Friday, May 31, 2013

The messy result of a galactic collision

Credit: ESA/Hubble & NASA
Acknowledgement: Luca Limatola
This new image from the NASA/ESA Hubble Space Telescope captures an ongoing cosmic collision between two galaxies — a spiral galaxy is in the process of colliding with a lenticular galaxy. The collision looks almost as if it is popping out of the screen in 3D, with parts of the spiral arms clearly embracing the lenticular galaxy’s bulge.

The image also reveals further evidence of the collision. There is a bright stream of stars coming out from the merging galaxies, extending out towards the right of the image. The bright spot in the middle of the plume, known as ESO 576-69, is what makes this image unique. This spot is believed to be the nucleus of the former spiral galaxy, which was ejected from the system during the collision and is now being shredded by tidal forces to produce the visible stellar stream.

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

Thursday, May 30, 2013

NASA's Swift Reveals New Phenomenon in a Neutron Star

Astronomers using NASA's Swift X-ray Telescope have observed a spinning neutron star suddenly slowing down, yielding clues they can use to understand these extremely dense objects.

A neutron star is the crushed core of a massive star that ran out of fuel, collapsed under its own weight, and exploded as a supernova. A neutron star can spin as fast as 43,000 times per minute and boast a magnetic field a trillion times stronger than Earth's. Matter within a neutron star is so dense a teaspoonful would weigh about a billion tons on Earth.

An artist's rendering of an outburst on an ultra-magnetic neutron star, also called a magnetar.Credit: NASA's Goddard Space Flight Center.  › Larger image -  › Download additional graphics from NASA Goddard's Scientific Visualization Studio

This neutron star, 1E 2259+586, is located about 10,000 light-years away toward the constellation Cassiopeia. It is one of about two dozen neutron stars called magnetars, which have very powerful magnetic fields and occasionally produce high-energy explosions or pulses.

Observations of X-ray pulses from 1E 2259+586 from July 2011 through mid-April 2012 indicated the magnetar's rotation was gradually slowing from once every seven seconds, or about eight revolutions per minute. On April 28, 2012, data showed the spin rate had decreased abruptly, by 2.2 millionths of a second, and the magnetar was spinning down at a faster rate.

The magnetar 1E 2259+586 shines a brilliant blue-white in this false-color X-ray image of the CTB 109 supernova remnant, which lies about 10,000 light-years away toward the constellation Cassiopeia. CTB 109 is only one of three supernova remnants in our galaxy known to harbor a magnetar. X-rays at low, medium and high energies are respectively shown in red, green, and blue in this image created from observations acquired by the European Space Agency's XMM-Newton satellite in 2002. Credit: ESA/XMM-Newton/M. Sasaki et al. › Larger image - › Download additional graphics from NASA Goddard's Scientific Visualization Studio

"Astronomers have witnessed hundreds of events, called glitches, associated with sudden increases in the spin of neutron stars, but this sudden spin-down caught us off guard," said Victoria Kaspi, a professor of physics at McGill University in Montreal. She leads a team that uses Swift to monitor magnetars routinely.

Astronomers dubbed the event an "anti-glitch," said co-author Neil Gehrels, principal investigator of the Swift mission at NASA's Goddard Space Flight Center in Greenbelt, Md. "It affected the magnetar in exactly the opposite manner of every other clearly identified glitch seen in neutron stars."

The discovery has important implications for understanding the extreme physical conditions present within neutron stars, where matter becomes squeezed to densities several times greater than an atomic nucleus. No laboratory on Earth can duplicate these conditions.

A report on the findings appears in the May 30 edition of the journal Nature.

A neutron star is the densest object astronomers can observe directly, crushing half a million times Earth's mass into a sphere about 12 miles across, or similar in size to Manhattan Island, as shown in this illustration. Credit: NASA's Goddard Space Flight Center. › Larger image - › Download additional graphics from NASA Goddard's Scientific Visualization Studio

The internal structure of neutron stars is a long-standing puzzle. Current theory maintains a neutron star has a crust made up of electrons and ions; an interior containing oddities that include a neutron superfluid, which is a bizarre state of matter without friction; and a surface that accelerates streams of high-energy particles through the star's intense magnetic field.
The streaming particles drain energy from the crust. The crust spins down, but the fluid interior resists being slowed. The crust fractures under the strain. When this happens, a glitch occurs. There is an X-ray outburst and the star gets a speedup kick from the faster-spinning interior.

Processes that lead to a sudden rotational slowdown constitute a new theoretical challenge.

On April 21, 2012, just a week before Swift observed the anti-glitch, 1E 2259+586 produced a brief, but intense X-ray burst detected by the Gamma-ray Burst Monitor aboard NASA's Fermi Gamma-ray Space Telescope. The scientists think this 36-millisecond eruption of high-energy light likely signaled the changes that drove the magnetar's slowdown.

"What is really remarkable about this event is the combination of the magnetar's abrupt slowdown, the X-ray outburst, and the fact we now observe the star spinning down at a faster rate than before," said lead author Robert Archibald, a graduate student at McGill.

Goddard manages Swift, which was launched in November 2004. The telescope is operated in collaboration with Pennsylvania State University in University Park, Pa., the Los Alamos National Laboratory in New Mexico and Orbital Sciences Corp. in Dulles, Va. International collaborators are in the United Kingdom and Italy, and the mission includes contributions from Germany and Japan.

Related Links

› Download additional graphics from NASA Goddard's Scientific Visualization Studio
› Penn State press release
› "NASA Taps the Power of Zombie Stars in Two-in-One Instrument" (04.05.13)
› "New NASA Explorer Mission to Uncover Physics of Neutron Stars and Demonstrate Game-Changing Navigation Technology" (04.05.13)
› "NASA's Chandra Finds Superfluid in Neutron Star's Core" (02.23.11)
› "Eclipsing Pulsar Promises Clues to Crushed Matter" (08.17.10)
› The McGill Pulsar Group's Magnetar Catalog
› NASA's Swift mission
› NASA's Fermi Gamma-ray Space Telescope

Francis Reddy
NASA's Goddard Space Flight Center, Greenbelt, Md.

Wednesday, May 29, 2013

Low Sodium Diet Key to Old Age for Stars

The globular star cluster NGC 6752
The globular star cluster NGC 6752 in the constellation of Pavo 


Zooming in on the globular star cluster NGC 6752
Zooming in on the globular star cluster NGC 6752

A close look at the globular star cluster NGC 6752
A close look at the globular star cluster NGC 6752

New VLT observations create major headache for stellar theories

Astronomers expect that stars like the Sun will blow off much of their atmospheres into space near the ends of their lives. But new observations of a huge star cluster made using ESO’s Very Large Telescope have shown — against all expectations — that a majority of the stars studied simply did not get to this stage in their lives at all. The international team found that the amount of sodium in the stars was a very strong predictor of how they ended their lives.

The way in which stars evolve and end their lives was for many years considered to be well understood. Detailed computer models predicted that stars of a similar mass to the Sun would have a period towards the ends of their lives — called the asymptotic giant branch, or AGB [1] — when they undergo a final burst of nuclear burning and puff off a lot of their mass in the form of gas and dust.

This expelled material [2] goes on to form the next generations of stars and this cycle of mass loss and rebirth is vital to explain the evolving chemistry of the Universe. This process is also what provides the material required for the formation of planets — and indeed even the ingredients for organic life.

But when Australian stellar theory expert Simon Campbell of the Monash University Centre for Astrophysics, Melbourne, scoured old papers he found tantalising suggestions that some stars may somehow not follow the rules and might skip the AGB phase entirely. He takes up the story:

“For a stellar modelling scientist this suggestion was crazy! All stars go through the AGB phase according to our models. I double-checked all the old studies but found that this had not been properly investigated. I decided to investigate myself, despite having little observational experience.”

Campbell and his team used ESO’s Very Large Telescope (VLT) to very carefully study the light coming from stars in the globular star cluster NGC 6752 in the southern constellation of Pavo (The Peacock). This vast ball of ancient stars contains both a first generation of stars and a second that formed somewhat later [3]. The two generations can be distinguished by the amount of sodium they contain — something that the very high-quality VLT data can be used to measure.

“FLAMES, the multi-object high-resolution spectrograph on the VLT, was the only instrument that could allow us to get really high-quality data for 130 stars at a time. And it allowed us to observe a large part of the globular cluster in one go,” adds Campbell.

The results were a surprise — all of the AGB stars in the study were first generation stars with low levels of sodium and none of the higher-sodium second generation stars had become AGB stars at all. As many as 70% of the stars were not undergoing the final nuclear burning and mass-loss phase [4] [5].

“It seems stars need to have a low-sodium “diet” to reach the AGB phase in their old age. This observation is important for several reasons. These stars are the brightest stars in globular clusters — so there will be 70% fewer of the brightest stars than theory predicts. It also means our computer models of stars are incomplete and must be fixed!” concludes Campbell.

The team expects that similar results will be found for other star clusters and further observations are planned.


[1] AGB stars get their odd name because of their position on the Hertzsprung Russell diagram, a plot of the brightnesses of stars against their colours.

[2] For a short period of time this ejected material is lit up by the strong ultraviolet radiation from the star and creates a planetary nebula (see for instance eso1317).

[3] Although the stars in a globular cluster all formed at about the same time, it is now well established that these systems are not as simple as they once thought to be. They usually contain two or more populations of stars with different amounts of light chemical elements such as carbon, nitrogen and — crucially for this new study — sodium.

[4] It is thought that stars which skip the AGB phase will evolve directly into helium white dwarf stars and gradually cool down over many billions of years.

[5] It is not thought that the sodium itself is the cause of the different behaviour, but must be strongly linked to the underlying cause — which remains mysterious.


More information

This research was presented in a paper entitled “Sodium content as a predictor of the advanced evolution of globular cluster stars” by Simon Campbell et al., to appear online in the journal Nature on 29 May 2013.

The team is composed of Simon W. Campbell (Monash University, Melbourne, Australia), Valentina D’Orazi (Macquarie University, Sydney, Australia; Monash University), David Yong (Australian National University, Canberra, Australia [ANU]), Thomas N. Constantino (Monash University), John C. Lattanzio (Monash University), Richard J. Stancliffe (ANU; Universität Bonn, Germany), George C. Angelou (Monash University), Elizabeth C. Wylie-de Boer (ANU), Frank Grundahl (Aarhus University, Denmark).

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”.





Simon Campbell
Monash University
Melbourne, Australia
Tel: +61 3 9905 4454

John Lattanzio
Monash University
Melbourne, Australia
Tel: +61 3 9905 4428

Richard Hook
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591

The Rapid Assembly of an Elliptical Galaxy of 400 Billion Solar Masses at a Redshift of 2.3

A rare encounter between two gas-rich galaxies indicates a solution to the problem of how giant elliptical galaxies developed so quickly in the early universe and why they stopped producing stars soon after. 

The galaxy pair was initially identified by ESA’s Herschel space observatory as a single bright source, named HXMM01. Follow-up observations using both space and ground-based telescopes, including the William Herschel Telescope (WHT), showed that it is in fact two interacting galaxies, each boasting a stellar mass equal to about 100 billion Suns and a similar mass of gas. 

The galaxies are the most efficient star-forming factory ever found in the Universe at this epoch, when the Universe was only 3 billion years old. Such a high star-formation rate is not sustainable, however, and the gas reservoir contained in the HXMM01 system will be quickly exhausted, quenching further star formation and leading to an aging population of low-mass, cool, red stars. Astronomers estimate that it will take about 200 million years to convert all the gas into stars, with the merging process completed within a billion years. The final product will be a massive red and dead elliptical galaxy of about 400 billion solar masses. 

It was long assumed that the large elliptical galaxies seen in the Universe today built up gradually over time via the gravitational acquisition of many small dwarf galaxies. The theory held that the gas in those galaxies would gradually be converted into cool, low-mass stars, so that by today they would have exhausted all of their star-forming material, leaving them ‘red and dead’. 

So the discovery in the last decade that very massive elliptical galaxies had managed to form during just the first 3–4 billion years of the Universe’s history posed something of a conundrum. Somehow, on short cosmological timescales, these galaxies had rapidly assembled vast quantities of stars and then ‘switched off’. 

One idea is that two spiral galaxies might collide and merge to produce a vast elliptical galaxy, with the collision triggering such a massive burst of star formation that it would rapidly deplete the gas reservoir. In the present study, astronomers have captured the onset of this short-lived process between two massive galaxies, providing the best observational evidence that massive elliptical galaxies can rapidly assemble from the merger of two spiral galaxies in the early Universe. 

Images of HXMM01 and its two major components, X01N and X01S, obtained using the CFHT, HST, WHT and Spitzer telescopes. The images of the WHT, obtained in the J and Ks bands using LIRIS instrument, are part of an International Time Programme, principal investigator: Pérez-Fournon (IAC). All images are 16"×14" and are aligned, with N up and E to the left. The ticks are at intervals of 2". For each filter, the original image is shown on the left and the residual image after subtracting the two foreground galaxies is shown on the right. The apertures used for photometry are outlined in the residual images (blue - X01N; red - X01S). [ JPEG | TIFF ]

More information

Research reference:

  • H. Fu et al. 2013, "The rapid assembly of an elliptical galaxy of 400 billion solar masses at a redshift of 2.3", Nature, doi:10.1038/nature12184 [ Paper | Supplementary information ]
Web sites:
Press releases:
  • "Descubren cómo se formaron las galaxias 'muertas' del universo temprano", IAC Press Release, 22/05/2013.
  • "Rare merger reveals secrets of galaxy evolution", ESA Press Release, 22/05/2013.
  • "Herschel Space Observatory Finds Galaxy Mega Merger", NASA/JPL Press Release, 22 May 2013.
  • "Fragile Mega-Galaxy is Missing Link in History of Cosmos: UC Irvine Discovery is Confirmed by Observatories Around the World", UC Irvine Press Release, 22 May 2013.
  • "Mega-Galaxy is Missing Link in History of Cosmos", Keck Press Release, 22 May 2013.

Source: Isaac Newton Group of Telescopes
Contact: Javier Méndez  (Public Relations Officer)

Tuesday, May 28, 2013

Sun Releases Slow CME

These three images show a coronal mass ejection, or CME, erupting into space on May 26, 2013. The pictures were captured by the ESA/NASA Solar Heliospheric Observatory with its coronagraph, which blocks out the bright light of the sun to better see its dimmer atmosphere, the corona. Credit: ESA&NASA/SOHO.  › View larger - › View unlabeled version

On May 26, 2013 at 3:24 p.m. EDT, the sun erupted with a coronal mass ejection or CME, a solar phenomenon that can send billions of tons of solar particles into space that can affect electronic systems in satellites. Experimental NASA research models show that the CME was not Earth-directed and it left the sun at 550 miles per second. It may, however, pass by STEREO A and its mission operators have been notified. The spacecraft can be put into safe mode if warranted.

NOAA's Space Weather Prediction Center ( is the U.S. government's official source for space weather forecasts, alerts, watches and warnings.

Updates will be provided as needed.

Related Links
› Frequently Asked Questions Regarding Space Weather
› View Other Past Solar Activity
Karen C. Fox
NASA's Goddard Space Flight Center, Greenbelt, MD.

Astronomers team up with the public to solve decade old puzzle

Schematic diagram of the white dwarf binary system SS Cygni. The two stars are close enough to one another that gas falls in from the companion star and swirls around the white dwarf in an accretion disc. The disc gets very hot, producing radiation that illuminates the surface of the companion star and heats it up. Gas from the inner part of the disc is accelerated outwards in fast-moving, oppositely-directed jets, which produce the radio waves that the astronomers used to study the star system and measure its distance from Earth. Image credit: J. Miller-Jones (ICRAR), using software created by R. Hynes.

The white dwarf and its companion star are separated by just under a million miles, and orbit each other once every six and a half hours. The strong gravity of the white dwarf distorts the companion star, so that gas from the star falls in towards the white dwarf via an accretion disc.
The disc gets so hot that it heats the facing surface of the companion star. Fast-moving jets are launched from the central parts of the disc and give off radio waves.
Astronomers used these radio waves to measure the distance to the star system as 372 light years from Earth. Credit: J. Miller-Jones (ICRAR), using software created by R. Hynes.

Measuring the distance to SS Cygni using the parallax technique. As the Earth orbits the Sun, SS Cygni appears to move back and forth relative to the position of a distant background galaxy, which is so far away that it stays stationary on the sky. The size of the apparent “wobble” of SS Cygni gives a direct measure of the distance; the further away SS Cygni is from Earth, the smaller the wobble. Image credit: J. Miller-Jones (ICRAR). An animation of the orbit of the white dwarf binary star system SS Cygni.

An extremely precise measurement of the distance to a star system has finally allowed astronomers to solve a decade-old puzzle, confirming understanding of the way exotic objects like black holes interact with nearby stars.

Published today in prestigious journal Science, a team of astronomers headed by Dr James Miller-Jones from the Curtin University node of the International Centre for Radio Astronomy Research (ICRAR), have measured the distance to star system SS Cygni to be 372 light years, much closer than a previous measurement made by the Hubble Space Telescope in the 1990s.

The measurement was made possible by amateur astronomers from the American Association of Variable Star Observers (AAVSO) who alerted the team to changes in the compact star system, triggering the team to start observations with two of the world’s most accurate radio telescopes.

Dr Miller-Jones’ team then measured the annual wobble of the system compared to distant background galaxies, allowing them to measure the distance to SS Cygni with unprecedented precision

“If you hold your finger out at arm’s length and move your head from side to side, you should see your finger appear to wobble against the background. If you move your finger closer to your head, you’ll see it starts to wobble more. We did the exact same thing with SS Cygni - we measured how far it moved against some very distant galaxies as the Earth moved around the Sun,” Dr James Miller-Jones said.

“The wobble we were detecting is the equivalent of trying to see someone stand up in New York from as far as away as Sydney.”

The distance to SS Cygni had previously been measured using the Hubble Space Telescope, producing a puzzling result that was much further than predicted.

“If SS Cygni was actually as far away as Hubble measured then it was far too bright to be what we thought it was, and we would have had to rethink the physics of how systems like this worked,” Dr Miller-Jones said.

Dr Miller-Jones said that SS Cygni is a double star system containing a normal low mass star and a white dwarf star.

A white dwarf is the remnant of a star like our Sun that has run out of fuel and collapsed into an object about the size of Earth. Because it’s so dense, its strong gravity strips gas off its companion star, which then swirls around the white dwarf.

Occasionally the flow of gas onto the white dwarf will increase dramatically, causing the system to appear up to 40 times brighter in visible light. It’s only during these rare periods that the star system emits radio waves, which allow for a much more precise measure of the distance.

“Our key advantage was using radio telescopes to observe the system. In visible light, optical telescopes like Hubble see hundreds of different stars, all of which are moving by different amounts, whereas in radio waves the background we compare against is much further away and therefore doesn’t appear to move at all,” co-author Assistant Professor Gregory Sivakoff from the University of Alberta, said.

The team used groups of telescopes called the Very Long Baseline Array (VLBA) in the United States and the European Very Long Baseline Interferometry Network (EVN) in Europe and South Africa to pinpoint the exact location of the system relative to the background galaxies.

“The system only emits radio waves for a short period of time. Without the cooperation of our many amateur observers who looked at SS Cygni night after night, we wouldn’t have known when to look - their contribution was invaluable,” co-author Dr Matthew Templeton from the AAVSO said.

The measured distance of just over 370 light years means the light detected by the team left SS Cygni around the time that famous physicist Sir Isaac Newton was born in the 1600s.

“The pull of gas off a nearby star onto the white dwarf in SS Cygni is the same process that happens when neutron stars and black holes are orbiting with a nearby companion, so a lot of effort has gone in to understanding how this works,” Dr Miller-Jones said.

“Our new distance measurement has solved the puzzle of SS Cygni’s brightness, it fits our theories after all.”
ICRAR is a joint venture between Curtin University and The University of Western Australia providing research excellence in the field of radio astronomy.


Dr James Miller-Jones
ICRAR, Curtin University
M: +61 488 484825

Assistant Professor Gregory Sivakoff
University of Alberta
P: +1 780 492 7992

Dr Matthew Templeton
American Association of Variable Star Observers (AAVSO)
P: +1-617-354-0484

Kirsten Gottschalk
Media Contact, ICRAR
M: +61 438 361 876

Megan Meates
Media Contact, Curtin University
Ph: +61 8 9266 4241
M: +61 401 103 755

Monday, May 27, 2013

Most detailed observations ever of the Ring Nebula

Hubble image of the Ring Nebula (Messier 57) 

The region around the Ring Nebula (Hubble/LBT composite)

The geometry and structure of the Ring Nebula (Messier 57)

Wide-field image of the Ring Nebula (ground-based image)


Hubblecast 66: Hubble uncovers the secrets of the Ring Nebula
Hubblecast 66: Hubble uncovers the secrets of the Ring Nebula

Fly-around and zoom into the Ring Nebula (3D)
Fly-around and zoom into the Ring Nebula (3D)

New Hubble observations reveal the structure of the Ring Nebula
New Hubble observations reveal the structure of the Ring Nebula

Visualisation of the 3D structure of the Ring Nebula
Visualisation of the 3D structure of the Ring Nebula

Exploring the Ring Nebula (3D)
Exploring the Ring Nebula (3D)

Zooming in on Messier 57, the Ring Nebula
Zooming in on Messier 57, the Ring Nebula

The NASA/ESA Hubble Space Telescope has produced the most detailed observations ever of the Ring Nebula (Messier 57). This image reveals intricate structure only hinted at in previous observations, and has allowed scientists to construct a model of the nebula in 3D — showing the true shape of this striking object.

Formed by a star throwing off its outer layers as it runs out of fuel, the Ring Nebula is an archetypal planetary nebula [1]. It is both relatively close to Earth and fairly bright, and so was first recorded in the late 18th century. As is common with astronomical objects, its precise distance is not known, but it is thought to lie just over 2000 light-years from Earth.

From Earth’s perspective, the nebula looks roughly elliptical. However, astronomers have combined ground-based data with new observations using the NASA/ESA Hubble Space Telescope to observe the nebula again, hunting for clues about its structure, evolution, physical conditions and motion.

It turns out that the nebula is shaped like a distorted doughnut. We are gazing almost directly down one of the poles of this structure, with a brightly coloured barrel of material stretching away from us. Although the centre of this doughnut may look empty, it is actually full of lower density material that stretches both towards and away from us, creating a shape similar to a rugby ball slotted into the doughnut’s central gap.

The brightest part of this nebula is what we see as the colourful main ring. This is composed of gas thrown off by a dying star at the centre of the nebula. This star is on its way to becoming a white dwarf — a very small, dense, and hot body that is the final evolutionary stage for a star like the Sun.

The Ring Nebula is one of the most notable objects in our skies. It was discovered in 1779 by astronomer Antoine Darquier de Pellepoix, and also observed later that same month by Charles Messier, and added to the Messier Catalogue. Both astronomers stumbled upon the nebula when trying to follow the path of a comet through the constellation of Lyra, passing very close to the Ring Nebula [2].


[1] Planetary nebulae take their name from their roughly circular appearance through low-magnification telescopes. The phenomenon has nothing to do with planets.

[2] Messier 57 was not the only object to be discovered during the tracking of this comet, named C/1779 A1. Messier and other astronomers added a handful of other nebulae to the catalogue during this observing period — Messiers 56, 58, 59, 60, and 61.

More information

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

The research on Messier 57 is described in a set of three papers, two published in The Astronomical Journal:

  • “Studies of NGC 6720 with Calibrated HST WFC3 Emission Line Filter Images — I: Structure and Evolution”, available here.
  • “Studies of NGC 6720 with Calibrated HST WFC3 Emission Line Filter Images — II: Physical Conditions”, available here.
And a third paper that has been accepted for publication in The Astronomical Journal:

  • “Studies of NGC 6720 with Calibrated HST WFC3 Emission Line Filter Images — III: Tangential Motions using AstroDrizzle Images”, available here.
The NASA/ESA Hubble Space Telescope observations used in this image were led by C. R. O’Dell (Vanderbilt University, USA), G. J. Ferland (University of Kentucky, USA), W. J. Henney (Universidad Nacional Autónoma de México, Mexico), and M. Peimbert (Universidad Nacional Autónoma de México, Mexico).

Image credit: NASA, ESA, and C. Robert O’Dell.



C. Robert O’Dell
Department of Physics and Astronomy, Vanderbilt University
Tennessee, USA
Tel: +1-615-343-1779

Nicky Guttridge
Garching bei München, Germany
Tel: +49-89-3200-6855

Saturday, May 25, 2013

Big Weather on Hot Jupiters

A new ScienceCast video explores the wild weather of hot Jupiters

 This exoplanet weather map shows temperatures on a hot Jupiter known as "HAT-P-2b".

Among the hundreds of new planets discovered by NASA's Kepler spacecraft are a class of exotic worlds known as "hot Jupiters."  Unlike the giant planets of our own solar system, which remain at a safe distance from the sun, these worlds are reckless visitors to their parent stars. They speed around in orbits a fraction the size of Mercury’s, blasted on just one-side by starlight hundreds of times more intense than the gentle heating experienced by Jupiter here at home." 

Meteorologists watching this video are probably wondering what kind of weather a world like that might have. The short answer is "big." 

Heather Knutson of Caltech made the first weather map of a hot Jupiter in 2007. 

"It's not as simple as taking a picture and--voila!—we see the weather," says Knutson. These planets are hundreds of light years from Earth and they are nearly overwhelmed by the glare of their parent stars. "Even to see the planet as a single pixel next to the star would be a huge accomplishment." 

Instead, Knutson and colleagues use a trick dreamed up by Nick Cowan of Northwestern University. The key, she explains, is that "most hot Jupiters are tidally locked to their stars. This means they have a permanent dayside and a permanent night side.  As we watch them orbit from our vantage point on Earth, the planets exhibit phases--e.g., crescent, gibbous and full.  By measuring the infrared brightness of the planet as a function of its phase, we can make a rudimentary map of temperature vs. longitude."

NASA’s Spitzer Space Telescope is the only infrared observatory with the sensitivity to do this work.  Since Knutson kick-started the research in 2007, nearly a dozen hot Jupiters have been mapped by astronomers using Spitzer. 

The most recent study, led by Nikole Lewis, a NASA Sagan Exoplanet Fellow working at MIT, shows a gas giant named HAT-P-2b. "We can see daytime temperatures as high as 2400 K," says Lewis, "while the nightside drops below 1200K.  Even at night," she marvels, "this planet is ten times hotter than Jupiter." 

These exoplanet maps may seem crude compared to what we’re accustomed to on Earth, but they are a fantastic accomplishment considering that the planets are trillions of miles away.

The maps show huge day-night temperature differences typically exceeding 1000 degrees.  Researchers believe these thermal gradients drive ferocious winds blowing thousands of miles per hour. 

Without regular pictures, researchers can’t say what this kind of windy weather looks like. Nevertheless, Knutson is willing to speculate using climate models of Jupiter as a guide. 

"Weather on hot Jupiters," she predicts, "is really big." 

Over the years, planetary scientists have developed computer models to reproduce the storms and cloud belts in Jupiter’s atmosphere.  If you take those models and turn up the heat, and slow down the rotation to match the tidally-locked spin of a hot Jupiter, weather patterns become super-sized. For instance, on a hot Jupiter the Great Red Spot might grow as large as a quarter the size of the planet and manifest itself in both the northern and southern hemispheres.

"Just imagine what that would look like--a pair of giant eyes staring out into space!" says Lewis.
Meanwhile, Jupiter’s famous belts would widen so much that only two or three would fit across the planet’s girth. 

Ordinary clouds of water and methane couldn’t form in such a hot environment. Instead, Knutson speculates that hot Jupiters might have clouds made of silicate—that is, "rock clouds." 

"Silicates are predicted to condense in such an environment," she says. "We're already getting some hints that clouds might be common on these planets, but we don’t yet know if they’re made of rock." 

For now just one thing is certain: The meteorology of hot Jupiters is out of this world.

Author: Dr. Tony PhillipsProduction editor: Dr. Tony Phillips | Credit: Science@NASA

Nikole Lewis of MIT is a NASA Sagan Exoplanet Fellow. The Sagan Fellowship Program is administered by the NASA Exoplanet Science Institute as part of NASA's Exoplanet Exploration Program at JPL. Caltech manages JPL for NASA

Galaxies Fed by Funnels of Fuel

Created with the help of supercomputers, this still from a simulation shows the formation of a massive galaxy during the first 2 billion years of the universe. Hydrogen gas is gray, young stars appear blue, and older stars are red. The simulation reveals that gas flows into galaxies along filaments akin to cosmic bendy, or swirly, straws. Image credit: Video courtesy of the N-Body Shop at University of Washington.  › Full image and caption

Cosmic Swirly Straws Feed Galaxy

Computer simulations of galaxies growing over billions of years have revealed a likely scenario for how they feed: a cosmic version of swirly straws.

The results show that cold gas -- fuel for stars -- spirals into the cores of galaxies along filaments, rapidly making its way to their "guts." Once there, the gas is converted into new stars, and the galaxies bulk up in mass.

"Galaxy formation is really chaotic," said Kyle Stewart, lead author of the new study appearing in the May 20th issue of the Astrophysical Journal. "It took us several hundred computer processors, over months of time, to simulate and learn more about how this process works." Stewart, who is now at the California Baptist University in Riverside, Calif., completed the majority of this work while at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

In the early universe, galaxies formed out of clumps of matter, connected by filaments in a giant cosmic web. Within the galaxies, nuggets of gas cooled and condensed, becoming dense enough to trigger the birth of stars. Our Milky Way spiral galaxy and its billions of stars took shape in this way.

The previous, standard model of galaxy formation held that hot gas sank into the centers of burgeoning galaxies from all directions. Gas clouds were thought to collide into each other, sending out shock waves, which then heated up the gas. The process is similar to jets creating sonic booms, only in the case of galaxies, the in-falling gas travels faster than the speed of sound, piling up into waves. Eventually, the gas cools and sinks to the galactic center. This process was theorized to be slow, taking up to 8 billion years.

Recent research has contradicted this scenario in smaller galaxies, showing that the gas is not heated. An alternate "cold-mode" theory of galaxy formation was proposed instead, suggesting the cold gas might funnel along filaments into galaxy centers. Stewart and his colleagues set out to test this theory and address the mysteries about how the cold gas gets into galaxies, as well as the rate at which it spirals in.

Since it would take billions of years to watch a galaxy grow, the team simulated the process using supercomputers at JPL; NASA's Ames Research Center, Moffett Field, Calif.; and the University of California, Irvine. They ran four different simulations of the formation of a galaxy like our Milky Way, starting from just 57 million years after the big bang until present day.

The simulations began with the starting ingredients for galaxies -- hydrogen, helium and dark matter -- and then let the laws of physics take over to create their galactic masterpieces. Supercomputers are needed due to the enormous number of interactions.

"The simulations are like a gigantic game of chess," said Alyson Brooks, a co-author of the paper and expert in galaxy simulations at the University of Wisconsin, Madison. "For each point in time, we have to figure out how a given particle -- our chess piece -- should move based on the positions of all of the other particles. There are tens of millions of particles in the simulation, so figuring out how the gravitational forces affect each particle is time-consuming."

When the galaxy concoctions were ready, the researchers inspected the data, finding new clues about how cold gas sinks into the galaxy centers. The new results confirm that cold gas flows along filaments and show, for the first time, that the gas is spinning around faster than previously believed. The simulations also revealed that the gas is making its way down to the centers of galaxies more quickly than what occurs in the "hot-mode" of galaxy formation, in about 1 billion years.

"We have found that the filamentary structures that galaxies are built on are key to how they build up over time, by threading gas into them efficiently," said Leonidas Moustakas, a co-author at JPL.

The researchers looked at dark matter too -- an invisible substance making up about 85 percent of matter in the universe. Galaxies form out of lumps of regular matter, so-called baryonic matter that is composed of atoms, and dark matter. The simulations showed that dark matter is also spinning at a faster rate along the filaments, spiraling into the galaxy centers.

The results help answer a riddle in astronomy about galaxies with large extended disks of material spinning around them, far from their centers. Researchers didn't understand how the outer material could be spinning so fast. The cold-mode allows for this rapid spinning, fitting another jigsaw piece into the puzzle of how galaxies grow.

"The goal of simulating galaxies is to compare them to what telescopes observe and see if we really understand how to build a galaxy," said Stewart. "It helps us makes sense of the real universe."

Other authors of the paper are: James Bullock of the University of California, Irvine; Ariyeh Maller of the New York City College of Technology, Brooklyn, N.Y., Jürg Diemand of the University of Zurich, Switzerland; and James Wadsley of the McMaster University, Hamilton, Ontario, Canada.

JPL is managed by the California Institute of Technology in Pasadena for NASA.

Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.

Friday, May 24, 2013

A swirl of star formation

Credit: ESA/Hubble & NASA, M. Hayes

This beautiful, glittering swirl is named, rather unpoetically, J125013.50+073441.5. A glowing haze of material seems to engulf the galaxy, stretching out into space in different directions and forming a fuzzy streak in this image. It is a starburst galaxy — a name given to galaxies that show unusually high rates of star formation. The regions where new stars are being born are highlighted by sparkling bright blue regions along the galactic arms.

Studying starburst galaxies can tell us a lot about galactic evolution and star formation. These galaxies start off with huge amounts of gas, which is used to form new stars. This period of furious star formation is only a phase; once all the gas is used up, this starbirth slows down. Other famous starbursts captured by Hubble include the Antennae Galaxies and Messier 82, the latter of which is forming new stars ten times faster than our galaxy, the Milky Way.

The data for this image were collected as part of a study named LARS (Lyman Alpha Reference Sample) [1], which is investigating the interaction between radiation and matter in relatively nearby starburst galaxies.

J125013.50+073441.5 is included as one of its fourteen targets. This study has characterised how a certain type of emission known as Lyman-alpha emission interacts with nearby gas, affecting how it travels out into space.

The data for this image were collected using Hubble’s Wide Field Camera 3.

More information

[1] Hayes, Östlin et al., The Lyman Alpha Reference Sample: extended Lyman alpha halos produced at low dust content, The Astrophysical Journal, 2013.

SGR 0418+5729: A Hidden Population of Exotic Neutron Stars

SGR 0418+5729
Credit  X-ray: NASA/CXC/CSIC-IEEC/N.Rea et al;
Optical: Isaac Newton Group of Telescopes, La Palma/WHT;
Infrared: NASA/JPL-Caltech; Illustration: NASA/CXC/M.Weiss


This graphic shows an exotic object in our galaxy called SGR 0418+5729 (SGR 0418 for short). As described in our press release, SGR 0418 is a magnetar, a type of neutron star that has a relatively slow spin rate and generates occasional large blasts of X-rays.

The only plausible source for the energy emitted in these outbursts is the magnetic energy stored in the star. Most magnetars have extremely high magnetic fields on their surface that are ten to a thousand times stronger than for the average neutron star. New data shows that SGR 0418 doesn't fit that pattern. It has a surface magnetic field similar to that of mainstream neutron stars. 

In the image on the left, data from NASA's Chandra X-ray Observatory shows SGR 0418 as a pink source in the middle (mouse over the image above). Optical data from the William Herschel telescope in La Palma and infrared data from NASA's Spitzer Space Telescope are shown in red, green and blue.
On the right is an artist's impression showing a close-up view of SGR 0418. This illustration highlights the weak surface magnetic field of the magnetar, and the relatively strong, wound-up magnetic field lurking in the hotter interior of the star. The X-ray emission seen with Chandra comes from a small hot spot, not shown in the illustration. At the end of the outburst this spot has a radius of only about 160 meters, compared with a radius for the whole star of about 12 km.

The researchers monitored SGR 0418 for over three years using Chandra, ESA's XMM-Newton as well as NASA's Swift and RXTE satellites. They were able to make an accurate estimate of the strength of the external magnetic field by measuring how its rotation speed changes during an X-ray outburst. These outbursts are likely caused by fractures in the crust of the neutron star precipitated by the buildup of stress in the stronger magnetic field lying below the surface.

By modeling the evolution of the cooling of the neutron star and its crust, as well as the gradual decay of its magnetic field, the researchers estimated that SGR 0418 is about 550,000 years old. This makes SGR 0418 older than most other magnetars, and this extended lifetime has probably allowed the surface magnetic field strength to decline over time. Because the crust weakened and the interior magnetic field is relatively strong, outbursts could still occur.

The implications of this result for understanding supernova explosions and the number and evolution of magnetars is discussed in the press release.

SGR 0418 is located in the Milky Way galaxy at a distance of about 6,500 light years from Earth. These new results on SGR 0418 appear online and will be published in the June 10, 2013 issue of The Astrophysical Journal. 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 SGR 0418+5729:

Scale:  Image is about 2 arcmin across (about 3 light years)
Coordinates: (J2000)  RA 04h 18m 33.90s | Dec +57° 32' 22.90''
Constellation:  Camelopardalis
Observation Date:  3 pointings between Nov 2010 and Nov 2011
Observation Time 45 hours 52 min (1 day 21 hours 52 min)
Obs. ID:  13148, 13235, 13236
Instrument:  ACISReferences: Rea, N. et al, 2013, ApJ in press; arXiv:1303.5579
Color Code:  X-ray (Pink); Optical (Luminosity); Infrared (Red, Green, Blue)
Distance Estimate:  About 6500 light years

Thursday, May 23, 2013

ESO's Very Large Telescope Celebrates 15 Years of Success

The Very Large Telescope Snaps a Stellar Nursery and Celebrates Fifteen Years of Operations - IC 2944
Fifteen years of the Very Large Telescope
The stellar nursery IC 2944 in the constellation of Centaurus
Fifteen years of the Very Large Telescope



ESOcast 57: ESO´s VLT Celebrates 15 Years of Success
ESOcast 57: ESO´s VLT Celebrates 15 Years of Success

Zooming in on the stellar nursery IC 2944 and Thackeray's Globules
Zooming in on the stellar nursery IC 2944 and Thackeray's Globules

A close-up look at the stellar nursery IC 2944 and Thackeray's Globules
A close-up look at the stellar nursery IC 2944 and Thackeray's Globules

With this new view (eso1322a) of a spectacular stellar nursery ESO is celebrating 15 years of the Very Large Telescope — the world's most advanced optical instrument. This picture reveals thick clumps of dust silhouetted against the pink glowing gas cloud known to astronomers as IC 2944. These opaque blobs resemble drops of ink floating in a strawberry cocktail, their whimsical shapes sculpted by powerful radiation coming from the nearby brilliant young stars.

This new picture celebrates an important anniversary for the Very Large Telescope – it is fifteen years since the first light on the first of its four Unit Telescopes, on 25 May 1998. Since then the four original giant telescopes have been joined by the four small Auxiliary Telescopes that form part of the VLT Interferometer (VLTI). The VLT is one of the most powerful and productive ground-based astronomical facilities in existence. In 2012 more than 600 refereed scientific papers based on data from the VLT and VLTI were published (ann13009).

Interstellar clouds of dust and gas are the nurseries where new stars are born and grow. The new picture shows one of them, IC 2944, which appears as the softly glowing pink background [1]. This image is the sharpest view of the object ever taken from the ground [2]. The cloud lies about 6500 light-years away in the southern constellation of Centaurus (The Centaur). This part of the sky is home to many other similar nebulae that are scrutinised by astronomers to study the mechanisms of star formation.

Emission nebulae like IC 2944 are composed mostly of hydrogen gas that glows in a distinctive shade of red, due to the intense radiation from the many brilliant newborn stars. Clearly revealed against this bright backdrop are mysterious dark clots of opaque dust, cold clouds known as Bok globules. They are named after the Dutch-American astronomer Bart Bok, who first drew attention to them in the 1940s as possible sites of star formation. This particular set is nicknamed the Thackeray Globules [3].

Larger Bok globules in quieter locations often collapse to form new stars but the ones in this picture are under fierce bombardment from the ultraviolet radiation from nearby hot young stars. They are both being eroded away and also fragmenting, rather like lumps of butter dropped into a hot frying pan. It is likely that Thackeray’s Globules will be destroyed before they can collapse and form stars.

Bok globules are not easy to study. As they are opaque to visible light it is difficult for astronomers to observe their inner workings, and so other tools are needed to unveil their secrets — observations in the infrared or in the submillimetre parts of the spectrum, for example, where the dust clouds, only a few degrees over absolute zero, appear bright. Such studies of the Thackeray globules have confirmed that there is no current star formation within them.

This region of sky has also been imaged in the past by the NASA/ESA Hubble Space Telescope (opo0201a). This new view from the FORS instrument on ESO’s Very Large Telescope at the Paranal Observatory in northern Chile [4] covers a wider patch of sky than Hubble and shows a broader landscape of star formation.


[1] The nebula IC 2944 is associated with the bright star cluster IC 2948 and both of these names are also sometimes associated with the whole region. Many of the bright cluster stars appear in this picture.

[2] The seeing of the blue image in this colour combination was better than 0.5 arcseconds, exceptionally good for a ground-based telescope.

[3] They were discovered from South Africa by the English astronomer A. David Thackeray in 1950.

[4] 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”.



Richard Hook
ESO, Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591