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Hubble spots a hidden treasure

Josh Lake's image of LHA 120-N11

Josh Lake’s image of LHA 120-N11, which comprises several adjacent pockets of gas and star formation. It is located in the Large Magellanic Cloud galaxy, roughly 200,000 light-years from Earth.

NEARLY 200,000 LIGHT-YEARS from Earth, the Large Magellanic Cloud, a satellite galaxy of the Milky Way, floats in space, in a long and slow dance around our galaxy.

Vast clouds of gas within it slowly collapse to form new stars. In turn, these light up the gas clouds in a riot of colours, visible in this image from the NASA/ESA Hubble Space Telescope.

The Large Magellanic Cloud (LMC) is ablaze with star-forming regions. From the Tarantula Nebula, the brightest stellar nursery in our cosmic neighbourhood, to LHA 120-N 11, part of which is featured in this Hubble image, the small and irregular galaxy is scattered with glowing nebulae, the most noticeable sign that new stars are being born.

The LMC is in an ideal position for astronomers to study the phenomena surrounding star formation. It lies in a fortuitous location in the sky, far enough from the plane of the Milky Way that it is neither outshone by too many nearby stars, nor obscured by the dust in the Milky Way’s centre.

It is also close enough to study in detail (less than a tenth of the distance of the Andromeda Galaxy, the closest spiral galaxy), and lies almost face-on to us, giving us a bird’s eye view.

Smokey remains of dead stars

LHA 120-N 11 (known as N11 for short) is a particularly bright region of the LMC, consisting of several adjacent pockets of gas and star formation. NGC 1769 (in the centre of this image) and NGC 1763 (to the right) are among the brightest parts.

In the centre of this image, a dark finger of dust blots out much of the light. While nebulae are mostly made of hydrogen, the simplest and most plentiful element in the universe, dust clouds are home to heavier and more complex elements, which go on to form rocky planets like the Earth.

Much finer than household dust (it is more like smoke), this interstellar dust consists of material expelled from previous generations of stars as they died.

The data in this image were identified by Josh Lake, an astronomy teacher at Pomfret School in Connecticut, USA, in the Hubble’s Hidden Treasures image processing competition. The competition invited members of the public to dig out unreleased scientific data from Hubble’s vast archive, and to process them into stunning images.

Josh Lake won first prize in the competition with an image (below) contrasting the light from glowing hydrogen and nitrogen in N 11. The image at the top of the page combines the data he identified with additional exposures taken in blue, green and near infrared light.

Josh Lake's image of NGC 1763

Josh Lake’s image of the NGC 1763 region of nebulosity and stars in the Large Magellanic Cloud galaxy. The image won him first prize in Hubble’s Hidden Treasures Image Processing Competition

More information: Hidden Treasures

Adapted from information issued by ESA / Hubble Information Centre. Images: NASA, ESA and J. Lake.

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Australian dish charts where stars are born

The Large Magellanic Cloud

The Large Magellanic Cloud (LMC) is the nearest sizeable galaxy to our Milky Way, and is therefore a popular target for astronomers studying the evolution of stars.

ASTRONOMERS HAVE MAPPED in detail the star-forming regions of the nearest star-forming galaxy to our own, a step toward understanding the conditions surrounding star creation.

The researchers, led by University of Illinois astronomy professor Tony Wong—and including Associate Professor Sarah Maddison and PhD student Annie Hughes, both of the Swinburne University of Technology in Melbourne, Australia—have published their findings in the December issue of the Astrophysical Journal Supplement Series.

The Large Magellanic Cloud (LMC) is a popular galaxy among astronomers both for its nearness to our Milky Way and for the spectacular view it provides, a big-picture vista impossible to capture of our own galaxy.

“If you imagine a galaxy being a disc, the LMC is tilted almost face-on so we can look down on it, which gives us a very clear view of what’s going on inside,” Wong said.

Mopra dish

CSIRO's 22-metre-diameter Mopra radio telescope, located near Coonabarabran in NSW.

As the LMC is in the far southern sky, it is an ideal target for Australian telescopes. And indeed, the team used the CSIRO’s 22-metre-diameter radio telescope at Mopra, near Coonabarabran in north-central New South Wales.

Where are stars born?

Although astronomers have a working theory of how individual stars form, they know very little about what triggers the process or the conditions in space that are optimal for star birth.

Wong’s team focused on areas called molecular clouds, which are dense patches of gas—primarily molecular hydrogen—where stars are born. By studying these clouds and their relationship to new stars in the galaxy, the team hoped to learn more about how gas clouds turn into stars.

Using the Mopra dish, the astronomers mapped more than 100 molecular clouds in the LMC and estimated their sizes and masses, identifying regions with ample material for making stars. This seemingly simple task engendered a surprising find.

Conventional wisdom states that most of the molecular gas in a galaxy is apportioned to a few large clouds. However, Wong’s team found many more low-mass clouds than they expected—so many, in fact, that a majority of the dense gas may be sprinkled across the galaxy in these small molecular clouds, rather than clumped together in a few large blobs.

MAGMA image of the LMC

False-colour image of the Large Magellanic Cloud galaxy combining maps of neutral atomic hydrogen gas (red), hydrogen energised by nearby young stars (blue), and new data from Wong’s team which roughly show the locations of dense clouds of molecular hydrogen (green). It's thought that stars form within molecular hydrogen clouds.

Star formation widespread in the LMC galaxy

The large numbers of these relatively low-mass clouds means that star-forming conditions in the LMC may be relatively widespread and easy to achieve.

To better understand the connection between molecular clouds and star formation, the team compared their molecular cloud maps to maps of infrared radiation, which reveal where young stars are heating cosmic dust.

“It turns out that there’s actually very nice correspondence between these young massive stars and molecular clouds,” Wong said.

“We can say with great confidence that these clouds are where the stars form, but we are still trying to figure out why they have the properties they do,” he added.

Adapted from information issued by University of Illinois at Urbana-Champaign. Mopra photo courtesy CSIRO. MAGMA image of LMC courtesy Tony Wong, University of Illinois.

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Cosmic superbubble shaped by stars

N 44 superbubble nebula

The N 44 superbubble nebula is being formed by hot winds from bright, young stars.

THIS STRIKING VIEW shows a ‘superbubble’ nebula surrounding the young star cluster NGC 1929 within the Large Magellanic Cloud galaxy.

The superbubble (formally known as LHA 120-N 44) has been produced by the combination of two processes. Firstly, stellar winds—streams of charged particles from the very hot and massive stars in the central cluster—cleared out the central region. Then massive stars exploded as supernovae, producing shockwaves and pushing the gas out further to form the glowing bubble.

The vast shell of material is around 325 by 250 light-years across. For comparison, the nearest star to our Sun is just over four light-years away.

The Large Magellanic Cloud is a small neighbouring galaxy to the Milky Way. It contains many regions where clouds of gas and dust are forming new stars.

Although the superbubble is shaped by destructive forces, new stars are forming around the edges where the gas is being compressed. Like recycling on a cosmic scale, this next generation of stars will breathe fresh life into NGC 1929.

The image was made by the European Southern Observatory (ESO) from observational data collected by the Very Large Telescope and identified by Manu Mejias, from Argentina, who participated in ESO’s Hidden Treasures 2010 astrophotography competition.

Download desktop wallpapers:

NGC 1929 superbubble 1024×768 (413.1 KB)

NGC 1929 superbubble 1280×1024 (657.3 KB)

NGC 1929 superbubble 1600×1200 (952.2 KB)

NGC 1929 superbubble 1920×1200 (986.2 KB)

Adapted from information issued by ESO / Manu Mejias.

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Blast from the past glows anew

Hubble image of SN 1987A

This Hubble Space Telescope image of SN 1987A shows an odd-shaped central blob of debris from the exploded star, which has now begun to brighten. The brightening is due to illumination by X-rays coming from the surrounding ring of hot gas.

IN 1987, LIGHT FROM AN EXPLODING STAR in a neighbouring galaxy, the Large Magellanic Cloud, reached Earth. Named Supernova 1987A, it was the closest supernova explosion witnessed in almost 400 years, and its proximity has enabled astronomers to study it in unprecedented detail as it evolves.

A team of astronomers has now announced that the supernova debris, which had been fading over the years, is now brightening. This shows that a different “power source” has begun to light up the debris, and marks its transition from a supernova to a supernova remnant.

“Supernova 1987A has become the youngest supernova remnant visible to us,” said Robert Kirshner of the Harvard-Smithsonian Centre for Astrophysics (CfA).

Kirshner leads a long-term study of SN 1987A with NASA’s Hubble Space Telescope. Since its launch in 1990, Hubble has provided a continuous record of the changes in SN 1987A.

A new power source

SN 1987A is surrounded by a ring of gas that blew off the progenitor star thousands of years before it exploded. The ring is about one light-year (10 trillion kilometres) across. Inside that ring, the “guts” of the star are rushing outward in an expanding debris cloud.

Most of a supernova’s light comes from radioactive decay of elements created in the explosion. As a result, it fades over time. However, the debris from SN 1987A has begun to brighten, suggesting that a new power source is lighting it.

Supernova 1987A

Supernova 1987A was the closest exploding star seen in almost 400 years. Astronomers are continuing with long-term studies of it.

“It’s only possible to see this brightening because SN 1987A is so close and Hubble has such sharp vision,” Kirshner said.

A supernova remnant consists of material ejected from an exploding star, as well as the pre-existing material the blast wave sweeps up.

The outflowing debris from SN 1987A is beginning to crash into the surrounding gas ring, creating powerful shock waves that generate X-rays, which have been detected by NASA’s Chandra X-ray Observatory. Those X-rays are illuminating the debris, and shock heating is making it glow.

The same process powers other well-known supernova remnants in our galaxy, such as Cassiopeia A.

Change you can see

Because it’s so young, the remnant of SN 1987A still shows the history of the last few thousand years of the star’s life recorded in the knots and whorls of gas. By studying it further, astronomers may decode that history.

“Young supernova remnants have personality,” Kirshner agreed.

Eventually, that history will be lost when the bulk of the expanding stellar debris hits the surrounding ring and shreds it. Until then, SN 1987A continues to offer an unprecedented opportunity to watch a cosmic object change over the course of a human lifetime. Few other objects in the sky evolve on such short time-scales.

Adapted from information issued by the Harvard-Smithsonian Centre for Astrophysics. Images courtesy NASA / P. Challis (CfA) / David Malin (AAO).

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Cosmic tails betray a close encounter

SMC and LMC

The Small (left) and Large (right) Magellanic Cloud galaxies orbit together around our Milky Way galaxy. A large stream of gas, not visible in this image, stretches between the two galaxies, the result of a close encounter around a billion years ago.

OUR NEAREST GALACTIC NEIGHBOURS became entangled in a cosmic dance over the past few billion years, with a dramatic close encounter around 1.2 billion years ago, say astronomers.

International Centre for Radio Astronomy Research (ICRAR) astronomers Jonathan Diaz and Dr Kenji Bekki have used computer modelling to study the movement of the Large and Small Magellanic Clouds around the Milky Way and the structure of the gas that surrounds them.

The Large Magellanic Cloud and the Small Magellanic Cloud are the two closest reasonable size galaxies to our own Milky Way. Southern Hemisphere stargazers can easily see them in the night sky from dark locations.

“An enormous stream of hydrogen gas trails behind the Magellanic Clouds as they orbit the Milky Way,” says ICRAR student Jonathan Diaz. ICRAR is a joint venture between Curtin University and The University of Western Australia, located in Perth.

Animation of the Magellanic Stream

Simulation of the orbits of the Large and Small Magellanic Cloud galaxies (red and green lines) around the Milky Way. A close approach around a billion years ago was responsible for forming a huge cloud of gas around the galaxies.

“Previous explanations for the oversized tail had it being stripped away from the Magellanic Clouds during a close approach of the Milky Way around 2 billion years ago.”

However, recent observations made by the Hubble Space Telescope have cast doubt on whether that close approach actually occurred. The new data from Hubble shows that the Magellanic Clouds are moving differently than originally thought.

“We have found a solution to the question raised by the Hubble data,” explains Diaz. “We’ve shown that its possible for the gas stream to form through a violent interaction between the two small galaxies around 1.2 billion years ago, without the need for a strong interaction with the much larger Milky Way.”

“Past models have assumed that the Magellanic Clouds have been cosmic companions since birth, but our work demonstrates a recent and quite dramatic coupling between the Clouds.”

“Our model shows the Magellanic Clouds have been drifting around the Milky Way for many billions of years, but have only just recently found each other,” says Dr Kenji Bekki, supervisor of the project.

“Were going to conduct further simulations and refine our model but this result shows us we still have more to learn about our galaxy and its neighbourhood.”

The research will be published in the Monthly Notices of the Royal Astronomical Society.

Adapted from information issued by ICRAR. Images courtesy Jonathan Diaz (ICRAR) / Eckhard-Slawik / Serge Brunier.

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Hubble’s cosmic bauble

Hubble image of SNR B0509-67.5

This delicate shell formed as the expanding blast wave and ejected material from a supernova (an exploding star) tore through the surrounding interstellar gas. It is located in the Large Magellanic Cloud (LMC), a small galaxy about 160 000 light-years from Earth.

  • Expanding shell of gas from an exploded star
  • Explosion occurred about 400 years ago
  • Image made from combined Hubble images

Hubble has spotted a festive bauble of gas in our neighbouring galaxy, the Large Magellanic Cloud. Formed in the aftermath of a supernova explosion that took place four centuries ago, this sphere of gas has been snapped in a series of observations made between 2006 and 2010.

The delicate shell, photographed by the NASA/ESA Hubble Space Telescope, appears to float serenely in the depths of space, but this apparent calm hides an inner turmoil. The gaseous envelope formed as the expanding blast wave and ejected material from a supernova tore through the nearby interstellar medium.

Called SNR B0509-67.5 (or SNR 0509 for short), the bubble is the visible remnant of a powerful stellar explosion in the Large Magellanic Cloud (LMC), a small galaxy about 160,000 light-years from Earth.

Ripples seen in the shell’s surface may be caused either by subtle variations in the density of the ambient interstellar gas, or possibly be driven from the interior by fragments from the initial explosion.

The bubble-shaped shroud of gas is 23 light-years across and is expanding at more than 18 million km/h.

Hubble and Chandra image of SNR B0509-67.5

The Hubble images overlaid with data (green) from NASA’s Chandra X-ray Observatory that show where the gas is so hot that it emits high-powered X-rays. The bubble-shaped shroud of gas is 23 light-years across and is expanding at more than 18 million km/h.

Astronomers have concluded that the explosion was an example of an especially energetic and bright variety of supernova. Known as Type Ia, such supernova events are thought to result when a white dwarf star in a binary system robs its partner of gas, taking on more mass than it is able to handle, so that it eventually explodes.

Hubble’s Advanced Camera for Surveys observed the supernova remnant on 28 October 2006 with a filter that isolates light from the glowing hydrogen seen in the expanding shell. These observations were then combined with visible-light images of the surrounding star field that were imaged with Hubble’s Wide Field Camera 3 on 4 November 2010.

With an age of about 400 years, the supernova might have been visible to Southern Hemisphere observers around the year 1600, although there are no known records of a “new star” in the direction of the LMC near that time.

A much more recent supernova in the LMC, SN 1987A, did catch the eye of Earth viewers and continues to be studied with ground- and space-based telescopes, including Hubble.

Adapted from information issued by the ESA–Hubble Information Centre. Image credit: NASA / ESA / Hubble Heritage Team (STScI/AURA) / CXC / SAO. Acknowledgement: J. Hughes (Rutgers University).

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Incredible Hubble video

This Hubblecast features a spectacular new NASA/ESA Hubble Space Telescope image—one of the largest ever released of a star-forming region. It highlights N11, part of a complex network of gas clouds and star clusters within our neighbouring galaxy, the Large Magellanic Cloud. This region of energetic star formation is one of the most active in the nearby Universe.

Download an amazing screen wallpaper image of N11:

Adapted from information issued by NASA / ESA / Jesús Maíz Apellániz (Instituto de Astrofísica de Andalucía, Spain).

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Baby stars and bubbles of gas

Region N11 in the Large Magellanic Cloud

Hubble snapped this broad vista of young stars and gas clouds in our neighbouring galaxy, the Large Magellanic Cloud. This region, known as N11, and is one of the most active star formation regions in the nearby Universe.

  • Region of starbirth in a neighbouring galaxy
  • Young stars blowing bubbles of gas
  • One starbirth region is over 1,000 light-years wide

A spectacular new NASA/ESA Hubble Space Telescope image — one of the largest ever released of a star-forming region — highlights N11, part of a complex network of gas clouds and star clusters within our neighbouring galaxy, the Large Magellanic Cloud.

This region of energetic star formation is one of the most active in the nearby Universe.

The Large Magellanic Cloud contains many bright bubbles of glowing gas. One of the largest and most spectacular has the name LHA 120-N 11, from its listing in a catalogue compiled by the American astronomer and astronaut Karl Henize in 1956, and is informally known as N11.

Close up, the billowing pink clouds of glowing gas make N11 resemble a puffy swirl of fairground candy floss. From further away, its distinctive overall shape led some observers to nickname it the Bean Nebula.

The dramatic and colourful features visible in the nebula are the telltale signs of star formation.

Baby stars blow bubbles

N11 is a well-studied region that extends over 1,000 light-years. It is the second largest star-forming region within the Large Magellanic Cloud and has produced some of the most massive stars known.

It is the process of star formation that gives N11 its distinctive look. Three successive generations of stars, each of which formed further away from the centre of the nebula than the last, have created shells of gas and dust.

These shells were blown away from the newborn stars in the turmoil of their energetic birth and early life, creating the ring shapes so prominent in this image.

See the full-size image here (0.7MB, will open in a new window).

In the upper left corner of the picture is the red bloom of nebula LHA 120-N 11A. Its rose-like petals of gas and dust are illuminated from within, thanks to the radiation from the group of massive, hot stars at its centre. N11A is relatively compact and dense and is the site of the most recent burst of star development in the region.

Large Magellanic Cloud

The Large Magellanic Cloud is a nearby, small, irregularly-shaped galaxy that is gravitationally tied to our Milky Way galaxy.

Other star clusters abound in N11, including NGC 1761 at the bottom of the image, which is a group of massive hot young stars busily pouring intense ultraviolet radiation out into space.

The Large Magellanic Cloud

Although it is much smaller than our own galaxy, the Large Magellanic Cloud is a very vigorous region of star formation. Studying these stellar nurseries helps astronomers understand a lot more about how stars are born and their ultimate development and lifespan.

Both the Large Magellanic Cloud and its small companion, the Small Magellanic Cloud, are easily seen with the unaided eye and have always been familiar to people living in the Southern Hemisphere.

The credit for bringing these galaxies to the attention of Europeans is usually given to Portuguese explorer Fernando de Magellan and his crew, who viewed it on their 1519 sea voyage.

However, the Persian astronomer Abd Al-Rahman Al Sufi and the Italian explorer Amerigo Vespucci recorded the Large Magellanic Cloud in 964 and 1503 respectively.

Adapted from information issued by NASA / ESA / Jesús Maíz Apellániz (Instituto de Astrofísica de Andalucía, Spain).