A stormy stellar nursery

A stormy stellar nursery

Copyright: ESA/Hubble & NASA; CC BY 4.0

Hi-res image

This shot from the NASA/ESA Hubble Space Telescope shows a maelstrom of glowing gas and dark dust within one of the Milky Way’s satellite galaxies, the Large Magellanic Cloud.

The stormy scene shows a stellar nursery known as N159, measuring over 150 light-years across. It is known as a HII region, meaning it is rich in ionised hydrogen. Indeed, it contains many hot young stars that are emitting intense ultraviolet light, which causes nearby hydrogen gas to glow. Torrential stellar winds are also carving out ridges, arcs and filaments from the surrounding material.

At the heart of this cosmic cloud lies the Papillon Nebula, a butterfly-shaped region of nebulosity dominating the left of the scene. This compact nebula likely contains massive stars in the very early stages of formation. Its shape earned it the name (papillon being French for butterfly) and was first resolved by Hubble in 1999.

N159 is located over 160 000 light-years away. It resides just south of the Tarantula Nebula, another massive star-forming complex within the Large Magellanic Cloud.

This image was first released as a Hubble picture of the week on 5 September 2016.

Source: ESA/Space in Images

NASA's Fermi Satellite Detects First Gamma-ray Pulsar in Another Galaxy

Explore Fermi's discovery of the first gamma-ray pulsar detected in a galaxy other than our own.

Credits: NASA's Goddard Space Flight Center.  

Download the video in HD at NASA's Scientific Visualization Studio

The pulsar lies in the outskirts of the Tarantula Nebula in the Large Magellanic Cloud, a small galaxy that orbits our Milky Way and is located 163,000 light-years away. The Tarantula Nebula is the largest, most active and most complex star-formation region in our galactic neighborhood. It was identified as a bright source of gamma rays, the highest-energy form of light, early in the Fermi mission. Astronomers initially attributed this glow to collisions of subatomic particles accelerated in the shock waves produced by supernova explosions.

   

"It's now clear that a single pulsar, PSR J0540-6919, is responsible for roughly half of the gamma-ray brightness we originally thought came from the nebula," said lead scientist Pierrick Martin, an astrophysicist at the National Center for Scientific Research (CNRS) and the Research Institute in Astrophysics and Planetology in Toulouse, France. "That is a genuine surprise."

NASA's Fermi Gamma-ray Space Telescope has detected the first extragalactic gamma-ray pulsar, PSR J0540-6919, near the Tarantula Nebula (top center) star-forming region in the Large Magellanic Cloud, a satellite galaxy that orbits our own Milky Way. Fermi detects a second pulsar (right) as well but not its pulses. PSR J0540-6919 now holds the record as the highest-luminosity gamma-ray pulsar. The angular distance between the pulsars corresponds to about half the apparent size of a full moon. Background: An image of the Tarantula Nebula and its surroundings in visible light.Credits: NASA's Goddard Space Flight Center; background: ESO/R. Fosbury (ST-ECF). Hi-res image

A gamma-ray view of the same region shown above in visible wavelengths. Lighter colors indicate greater numbers of gamma rays with energies between 2 and 200 billion electron volts. For comparison, visible light ranges between 2 and 3 electron volts. The two pulsars, PSR J0540−6919 (left) and PSR J0537−6910, clearly stand out. Credits: NASA/DOE/Fermi LAT Collaboration. Hi-res image

When a massive star explodes as a supernova, the star's core may survive as a neutron star, where the mass of half a million Earths is crushed into a magnetized ball no larger than Washington, D.C. A young isolated neutron star spins tens of times each second, and its rapidly spinning magnetic field powers beams of radio waves, visible light, X-rays and gamma rays. If the beams sweep past Earth, astronomers observe a regular pulse of emission and the object is classified as a pulsar.

The Tarantula Nebula was known to host two pulsars, PSR J0540-6919 (J0540 for short) and PSR J0537−6910 (J0537), which were discovered with the help of NASA's Einstein and Rossi X-ray Timing Explorer (RXTE) satellites, respectively. J0540 spins just under 20 times a second, while J0537 whirls at nearly 62 times a second -- the fastest-known rotation period for a young pulsar.

Nevertheless, it took more than six years of observations by Fermi's Large Area Telescope (LAT), as well as a complete reanalysis of all LAT data in a process called Pass 8, to detect gamma-ray pulsations from J0540. The Fermi data establish upper limits for gamma-ray pulses from J0537 but do not yet detect them.

Martin and his colleagues present these findings in a paper to be published in the Nov. 13 edition of the journal Science.

"The gamma-ray pulses from J0540 have 20 times the intensity of the previous record-holder, the pulsar in the famous Crab Nebula, yet they have roughly similar levels of radio, optical and X-ray emission," said coauthor Lucas Guillemot, at the Laboratory for Physics and Chemistry of Environment and Space, operated by CNRS and the University of Orléans in France. "Accounting for these differences will guide us to a better understanding of the extreme physics at work in young pulsars."

J0540 is a rare find, with an age of roughly 1,700 years, about twice that of the Crab Nebula pulsar. By contrast, most of the more than 2,500 known pulsars are from 10,000 to hundreds of millions of years old.

Despite J0540's luminosity, too few gamma rays reach the LAT to detect pulsations without knowing the period in advance. This information comes from a long-term X-ray monitoring campaign using RXTE, which recorded both pulsars from the start of the Fermi mission to the end of 2011, when RXTE operations ceased.

"This campaign began as a search for a pulsar created by SN 1987A, the closest supernova seen since the invention of the telescope," said co-author Francis Marshall, an astrophysicist at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "That search failed, but it discovered J0537."

Prior to the launch of Fermi in 2008, only seven gamma-ray pulsars were known. To date, the mission has found more than 160.

NASA's Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy and with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the United States.

---

Francis Reddy
NASA's Goddard Space Flight Center, Greenbelt, Maryland

Source: NASA/Fermi Space Telescope

Astronomers dissect the aftermath of a Supernova

A labeled panel of images showing different views of Supernova Remnant 1987A

Left Panel: SNR1987A as seen by the Hubble Space Telescope in 2010.Middle Panel: SNR1987A as seen by the Australia Telescope Compact Array (ATCA) in New South Wales and the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile. Right Panel: A computer generated visualisation of the remnant showing the possible location of a Pulsar. Credit: ATCA & ALMA Observations & data - G. Zanardo et al. / HST Image: NASA, ESA, K. France (University of Colorado, Boulder), P. Challis and R. Kirshner (Harvard-Smithsonian Center for Astrophysics). Labeled image - No labels image

A mosaic of images showing the latest observations of Supernova remnant 1987A at radio frequencies to the far infrared. Images below 100 GHz are from observations made with the ATCA telescope (NSW, Australia), and images above 100 GHz are from the ALMA telescope (Chile). The map on the bottom right of the mosaic is obtained by combining five images. This is used to investigate whether there is a pulsar wind nebula inside the remnant. Credit: G. Zanardo, ICRAR-UWA 

An outline of the equatorial ring and inner debris, as seen with the Hubble Space Telescope (green/blue contours), on top of ALMA observations of the remnant at 345 GHz (red/orange, with rendering). Credit: G. Zanardo, ICRAR-UWA

A simulated still showing components of Supernova Remnant 1987A. 

Credit: ICRAR

 

Dissecting a Supernova from ICRAR on Vimeo

A video compilation showing Supernova Remnant 1987A as seen by the Hubble Space Telescope in 2010, and by radio telescopes located in Australia and Chile in 2012. The piece ends with a computer generated visualisation of the remnant showing the possible location of a Pulsar.

Evolution of Supernova 1987A from ICRAR on Vimeo

A visualisation showing how Supernova1987A evolves between May of 1989 and July of 2014

Credit: Dr Toby Potter, ICRAR-UWA, Dr Rick Newton, ICRAR-UWA 

In research published today in the Astrophysical Journal, an Australian led team of astronomers has used radio telescopes in Australia and Chile to see inside the remains of a supernova. 

The supernova, known as SN1987A, was first seen by observers in the Southern Hemisphere in 1987 when a giant star suddenly exploded at the edge of a nearby dwarf galaxy called the Large Magellanic Cloud.

In the two and a half decades since then the remnant of Supernova 1987A has continued to be a focus for researchers the world over, providing a wealth of information about one of the Universe’s most extreme events.

PhD Candidate Giovanna Zanardo at The University of Western Australia node of the International Centre for Radio Astronomy Research led the team that used the Atacama Large Millimetre/submillimeter Array (ALMA) in Chile’s Atacama Desert and the Australia Telescope Compact Array (ATCA) in New South Wales to observe the remnant at wavelengths spanning the radio to the far infrared.

"By combining observations from the two telescopes we’ve been able to distinguish radiation being emitted by the supernova’s expanding shock wave from the radiation caused by dust forming in the inner regions of the remnant,” said Giovanna Zanardo of the International Centre for Radio Astronomy Research (ICRAR) in Perth, Western Australia.

"This is important because it means we’re able to separate out the different types of emission we’re seeing and look for signs of a new object which may have formed when the star's core collapsed. It's like doing a forensic investigation into the death of a star."

“Our observations with the ATCA and ALMA radio telescopes have shown signs of something never seen before, located at the centre or the remnant. It could be a pulsar wind nebula, driven by the spinning neutron star, or pulsar, which astronomers have been searching for since 1987. It’s amazing that only now, with large telescopes like ALMA and the upgraded ATCA, we can peek through the bulk of debris ejected when the star exploded and see what’s hiding underneath."

More research published recently in the Astrophysical Journal also attempts to shine a light on another long-standing mystery surrounding the supernova remnant. Since 1992 the radio emission from one side of the remnant has appeared ‘brighter’ than the other.  

In an effort to solve this puzzle, Dr Toby Potter, another researcher from ICRAR’s UWA node has developed a detailed three-dimensional simulation of the expanding supernova shockwave.

“By introducing asymmetry into the explosion and adjusting the gas properties of the surrounding environment, we were able to reproduce a number of observed features from the real supernova such as the persistent one-sidedness in the radio images”, said Dr Toby Potter.

The time evolving model shows that the eastern (left) side of the expanding shock front expands more quickly than the other side, and generates more radio emission than its weaker counterpart. This effect becomes even more apparent as the shock collides into the equatorial ring, as observed in Hubble Space Telescope images of the supernova.

"Our simulation predicts that over time the faster shock will move beyond the ring first. When this happens, the lop-sidedness of radio asymmetry is expected to be reduced and may even swap sides.”

“The fact that the model matches the observations so well means that we now have a good handle on the physics of the expanding remnant and are beginning to understand the composition of the environment surrounding the supernova – which is a big piece of the puzzle solved in terms of how the remnant of SN1987A formed.”


Supporting Multimedia:  

The animation and images below are available for download from this link.

Original publication details:

‘Spectral and Morphological Analysis of the Remnant of Supernova 1987a with ALMA & ATCA’ G. Zanardo, L. Staveley-Smith, R. Indebetouw et al. Published in the in the Astrophysical Journal November 10th, 2014. Pre-print paper available at: http://arxiv.org/abs/1409.7811 and http://iopscience.iop.org/0004-637X/796/2/82 after 8am EST, November 10th.

‘Multi-dimensional simulations of the expanding supernova remnant SN 1987a’ T.M Potter, L Staveley-Smith, B. Reville et al. Published in the Astrophysical Journal October 20th, 2014. Available at http://arxiv.org/abs/1409.4068 and http://iopscience.iop.org/0004-637X/794/2/174.

Further information:

ICRAR is a joint venture between Curtin University and The University of Western Australia with support and funding from the State Government of Western Australia. 

Contact Details:

Dr Giovana Zanardo, ICRAR - UWA 
Ph: +61 8 6488 7765 | M: +61 414 531 081
E: Giovanna.Zanardo@gmail.com

Professor Lister Staveley-Smith, ICRAR Science Director - UWA 
Ph: +61 8 6488 4550 | M: +61 425 212 592
E: Lister.Staveley-smith@icrar.org

Pete Wheeler, ICRAR Media Contact 
Ph: +61 8 6488 7771 | M: +61 423 982 018
E: Pete.Wheeler@icrar.org

David Stacey, UWA Media Manager 
Ph: +61 8 6488 7977 
E: David.Stacey@uwa.edu.au

Source: ICRAR - International Centre for Astronomy Research

Turquoise-tinted plumes in the Large Magellanic Cloud

Large Magellanic Cloud (LMC)

Credit: ESA/Hubble & NASA
Acknowledgement: Josh Barrington

The brightly glowing plumes seen in this image are reminiscent of an underwater scene, with turquoise-tinted currents and nebulous strands reaching out into the surroundings.

However, this is no ocean. This image actually shows part of the Large Magellanic Cloud (LMC), a small nearby galaxy that orbits our galaxy, the Milky Way, and appears as a blurred blob in our skies. The NASA/ESA Hubble Space Telescope has peeked many times into this galaxy, releasing stunning images of the whirling clouds of gas and sparkling stars (opo9944a, heic1301, potw1408a).

This image shows part of the Tarantula Nebula's outskirts. This famously beautiful nebula, located within the LMC, is a frequent target for Hubble (heic1206, heic1402). 

In most images of the LMC the colour is completely different to that seen here. This is because, in this new image, a different set of filters was used. The customary R filter, which selects the red light, was replaced by a filter letting through the near-infrared light. In traditional images, the hydrogen gas appears pink because it shines most brightly in the red. Here however, other less prominent emission lines dominate in the blue and green filters.

This data is part of the Archival Pure Parallel Project (APPP), a project that gathered together and processed over 1000 images taken using Hubble’s Wide Field Planetary Camera 2, obtained in parallel with other Hubble instruments. Much of the data in the project could be used to study a wide range of astronomical topics, including gravitational lensing and cosmic shear, exploring distant star-forming galaxies, supplementing observations in other wavelength ranges with optical data, and examining star populations from stellar heavyweights all the way down to solar-mass stars.

A version of this image was entered into the Hubble’s Hidden Treasures image processing competition by contestant Josh Barrington.

Source:  ESA/Hubble - Space Telescope

Hubble Watches Stars' Clockwork Motion in Nearby Galaxy

Stars' Clockwork Motion Captured in Nearby Galaxy

Image Credit: NASA, ESA, A. Feild and Z. Levay (STScI), Y. Beletsky (Las Campanas Observatory), and R. van der Marel (STScI) 

Science Credit: NASA, ESA, R. van der Marel (STScI), and N. Kallivayalil (University of Virginia). Release Images

This animation illustrates the rotation rate of the Large Magellanic Cloud (LMC). Hubble Space Telescope observations have determined that the central part of the LMC completes a rotation every 250 million years. Hence, it takes more than 10 million years for even the small amount of rotation illustrated here.

Credit: NASA, ESA, and G. Bacon, R. van der Marel, A. Feild, L. Frattare, Z. Levay, and F. Summers (STScI).  Acknowlegment: S. Guisard (http://sguisard.astrosurf.com/). Release Videos

Using the sharp-eyed NASA Hubble Space Telescope, astronomers have for the first time precisely measured the rotation rate of a galaxy based on the clock-like movement of its stars.

According to their analysis, the central part of the neighboring galaxy, called the Large Magellanic Cloud (LMC), completes a rotation every 250 million years. Coincidentally, it takes our Sun the same amount of time to complete a rotation around the center of our Milky Way galaxy.

The Hubble team, composed of Roeland van der Marel of the Space Telescope Science Institute in Baltimore, Md., and Nitya Kallivayalil of the University of Virginia in Charlottesville, Va., used Hubble to measure the average motion of hundreds of individual stars in the LMC, located 170,000 light-years away. Hubble recorded the stars' slight movements over a seven-year period.

Disk-shaped galaxies, like the Milky Way and the LMC, generally rotate like a carousel. Hubble's precision tracking offers a new way to determine a galaxy's rotation by the "sideways" proper motion of its stars, as seen in the plane of sky. Astronomers have long measured the sideways motions of nearby celestial objects, but this is the first time that the precision has become sufficient to see another distant galaxy rotate.

For the past century astronomers have calculated galaxy rotation rates by observing a slight shift in the spectrum — called the Doppler effect — of its starlight. On one side of a galaxy's spinning stellar disk, the stars swinging in the direction of Earth will show a spectral blueshift (the compression of light waves due to motion toward the observer). Stars swinging away from Earth on the opposite side of a galaxy will show a spectral redshift (the stretching of light to redder wavelengths due to motion away from the observer).

The newly measured Hubble sideways motions and the Doppler motions measured previously each provide complementary information about the LMC's rotation rate. By combining the results, the Hubble team for the first time obtained a fully three-dimensional view of stellar motions in another galaxy.

"Determining a galaxy's rotation by measuring its instantaneous back and forth motions doesn't allow one to actually see things change over time," said van der Marel, the lead author on a paper in the Feb. 1 issue of the Astrophysical Journal describing and interpreting the results. "By using Hubble to study the stars' motions over several years, we can actually for the first time see a galaxy rotate in the plane of the sky."

Kallivayalil, who led the data analysis, added: "Studying this nearby galaxy by tracking the stars' movements gives us a better understanding of the internal structure of disk galaxies. Knowing a galaxy's rotation rate offers insight into how a galaxy formed, and it can be used to calculate its mass."

Hubble is the only telescope that can make this kind of observation because of its sharp resolution, its image stability, and its 24 years in space. "If we imagine a human on the Moon," van der Marel explained, "Hubble's precision would allow us to determine the speed at which the person's hair grows."

"This precision is crucial, because the apparent stellar motions are so small because of the galaxy's distance," he said. "You can think of the LMC as a clock in the sky, on which the hands take 250 million years to make one revolution. We know the clock's hands move, but even with Hubble we need to stare at them for several years to see any movement."

The research team used Hubble's Wide Field Camera 3 and Advanced Camera for Surveys to observe stars in 22 fields spread across the vast disk of the LMC, which appears in the southern night sky as an object about 20 times the angular diameter of the full moon. Arrows on the accompanying image show the predicted motion over the next 7 million years, based on the Hubble measurements.

Each field was chosen to contain not only dozens of LMC stars, but also a background quasar, a brilliant beacon of light powered by a black hole in the core of a distant active galaxy. The astronomers needed the quasars as fixed background reference points to measure the extremely subtle motion of the LMC stars.

This measurement is the culmination of ongoing work with Hubble by van der Marel and another team to refine the LMC's rotation rate. Van der Marel began analyzing the galaxy's rotation in 2002 by creating detailed predictions, now confirmed by Hubble, of what the rotation should look like.

"The LMC is a very important galaxy because it is very near to our Milky Way," he said. "Studying the Milky Way is very hard because everything you see is spread all over the sky. It's all at different distances, and you're sitting in the middle of it. Studying structure and rotation is much easier if you view a nearby galaxy from the outside."

"Because the LMC is so nearby, it is a benchmark for studies of stellar evolution and populations. For this, it's important to understand the galaxy's structure," Kallivayalil said. "Our technique for measuring the galaxy's rotation rate using fully three-dimensional motions is a new way to shed light on that structure. It opens a new window to our understanding of how stars in galaxies move."

In addition to the LMC's own rotation, it is also moving around the Milky Way as a whole. In earlier science papers, the team and its collaborators used Hubble data to show that the LMC moves faster around the Milky Way than previously believed. This research has revised our understanding of how many times these neighboring galaxies might have met and interacted in the past.

The team next plans to use Hubble to measure the stellar motions in the LMC's diminutive cousin, the Small Magellanic Cloud, using the same technique. The galaxies are interacting, and that study should also yield improved insight into how the galaxies are moving around each other and around the Milky Way.

CONTACT

Donna Weaver / Ray Villard
Space Telescope Science Institute, Baltimore, Md.
410-338-4493 / 410-338-4514
dweaver@stsci.edu / villard@stsci.edu

Roeland van der Marel
Space Telescope Science Institute, Baltimore, Md.
410-338-4931
marel@stsci.edu

Source: Hubble Site

Hubble Finds Source of Magellanic Stream

The Magellanic Stream  

Credit for the radio/visible-light image: David L. Nidever et al., NRAO/AUI/NSF and A. Mellinger, LAB Survey, Parkes Observatory, Westerbork Observatory, and Arecibo Observatory. Credit for the radio image: LAB Surve. More Images

Astronomers using NASA's Hubble Space Telescope have solved a 40-year mystery on the origin of the Magellanic Stream, a long ribbon of gas stretching nearly halfway around our Milky Way galaxy.

The Large and Small Magellanic Clouds, two dwarf galaxies orbiting the Milky Way, are at the head of the gaseous stream. Since the stream's discovery by radio telescopes in the early 1970s, astronomers have wondered whether the gas comes from one or both of the satellite galaxies. Now, new Hubble observations reveal that most of the gas was stripped from the Small Magellanic Cloud about 2 billion years ago, and a second region of the stream originated more recently from the Large Magellanic Cloud.

A team of astronomers, led by Andrew J. Fox of the Space Telescope Science Institute in Baltimore, Md., and the European Space Agency, determined the source of the gas filament by using Hubble's Cosmic Origins Spectrograph (COS) to measure the amount of heavy elements, such as oxygen and sulfur, at six locations along the Magellanic Stream. COS observed faraway quasars whose emitted light passes through the stream and detected these elements from the way they absorb ultraviolet light. Quasars are the brilliant cores of active galaxies.

Fox's team found a low amount of oxygen and sulfur along most of the stream, matching the levels in the Small Magellanic Cloud about 2 billion years ago, when the gaseous ribbon was thought to have been formed.

In a surprising twist, the team discovered a much higher level of sulfur in a region closer to the Magellanic Clouds. "We're finding a consistent amount of heavy elements in the stream until we get very close to the Magellanic Clouds, and then the heavy element levels go up," said Fox. "This inner region is very similar in composition to the Large Magellanic Cloud, suggesting it was ripped out of that galaxy more recently."

This discovery was a wrinkle Fox's team didn't expect, because computer models of the stream predicted that the gas came entirely out of the Small Magellanic Cloud, which has less gravity than its more massive cousin.

"Only Hubble can measure these abundances," Fox explained. "You have to go to space because the absorption lines we need to measure these abundances are all in the ultraviolet, and Earth's atmosphere absorbs ultraviolet light."

Astronomers have debated whether the two Magellanic Clouds are on their first pass near our Milky Way or are bound to it.

"What's interesting is that all the other nearby satellite galaxies of the Milky Way have lost their gas," Fox said. "The Magellanic Clouds have been able to retain their gas and are still forming stars because they're more massive than the other satellites. However, as they're now approaching the Milky Way, they're feeling its gravity more and also encountering its halo of hot gas, which puts pressure on them. That process, together with the gravitational tug-of-war between the Magellanic Clouds, leads to the production of the stream. You're seeing material stripped out of the Clouds as they come in toward the Milky Way."

Ultimately, the gaseous stream may rain down onto the Milky Way's disk, fueling the birth of new stars. This infusion of fresh gas is part of one process that triggers star formation in a galaxy. Astronomers want to know the origin of that wayward gas in order to more fully understand how galaxies make new stars.

"We want to understand how galaxies like the Milky Way strip the gas from small galaxies that fall into them and use that to form new stars," Fox explained. "This seems like it's an episodic process. It's not a smooth process where a slow stream of gas comes in continuously. Instead, once in a while a large gas cloud falls in. We've got a way of testing that here, where two galaxies are coming in. We have shown which of them is producing the gas that ultimately will fall into the Milky Way."

The team reported its results in two papers that appeared in the Aug. 1 issue of The Astrophysical Journal. Fox is the lead author of one paper; the other paper's lead author is Philipp Richter of the University of Potsdam in Germany.

CONTACT

Donna Weaver / Ray Villard
Space Telescope Science Institute, Baltimore, Md.
410-338-4493/4514
dweaver@stsci.edu / villard@stsci.edu

Andrew Fox
Space Telescope Science Institute, Baltimore, Md.
410-338-5083
afox@stsci.edu

 

The Odd Couple

PR Image eso1335a

Two very different glowing gas clouds in the Large Magellanic Cloud

 

PR Image eso1335b

An odd couple of glowing gas clouds in the constellation of Dorado

 

PR Image eso1335c

Wide-field view of NGC 2014 and NGC 2020 in the Large Magellanic Cloud

Videos

PR Video eso1335a

Zooming in on glowing gas clouds NGC 2014 and NGC 2020

PR Video eso1335b

Pan across new VLT image of NGC 2014 and NGC 2020

Two very different gas clouds in the galaxy next door

ESO’s Very Large Telescope has captured an intriguing star-forming region in the Large Magellanic Cloud — one of the Milky Way’s satellite galaxies. This sharp image reveals two distinctive glowing clouds of gas: red-hued NGC 2014, and its blue neighbour NGC 2020. While they are very different, they were both sculpted by powerful stellar winds from extremely hot newborn stars that also radiate into the gas, causing it to glow brightly.

This image was taken by the Very Large Telescope (VLT) at ESO's Paranal Observatory in Chile — the best place in the southern hemisphere for astronomical observing. But even without the help of telescopes like the VLT, a glance towards the southern constellation of Dorado (The Swordfish or Dolphinfish [1]) on a clear, dark night reveals a blurry patch which, at first sight, appears to be just like a cloud in the Earth's atmosphere.

At least, this may have been explorer Ferdinand Magellan's first impression during his famous voyage to the southern hemisphere in 1519. Although Magellan himself was killed in the Philippines before his return, his surviving crew announced the presence of this cloud and its smaller sibling when they returned to Europe, and these two small galaxies were later named in Magellan's honour. However, they were undoubtedly seen by both earlier European explorers and observers in the southern hemisphere, although they were never reported.

The Large Magellanic Cloud (LMC) is actively producing new stars. Some of its star-forming regions can even be seen with the naked eye, for example, the famous Tarantula Nebula. However, there are other smaller — but no less intriguing — regions that telescopes can reveal in intricate detail. This new VLT image explores an oddly mismatched pair: NGC 2014 and NGC 2020.

The pink-tinged cloud on the right, NGC 2014, is a glowing cloud of mostly hydrogen gas. It contains a cluster of hot young stars. The energetic radiation from these new stars strips electrons from the atoms within the surrounding hydrogen gas, ionising it and producing a characteristic red glow.

In addition to this strong radiation, massive young stars also produce powerful stellar winds that eventually cause the gas around them to disperse and stream away. To the left of the main cluster, a single brilliant and very hot star [2] seems to have started this process, creating a cavity that appears encircled by a bubble-like structure called NGC 2020. The distinctive blueish colour of this rather mysterious object is again created by radiation from the hot star — this time by ionising oxygen instead of hydrogen.

The strikingly different colours of NGC 2014 and NGC 2020 are the result of both the different chemical makeup of the surrounding gas and the temperatures of the stars that are causing the clouds to glow. The distances between the stars and the respective gas clouds also play a role.

The LMC is only about 163 000 light-years from our galaxy, the Milky Way, and so is very close on a cosmic scale. This proximity makes it a very important target for astronomers, as it can be studied in far more detail than more distant systems. It was one of the motivations for building telescopes in the southern hemisphere, which led to the establishment of ESO over 50 years ago. Although enormous on a human scale, the LMC contains less than one tenth of the mass of the Milky Way, and spans just 14 000 light-years — by contrast, the Milky Way covers some 100 000 light-years. Astronomers refer to the LMC as an irregular dwarf galaxy; its irregularity, combined with its prominent central bar of stars, suggests that interactions with the Milky Way and another nearby galaxy, the Small Magellanic Cloud, could have caused its chaotic shape.

This image was acquired using the visual and near-ultraviolet FOcal Reducer and low dispersion Spectrograph (FORS2) instrument attached to ESO's VLT, as part of the ESO Cosmic Gems programme [3].

Notes

[1] Although this constellation is often identified with the swordfish there are reasons to think that the less commonly known dolphinfish may be a better match. More details are given here.

[2] This star is an example of a rare class called Wolf-Rayet stars. These short-lived objects are very hot — their surfaces can be more than ten times as hot as the surface of the Sun — and very bright and dominate the regions around them.

[3] This picture comes from the ESO Cosmic Gems programme, an outreach initiative to produce images of interesting, intriguing or visually attractive objects using ESO telescopes, for the purposes of education and public outreach. The programme makes use of telescope time that cannot be used for science observations. All data collected may also be suitable for scientific purposes, and are made available to astronomers through ESO’s science archive.

More information

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning the 39-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Links

• ESO Cosmic Gems programme
• Photos of the VLT
• Images taken with FORS
• Images taken with the VLT

Contacts

Richard Hook
ESO, Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org

 

Measuring the Universe More Accurately Than Ever Before

PR Image eso1311a

Artist’s impression of eclipsing binary

PR Image eso1311b

Explanation of eclipsing binaries

PR Image eso1311c

Map of the Large Magellanic Cloud

  Videos

PR Video eso1311a

Zooming in on an eclipsing binary in the Large Magellanic Cloud

PR Video eso1311b

Artist’s impression of eclipsing binary

New results pin down the distance to the galaxy next door

After nearly a decade of careful observations an international team of astronomers has measured the distance to our neighbouring galaxy, the Large Magellanic Cloud, more accurately than ever before. This new measurement also improves our knowledge of the rate of expansion of the Universe — the Hubble Constant — and is a crucial step towards understanding the nature of the mysterious dark energy that is causing the expansion to accelerate. The team used telescopes at ESO’s La Silla Observatory in Chile as well as others around the globe. These results appear in the 7 March 2013 issue of the journal Nature.

Astronomers survey the scale of the Universe by first measuring the distances to close-by objects and then using them as standard candles [1] to pin down distances further and further out into the cosmos. But this chain is only as accurate as its weakest link. Up to now finding an accurate distance to the Large Magellanic Cloud (LMC), one of the nearest galaxies to the Milky Way, has proved elusive. As stars in this galaxy are used to fix the distance scale for more remote galaxies, it is crucially important.

But careful observations of a rare class of double star have now allowed a team of astronomers to deduce a much more precise value for the LMC distance: 163 000 light-years.

“I am very excited because astronomers have been trying for a hundred years to accurately measure the distance to the Large Magellanic Cloud, and it has proved to be extremely difficult,” says Wolfgang Gieren (Universidad de Concepción, Chile) and one of the leaders of the team. “Now we have solved this problem by demonstrably having a result accurate to 2%.”

The improvement in the measurement of the distance to the Large Magellanic Cloud also gives better distances for many Cepheid variable stars [2]. These bright pulsating stars are used as standard candles to measure distances out to more remote galaxies and to determine the expansion rate of the Universe — the Hubble Constant. This in turn is the basis for surveying the Universe out to the most distant galaxies that can be seen with current telescopes. So the more accurate distance to the Large Magellanic Cloud immediately reduces the inaccuracy in current measurements of cosmological distances.

The astronomers worked out the distance to the Large Magellanic Cloud by observing rare close pairs of stars, known as eclipsing binaries [3]. As these stars orbit each other they pass in front of each other. When this happens, as seen from Earth, the total brightness drops, both when one star passes in front of the other and, by a different amount, when it passes behind [4].

By tracking these changes in brightness very carefully, and also measuring the stars’ orbital speeds, it is possible to work out how big the stars are, their masses and other information about their orbits. When this is combined with careful measurements of the total brightness and colours of the stars [5] remarkably accurate distances can be found.

This method has been used before, but with hot stars. However, certain assumptions have to be made in this case and such distances are not as accurate as is desirable. But now, for the first time, eight extremely rare eclipsing binaries where both stars are cooler red giant stars have been identified [6]. These stars have been studied very carefully and yield much more accurate distance values — accurate to about 2%.

“ESO provided the perfect suite of telescopes and instruments for the observations needed for this project: HARPS for extremely accurate radial velocities of relatively faint stars, and SOFI for precise measurements of how bright the stars appeared in the infrared,” adds Grzegorz Pietrzyński (Universidad de Concepción, Chile and Warsaw University Observatory, Poland), lead author of the new paper in Nature.

 

“We are working to improve our method still further and hope to have a 1% LMC distance in a very few years from now. This has far-reaching consequences not only for cosmology, but for many fields of astrophysics,” concludes Dariusz Graczyk, the second author on the new Nature paper.

Notes

[1] Standard candles are objects of known brightness. By observing how bright such an object appears astronomers can work out the distance — more distant objects appear fainter. Examples of such standard candles are Cepheid variables [2] and Type Ia supernovae. The big difficulty is calibrating the distance scale by finding relatively close examples of such objects where the distance can be determined by other means.

[2] Cepheid variables are bright unstable stars that pulsate and vary in brightness. But there is a very clear relationship between how quickly they change and how bright they are. Cepheids that pulsate more quickly are fainter than those that pulsate more slowly. This period-luminosity relation allows them to be used as standard candles to measure the distances of nearby galaxies.

[3] This work is part of the long-term Araucaria Project to improve measurements of the distances to nearby galaxies.

[4] The exact light variations depend on the relative sizes of the stars, their temperatures and colours and the details of the orbit.

[5] The colours are measured by comparing the brightness of the stars at different near-infrared wavelengths.

[6] These stars were found by searching the 35 million LMC stars that were studied by the OGLE project.

More information

This research was presented in a paper “An eclipsing binary distance to the Large Magellanic Cloud accurate to 2 per cent”, by G. Pietrzyński et al., to appear in the 7 March 2013 issue of the journal Nature.

The team is composed of G. Pietrzyński (Universidad de Concepción, Chile; Warsaw University Observatory, Poland), D. Graczyk (Universidad de Concepción), W. Gieren (Universidad de Concepción), I. B. Thompson (Carnegie Observatories, Pasadena, USA), B., Pilecki (Universidad de Concepción; Warsaw University Observatory), A. Udalski (Warsaw University Observatory), I. Soszyński (Warsaw University Observatory), S. Kozłowski (Warsaw University Observatory), P. Konorski (Warsaw University Observatory), K. Suchomska (Warsaw University Observatory), G. Bono (Università di Roma Tor Vergata, Rome, Italy; INAF-Osservatorio Astronomico di Roma, Italy), P. G. Prada Moroni (Università di Pisa, Italy; INFN, Pisa, Italy), S. Villanova (Universidad de Concepción ), N. Nardetto (Laboratoire Fizeau, UNS/OCA/CNRS, Nice, France),  F. Bresolin (Institute for Astronomy, Hawaii, USA), R. P. Kudritzki (Institute for Astronomy, Hawaii, USA), J. Storm (Leibniz Institute for Astrophysics, Potsdam, Germany), A. Gallenne (Universidad de Concepción), R. Smolec (Nicolaus Copernicus Astronomical Centre, Warsaw, Poland), D. Minniti (Pontificia Universidad Católica de Chile, Santiago, Chile; Vatican Observatory, Italy), M. Kubiak (Warsaw University Observatory), M. Szymański (Warsaw University Observatory), R. Poleski (Warsaw University Observatory), Ł. Wyrzykowski (Warsaw University Observatory), K. Ulaczyk (Warsaw University Observatory), P. Pietrukowicz (Warsaw University Observatory), M. Górski (Warsaw University Observatory), P. Karczmarek (Warsaw University Observatory).

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning the 39-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Links

• Research paper in Nature
• Photos of HARPS/3.6m
• Photos of NTT
• Photos taken using SOFI

Contacts

Grzegorz Pietrzyński
Universidad de Concepción
Chile
Tel: +56 41 220 7268
Cell: +56 9 6245 4545
Email: pietrzyn@astrouw.edu.pl

Wolfgang Gieren
Universidad de Concepción
Chile
Tel: +56 41 220 3103
Cell: +56 9 8242 8925
Email: wgieren@astro-udec.cl

Richard Hook
ESO, Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org

A hidden treasure in the Large Magellanic Cloud

 PR Image heic1301a
LHA 120-N11 in the Large Magellanic Cloud 

PR Image heic1301b
Overview of the Large Magellanic Cloud (ground-based image)

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PR Video heic1301a
Zoom into LHA 120-N11

PR Video heic1301b
Pan across LHA 120-N11

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 [1], giving us a bird’s eye view.

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, see heic1011) 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 contrasting the light from glowing hydrogen and nitrogen in N11. The image above combines the data he identified with additional exposures taken in blue, green and near infrared light.

Notes

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

[1] Although the Large Magellanic Cloud is generally classified as an irregular galaxy, it shares some features with spiral galaxies, including a clearly visible bar, and a single spiral-arm-like structure. It is thought that the LMC may be a small spiral galaxy that was pulled out of shape by the Milky Way.

Links

• Hidden Treasures

• Josh Lake's image of N11

Contacts

Oli Usher
Hubble/ESA
Garching, Germany
Tel: +49-89-3200-6855
Email: ousher@eso.org

NGC 1929 in N44: A Surprisingly Bright Superbubble

Credit X-ray: NASA/CXC/U.Mich./S.Oey,

IR: NASA/JPL, Optical: ESO/WFI/2.2-m

View Wavelengths: Composite - X-ray - Infrared - Optical

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This composite image shows a superbubble in the Large Magellanic Cloud (LMC), a small satellite galaxy of the Milky Way, located about 160,000 light years from Earth. Many new stars, some of them very massive, are forming in the star cluster NGC 1929, which is embedded in the nebula N44. The massive stars produce intense radiation, expel matter at high speeds, and race through their evolution to explode as supernovas. The winds and supernova shock waves carve out huge cavities called superbubbles in the surrounding gas. X-rays from NASA's Chandra X-ray Observatory (blue) show hot regions created by these winds and shocks, while infrared data from NASA's Spitzer Space Telescope (red) outline where the dust and cooler gas are found. The optical light from the 2.2m Max-Planck-ESO telescope (yellow) in Chile shows where ultraviolet radiation from hot, young stars is causing gas in the nebula to glow.

A long-running problem in high-energy astrophysics has been that some superbubbles in the LMC, including N44, give off a lot more X-rays than expected from models of their structure. A Chandra study published in 2011 showed that there are two extra sources of the bright X-ray emission: supernova shock waves striking the walls of the cavities, and hot material evaporating from the cavity walls. The observations show no evidence for an enhancement of elements heavier than hydrogen and helium in the cavities, thus ruling out this possibility as an explanation for the bright X-ray emission. This is the first time that the data have been good enough to distinguish between different sources of the X-rays produced by superbubbles.

The Chandra study of N44 and another superbubble in the LMC was led by Anne Jaskot from the University of Michigan in Ann Arbor. The co-authors were Dave Strickland from Johns Hopkins University in Baltimore, MD, Sally Oey from University of Michigan, You-Hua Chu from University of Illinois and Guillermo Garcia-Segura from Instituto de Astronomia-UNAM in Ensenada, Mexico.

NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.

Fast Facts for NGC 1929:

Release Date: August 30, 2012
Scale: Image is 25 arcmin across (1200 light years)
Category: Normal Stars & Star Clusters
Coordinates: (J2000) RA 05h 22m 17.00s | Dec -67° 76' 38.00"
Constellation: Dorado
Observation Date: Sept 22, 2002
Observation Time: 5 hours 33 min.
Obs. ID: 3356
Instrument: ACIS
References: Jaskot, A.E. et al 2011, ApJ, 729, 28; arXiv:1101.0280

Herschel and Spitzer See Nearby Galaxies' Stardust

This new image shows the Large Magellanic Cloud galaxy in infrared light as seen by the Herschel Space Observatory, a European Space Agency-led mission with important NASA contributions, and NASA's Spitzer Space Telescope. Image credit: ESA/NASA/JPL-Caltech/STScI. Full image and caption

This new image shows the Small Magellanic Cloud galaxy in infrared light from the Herschel Space Observatory a European Space Agency-led mission with important NASA contributions, and NASA's Spitzer Space Telescope. Image credit: ESA/NASA/JPL-Caltech/STScI. Full image and caption - enlarge image

PASADENA, Calif. - The cold dust that builds blazing stars is revealed in new images that combine observations from the Herschel Space Observatory, a European Space Agency-led mission with important NASA contributions; and NASA's Spitzer Space Telescope. The new images map the dust in the galaxies known as the Large and Small Magellanic Clouds, two of the closest neighbors to our own Milky Way galaxy.

The new images are available at the following links: http://www.nasa.gov/mission_pages/herschel/multimedia/pia15254.html and http://www.nasa.gov/mission_pages/herschel/multimedia/pia15255.html

The Large Magellanic Cloud looks like a fiery, circular explosion in the combined Herschel-Spitzer infrared data. Ribbons of dust ripple through the galaxy, with significant fields of star formation noticeable in the center, center-left and top right (the brightest center-left region is called 30 Doradus, or the Tarantula Nebula, for its appearance in visible light). The Small Magellanic Cloud has a much more irregular shape. A stream of dust extends to the left in this image, known as the galaxy's "wing," and a bar of star formation appears on the right.

The colors in these images indicate temperatures in the dust that permeate the Magellanic Clouds. Colder regions show where star formation is at its earliest stages or is shut off, while warm expanses point to new stars heating dust surrounding them. The coolest areas and objects appear in red, corresponding to infrared light taken up by Herschel's Spectral and Photometric Imaging Receiver at 250 microns, or millionths of a meter. Herschel's Photodetector Array Camera and Spectrometer fills out the mid-temperature bands, shown in green, at 100 and 160 microns. The warmest spots appear in blue, courtesy of 24- and 70-micron data from Spitzer.

"Studying these galaxies offers us the best opportunity to study star formation outside of the Milky Way," said Margaret Meixner, an astronomer at the Space Telescope Science Institute, Baltimore, Md., and principal investigator for the mapping project. "Star formation affects the evolution of galaxies, so we hope understanding the story of these stars will answer questions about galactic life cycles."

The Large and Small Magellanic Clouds are the two biggest satellite galaxies of our home galaxy, the Milky Way, though they are still considered dwarf galaxies compared to the big spiral of the Milky Way. Dwarf galaxies also contain fewer metals, or elements heavier than hydrogen and helium. Such an environment is thought to slow the growth of stars. Star formation in the universe peaked around 10 billion years ago, even though galaxies contained lesser abundances of metallic dust. Previously, astronomers only had a general sense of the rate of star formation in the Magellanic Clouds, but the new images enable them to study the process in more detail.

The results were presented today at the 219th meeting of the American Astronomical Society in Austin, Texas.

Herschel is a European Space Agency cornerstone mission, with science instruments provided by consortia of European institutes and with important participation by NASA. NASA's Herschel Project Office is based at NASA's Jet Propulsion Laboratory, Pasadena, Calif. JPL contributed mission-enabling technology for two of Herschel's three science instruments. The NASA Herschel Science Center, part of the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena, supports the United States' astronomical community.

JPL manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at Caltech. Caltech manages JPL for NASA.

For more information about Herschel, visit http://www.herschel.caltech.edu, http://www.nasa.gov/herschel and http://www.esa.int/SPECIALS/Herschel/index.html.

For more information about Spitzer, visit http://spitzer.caltech.edu/ and http://www.nasa.gov/spitzer .

Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.
whitney.clavin@jpl.nasa.gov

Trent J. Perrotto 202-358-0321
NASA Headquarters, Washington
trent.j.perrotto@nasa.gov