the glow of a given chemical element, namely hydrogen, oxygen and nitrogen.

Source: ESO

Planetary Nebulae

No, planetary nebulae are not nebulae found around planets; nor are they nebulae produced by planets … rather, they got stuck with this name because the first ones to be observed (and written about) look like planets (well, they did through the eyepieces of the telescopes of the time … somewhat).

Charles Messier – yep, the comet hunting guy – listed M27 in his famous catalog; that’s the Dumbbell Nebula, and the first planetary nebula recorded (1764). It was Herschel – the guy who discovered Uranus – who dreamed up the name ‘planetary nebula’; and why? Because, to him, they looked a bit like the gas giants Jupiter, Saturn, and Uranus (Neptune wasn’t discovered then). There are four planetary nebulae in Messier’s list; in addition to M27, there’s M57 (the Ring Nebula), M76 (Little Dumbbell Nebula), and M97 (Owl Nebula). So why did Herschel say planetary nebulae looked like giant planets, including Saturn? Because, in 1781, he discovered one – NGC 7009 – that looked like Saturn! Guess what it’s called? The Saturn Nebula.

When spectroscopes were used to observe planetary nebulae, they caused excitement; unlike stars and (what we today call) galaxies – which have dark absorption lines in their spectra – planetary nebula have bright emission lines (and essentially nothing else, i.e. no continuum emission). Further, the brightest of the lines (actually two, close together), in most planetary nebulae, corresponded to nothing ever seen in any laboratory spectrum … so they were thought to be caused by an as yet undiscovered element, called nebulium.

Today we understand planetary nebulae to be a short-lived phase of (most) stars … after the red giant phase, when the star’s fuel has been exhausted, it shrinks to become a white dwarf. The gas expelled during the red giant phase become heated and ionized by the intense UV radiation of the new white dwarf (these central objects, in most planetary nebulae, are among the hottest stars). The plasma has an extremely low density, which means that certain excited, meta-stable states of ions such as O2+ can jump to a lower energy state by emission of ‘forbidden’ radiation (rather than by collision).

Such spectacular objects … no surprise that Universe Today has many stories and articles on planetary nebulae! Here are just a few Found: Planetary Nebula Around Heavy Stars, Planets May Actually Shape Planetary Nebulae, Will We Look Like This in 5 Billion Years?, and Penetrating New View Into The Helix Nebula.

Astronomy Cast’s Nebulae has more on planetary nebulae; the following episodes put planetary nebulae into a broader astronomical context: The End of the Universe Part 1: The End of the Solar System, The Life of the Sun, and The Life of Other Stars.

Source: SEDS

Very First Image of a Very Hot Star

No, this article is not about Johnny Depp or Angelina Jolie. They may be hot stars, but in comparison to the star at the center of the Bug Nebula, pictured left, they’ve got nothin’. The first image of the star at the center of the Bug Nebula (NGC 6302) has been taken by a team of astronomers at the Jodrell Bank Centre for Astrophysics, using the newly refurbished Hubble Space Telescope. This star, one of the hottest in the galaxy, has a temperature of about 200,000 Kelvin – 33 times hotter than the Sun – and is at the center of one of the most beautiful planetary nebula in the galaxy.

The star at the heart of the Bug Nebula, which lies about 3500 light-years away from Earth in the constellation Scorpius, is what gives the two lobes of the formation their glow. Its extreme temperature of at least 200,000 K (and possibly up to 400,000 K) ionizes the gas in the nebula, which is itself composed of ejecta from the star as it shed its corona during the later stages of its life. The star has gone through its red giant phase and is now a late-stage white dwarf.

As a comparison to how hot the star powering the luminosity of the Bug Nebula is, our Sun’s hottest temperature is 5,800 Kelvin which is about 5,500 degrees Celsius and almost 10,000 degrees Fahrenheit. The mass of the star is calculated to be 0.64 solar masses, though it was many times heavier than the Sun before it ejected much of its matter into the nebula.

The astronomers were lucky to have been able to image the star at this point in its life, as the light it is emitting is fading at about 1% a year. Professor Albert Zijlstra of the University of Manchester said in an email interview, “The star seems to be in a phase where nuclear burning has ceased very recently (within the past 100-1000 yr). It is radiating its left-over surface heat away, and that goes quickly. At some time heat from interior will take over, and as that is a much larger heat reservoir, the star will fade much more slowly from that point.”

This does not mean, however, that the ionized gas in the nebula will fade out quite as quickly, Zijlstra said. ‘The nebula is ionized by ultra-violet photons from the star. The ionized elements recombine with electrons, before being re-ionized. Normally, there is a good balance between ionizations and recombinations. In NGC 6302, if the star is fading rapidly, it is possible that the time scale for recombinations is longer than the time over which the star fades. The nebula would ‘remember’ a more luminous star, and be ionized to a higher degree than the star could currently support. It is like living off your savings.”The Bug Nebula, as imaged by the Hubble Space Telescope's Wide-Field Camera 3. Image Credit: Anthony Holloway, JBCA

There have been many attempts at imaging this star, but the brightness of the nebula combined with the dust obscuring the star made imaging difficult. Only with the new Wide-Field Camera 3, installed on the Hubble earlier this year, were the astronomers able to make out the star buried in the heart of the Bug Nebula.

Zijlstra said of the Hubble’s capabilities, “It is a combination of sensitivity and available filters. The nebula is very bright, and it is difficult to detect the faint star against the very bright nebular background. To get the best sensitivity, you need high resolution (which dilutes the nebulae light while concentrating the stellar light – this requires HST), good sensitivity and ideally, a filter which excludes the brightest emission lines (H alpha, [O III]). We detected the star with two different filters which select fainter emission lines, which reduces the glare from the nebula. The extinction through the dust in the nebula is also very high, which makes the star even fainter especially in the blue.”

Further observations of the star are definitely in order, including molecular and dust spectroscopy, but Zijlstra said his team does not have any observations of the star planned as of now. The results of the imaging and calculations detailing the properties of the star will be published in The Astrophysical Journal, but a pre-print article is available on Arxiv.

A zoom animation of some of the images put together is also available on the Jodrell Bank Centre for Astrophysics site right here.

Source: Jodrell Bank press release, email interview with Albert Zijlstra