Astronomy Cmarchesin

Releases from NASA, NASA Galex, NASA's Goddard Space Flight Center, Hubble, Hinode, Spitzer, Cassini, ESO, ESA, Chandra, HiRISE, Royal Astronomical Society, NRAO, Astronomy Picture of the Day, Harvard-Smithsonian Center For Astrophysics, etc.

Wednesday, July 23, 2014

NASA's Fermi Finds A 'Transformer' Pulsar

These artist's renderings show one model of pulsar J1023 before (top) and after (bottom) its radio beacon (green) vanished. Normally, the pulsar's wind staves off the companion's gas stream. When the stream surges, an accretion disk forms and gamma-ray particle jets (magenta) obscure the radio beam. Image Credit: NASA's Goddard Space Flight Center

Zoom into an artist's concept of AY Sextantis, a binary star system whose pulsar switched from radio emissions to high-energy gamma rays in 2013. This transition likely means the pulsar's spin-up process is nearing its end. 

In late June 2013, an exceptional binary containing a rapidly spinning neutron star underwent a dramatic change in behavior never before observed. The pulsar's radio beacon vanished, while at the same time the system brightened fivefold in gamma rays, the most powerful form of light, according to measurements by NASA's Fermi Gamma-ray Space Telescope.

"It's almost as if someone flipped a switch, morphing the system from a lower-energy state to a higher-energy one," said Benjamin Stappers, an astrophysicist at the University of Manchester, England, who led an international effort to understand this striking transformation. "The change appears to reflect an erratic interaction between the pulsar and its companion, one that allows us an opportunity to explore a rare transitional phase in the life of this binary."

A binary consists of two stars orbiting around their common center of mass. This system, known as AY Sextantis, is located about 4,400 light-years away in the constellation Sextans. It pairs a 1.7-millisecond pulsar named PSR J1023+0038 -- J1023 for short -- with a star containing about one-fifth the mass of the sun. The stars complete an orbit in only 4.8 hours, which places them so close together that the pulsar will gradually evaporate its companion.

When a massive star collapses and explodes as a supernova, its crushed core may survive as a compact remnant called a neutron star or pulsar, an object squeezing more mass than the sun's into a sphere no larger than Washington, D.C. Young isolated neutron stars rotate tens of times each second and generate beams of radio, visible light, X-rays and gamma rays that astronomers observe as pulses whenever the beams sweep past Earth. Pulsars also generate powerful outflows, or "winds," of high-energy particles moving near the speed of light. The power for all this comes from the pulsar's rapidly spinning magnetic field, and over time, as the pulsars wind down, these emissions fade.

More than 30 years ago, astronomers discovered another type of pulsar revolving in 10 milliseconds or less, reaching rotational speeds up to 43,000 rpm. While young pulsars usually appear in isolation, more than half of millisecond pulsars occur in binary systems, which suggested an explanation for their rapid spin.

"Astronomers have long suspected millisecond pulsars were spun up through the transfer and accumulation of matter from their companion stars, so we often refer to them as recycled pulsars," explained Anne Archibald, a postdoctoral researcher at the Netherlands Institute for Radio Astronomy (ASTRON) in Dwingeloo who discovered J1023 in 2007.

During the initial mass-transfer stage, the system would qualify as a low-mass X-ray binary, with a slower-spinning neutron star emitting X-ray pulses as hot gas raced toward its surface. A billion years later, when the flow of matter comes to a halt, the system would be classified as a spun-up millisecond pulsar with radio emissions powered by a rapidly rotating magnetic field.

To better understand J1023's spin and orbital evolution, the system was regularly monitored in radio using the Lovell Telescope in the United Kingdom and the Westerbork Synthesis Radio Telescope in the Netherlands. These observations revealed that the pulsar's radio signal had turned off and prompted the search for an associated change in its gamma-ray properties.

A few months before this, astronomers found a much more distant system that flipped between radio and X-ray states in a matter of weeks. Located in M28, a globular star cluster about 19,000 light-years away, a pulsar known as PSR J1824-2452I underwent an X-ray outburst in March and April 2013. As the X-ray emission dimmed in early May, the pulsar's radio beam emerged.

While J1023 reached much higher energies and is considerably closer, both binaries are otherwise quite similar. What's happening, astronomers say, are the last sputtering throes of the spin-up process for these pulsars.

In J1023, the stars are close enough that a stream of gas flows from the sun-like star toward the pulsar. The pulsar's rapid rotation and intense magnetic field are responsible for both the radio beam and its powerful pulsar wind. When the radio beam is detectable, the pulsar wind holds back the companion's gas stream, preventing it from approaching too closely. But now and then the stream surges, pushing its way closer to the pulsar and establishing an accretion disk.

Gas in the disk becomes compressed and heated, reaching temperatures hot enough to emit X-rays. Next, material along the inner edge of the disk quickly loses orbital energy and descends toward the pulsar. When it falls to an altitude of about 50 miles (80 km), processes involved in creating the radio beam are either shut down or, more likely, obscured.

The inner edge of the disk probably fluctuates considerably at this altitude. Some of it may become accelerated outward at nearly the speed of light, forming dual particle jets firing in opposite directions -- a phenomenon more typically associated with accreting black holes. Shock waves within and along the periphery of these jets are a likely source of the bright gamma-ray emission detected by Fermi.

The findings were published in the July 20 edition of The Astrophysical Journal. The team reports that J1023 is the first example of a transient, compact, low-mass gamma-ray binary ever seen. The researchers anticipate that the system will serve as a unique laboratory for understanding how millisecond pulsars form and for studying the details of how accretion takes place on neutron stars.

"So far, Fermi has increased the number of known gamma-ray pulsars by about 20 times and doubled the number of millisecond pulsars within in our galaxy," said Julie McEnery, the project scientist for the mission at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "Fermi continues to be an amazing engine for pulsar discoveries."

Related Links:


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



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Tuesday, July 22, 2014

Four Supernova Remnants: NASA’s Chandra X-ray Observatory Celebrates 15th Anniversary

Four Supernova Remnants
Credit: NASA/CXC/SAO


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 A Tour of IGR J11014-6103

A Tour of IGR J11014-6103

In commemoration of the 15th anniversary of NASA's Chandra X-ray Observatory, four newly processed images of supernova remnants dramatically illustrate Chandra's unique ability to explore high-energy processes in the cosmos (see the accompanying press release).

The images of the Tycho and G292.0+1.8 supernova remnants show how Chandra can trace the expanding debris of an exploded star and the associated shock waves that rumble through interstellar space at speeds of millions of miles per hour. The images of the Crab Nebula and 3C58 show how extremely dense, rapidly rotating neutron stars produced when a massive star explodes can create clouds of high-energy particles light years across that glow brightly in X-rays.

tycho
Tycho:
More than four centuries after Danish astronomer Tycho Brahe first observed the supernova that bears his name, the supernova remnant it created is now a bright source of X-rays. The supersonic expansion of the exploded star produced a shock wave moving outward into the surrounding interstellar gas, and another, reverse shock wave moving back into the expanding stellar debris. This Chandra image of Tycho reveals the dynamics of the explosion in exquisite detail. The outer shock has produced a rapidly moving shell of extremely high-energy electrons (blue), and the reverse shock has heated the expanding debris to millions of degrees (red and green). There is evidence from the Chandra data that these shock waves may be responsible for some of the cosmic rays - ultra-energetic particles - that pervade the Galaxy and constantly bombard the Earth.

g292
G292.0+1.8:
At a distance of about 20,000 light years, G292.0+1.8 is one of only three supernova remnants in the Milky Way known to contain large amounts of oxygen. These oxygen-rich supernovas are of great interest to astronomers because they are one of the primary sources of the heavy elements (that is, everything other than hydrogen and helium) necessary to form planets and people. The X-ray image from Chandra shows a rapidly expanding, intricately structured, debris field that contains, along with oxygen (yellow and orange), other elements such as magnesium (green) and silicon and sulfur (blue) that were forged in the star before it exploded.

crab nebula
The Crab Nebula:
In 1054 AD, Chinese astronomers and others around the world noticed a new bright object in the sky. This “new star” was, in fact, the supernova explosion that created what is now called the Crab Nebula. At the center of the Crab Nebula is an extremely dense, rapidly rotating neutron star left behind by the explosion. The neutron star, also known as a pulsar, is spewing out a blizzard of high-energy particles, producing the expanding X-ray nebula seen by Chandra. In this new image, lower-energy X-rays from Chandra are red, medium energy X-rays are green, and the highest-energy X-rays are blue.

3c58
3C58:
3C58 is the remnant of a supernova observed in the year 1181 AD by Chinese and Japanese astronomers. This new Chandra image shows the center of 3C58, which contains a rapidly spinning neutron star surrounded by a thick ring, or torus, of X-ray emission. The pulsar also has produced jets of X-rays blasting away from it to both the left and right, and extending trillions of miles. These jets are responsible for creating the elaborate web of loops and swirls revealed in the X-ray data. These features, similar to those found in the Crab, are evidence that 3C58 and others like it are capable of generating both swarms of high-energy particles and powerful magnetic fields. In this image, low, medium, and high-energy X-rays detected by Chandra are red, green, and blue respectively.

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Fast Facts for 3C58:

Scale: Image is 12 arcmin across (35 light years) across.
Coordinates (J2000): RA 02h 05m 37.00s | Dec +64 49 48.00
Constellation: Cassiopeia
Observation Dates: 4 pointings between Sep 2000 and Apr 2003
Observation Time: 108 hours 52 min (4 days 12 hours 52 min
Obs. IDs: 728, 3832, 4382, 4383
Instrument: ACIS
Color Code: X-ray (Red, Green, Blue)
Distance Estimate: About 10,000 light years

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Fast Facts for Crab Nebula:

Scale: Image is 4.6 arcmin across (8.7 light years) across.
Coordinates (J2000): RA 05h 34m 32s | Dec +22 0.0 52.00
Constellation: Taurus
Observation Dates: 48 pointings between March 2000 and Nov 2013
Observation Time: 25 hours 28 min (1 day 1 hour 28 min)
Obs. IDs: 769-773,1994-2001,4607,13139,13146,13147,13150-13154,13204-132
Instrument: ACIS
Color Code: X-ray (Red, Green, Blue)
Distance Estimate: About 6,500 light years light years

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Fast Facts for Tycho's Supernova Remnant:

Scale: Image is 9.5 arcmin across (36 light years) across.
Coordinates (J2000): RA 00h 25m 17s | Dec +64 08 37
Constellation: Cassiopeia
Observation Dates: 13 pointings between Sep 2000 and May 2009
Observation Time: 297 hours 26 min (12 days 9 hours 26 min)
Obs. IDs: 115, 3837, 7639, 8551, 10093-10097, 10902-10906
Instrument: ACIS
Also Knows As: G120.1+01.4, SN 1572
Color Code: X-ray (Red, Green, Blue)
Distance Estimate: About 6,500 light years light years


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Fast Facts for G292.0+1.8:

Scale: Image is 11.4 arcmin across (about 66 light years) across.
Coordinates (J2000): RA 11h 24m 36.00s | Dec -59 16 00.00
Constellation: Centaurus
Observation Dates: 6 pointings between 13 Sep and 16 Oct 2006
Observation Time: 141 hours 30 min (5 days 21 hours 30 min)
Obs. IDs: 6677-6680, 8221, 8447
Instrument: ACIS
Color Code: X-ray X-ray (Red, Orange, Green, Blue)
Distance Estimate: About 20,000 light years light years



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Hubble traces the halo of a galaxy more accurately than ever before

Centaurus A halo
Centaurus A halo annotated

Area of Centaurus A halo probed by Hubble
Area of Centaurus A halo probed by Hubble


An in-depth look at the giant elliptical galaxy Centaurus A


Astronomers using the NASA/ESA Hubble Space Telescope have probed the extreme outskirts of the stunning elliptical galaxy Centaurus A. The galaxy’s halo of stars has been found to extend much further from the galaxy’s centre than expected and the stars within this halo seem to be surprisingly rich in heavy elements. This is the most remote portion of an elliptical galaxy ever to have been explored.

There is more to a galaxy than first meets the eye. Extending far beyond the bright glow of a galaxy's centre, the swirling spiral arms, or the elliptical fuzz, is an extra component: a dim halo of stars sprawling into space.

These expansive haloes are important components of a galaxy. The halo of our own galaxy, the Milky Way, preserves signatures of both its formation and evolution. Yet, we know very little about the haloes of galaxies beyond our own as their faint and spread-out nature makes exploring them more difficult. Astronomers have so far managed to detect very few starry haloes around other galaxies.

Now, by utilising the unique space-based location of the NASA/ESA Hubble Space Telescope and its sensitive Advanced Camera for Surveys and Wide Field Camera 3, a team of astronomers has probed the halo surrounding the prominent giant elliptical galaxy Centaurus A [1], also known as NGC 5128, to unprecedented distances. They have found that its halo spreads far further into space than expected and does so in an unexpected form.

"Tracing this much of a galaxy's halo gives us surprising insights into a galaxy's formation, evolution, and composition," says Marina Rejkuba of the European Southern Observatory in Garching, Germany, lead author of the new Hubble study. "We found more stars scattered in one direction than the other, giving the halo a lopsided shape — which we hadn't expected!" 

Along the galaxy's length the astronomers probed out 25 times further than the galaxy's radius — mapping a region some 450 000 light-years across. For the width they explored along 295 000 light-years, 16 times further than its "effective radius" [2]. These are large distances if you consider that the main visible component of the Milky Way is around 120 000 light-years in diameter. In fact, the diameter of the halo probed by this team extends across 4 degrees in the sky — equivalent to eight times the apparent width of the Moon.

Alongside their unexpected uneven distribution, the stars within the halo also showed surprising properties relating to the proportion of elements heavier than hydrogen and helium found in the gas that makes up the stars. While the stars within the haloes of the Milky Way and other nearby spirals are generally low in heavy elements, the stars within Centaurus A's halo appear to be rich in heavy elements, even at the outermost locations explored.

"Even at these extreme distances, we still haven't reached the edge of Centaurus A's halo, nor have we detected the very oldest generation of stars," adds co-author Laura Greggio of INAF, Italy. "This aged generation is very important. The larger stars from it are responsible for manufacturing the heavy elements now found in the bulk of the galaxy's stars. And even though the large stars are long dead, the smaller stars of the generation still live on and could tell us a great deal."

The small quantity of heavy elements in the stellar haloes of large spiral galaxies like the Milky Way, is thought to originate from the way that the galaxies formed and evolved, slowly pulling in numerous small satellite galaxies and taking on their stars. For Centaurus A, the presence of stars rich in heavy elements in such remote locations suggests a single past merger with a large spiral galaxy. This event would have ejected stars from the spiral galaxy's disc and these are now seen as part of Centaurus A's outer halo.

"Measuring the amount of heavy elements in individual stars in a giant elliptical galaxy such as Centaurus A is uniquely the province of Hubble — we couldn't do it with any other telescope, and certainly not yet from the ground," adds Rejkuba. "These kinds of observations are fundamentally important to understanding the galaxies in the Universe around us."

These results are being published online in Astrophysical Journal on the 22 July and will appear in the 10 August 2014 issue.

Notes

[1] As it is relatively near to Earth, Centaurus A is prominent in our night sky and is well known for its striking and beautiful appearance (heic1110, opo9814e). To see more about this galaxy, see Hubblecast 46: A tour of Centaurus A.

[2] The effective radius of a galaxy, as referenced here, is the radius of the area in which half of the galaxy’s light is emitted. Astronomers use this effective radius rather than the full radius because the galaxy becomes faint and undefined at its outskirts.

Notes for editors

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

The international team of astronomers in this study consists of M. Rejkuba (European Southern Observatory, Germany; Excellence Cluster Universe, Germany), W. E. Harris (McMaster University, Canada), L. Greggio (INAF, Italy), G. L. H. Harris (University of Waterloo, Canada), H. Jerjen (Australian National University, Australia), O. A. Gonzalez (European Southern Observatory, Chile).

More information

Image credit: NASA, ESA & M. Rejkuba (European Southern Observatory)

Links

Contacts

Marina Rejkuba
European Southern Observatory
Garching bei München, Germany
Tel: +49 89 3200 6453
Email:
mrejkuba@eso.org

Laura Greggio
INAF, Osservatorio Astronomico di Padova
Padova, Italy
Tel: +39 049 8293463
Cell: +39 347 73189089
Email:
laura.greggio@oapd.inaf.it

Georgia Bladon
ESA/Hubble, Public Information Officer
Garching bei München, Germany
Cell: +44 7816291261
Email:
gbladon@partner.eso.org
Source:  ESA/HUBBLE - Space Telescope


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Monday, July 21, 2014

Transiting Exoplanet with Longest Known Year

"Finding Kepler-421b was a stroke of luck," says lead author David Kipping of the Harvard-Smithsonian Center for Astrophysics (CfA). "The farther a planet is from its star, the less likely it is to transit the star from Earth's point of view. It has to line up just right."

Kepler-421b orbits an orange, type K star that is cooler and dimmer than our Sun. It circles the star at a distance of about 110 million miles. As a result, this Uranus-sized planet is chilled to a temperature of -135° Fahrenheit.

As the name implies, Kepler-421b was discovered using data from NASA's Kepler spacecraft. Kepler was uniquely suited to make this discovery. The spacecraft stared at the same patch of sky for 4 years, watching for stars that dim as planets cross in front of them. No other existing or planned mission shows such long-term, dedicated focus. Despite its patience, Kepler only detected two transits of Kepler-421b due to that world's extremely long orbital period.

The planet's orbit places it beyond the "snow line" - the dividing line between rocky and gas planets. Outside of the snow line, water condenses into ice grains that stick together to build gas giant planets.

"The snow line is a crucial distance in planet formation theory. We think all gas giants must have formed beyond this distance," explains Kipping.

Since gas giant planets can be found extremely close to their stars, in orbits lasting days or even hours, theorists believe that many exoplanets migrate inward early in their history.

Kepler-421b shows that such migration isn't necessary. It could have formed right where we see it now.

"This is the first example of a potentially non-migrating gas giant in a transiting system that we've found," adds Kipping.

The host star, Kepler-421, is located about 1,000 light-years from Earth in the direction of the constellation Lyra.

This research has been accepted for publication in The Astrophysical Journal and is available online. Additional information can be found at https://www.cfa.harvard.edu/~dkipping/kepler421.html

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

For more information, contact:

David A. Aguilar
Director of Public Affairs
Harvard-Smithsonian Center for Astrophysics
617-495-7462

daguilar@cfa.harvard.edu

Christine Pulliam
Public Affairs Specialist
Harvard-Smithsonian Center for Astrophysics
617-495-7463

cpulliam@cfa.harvard.edu



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Friday, July 18, 2014

The oldest cluster in its cloud

Credit:  ESA/Hubble & NASA
Acknowlegement: Stefano Campani

This image shows NGC 121, a globular cluster in the constellation of Tucana (The Toucan). Globular clusters are big balls of old stars that orbit the centres of their galaxies like satellites — the Milky Way, for example, has around 150.

NGC 121 belongs to one of our neighbouring galaxies, the Small Magellanic Cloud (SMC). It was discovered in 1835 by English astronomer John Herschel, and in recent years it has been studied in detail by astronomers wishing to learn more about how stars form and evolve.

Stars do not live forever — they develop differently depending on their original mass. In many clusters, all the stars seem to have formed at the same time, although in others we see distinct populations of stars that are different ages. By studying old stellar populations in globular clusters, astronomers can effectively use them as tracers for the stellar population of their host galaxies. With an object like NGC 121, which lies close to the Milky Way, Hubble is able to resolve individual stars and get a very detailed insight.

NGC 121 is around 10 billion years old, making it the oldest cluster in its galaxy; all of the SMC's other globular clusters are 8 billion years old or younger. However, NGC 121 is still several billions of years younger than its counterparts in the Milky Way and in other nearby galaxies like the Large Magellanic Cloud. The reason for this age gap is not completely clear, but it could indicate that cluster formation was initially delayed for some reason in the SMC, or that NGC 121 is the sole survivor of an older group of star clusters.
This image was taken using Hubble’s Advanced Camera for Surveys (ACS). A version of this image was submitted to the Hubble’s Hidden Treasures image processing competition by contestant Stefano Campani.

Source: ESA/Hubble - Space Telescope


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Thursday, July 17, 2014

The Dual Personality of Comet 67P/C-G

Comet 67P/C-G on 14 July 2014
Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Comet 67P/C-G on 14 July 2014 - (processed view)
Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

This week's images of comet 67P/Churyumov-Gerasimenko reveal an extraordinarily irregular shape. We had hints of that in last week's images and in the unscheduled previews that were seen a few days ago, and in that short time it has become clear that this is no ordinary comet. Like its name, it seems that comet 67P/C-G is in two parts. 

What the spacecraft is actually seeing is the pixelated image shown at right, which was taken by Rosetta's OSIRIS narrow angle camera on 14 July from a distance of 12 000 km.

A second image and a movie show the comet after the image has been processed. The technique used, called "sub-sampling by interpolation", only acts to remove the pixelisation and make a smoother image, and it is important to note that the comet's surface features won't be as smooth as the processing implies. The surface texture has yet to be resolved simply because we are still too far away; any apparent brighter or darker regions may turn out to be false interpretations at this early stage.

But the movie, which uses a sequence of 36 interpolated images each separated by 20 minutes, certainly provides a truly stunning 360-degree preview of the overall complex shape of the comet. Regardless of surface texture, we can certainly see an irregular shaped world shining through. Indeed, some people have already likened the shape to a duck, with a distinct body and head.

Although less obvious in the 'real' image, the movie of interpolated images supports the presence of two definite components. One segment seems to be rather elongated, while the other appears more bulbous.

Rotating view of comet 67P/C-G on 14 July 2014.  
Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Dual objects like this – known as 'contact binaries' in comet and asteroid terminology – are not uncommon.

Indeed, comet 8P/Tuttle is thought to be such a contact binary; radio imaging by the ground-based Arecibo telescope in Puerto Rico in 2008 suggested that it comprises two sphere-like objects. Meanwhile, the bone-shaped comet 103P/Hartley 2, imaged during NASA's EPOXI flyby in 2011, revealed a comet with two distinct halves separated by a smooth region. In addition, observations of asteroid 25143 Itokawa by JAXA's Hayabusa mission, combined with ground-based data, suggest an asteroid comprising two sections of highly contrasting densities.

Is Rosetta en-route to rendezvous with a similar breed of comet? The scientific rewards of studying such a comet would be high, as a number of possibilities exist as to how they form.

One popular theory is that such an object could arise when two comets – even two compositionally distinct comets – melded together under a low velocity collision during the Solar System's formation billions of years ago, when small building blocks of rocky and icy debris coalesced to eventually create planets. Perhaps comet 67P/C-G will provide a unique record of the physical processes of accretion.

Or maybe it is the other way around – that is, a single comet could be tugged into a curious shape by the strong gravitational pull of a large object like Jupiter or the Sun; after all, comets are rubble piles with weak internal strength as directly witnessed in the fragmentation of comet Shoemaker-Levy 9 and the subsequent impacts into Jupiter, 20 years ago this week. Perhaps the two parts of comet 67P/C-G will one day separate completely.

On the other hand, perhaps comet 67P/C-G may have once been a much rounder object that became highly asymmetric thanks to ice evaporation. This could have happened when the comet first entered the Solar System from the Kuiper Belt, or on subsequent orbits around the Sun.

One could also speculate that the striking dichotomy of the comet's morphology is the result of a near catastrophic impact event that ripped out one side of the comet. Similarly, it is not unreasonable to think that a large outburst event may have weakened one side of the comet so much that it simply gave away, crumbling into space.

But, while the interpolated images are certainly brilliant, we need to be closer still to see a better three-dimensional view – not to mention to perform a spectroscopic analysis to determine the comet's composition – in order to draw robust scientific conclusions about this exciting comet.

Rosetta Mission Manager Fred Jansen comments: "We currently see images that suggest a rather complex cometary shape, but there is still a lot that we need to learn before jumping to conclusions. Not only in terms of what this means for comet science in general, but also regarding our planning for science observations, and the operational aspects of the mission such as orbiting and landing.

"We will need to perform detailed analyses and modelling of the shape of the comet to determine how best we can fly around such a uniquely shaped body, taking into account flight control and astrodynamics, the science requirements of the mission, and the landing-related elements like landing site analysis and lander-to-orbiter visibility. But, with fewer than 10 000 km to go before the 6 August rendezvous, our open questions will soon be answered."



Source: ESA/Rosseta


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Fingerprinting the formation of giant planets

Difference in chemical composition between the stars 16 Cyg A and 16 Cyg B, versus the condensation temperature of the elements in the proto-planetary nebula. If the stars had identical chemical compositions then the difference (A-B) would be zero. The star 16 Cyg A is richer in all elements relative to star 16 Cyg B. In other words, star 16 Cyg B, the host star of a giant planet, is deficient in all chemical elements, especially in the refractory elements (those with high condensation temperatures and that form dust grains more easily), suggesting evidence of a rocky core in the giant planet 16 Cyg Bb. Credits: M. Tucci Maia, J. Meléndez, I. Ramírez.

A team of Brazilian and American astronomers used CFHT observations of the system 16 Cygni to discover evidence of how giant planets like Jupiter form.

One of the main models to form giant planets is called “core accretion”. In this scenario, a rocky core forms first by aggregation of solid particles until it reaches a few Earth masses when it becomes massive enough to accrete a gaseous envelope. For the first time, astronomers have detected evidence of this rocky core, the first step in the formation of a giant planet like our own Jupiter.

The astronomers used the Canada-France-Hawaii Telescope (CFHT) to analyze the starlight of the binary stars 16 Cygni A and 16 Cygni B. The system is a perfect laboratory to study the formation of giant planets because the stars were born together and are therefore very similar, and both resemble the Sun. However, observations during the last decades show that only one of the two stars, 16 Cygni B, hosts a giant planet which is about 2.4 times as massive as Jupiter. By decomposing the light from the two stars into their basic components and looking at the difference between the two stars, the astronomers were able to detect signatures left from the planet formation process on 16 Cygni B.

The fingerprints detected by the astronomers are twofold. First, they found that the star 16 Cygni A is enhanced in all chemical elements relative to 16 Cygni B. This means that 16 Cygni B, the star that hosts a giant planet, is metal deficient. As both stars were born from the same natal cloud, they should have exactly the same chemical composition. However, planets and stars form at about the same time, hence the metals that are missing in 16 Cygni B (relative to 16 Cygni A) were probably removed from its protoplanetary disk to form its giant planet, so that the remaining material that was falling into 16 Cygni B in the final phases of its formation was deficient in those metals.

The second fingerprint is that on top of an overall deficiency of all analyzed elements in 16 Cygni B, this star has a systematic deficiency in the refractory elements such as iron, aluminum, nickel, magnesium, scandium, and silicon. This is a remarkable discovery because the rocky core of a giant planet is expected to be rich in refractory elements. The formation of the rocky core seems to rob refractory material from the proto-planetary disk, so that the star 16 Cygni B ended up with a lower amount of refractories. This deficiency in the refractory elements can be explained by the formation of a rocky core with a mass of about 1.5 – 6 Earth masses, which is similar to the estimate of Jupiter's core.

"Our results show that the formation of giant planets, as well as terrestrial planets like our own Earth, leaves subtle signatures in stellar atmospheres", says Marcelo Tucci Maia (Universidade de São Paulo), the lead author of the paper. "It is fascinating that our differential technique can measure these subtle differences in chemical abundances; we achieve a precision that was unthinkable until now", adds team member Jorge Meléndez (Universidade de São Paulo). Ivan Ramírez (University of Texas) concludes: "16 Cyg is a remarkable system, but certainly not unique. It is special because it is nearby; however, there are many other binary stars with twin components on which this experiment could be performed. This could help us find planet-host stars in binaries in a much more straightforward manner compared to all other planet-finding techniques we have available today."

The team is composed of the PhD student Marcelo Tucci Maia, Prof. Dr. Jorge Meléndez (Universidade de São Paulo) and Dr. Iván Ramírez (University of Texas at Austin). This research will appear in the paper “High precision abundances in the 16 Cyg binary system: a signature of the rocky core in the giant planet”, by M. Tucci Maia, J. Meléndez and I. Ramírez, in the  Astrophysical Journal Letters.  

Contact information:

Media contact

Dr. Daniel Devost
Canada-France-Hawaii Telescope
(808) 885-3163
devost@cfht.hawaii.edu

Science contacts

Marcelo Tucci Maia
Universidade do São Paulo
marcelotuccimaia@usp.br

Prof. Jorge Meléndez
Universidade de São Paulo
jorge.melendez@iag.usp.br

Dr. Ivan Ramírez
University of Texas
ivan@astro.as.utexas.edu



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Wednesday, July 16, 2014

Large number of Dark Matter peaks found using Gravitational Lensing

This map shows the distribution of dark matter (black) in the Universe, overlapping with optical measured clusters of galaxies (red circles). The mass peaks in the map contain significant cosmological information, will provide us with an improved understanding about the dark side of the Universe. The size of this map is about 4 square degrees corresponding to only 2.5% of the full CS82 survey footprint shown in the next figure.


The background image (in brown colours) represent the SDSS imaging survey of the South Galactic cap comprising about 3200 square degrees. Over-plotted in white/blue is the distribution of Dark Matter derived from the CFHT/Megacam Stripe-82 observation over 170 square degrees. The mass peaks in the map contain significant cosmological information, and will provide us with an improved understanding about the dark side of the Universe.

A number of studies have shown that Dark Matter is the principle mass component of the Universe making up about 80% of the mass budget. The most direct technique to reveal the Dark Matter distribution is by using the gravitational lensing technique. Indeed, following Einstein's theory of Gravitation, we know that a mass concentration will deform locally the Space-Time and the observed shapes of distant galaxies seen through the such concentration will be deflected and distorted. By measuring the exact shapes of millions of these distant galaxies we can then map accurately the mass distribution in the Universe, and identify the mass peaks tracing mass concentration along their line of sight. Importantly, the number of mass peaks as a function of the mass peak significance encodes important information on the cosmological world model. In particular this distribution is sensitive to the nature of Gravitational force at large scales as well as the geometry of the Universe. Measuring mass peaks is thus one of the most attractive way to probe the relative importance and nature of Dark Matter and Dark Energy, measure the evolution the Universe and predict its fate. 

In a new publication of the Monthly Notice of Royal Astronomical Society, an international team, comprising researchers from Swiss, France, Brazil, Canada, and Germany present the first detailed analysis of the weak lensing peaks. This work is considered as a milestone, given the possible importance of the weak lensing peaks for cosmology. Because mass peaks are identified in two–dimensional dark matter maps directly, they can provide constraints that are free from potential selection effects and biases involved in identifying and measuring the masses of galaxy clusters. In fact a small fraction of the max peaks are just mass concentration excess along the line of sight, and not genuine massive clusters.

To detect the weak lensing mass peaks, the research team used the Canada-France-Hawaii Telescope Stripe 82 Survey (CS82 in short), still one of the largest weak lensing survey yet. The Survey covers ~170 square degrees of the Stripe 82 of the Sloan Digital Sky Survey (SDSS), an equatorial region of the South Galactic Cap that has been extensively studied by the SDSS project. With the precise shape measurement for more than four million faint distant galaxies, a dark matter mass map was generated. Huan Yuan Shan, the lead author of this publication explains that: "By studying the mass peaks in the map, we found that the abundance of mass peaks detected in CS82 is consistent with predictions from a ΛCDM cosmological model. This result confirms that the dark matter distribution from weak lensing measurement can be used as a cosmological probe".

The abundance of mass peaks in the Dark Matter mass map confirms the theories of structure formation. In the near future, with the up-coming weak lensing surveys (to be conducted with the DES survey, LSST and Euclid), by precisely counting the peaks of dark matter mass maps, we will be able to set constrains on the nature of Dark Matter and Dark Energy.

About the CFHT 


Stripe 82 survey: The CFHT Stripe 82 (CS82) collaboration comprises scientists from the following institutions: University of British Columbia (Canada), Laboratoire d'Astrophysique de Marseille (France), Brazilian Center for Physics Research (Brazil), École Polytechnique Fédérale de Lausanne (Switzerland), Institute for the Physics and Mathematics of the Universe (Japan), Universität Bonn (Germany), Institut d'Astrophysique de Paris (France), Valongo Observatory/Federal University of Rio de Janeiro (Brazil), Instituto de Astronomia, Geofísica e Ciências Atmosféricas - USP (Brazil), Instituto de Física - UFRGS (Brazil), Observatório Nacional (Brazil), Universitá deli studi di Ferrara (Italy), University of Hertfordshire (UK), University of Oxford (UK), University College London (UK), University of Waterloo (Canada), Leiden Observatory (Netherlands), Lawrence Berkeley National Laboratory (USA), University of California Berkeley (USA), Stanford (USA). 

The CS82 survey is based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT), which is operated by the National Research Council (NRC) of Canada, the Institut National des Science de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii. The Brazilian partnership on CFHT is managed by the Laboratório Nacional de Astrofísica (LNA). We thank the support of the Laboratório Interinstitucional de e-Astronomia (LIneA). We thank the CFHTLensS team through the expertise they built in analysing CFHT/Megacam weak lensing data. 

Contact information:
Dr. HuanYuan Shan
Affiliation: EPFL, Switzerland
Phone number: +41 22 379 2427

huanyuan.shan@epfl.ch

Prof. Jean-Paul Kneib.
Affiliation: EPFL, Switzerland
Phone number +33 695 795 392

jean-paul.kneib@epfl.ch

Prof. Martin Makler.
Affiliation: CBPF, Brazil
Phone number +55 21 2141 7191

martinmakler@gmail.com

Prof. Ludovic van Waerbeke
Affiliation: UBC, Canada
Phone number +1 604 822 5515

waerbeke@physics.ubc.ca

Dr. Eric Jullo.
Affiliation: LAM, France
Phone number +33 491 05 59 51

eric.jullo@lam.fr

Dr. Daniel Devost
Director of Science Operations
Phone: (808)885-3163

devost@cfht.hawaii.edu

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Tuesday, July 15, 2014

Radio-burst discovery deepens astrophysics mystery

 
Optical sky image of the area in the constellation Auriga where the fast radio burst FRB 121102 has been detected. The position of the burst, between the old supernova remnant S147 (left) and the star formation region IC 410 (right) is marked with a green circle. The burst appears to originate from much deeper in space, far beyond our galaxy. © Rogelio Bernal Andreo (DeepSkyColors.com)

Arecibo 305 m radio telescope, located in a natural valley in Puerto Rico. © NAIC

Newly detected short radio pulse appears to come from far beyond our galaxy

The discovery of a split-second burst of radio waves using the Arecibo radio telescope in Puerto Rico provides important new evidence of mysterious pulses that appear to come from deep in outer space.
The findings by an international team of astronomers led by Laura Spitler from the Max Planck Institute for Radio Astronomy in Bonn, Germany are published on July 10 in the online issue of The Astrophysical Journal. They mark the first time that a so-called "fast radio burst" has been detected in the Northern hemisphere of the sky

Fast radio bursts (FRBs) are bright flashes of radio waves that last only a few thousandths of a second. Scientists using the Parkes Observatory in Australia have recorded such events for the first time, but the lack of any similar findings by other facilities led to speculation that the Australian instrument might have been picking up signals originating from sources on or near Earth. The discovery at Arecibo is the first detection of a fast radio burst using an instrument other than the Parkes radio telescope. The position of the radio burst is in the direction of the constellation Auriga in the Northern sky.

"There are only seven bursts every minute somewhere in the sky on average, so you have to be pretty lucky to have your telescope pointed in the right place at the right time", says Laura Spitler from Max Planck Institute for Radio Astronomy (MPIfR) in Bonn, the lead author of the paper. "The characteristics of the burst seen by the Arecibo telescope, as well as how often we expect to catch one, are consistent with the characteristics of the previously observed bursts from Parkes."

"Our result is important because it eliminates any doubt that these radio bursts are truly of cosmic origin," continues Victoria Kaspi, an astrophysics professor at McGill University in Montreal and Principal Investigator for the pulsar-survey project that detected this fast radio burst. "The radio waves show every sign of having come from far outside our galaxy – a really exciting prospect."

Exactly what may be causing such radio bursts represents a major new enigma for astrophysicists.  Possibilities include a range of exotic astrophysical objects, such as evaporating black holes, mergers of neutron stars, or flares from magnetars — a type of neutron star with extremely powerful magnetic fields.

"Another possibility is that they are bursts much brighter than the giant pulses seen from some pulsars," notes James Cordes, a professor of astronomy at Cornell University and co-author of the new study.
The unusual pulse was detected on November 02, 2012, at the Arecibo Observatory with the world’s largest and most sensitive single-dish radio telescope, with a radio-mirror  spanning 305 metres and covering about 20 acres.

While fast radio bursts last just a few thousandths of a second and have rarely been detected, the new result confirms previous estimates that these strange cosmic bursts occur roughly 10,000 times a day over the whole sky. This astonishingly large number is inferred by calculating how much sky was observed, and for how long, in order to make the few detections that have so far been reported.

The bursts appear to be coming from beyond the Milky Way galaxy based on measurements of an effect known as plasma dispersion. Pulses that travel through the cosmos are  distinguished from man-made interference by the effect of interstellar electrons, which cause radio waves to travel more slowly at lower radio frequencies. The burst detected by the Arecibo telescope has three times the maximum dispersion measurement that would be expected from a source within the galaxy, the scientists report.

The discovery was made as part of the Pulsar Arecibo L-Band Feed Array (PALFA) survey, which aims to find a large sample of pulsars and to discover rare objects useful for probing fundamental aspects of neutron star physics and testing theories of gravitational physics.

Background Information

The research was supported by grants from the European Research Council, the National Science Foundation, the Natural Sciences and Engineering Research Council of Canada, the Fonds de recherche du Québec - Nature et technologies, and the Canadian Institute for Advanced Research, among others.

The Arecibo Observatory is operated by SRI International in alliance with Ana G. Méndez-Universidad Metropolitana and the Universities Space Research Association, under a cooperative agreement with the National Science Foundation (AST-1100968).

The data were processed on the ATLAS cluster of the Max Planck Institute for Gravitational Physics/Albert Einstein Institute, Hannover, Germany.

Local Contacts


Dr. Laura Spitler
Phone:+48 228 525-108
Max-Planck-Institut für Radioastronomie, Bonn

Dr. Paulo Freire
Phone:+49 228 525-396
Max-Planck-Institut für Radioastronomie, Bonn

Dr. Norbert Junkes
Presse- und Öffentlichkeitsarbeit
Phone:+49 228 525-399
Max-Planck-Institut für Radioastronomie, Bonn

Original Paper

Earlier Press Release



Further Information




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Monday, July 14, 2014

Carbon monoxide predicts ‘red and dead’ future of gas guzzler galaxy

Radio waves emitted from ALESS65 as observed by the Australia Telescope Compact Array. Credit: Huynh et al.

NGC5044, a ‘red and dead’ galaxy like ALESS65 will become in about 25 million years. (the X-Rays are shown in blue and the visible light is shown in yellow). Credit: X-ray: NASA/CXC/Stanford Univ/N.Werner et al; Optical: DSS) 

Arp220, a nearby ‘Ultraluminous Infrared Galaxy’ similar to what ALESS65 would look like if it were closer to Earth. Credit: NASA, ESA, and the Hubble Team

Dr Minh Huynh, Credit: ICRAR

Astronomers have studied the carbon monoxide in a galaxy over 12 billion light years from Earth and discovered that it’s running out of gas, quite literally, and headed for a ‘red and dead’ future.

The galaxy, known as ALESS65, was observed by the Atacama Large Millimeter Array (ALMA) in 2011 and is one of less than 20 known distant galaxies to contain carbon monoxide.

Dr Minh Huynh from The University of Western Australia node of the International Centre for Radio Astronomy Research (ICRAR) led the team on their search for galactic carbon monoxide in work published today in the Monthly Notices of the Royal Astronomical Society.

“We’re familiar with carbon monoxide here on Earth as the deadly gas that can cause suffocation, but in galaxies it plays an important role in the lifecycle of stars,” said Huynh.

“Out of the galaxies that we know contain carbon monoxide, less than 20 are as far away from Earth as ALESS65. Out of the billions of galaxies out there, the detections are very rare!”

Huynh, who grew up in Perth, said that at first astronomers didn’t think there could be massive ‘red and dead’ galaxies in the distant Universe, so studying galaxies heading towards that fate is important to solve the puzzle of their existence.
 
Using the Australia Telescope Compact Array (ATCA) radio telescope in NSW, Australia, Huynh and the team worked out how much carbon monoxide they could see in ALESS65 and extrapolated that out into how much fuel the galaxy has left – how much gas it has.

“All galaxies have a certain amount of fuel to make new stars,” said Huynh.

“Our galaxy, the Milky Way, has about five billion years before it runs out of fuel and becomes ‘red and dead’, but ALESS65 is a gas guzzler and only has 10s of millions of years left – very fast in astronomical terms.”

The team also combined their observations of the galaxy with the original data from ALMA to work out how similar ALESS65 is to galaxies nearer to Earth.

“We were able to work out the strength of the UV radiation in ALESS65; it’s similar to some ‘starbursting’ galaxies in the local universe, but the stars in ALESS65 are forming in much larger areas when compared to local galaxies,” said Huynh.  

The team will now turn their attentions to the search for carbon monoxide in another galaxy near to ALESS65, named ALESS61.

“Finding and studying carbon monoxide in more galaxies will tell us even more about how stars formed in the early days of the Universe and help solve the mystery of far away ‘red and dead’ galaxies” said Huynh.

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.

Original Publication


“Detection of molecular gas in an ALMA [CII]-identified Submillimetre Galaxy at z=4.44” Huynh et al. Monthly Notices of the Royal Astronomical Society (Oxford University Press), Published 9th of July 2014.



Contacts

Dr Minh Huynh
ICRAR - UWA
Ph: +61 8 6488 4594
M: +61 413 698 670
E:
minh.huynh@icrar.org

Kirsten Gottschalk
Media Contact, ICRAR
Ph: +61 8 6488 7771
M: +61 438 361 876
E:
kirsten.gottschalk@icrar.org

David Stacey
Media Manager, UWA
Ph: +61 8 6488 3229
M: +61 432 637 716
E:
david.stacey@uwa.edu.au

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Astronomers bring the third dimension to a doomed star's outburst

A new shape model of the Homunculus Nebula reveals protrusions, trenches, holes and irregularities in its molecular hydrogen emission. The protrusions appear near a dust skirt seen at the nebula's centre in visible light (inset) but not found in this study, so they constitute different structures.  Credit: NASA Goddard Space Flight Centre, inset: NASA, ESA, Hubble SM4 ERO Team. Hi-res Image
 
Astronomers have created a detailed 3D model of the expanding cloud of debris produced in the outburst of a doomed star. The model can be reproduced at home by anyone with a 3D printer. The team report their findings in a paper published today in the journal Monthly Notices of the Royal Astronomical Society.

In the middle of the 19th century, the massive binary system eta Carinae (η Car) underwent an eruption that ejected more than 10 solar masses of debris and briefly made it the second-brightest star in the sky. The researchers used extensive new observations to create a detailed 3D model of the expanding debris cloud.

"Our model indicates that this vast shell of gas and dust has a more complex origin than is generally assumed," said Thomas Madura, of NASA's Goddard Space Flight Center and a member of the team. "For the first time, we see evidence suggesting that intense interactions between the stars in the central binary played a significant role in sculpting the nebula we see today."

Eta Carinae lies about 7,500 light-years away in the southern constellation of Carina and is one of the most massive binary systems astronomers can study in detail. The smaller star is about 30 times the mass of the sun and may be as much as a million times more luminous. The primary star contains about 90 solar masses and emits 5 million times the sun's energy output. Both stars are fated to end their lives in spectacular supernova explosions.

Animation of the 3D Homunculus Nebula model
Credit: NASA Goddard Space Flight Center Conceptual Image La
 
Between 1838 and 1845, eta Carinae underwent a period of unusual variability during which it briefly outshone Canopus, normally the second-brightest star. As a part of this event, which astronomers call the Great Eruption, a gaseous shell containing at least 10 and perhaps as much as 40 times the sun's mass was shot into space. This material forms a twin-lobed dust-filled cloud known as the Homunculus Nebula, which is now about a light-year long and continues to expand at more than 1.3 million mph (2.1 million km/h).

Using the European Southern Observatory's Very Large Telescope and its X-Shooter spectrograph over two nights in March 2012, the team observed the nebula in near-infrared, visible and ultraviolet wavelengths in 92 separate areas, making the most complete map to date. The researchers have used the spatial and velocity information provided by this data to create the first high-resolution 3D model of the Homunculus Nebula.

The shape model was developed using only a single emission line of near-infrared light emitted by molecular hydrogen gas. The characteristic light at 2.12 microns shifts in wavelength slightly depending on the speed and direction of the expanding gas, allowing the team to probe even dust-obscured portions of the Homunculus Nebula that face away from Earth.

"Our next step was to process all of this using 3D modelling software I developed in collaboration with Nico Koning from the University of Calgary in Canada. The program is simply called 'Shape,' and it analyses and models the three-dimensional motions and structure of nebulae in a way that can be compared directly with observations," said Wolfgang Steffen, of the National Autonomous University of Mexico and the lead author of the paper.
 
NASA astrophysicists Ted Gull and Tom Madura discuss eta Carinae and their new model of the Homunculus Nebula, a shell of gas and dust ejected during the star's mid-19th century eruption. Credit: NASA Goddard Space Flight Center. Video Youtube
 
The new shape model confirms several features identified by previous studies, including pronounced holes located at the ends of each lobe and the absence of any extended molecular hydrogen emission from a dust skirt apparent in visible light near the centre of the nebula. New features include curious arm-like protrusions emanating from each lobe near the dust skirt; vast, deep trenches curving along each lobe; and irregular divots on the side facing away from Earth.

"One of the questions we set out to answer with this study is whether the Homunculus contains any imprint of the star's binary nature, since previous efforts to explain its shape have assumed that both lobes were more or less identical and symmetric around their long axis," explained team member Jose Groh, of the University of Geneva. "The new features strongly suggest that interactions between eta Carinae's stars helped mould the Homunculus."

Every 5.5 years, when their orbits carry them to their closest approach, the immense and brilliant stars of eta Carinae are only as far apart as the distance between Mars and the Sun. Both stars possess powerful gaseous outflows called stellar winds, which interact most dramatically during closest approach. The faster wind from the smaller star then carves a tunnel through the denser wind of its companion. The opening angle of the cavity created closely matches the extent of the trenches (130 degrees) and the angle between the arm-like protrusions (110 degrees). This indicates that the shape of the nebula likely continues to carry an impression from a binary close approach around the time of the Great Eruption.

A 3D-printed model of the Homunculus Nebula is compared to a Hubble Space Telescope image of the object.  Credit: NASA Goddard Space Flight Center/Ed Campion. Hi-Res Image

Once the researchers had developed their Homunculus model, they took things one step further. They converted it to a format that can be used by 3D printers and made the file available along with the published paper.

"Now anyone with access to a 3D printer can produce their own version of this incredible object," said Theodore Gull, who is also at Goddard and a co-author of the paper. "While 3D-printed models will make a terrific visualization tool for anyone interested in astronomy, I see them as particularly valuable for the blind, who now will be able to compare embossed astronomical images with a scientifically accurate representation of the real thing."

Media contacts

Francis Reddy
NASA Goddard Space Flight Center

francis.j.reddy@nasa.gov
+1 301 286 4453

Dr Keith Smith
Royal Astronomical Society
+44 (0)20 7734 4582

kts@ras.org.uk

Science contact

Prof. Wolfgang Steffen
National Autonomous University of Mexico
Please contact Francis Reddy (details above) in the first instance.


Images and captions


The 3D printing model is available, along with a custom stand.
Credit: Steffen, W., Teodoro, M., Madura, T., et al. (2014)
More media and captions are available from http://svs.gsfc.nasa.gov/goto?11568

Further information

This research has been published in Steffen W. el al., 2014, "The three-dimensional structure of the Eta Carinae Homunculus", Monthly Notices of the Royal Astronomical Society, vol. 442, p. 3316-3328, published by Oxford University Press.
Notes for editors

The Royal Astronomical Society (RAS), founded in 1820, encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science. The RAS organises scientific meetings, publishes international research and review journals, recognizes outstanding achievements by the award of medals and prizes, maintains an extensive library, supports education through grants and outreach activities and represents UK astronomy nationally and internationally. Its more than 3800 members (Fellows), a third based overseas, include scientific researchers in universities, observatories and laboratories as well as historians of astronomy and others. Follow the RAS on Twitter via @royalastrosoc


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