Friday, December 19, 2014

A messy star factory

Credit: ESA/Hubble & NASA
Acknowledgement: Nick Rose

This sprinkle of cosmic glitter is a blue compact dwarf galaxy known as Markarian 209. Galaxies of this type are blue-hued, compact in size, gas-rich, and low in heavy elements. They are often used by astronomers to study star formation, as their conditions are similar to those thought to exist in the early Universe.

Markarian 209 in particular has been studied extensively. It is filled with diffuse gas and peppered with star-forming regions towards its core. This image captures it undergoing a particularly dramatic burst of star formation, visible as the lighter blue cloudy region towards the top right of the galaxy. This clump is filled with very young and hot newborn stars.

This galaxy was initially thought to be a young galaxy undergoing its very first episode of star formation, but later research showed that Markarian 209 is actually very old, with an almost continuous history of forming new stars. It is thought to have never had a dormant period — a period during which no stars were formed — lasting longer than 100 million years.

The dominant population of stars in Markarian 209 is still quite young, in stellar terms, with ages of under 3 million years. For comparison, the Sun is some 4.6 billion years old, and is roughly halfway through its expected lifespan.

The observations used to make this image were taken using Hubble’s Wide Field Camera 3 and Advanced Camera for Surveys, and span the ultraviolet, visible, and infrared parts of the spectrum. A scattering of other bright galaxies can be seen across the frame, including the bright golden oval that could, due to a trick of perspective, be mistaken as part of Markarian 209 but is in fact a background galaxy.

A version of this image was entered into the Hubble's Hidden Treasures image processing competition by contestant Nick Rose.

 

Links:


 Source:   ESA/Hubble - Space Telescope


Thursday, December 18, 2014

Kepler Proves It Can Still Find Planets

This artist's conception portrays the first planet discovered by the Kepler spacecraft during its K2 mission. A transit of the planet was teased out of K2's noisier data using ingenious computer algorithms developed by a CfA researcher. The newfound planet, HIP 116454b, has a diameter of 20,000 miles (two and a half times the size of Earth) and weighs 12 times as much. It orbits its star once every 9.1 days. Credit: David A. Aguilar (CfA). High Resolution (jpg) - Low Resolution (jpg)

"Like a phoenix rising from the ashes, Kepler has been reborn and is continuing to make discoveries. Even better, the planet it found is ripe for follow-up studies," says lead author Andrew Vanderburg of the Harvard-Smithsonian Center for Astrophysics (CfA).

NASA's Kepler spacecraft detects planets by looking for transits, when a star dims slightly as a planet crosses in front of it. The smaller the planet, the weaker the dimming, so brightness measurements must be exquisitely precise. To enable that precision, the spacecraft must maintain a steady pointing.

Kepler's primary mission came to an end when the second of four reaction wheels used to stabilize the spacecraft failed. Without at least three functioning reaction wheels, Kepler couldn't be pointed accurately.

Rather than giving up on the plucky spacecraft, a team of scientists and engineers developed an ingenious strategy to use pressure from sunlight as a virtual reaction wheel to help control the spacecraft. The resulting second mission, K2, promises to not only continue Kepler's search for other worlds, but also introduce new opportunities to observe star clusters, active galaxies, and supernovae.

Due to Kepler's reduced pointing capabilities, extracting useful data requires sophisticated computer analysis. Vanderburg and his colleagues developed specialized software to correct for spacecraft movements, achieving about half the photometric precision of the original Kepler mission.

Kepler's new life began with a 9-day test in February 2014. When Vanderburg and his colleagues analyzed that data, they found that Kepler had detected a single planetary transit.

They confirmed the discovery with radial velocity measurements from the HARPS-North spectrograph on the Telescopio Nazionale Galileo in the Canary Islands. Additional transits were weakly detected by the Microvariability and Oscillations of STars (MOST) satellite.

The newfound planet, HIP 116454b, has a diameter of 20,000 miles, two and a half times the size of Earth. HARPS-N showed that it weighs almost 12 times as much as Earth. This makes HIP 116454b a super-Earth, a class of planets that doesn't exist in our solar system. The average density suggests that this planet is either a water world (composed of about three-fourths water and one-fourth rock) or a mini-Neptune with an extended, gaseous atmosphere.

This close-in planet circles its star once every 9.1 days at a distance of 8.4 million miles. Its host star is a type K orange dwarf slightly smaller and cooler than our sun. The system is 180 light-years from Earth in the constellation Pisces.

Since the host star is relatively bright and nearby, follow-up studies will be easier to conduct than for many Kepler planets orbiting fainter, more distant stars.

"HIP 116454b will be a top target for telescopes on the ground and in space," says Harvard astronomer and co-author John Johnson of the CfA.

The research paper reporting this discovery has been accepted for publication in The Astrophysical Journal.

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




Life on an aquaplanet

Illustration: Christine Daniloff/MIT


MIT study finds an exoplanet, tilted on its side, could still be habitable if covered in ocean.

Nearly 2,000 planets beyond our solar system have been identified to date. Whether any of these exoplanets are hospitable to life depends on a number of criteria. Among these, scientists have thought, is a planet’s obliquity — the angle of its axis relative to its orbit around a star.

Earth, for instance, has a relatively low obliquity, rotating around an axis that is nearly perpendicular to the plane of its orbit around the sun. Scientists suspect, however, that exoplanets may exhibit a host of obliquities, resembling anything from a vertical spinning top to a horizontal rotisserie. The more extreme the tilt, the less habitable a planet may be — or so the thinking has gone.

Now scientists at MIT have found that even a high-obliquity planet, with a nearly horizontal axis, could potentially support life, so long as the planet were completely covered by an ocean. In fact, even a shallow ocean, about 50 meters deep, would be enough to keep such a planet at relatively comfortable temperatures, averaging around 60 degrees Fahrenheit year-round.

David Ferreira, a former research scientist in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS), says that on the face of it, a planet with high obliquity would appear rather extreme: Tilted on its side, its north pole would experience daylight continuously for six months, and then darkness for six months, as the planet revolves around its star.

“The expectation was that such a planet would not be habitable: It would basically boil, and freeze, which would be really tough for life,” says Ferreira, who is now a lecturer at the University of Reading, in the United Kingdom. “We found that the ocean stores heat during summer and gives it back in winter, so the climate is still pretty mild, even in the heart of the cold polar night. So in the search for habitable exoplanets, we're saying, don't discount high-obliquity ones as unsuitable for life.”

Details of the group’s analysis are published in the journal Icarus. The paper’s co-authors are Ferreira; Sara Seager, the Class of 1941 Professor in EAPS and MIT’s Department of Physics; John Marshall, the Cecil and Ida Green Professor in Earth and Planetary Sciences; and Paul O’Gorman, an associate professor in EAPS.


Tilting toward a habitable exoplanet

Ferreira and his colleagues used a model developed at MIT to simulate a high-obliquity “aquaplanet” — an Earth-sized planet, at a similar distance from its sun, covered entirely in water. The three-dimensional model is designed to simulate circulations among the atmosphere, ocean, and sea ice, taking into the account the effects of winds and heat in driving a 3000-meter deep ocean. For comparison, the researchers also coupled the atmospheric model with simplified, motionless “swamp” oceans of various depths: 200 meters, 50 meters, and 10 meters.

The researchers used the detailed model to simulate a planet at three obliquities: 23 degrees (representing an Earth-like tilt), 54 degrees, and 90 degrees.

For a planet with an extreme, 90-degree tilt, they found that a global ocean — even one as shallow as 50 meters — would absorb enough solar energy throughout the polar summer and release it back into the atmosphere in winter to maintain a rather mild climate. As a result, the planet as a whole would experience spring-like temperatures year round.

“We were expecting that if you put an ocean on the planet, it might be a bit more habitable, but not to this point,” Ferreira says. “It’s really surprising that the temperatures at the poles are still habitable.”


A runaway “snowball Earth”

In general, the team observed that life could thrive on a highly tilted aquaplanet, but only to a point. In simulations with a shallower ocean, Ferreira found that waters 10 meters deep would not be sufficient to regulate a high-obliquity planet’s climate. Instead, the planet would experience a runaway effect: As soon as a bit of ice forms, it would quickly spread across the dark side of the planet. Even when this side turns toward the sun, according to Ferreira, it would be too late: Massive ice sheets would reflect the sun’s rays, allowing the ice to spread further into the newly darkened side, and eventually encase the planet.

“Some people have thought that a planet with a very large obliquity could have ice just around the equator, and the poles would be warm,” Ferreira says. “But we find that there is no intermediate state. If there’s too little ocean, the planet may collapse into a snowball. Then it wouldn’t be habitable, obviously.”

Darren Williams, a professor of physics and astronomy at Pennsylvania State University, says past climate modeling has shown that a wide range of climate scenarios are possible on extremely tilted planets, depending on the sizes of their oceans and landmasses. Ferreira’s results, he says, reach similar conclusions, but with more detail.

“There are one or two terrestrial-sized exoplanets out of a thousand that appear to have densities comparable to water, so the probability of an all-water planet is at least 0.1 percent,” Williams says. “The upshot of all this is that exoplanets at high obliquity are not necessarily devoid of life, and are therefore just as interesting and important to the astrobiology community.”


Jennifer Chu | MIT News Office 



Wednesday, December 17, 2014

NASA's Sun Watching Observatory Sees Mid-level Solar Flare on Dec. 16, 2014

NASA's Solar Dynamics Observatory captured this image of a mid-level solar flare – as seen in the bright flash in the middle –on Dec. 16, 2014 shortly before midnight EST. Image Credit:  NASA/SDO. › View full disk image


The sun emitted a mid-level solar flare, peaking at 11:50 p.m. EST on Dec. 16, 2014. NASA’s Solar Dynamics Observatory, which watches the sun constantly, captured an image of the event. Solar flares are powerful bursts of radiation. Harmful radiation from a flare cannot pass through Earth's atmosphere to physically affect humans on the ground, however -- when intense enough -- they can disturb the atmosphere in the layer where GPS and communications signals travel.

To see how this event may affect Earth, please visit NOAA's Space Weather Prediction Center at http://spaceweather.gov, the U.S. government's official source for space weather forecasts, alerts, watches and warnings.

This flare is classified as an M8.7-class flare. M-class flares are a tenth the size of the most intense flares, the X-class flares. The number provides more information about its strength. An M2 is twice as intense as an M1, an M3 is three times as intense, etc.

Updates will be provided as needed.


What is a solar flare?

For answers to this and other space weather questions, please visit the Spaceweather Frequently Asked Questions page.


Related Links

Karen C. Fox
NASA's Goddard Space Flight Center, Greenbelt, Maryland


Source:  Solar Dynamics Observatory (SDO) - NASA


The Hot Blue Stars of Messier 47

The star cluster Messier 47

The bright star clusters Messier 47 and Messier 46 in the constellation of Puppis

Wide-field view of the bright star clusters Messier 47 and Messier 46


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Videos


Zooming in on the star cluster Messier 47
Zooming in on the star cluster Messier 47

Close up view of the bright star cluster Messier 47
Close up view of the bright star cluster Messier 47


This spectacular image of the star cluster Messier 47 was taken using the Wide Field Imager camera, installed on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile. This young open cluster is dominated by a sprinkling of brilliant blue stars but also contains a few contrasting red giant stars.

Messier 47 is located approximately 1600 light-years from Earth, in the constellation of Puppis (the poop deck of the mythological ship Argo). It was first noticed some time before 1654 by Italian astronomer Giovanni Battista Hodierna and was later independently discovered by Charles Messier himself, who apparently had no knowledge of Hodierna’s earlier observation.

Although it is bright and easy to see, Messier 47 is one of the least densely populated open clusters. Only around 50 stars are visible in a region about 12 light-years across, compared to other similar objects which can contain thousands of stars.

Messier 47 has not always been so easy to identify. In fact, for years it was considered missing, as Messier had recorded the coordinates incorrectly. The cluster was later rediscovered and given another catalogue designation — NGC 2422. The nature of Messier’s mistake, and the firm conclusion that Messier 47 and NGC 2422 are indeed the same object, was only established in 1959 by Canadian astronomer T. F. Morris.

The bright blue–white colours of these stars are an indication of their temperature, with hotter stars appearing bluer and cooler stars appearing redder. This relationship between colour, brightness and temperature can be visualised by use of the Planck curve. But the more detailed study of the colours of stars using spectroscopy also tells astronomers a lot more — including how fast the stars are spinning and their chemical compositions. There are also a few bright red stars in the picture — these are red giant stars that are further through their short life cycles than the less massive and longer-lived blue stars [1].

By chance Messier 47 appears close in the sky to another contrasting star cluster — Messier 46. Messier 47 is relatively close, at around 1600 light-years, but Messier 46 is located around 5500 light-years away and contains a lot more stars, with at least 500 stars present. Despite containing more stars, it appears significantly fainter due to its greater distance.

Messier 46 could be considered to be the older sister of Messier 47, with the former being approximately 300 million years old compared to the latter’s 78 million years. Consequently, many of the most massive and brilliant of the stars in Messier 46 have already run through their short lives and are no longer visible, so most stars within this older cluster appear redder and cooler.

This image of Messier 47 was produced as part of the ESO Cosmic Gems programme [2].


Notes

[1] The lifetime of a star depends primarily on its mass. Massive stars, containing many times as much material as the Sun, have short lives measured in millions of years. On the other hand much less massive stars can continue to shine for many billions of years. In a cluster, the stars all have about the same age and same initial chemical composition. So the brilliant massive stars evolve quickest, become red giants sooner, and end their lives first, leaving the less massive and cooler ones to long outlive them.

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


More Information

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


Links

Contacts

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

Source: ESO

Tuesday, December 16, 2014

Magnetic Fields on Solar-Type Stars

Vivid orange streamers of super-hot, electrically charged gas (plasma) arc from the surface of the Sun reveal the structure of the solar magnetic field rising vertically from a sunspot. Astronomers are now studying the magnetic fields on solar-type stars using techniques of polarimetry. Credit: Hinode, JAXA/NASA


The Sun rotates slowly, about once every 24 days at its equator although the hot gas at every latitude rotates at a slightly different rate. Rotation helps to drive the mechanisms that power stellar magnetic fields, and in slowly rotating solar-type stars also helps to explain the solar activity cycle. In the case of solar-type stars that rotate much faster than does the modern-day Sun, the dynamo appears to be generated by fundamentally different mechanisms that, along with many details of solar magnetic field generation, are not well understood. Astronomers trying to understand dynamos across a range of solar-type stars (and how they evolve) have been observing a variety of active stars, both slow and fast rotators, to probe how various physical parameters of stars enhance or inhibit dynamo processes.

Most techniques used to observe stellar magnetism rely on indirect proxies of the field, for example on characteristics of the radiation emitted by atoms. Surveys using these proxies have found clear dependencies between rotation and the stellar dynamo and the star’s magnetic cycles, among other things. Recent advances in instrumentation that can sense the polarization of the light extend these methods and have made it possible to directly measure solar-strength magnetic fields on other stars.

CfA astronomer Jose-Dias do Nascimento is a member of a team of astronomers that has just completed the most extensive polarization survey of stars to date. They detected magnetic fields on sixty-seven stars, twenty-one of them classified as solar-type, about four times as many solar-type stars as had been previously classified. The scientists found that the average field increases with the stellar rotation rate and decreases with stellar age, and that its strength correlates with emission from the stars’ hot outer layers, their chromospheres.

Not only does this paper represent the most extensive survey to date of its kind, it demonstrates the power of the polarization technique. It signals that it is possible to greatly expand the study of magnetic fields in solar-type stars, which efforts will continue to improve our understanding of the surface fields in the Sun.

Reference(s): 

"A BCool Magnetic Snapshot Survey of Solar-Type Stars," S. C. Marsden, P. Petit, S. V. Jeffers, J. Morin, R. Fares, A. Reiners, J.-D. do Nascimento Jr., M. Auriere, J. Bouvier, B. D. Carter, C. Catala, B. Dintrans, J.-F. Donati, T. Gastine, M. Jardine, R. Konstantinova-Antova, J. Lanoux, F. Lignieres, A. Morgenthaler, J.C. Ramırez-Velez, S. Theado, V. Van Grootel and the BCool Collaboration, MNRAS 444, 3517, 2014.




Stretched-out solid exoplanets

An artist’s impression of a stretched rocky planet in orbit around a red dwarf star. So close to the star, there is a difference in the strength of the gravitational field on each side of the planet, stretching it significantly. Credit: Shivam Sikroria. Click  here for a full size image


Astronomers could soon be able to find rocky planets stretched out by the gravity of the stars they orbit, according to a group of researchers in the United States. The team, led by Prabal Saxena of George Mason University, describe how to detect these exotic worlds in a paper in the journal Monthly Notices of the Royal Astronomical Society.

Since the first discovery in 1993, more than 1800 planets have been found in orbit around stars other than our Sun. These 'exoplanets' are incredibly diverse, with some gaseous like Jupiter and some mostly rocky like the Earth. The worlds also orbit their stars at very different distances, from less than a million km to nearly 100 billion km away. Planets that are very close to their stars experience harsh conditions, often with very high temperatures (>1000 degrees Celsius) and significant stretching from the tidal forces resulting from the stellar gravitational field. This is most obvious with planets with a large atmosphere (so-called 'hot Jupiters') but harder to see with rockier objects.

Prabal and his team modelled cases where the planets are in orbit close to small red dwarf stars, much fainter than our Sun, but by far the most common type of star in the Galaxy. The planets’ rotation is locked, so the worlds keep the same face towards the stars they orbit, much like the Moon does as it moves around the Earth. According to the scientists, in these circumstances the distortion of the planets should be detectable in transit events, where the planets moves in front of their stars and blocks out some of their light.

If astronomers are able to find these extreme exoplanets, it could give them new insights into the properties of Earth-like planets as a whole. Prabal comments, "Imagine taking a planet like the Earth or Mars, placing it near a cool red star and stretching it out. Analysing the new shape alone will tell us a lot about the otherwise impossible to see internal structure of the planet and how it changes over time."

The subtle signals from stretched rocky planets could be found by some current telescopes, and certainly by much more powerful observatories like the James Webb Space Telescope (JWST) and the European Extremely Large Telescope (E-ELT) that are due to enter service in the next few years.

Media contact
Dr Robert Massey
Royal Astronomical Society
Tel: +44 (0)20 7734 3307 x214
Mob: +44 (0)794 124 8035

rm@ras.org.uk

Science contact
Prabal Saxena
School of Physics, Astronomy and Computational Sciences
George Mason University
Virginia
United States
Tel: +1 516 978 2158

psaxena2@masonlive.gmu.edu

Further information
The new work appears in P. Saxena et al. "The observational effects and signatures of tidally distorted solid exoplanets", Monthly Notices of the Royal Astronomical Society, vol. 446, pp. 4271–4277, 2015, 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 organizes 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



Monday, December 15, 2014

The magnetic field along the Galactic plane

The magnetic field along the Galactic plane
Copyright: ESA/Planck Collaboration. 
Acknowledgment: M.-A. Miville-Deschênes, CNRS – Institut d’Astrophysique Spatiale, Université Paris-XI, Orsay, France
Hi-Res Image (5.58 MB)

While the pastel tones and fine texture of this image may bring to mind brush strokes on an artist’s canvas, they are in fact a visualisation of data from ESA’s Planck satellite. The image portrays the interaction between interstellar dust in the Milky Way and the structure of our Galaxy’s magnetic field.

Between 2009 and 2013, Planck scanned the sky to detect the most ancient light in the history of the Universe – the cosmic microwave background. It also detected significant foreground emission from diffuse material in our Galaxy which, although a nuisance for cosmological studies, is extremely important for studying the birth of stars and other phenomena in the Milky Way.

Among the foreground sources at the wavelengths probed by Planck is cosmic dust, a minor but crucial component of the interstellar medium that pervades the Galaxy. Mainly gas, it is the raw material for stars to form.

Interstellar clouds of gas and dust are also threaded by the Galaxy’s magnetic field, and dust grains tend to align their longest axis at right angles to the direction of the field. As a result, the light emitted by dust grains is partly ‘polarised’ – it vibrates in a preferred direction – and, as such, could be caught by the polarisation-sensitive detectors on Planck.

Scientists in the Planck collaboration are using the polarised emission of interstellar dust to reconstruct the Galaxy’s magnetic field and study its role in the build-up of structure in the Milky Way, leading to star formation.

In this image, the colour scale represents the total intensity of dust emission, revealing the structure of interstellar clouds in the Milky Way. The texture is based on measurements of the direction of the polarised light emitted by the dust, which in turn indicates the orientation of the magnetic field.

This image shows the intricate link between the magnetic field and the structure of the interstellar medium along the plane of the Milky Way. In particular, the arrangement of the magnetic field is more ordered along the Galactic plane, where it follows the spiral structure of the Milky Way. Small clouds are seen just above and below the plane, where the magnetic field structure becomes less regular.

From these and other similar observations, Planck scientists found that filamentary interstellar clouds are preferentially aligned with the direction of the ambient magnetic field, highlighting the strong role played by magnetism in galaxy evolution.

The emission from dust is computed from a combination of Planck observations at 353, 545 and 857 GHz, whereas the direction of the magnetic field is based on Planck polarisation data at 353 GHz.


Source: ESA


Swarms of Pluto-Size Objects Kick Up Dust around Adolescent Sun-Like Star

Artist impression of the debris disk around HD 107146. This adolescent star system shows signs that in its outer reaches, swarms of Pluto-size objects are jostling nearby smaller objects, causing them to collide and "kick up" considerable dust. Credit: A. Angelich (NRAO/AUI/NSF)

ALMA image of the dust surrounding the star HD 107146. Dust in the outer reaches of the disk is thicker than in the inner regions, suggesting that a swarm of Pluto-size planetesimals is causing smaller objects to smash together. The dark ring-like structure in the middle portion of the disk may be evidence of a gap where a planet is sweeping its orbit clear of dust. Credit: L. Ricci ALMA (NRAO/NAOJ/ESO); B. Saxton (NRAO/AUI/NSF)

Cambridge, MA - Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) may have detected the dusty hallmarks of an entire family of Pluto-size objects swarming around an adolescent version of our own Sun.

By making detailed observations of the protoplanetary disk surrounding the star known as HD 107146, the astronomers detected an unexpected increase in the concentration of millimeter-size dust grains in the disk's outer reaches. This surprising increase, which begins remarkably far -- about 13 billion kilometers -- from the host star, may be the result of Pluto-size planetesimals stirring up the region, causing smaller objects to collide and blast themselves apart.

Dust in debris disks typically consists of material left over from the formation of planets. Very early in the lifespan of the disk, this dust is continuously replenished by collisions of larger bodies, such as comets and asteroids. In mature solar systems with fully formed planets, comparatively little dust remains. In between these two ages -- when a solar system is in its awkward teenage years -- certain models predict that the concentration of dust would be much denser in the most distant regions of the disk. This is precisely what ALMA has found.

"The dust in HD 107146 reveals this very interesting feature -- it gets thicker in the very distant outer reaches of the star's disk," said Luca Ricci, an astronomer at the Harvard-Smithsonian Center for Astrophysics (CfA), and lead author on a paper accepted for publication in the Astrophysical Journal. At the time of the observations, Ricci was with the California Institute of Technology.

"The surprising aspect is that this is the opposite of what we see in younger primordial disks where the dust is denser near the star. It is possible that we caught this particular debris disk at a stage in which Pluto-size planetesimals are forming right now in the outer disk while other Pluto-size bodies have already formed closer to the star," said Ricci.

According to current computer models, the observation that the density of dust is higher in the outer regions of the disk can only be explained by the presence of recently formed Pluto-sized bodies. Their gravity would disturb smaller planetesimals, causing more frequent collisions that generate the dust ALMA sees.

The new ALMA data also hint at another intriguing feature in the outer reaches of the disk: a possible "dip" or depression in the dust about 1.2 billion kilometers wide, beginning approximately 2.5 times the distance of the Sun to Neptune from the central star. Though only suggested in these preliminary observations, this depression could be a gap in the disk, which would be indicative of an Earth-mass planet sweeping the area clear of debris. Such a feature would have important implications for the possible planet-like inhabitants of this disk and may suggest that Earth-size planets could form in an entirely new range of orbits than have ever been seen before.

The star HD 107146 is of particular interest to astronomers because it is in many ways a younger version of our own Sun. It also represents a period of transition from a solar system's early life to its more mature, final stages where planets have finished forming and have settled into their final orbits around their host star. 

"This system offers us the chance to study an intriguing time around a young, Sun-like star," said ALMA Deputy Director and coauthor Stuartt Corder. "We are possibly looking back in time here, back to when the Sun was about 2 percent of its current age."

The star HD 107146 is located approximately 90 light-years from Earth in the direction of the constellation Coma Berenices. It is approximately 100 million years old. Further observations with ALMA's new long-baseline, high-resolution capabilities will shed more light on the dynamics and composition of this intriguing object.

Additional authors on the paper include John M. Carpenter and B. Fu, Caltech; A. M. Hughes, Wesleyan University; and Andrea Isella, Rice University.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA is funded in Europe by the European Organization for Astronomical Research in the Southern Hemisphere (ESO), in North America by the U.S. National Science Foundation (NSF) in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and in East Asia by the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), which is managed by Associated Universities, Inc. (AUI) and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.


Contacts: 

Charles E. Blue
Public Information Officer
(434) 296-0314 
Emailcblue@nrao.edu

Luca Ricci
Harvard-Smithsonian Center for Astrophysics

 Email: lucaricci83@gmail.com

Friday, December 12, 2014

All that glitters

Credit:  ESA/Hubble & NASA 
Acknowledgement: Gilles Chapdelaine

This striking new NASA/ESA Hubble Space Telescope image shows a glittering bauble named Messier 92. Located in the northern constellation of Hercules, this globular cluster — a ball of stars that orbits a galactic core like a satellite — was first discovered by astronomer Johann Elert Bode in 1777.

Messier 92 is one of the brightest globular clusters in the Milky Way, and is visible to the naked eye under good observing conditions. It is very tightly packed with stars, containing some 330 000 stars in total. As is characteristic of globular clusters, the predominant elements within Messier 92 are hydrogen and helium, with only traces of others. It is actually what is known as an Oosterhoff type II (OoII) globular cluster, meaning that it belongs to a group of metal-poor clusters — to astronomers, metals are all elements heavier than hydrogen and helium.

By exploring the composition of globulars like Messier 92, astronomers can figure out how old these clusters are. As well as being bright, Messier 92 is also old, being one of the oldest star clusters in the Milky Way, with an age almost the same as the age of the Universe.

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

Links


Source: ESA/Hubble - Space Telescope

Thursday, December 11, 2014

NGC 2207 and IC 2163: Galactic Get-Together has Impressive Light Display

NGC 2207 and IC 2163 (Composite)
Credit  X-ray: NASA/CXC/SAO/S.Mineo et al, Optical: NASA/STScI, Infrared: NASA/JPL-Caltech



At this time of year, there are lots of gatherings often decorated with festive lights. When galaxies get together, there is the chance of a spectacular light show as is the case with NGC 2207 and IC 2163

Located about 130 million light years from Earth, in the constellation of Canis Major, this pair of spiral galaxies has been caught in a grazing encounter. NGC 2207 and IC 2163 have hosted three supernova explosions in the past 15 years and have produced one of the most bountiful collections of super bright X-ray lights known. These special objects - known as "ultraluminous X-ray sources" (ULXs) - have been found using data from NASA's Chandra X-ray Observatory.

As in our Milky Way galaxy, NGC 2207 and IC 2163 are sprinkled with many star systems known as X-ray binaries, which consist of a star in a tight orbit around either a neutron star or a "stellar-mass" black hole. The strong gravity of the neutron star or black hole pulls matter from the companion star. As this matter falls toward the neutron star or black hole, it is heated to millions of degrees and generates X-rays.

ULXs have far brighter X-rays than most "normal" X-ray binaries. The true nature of ULXs is still debated, but they are likely a peculiar type of X-ray binary. The black holes in some ULXs may be heavier than stellar mass black holes and could represent a hypothesized, but as yet unconfirmed, intermediate-mass category of black holes.

This composite image of NGC 2207 and IC 2163 contains Chandra data in pink, optical light data from the Hubble Space Telescope in red, green, and blue (appearing as blue, white, orange, and brown), and infrared data from the Spitzer Space Telescope in red.

The new Chandra image contains about five times more observing time than previous efforts to study ULXs in this galaxy pair. Scientists now tally a total of 28 ULXs between NGC 2207 and IC 2163. Twelve of these vary over a span of several years, including seven that were not detected before because they were in a "quiet" phase during earlier observations.

The scientists involved in studying this system note that there is a strong correlation between the number of X-ray sources in different regions of the galaxies and the rate at which stars are forming in these regions. The composite image shows this correlation through X-ray sources concentrated in the spiral arms of the galaxies, where large amounts of stars are known to be forming. This correlation also suggests that the companion star in the binary systems is young and massive.

Colliding galaxies like this pair are well known to contain intense star formation. Shock waves - like the sonic booms from supersonic aircraft - form during the collision, leading to the collapse of clouds of gas and the formation of star clusters. In fact, researchers estimate that the stars associated with the ULXs are very young and may only be about 10 million years old. In contrast, our Sun is about halfway through its 10-billion-year lifetime. Moreover, analysis shows that stars of various masses are forming in this galaxy pair at a rate equivalent to form 24 stars the mass of our sun per year. In comparison, a galaxy like our Milky Way is expected to spawn new stars at a rate equivalent to only about one to three new suns every year.

A paper describing these results has been accepted for publication in The Astrophysical Journal and is available online. The authors of the paper are Stefano Mineo of the Harvard-Smithsonian Center for Astrophysics in Cambridge, MA; Saul Rappaport from the Massachusetts Institute of Technology (MIT) in Cambridge, MA; Alan Levine from MIT; David Pooley from Sam Houston State University in Huntsville, TX; Benjamin Steinhorn from Harvard Medical School in Boston, MA, and Jeroen Homan from MIT.


Fast Facts for NGC 2207 and IC 2163:

Scale: Image is 5 arcmin across (about 180,000 light years)
Category: Normal Galaxies & Starburst Galaxies
Coordinates (J2000): RA 06h 16m 22.10s | Dec -21° 22' 21.80"
Constellation: Canis Major
Observation Date: 4 pointings between Jul 2010 and Aug 2013
Observation Time: 17 hours 20 min
Obs. ID: 11228, 14799, 14914, 14915
Instrument: ACIS
References: Mineo, S. et al, 2014, ApJ, 797, 91; arXiv:1410.2472
Color Code: X-ray (Pink), Optical (Red, Green, Blue), Infrared (Red)
Distance Estimate: About 130 million light years




Mapping Mass in a Frontier Fields Cluster

The galaxy clusters under observation in Frontier Fields are so dense in mass that their gravity distorts and bends the light from the more-distant galaxies behind them, creating the magnifying effect known as gravitational lensing. Astronomers use the lensing effect to determine the location of concentrations of mass in the cluster, depicted here as a blue haze. Credit: ESA/Hubble, NASA, HST Frontier Field. Hi-Res Image

Stronger lensing produces greater distortions. Astronomers can work backwards from the distortions to pinpoint the greater concentrations of mass responsible for producing such altered images. Credit: A. Feild (STScI). Hi-Res Image


The Frontier Fields project’s examination of galaxy cluster MACS J0416.1-2403 has led to a precise map that shows both the amount and distribution of matter in the cluster. MACS J0416.1-2403 has 160 trillion times the mass of the Sun in an area over 650,000 light-years across.

The mass maps have a two-fold purpose: they identify the location of mass in the galaxy clusters, and by doing so make it easier to characterize lensed background galaxies.

Astronomers use the distortions of light caused by mass concentrations to pinpoint the distribution of mass within the cluster, including invisible dark matter. Weakly lensed background galaxies, visible in the outskirts of the cluster where less mass accumulates, may be stretched into slightly more elliptical shapes or transformed into smears of light. Strongly lensed galaxies, visible in the inner core of the cluster where greater concentrations of mass occur, can appear as sweeping arcs or rings, or even appear multiple times throughout the image. And as a dual benefit, as the clusters’ mass maps improve, it becomes easier to identify which galaxies are strongly lensed, and which galaxies are farther away.

The depth of the Frontier Fields images allows astronomers to see extremely faint objects, including many more strongly lensed galaxies than seen in previous observations of the cluster. Hubble identified 51 new multiply imaged galaxies around this cluster, for instance, quadrupling the number found in previous surveys.

Because the galaxies are multiples, that means almost 200 strongly lensed images appear in the new observations, allowing astronomers to produce a highly constrained map of the cluster’s mass, inclusive of both visible and dark matter.

The dark matter aspect is particularly intriguing. Because these types of Frontier Fields analyses create extremely precise maps of the locations of dark matter, they provide the potential for testing the nature of dark matter. Learning where dark matter concentrates in massive galaxy clusters can give clues to how it behaves and changes. And as the mass maps become more precise, astronomers are better able to determine the distance of the lensed galaxies.

In order to obtain a complete picture of MACS J0416.1-2403’s mass, astronomers will also need to include weak lensing measurements. Follow up observations will include further Frontier Fields imaging, as well as X-ray measurements of hot gas and spectroscopic redshifts to break down the total mass distribution into dark matter, gas, and stars.

Source:  Frontier Fields


Tuesday, December 09, 2014

Twinkle, Twinkle New-Born Star

Newborn stars in the Rho Ophiuchi star-forming region as seen in the infrared by the Spitzer Space Telescope. The youngest stars, the reddest ones in the image, are surrounded by disks of dust and gas from which planetary systems are possibly forming. New observations of the light variability from these young stars confirm that probably all of them have clumpy dust disks. NASA/Spitzer

Stars are born in dense, cool clouds of molecular gas and dust. When the local density is high enough, the matter can gravitationally collapse to form a new star, a so-called young stellar object (YSO). In its early phases, a thick envelope dominates the infrared emission from the YSO, hiding what is going on within, but eventually the envelope flattens out into a warm circumstellar accretion disk. The disk emits more infrared than does the young star, and that excess radiation can be used to distinguish young stars from more mature stars whose disks and envelopes have disappeared. In recent years it has become possible to investigate these envelopes and disks in more detail, and astronomers have been building on these studies to address how planetary systems develop.

It turns out that an accretion disk does not extend all the way in to the central star. Instead, a gap is produced between the star and disk because the dust grains closer in are destroyed by the starlight or blown away by stellar winds. Disks can contain clumps or irregular structures which orbit around with the disk. 

When a YSO happens to be aligned such that we observe its light through its disk, these structures make it appear to twinkle, or more precisely, to vary in intensity. Clumps at a distance of about one astronomical unit (the average distance of the Earth from the Sun) produce flickering over times of years as they rotate, while those in the disk ten times closer in result in variations over timescales of days.

CfA astronomers Hans Gunther, Katja Poppenhaeger, Scott Wolk, and Joe Hora and their colleagues used the infrared camera, IRAC, on the Spitzer Space Telescope to monitor the variability of light from 882 previously identified YSOs in a nearby region of star formation, Lynds 1688, over a period of 1.6 years.

They report finding that seventy of them vary; ten have roughly periodic variations although none of these variations has the regularity or characteristics to suggest transit exoplanet transits. Combined with other information about these YSOs, the new results confirm that probably all YSOs are variable at infrared wavelengths to some degree, and moreover that the younger, more deeply embedded stars often have longer and larger intensity variations, consistent with the current disk evolution picture.

Reference(s):

"YSOVAR: Mid-Infrared Variability in the Star-Forming Region Lynds 1688," H. M. Gunther, A. M. Cody, K. R. Covey, L. A. Hillenbrand, P. Plavchan, K. Poppenhaeger, L. M. Rebull, J. R. Stauffer, S. J. Wolk, L. Allen, A. Bayo, R. A. Gutermuth, J. L. Hora, H. Y. A. Meng, M. Morales-Calder´on, J. R. Parks, and Inseok Song, ApJ 148, 122, 2014.


Warm Gas Pours 'Cold Water' on Galaxy's Star-Making

A new feature in the evolution of galaxies has been captured in this image of galactic interactions. (Annotated Version)
Credit: NASA/CFHT/NRAO/JPL-Caltech/Duc/Cuillandre› Full image and caption


Some like it hot, but for creating new stars, a cool cosmic environment is ideal. As a new study suggests, a surge of warm gas into a nearby galaxy -- left over from the devouring of a separate galaxy -- has extinguished star formation by agitating the available chilled gas.

The unique findings illustrate a new dimension to galaxy evolution, and come courtesy of the European Space Agency's Herschel space observatory, in which NASA played a key role, and NASA's Spitzer and Hubble space telescopes.

Astronomers want to understand why galaxies in the local universe fall into two major categories: younger, star-forming spirals (like our own Milky Way), and older ellipticals, in which fresh star making has ceased. The new study's galaxy, NGC 3226, occupies a transitional middle ground, so getting a bead on its star formation is critical.

"We have explored the fantastic potential of big data archives from NASA's Hubble, Spitzer and ESA's Herschel observatory to pull together a picture of an elliptical galaxy that has undergone huge changes in its recent past due to violent collisions with its neighbors," said Philip Appleton, project scientist for the NASA Herschel Science Center at the California Institute of Technology in Pasadena and lead author of a recent Astrophysical Journal paper detailing the results. "These collisions are modifying not only its structure and color, but also the condition of the gas that resides in it, making it hard -- at the moment -- for the galaxy to form many stars."

NGC 3226 is relatively close, just 50 million light-years away. Several star-studded, gassy loops emanate from NGC 3226. Filaments also run out from it and between a companion galaxy, NGC 3227. These streamers of material suggest that a third galaxy probably existed there until recently -- that is, until NGC 3226 cannibalized it, strewing pieces of the shredded galaxy all over the area.
A prominent piece of these messy leftovers stretches 100,000 light-years and extends right into the core of NGC 3226. This long tail ends as a curved plume in a disk of warm hydrogen gas and a ring of dust. Contents of the tail, thought to be the debris from that departed galaxy, are falling into NGC 3226, drawn by its gravity.

In many instances, adding material to galaxies in this manner rejuvenates them, triggering new rounds of star birth thanks to gas and dust gelling together. Yet data from the three telescopes agree that NGC 3226 has a very low rate of star formation. It appears that in this case, the material falling into NGC 3226 is heating up as it collides with other galactic gas and dust, quenching star formation instead of fueling it.

The outcome could have been different, as NGC 3226 hosts a supermassive black hole at its center. The influx of gas and dust might have ended up just feeding the black hole, setting off energetic outpourings as the material crashed together while whirling toward its doom. Instead, the black hole in NGC 3226's core is just snacking, not gorging, as the material has spread out in the galaxy's central regions.

"We are discovering that gas does not simply funnel down into the center of a galaxy and feed the supermassive black hole known to be lurking there," Appleton said. "Rather, it gets hung up in a warm disk, shutting down star formation and probably frustrating the black hole's growth by being too turbulent at this point in time."

NGC 3226 is considered something between a youthful "blue" galaxy and an old "red" galaxy. The colors refer to the predominantly galactic blue light radiated by giant, young stars -- a telltale sign of recent star formation -- and the reddish light cast by mature stars in the absence of new, blue ones.

This intermediary galaxy illuminates how galaxies accruing fresh gas and dust can bloom with new stars or have their stellar factories close shop, at least temporarily. After all, as the warm gas flooding NGC 3226 cools to star-forming temperatures, the galaxy should get a second wind.

Intriguingly, ultraviolet and optical light observations suggest that NGC 3226 may have produced more stars in the past, leading to its current intermediate color, somewhere between red and blue. The new study indicates that those traces of youth must indeed be lingering from higher levels of star formation, before the infalling gas scrambled the scene.

"NGC 3226 will continue to evolve and may hatch abundant new stars in the future," said Appleton. "We're learning that the transition from young- to old-looking galaxies is not a one-way, but a two-way street."
Other authors of the report are: C. Mundell of Liverpool John Moores University, England; M. Lacy of National Radio Astronomy Observatory, Charlottesville, Virginia; V. Charmandaris of University of Creete, Greece; P-A. Duc of CEA-Saclay, France; U. Lisenfeld of University of Granda, Spain; and T. Bitsakis, K. Alatalo, L. Armus and P. Ogle of Caltech.

Herschel is a European Space Agency mission, with science instruments provided by consortia of European institutes and with important participation by NASA. While the observatory stopped making science observations in April 2013, after running out of liquid coolant, as expected, scientists continue to analyze its data. NASA's Herschel Project Office is based at NASA's Jet Propulsion Laboratory, Pasadena, California. JPL contributed mission-enabling technology for two of Herschel's three science instruments. The NASA Herschel Science Center, part of the Infrared Processing and Analysis Center at Caltech, supports the U.S. astronomical community.

JPL manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at Caltech. Spacecraft operations are based at Lockheed Martin Space Systems Company, Littleton, Colorado. Data are archived at the Infrared Science Archive housed at the Infrared Processing and Analysis Center at Caltech.

Caltech manages JPL for NASA.

The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington.

Fore more information about NASA's role in Herschel, visit: http://www.nasa.gov/herschel

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

For more information about Hubble, visit: http://www.nasa.gov/hubble


Media Contact

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

whitney.clavin@jpl.nasa.gov



Monday, December 08, 2014

Cassini’s view of Jupiter’s southern hemisphere

Cassini’s view of Jupiter’s southern hemisphere
Copyright: NASA/JPL/Space Science Institute

This Cassini image shows Jupiter from an unusual perspective. If you were to float just beneath the giant planet and look directly up, you would be greeted with this striking sight: red, bronze and white bands encircling a hazy south pole. The multicoloured concentric layers are broken in places by prominent weather systems such as Jupiter’s famous Great Red Spot, visible towards the upper left, chaotic patches of cloud and pale white dots. Many of these lighter patches contain lightning-filled thunderstorms.

Jupiter has very dramatic weather – the planet’s axis is not as tilted (towards or away from the Sun) as much as Earth’s so it does not have significant seasonal changes, but it does have a thick and tumultuous atmosphere filled with raging storms and chaotic cloud systems.

These clouds, formed from dense layers of ammonia crystals, are tugged, stretched and tangled together by Jupiter’s turbulence and strong winds, creating vortices and hurricane-like storms with wind speeds of up to 360 km per hour.

The Great Red Spot is actually an anticyclone that has been violently churning for hundreds of years. It was at one stage large enough to contain several Earth-sized planets but recent images from the Hubble Space Telescope show it to be shrinking. There are other similarly striking storms raging in both Jupiter’s cool upper atmosphere and hotter lower layers, including a Great Dark Spot and Oval BA, more affectionately nicknamed Red Spot Jr.

Jupiter’s south pole is at the very centre of this image, visible as a murky grey-toned circle. This patch is not as detailed as the rest of the planet because Cassini had to peer through a lot more atmospheric haze in the polar region, making it harder to see.

This polar map is composed of 18 colour images taken by the narrow-angle camera on NASA’s Cassini spacecraft during a flyby on 11–12 December 2000. This map is incredibly detailed; the smallest visible features in this image are about 120 km across. There is also an accompanying map of the planet’s north pole. In 2016, NASA’s Juno spacecraft will arrive at Jupiter and start to beam back images of the planet’s poles.

The Cassini–Huygens mission, launched in 1997 as a joint endeavour of ESA, NASA and Italy’s ASI space agency, flew past Venus, Earth and Jupiter en route to observe Saturn, its moons and rings. Observations with Cassini have given us an unprecedented understanding of the Saturnian system. ESA’s Juice mission aims to do the same for Jupiter. Planned for launch in 2022, the spacecraft will reach Jupiter in 2030 and begin observing the planet and three of its moons – Ganymede, Callisto and Europa. Previous flybys of these moons have raised the exciting prospect that some of them might harbour subsurface liquid oceans and conditions suitable to support some forms of life.

Juice was recently given the green light to continue to the next stage of development.


Source: ESA



Strange Galaxy Perplexes Astronomers

Radio-optical overlay image of galaxy J1649+2635. 
Yellow is visible-light image; Blue is the radio image, indicating the presence of jets.
Credit: Mao et al., NRAO/AUI/NSF, Sloan Digital Sky Survey

With the help of citizen scientists, a team of astronomers has found an important new example of a very rare type of galaxy that may yield valuable insight on how galaxies developed in the early Universe. The new discovery technique promises to give astronomers many more examples of this important and mysterious type of galaxy.

The galaxy they studied, named J1649+2635, nearly 800 million light-years from Earth, is a spiral galaxy, like our own Milky Way, but with prominent "jets" of subatomic particles propelled outward from its core at nearly the speed of light. The problem is that spiral galaxies are not supposed to have such large jets.

"The conventional wisdom is that such jets come only from elliptical galaxies that formed through the merger of spirals. We don't know how spirals can have these large jets," said Minnie Mao, of the National Radio Astronomy Observatory (NRAO).

J1649+2635 is only the fourth jet-emitting spiral galaxy discovered so far. The first was found in 2003, when astronomers combined a radio-telescope image from the Karl G. Jansky Very Large Array (VLA) and a visible-light image of the same object from the Hubble Space Telescope. The second was revealed in 2011 by images from the Sloan Digital Sky Survey and the VLA, and the third, found earlier this year, also was discovered by combining radio and visible-light images.

"In order to figure out how these jets can be produced by the 'wrong' kind of galaxy, we realized we needed to find more of them," Mao said.

To do that, the astronomers looked for help. That help came in the form of large collections of images from both radio and optical telescopes, and the hands-on assistance of volunteer citizen scientists. The volunteers are participants in an online project called the Galaxy Zoo, in which they look at images from the visible-light Sloan Digital Sky Survey and classify the galaxies as spiral, elliptical, or other types. Each galaxy image is inspected by multiple volunteers to ensure accuracy in the classification.

So far, more than 150,000 Galaxy Zoo participants have classified some 700,000 galaxies. Mao and her collaborators used a "superclean" subset of more than 65,000 galaxies, for which 95 percent of those viewing each galaxy's image agreed on the classification. About 35,000 of those are spiral galaxies. J1649+2635 had been classified by 31 Galaxy Zoo volunteers, 30 of whom agreed that it is a spiral.

Next, the astronomers decided to cross-match the visible-light spirals with galaxies in a catalog that combines data from the NRAO VLA Sky Survey and the Faint Images of the Radio Sky at Twenty Centimeters survey, both done using the VLA. This job was done by Ryan Duffin, a University of Virginia undergraduate working as an NRAO summer student. Duffin's cross-matching showed that J1649+2635 is both a spiral galaxy and has powerful twin radio jets.

"This is the first time that a galaxy was first identified as a spiral, then subsequently found to have large radio jets," Duffin said. "It was exciting to make such a rare find," he added.

Jets such as those seen coming from J1649+2635 are propelled by the gravitational energy of a supermassive black hole at the core of the galaxy. Material pulled toward the black hole forms a rapidly-rotating disk, and particles are accelerated outward along the poles of the disk. The collision that presumably forms an elliptical galaxy disrupts gas in the merging galaxies and provides "fuel" for the disk and acceleration mechanism. That same disruption, however, is expected to destroy any spiral structure as the galaxies merge into one.

J1649+2635 is unusual not only because of its jets, but also because it is the first example of a "grand design" spiral galaxy with a large "halo" of visible-light emission surrounding it.

"This galaxy presents us with many mysteries. We want to know how it became such a strange beast," Mao said. "Did it have a unique type of merger that preserved its spiral structure? Was it an elliptical that had another collision that made it re-grow spiral arms? Is its unique character the result of interaction with its environment?"

"We will study it further, but in addition, we need to see if there are more like it," Mao said.

"We hope that with projects like the Galaxy Zoo and another called Radio Galaxy Zoo, those thousands of citizen scientists can help us find many more galaxies like this one so we can answer all our questions," Mao said. Mao and her colleagues have dubbed these rare galaxies "Spiral DRAGNs," an acronym for the technical description, "Double-lobed Radio sources Associated with Galactic Nuclei."

Mao and Duffin worked with Frazer Owen, Emmanuel Momjian, and Mark Lacy, also of the NRAO; Bill Keel of the University of Alabama; Glenn Morrison of the University of Hawaii and the Canada-France-Hawaii Telescope; Tony Mroczkowski of the Naval Research Laboratory; Susan Neff of NASA's Goddard Space Flight Center; Ray Norris of CSIRO Astronomy and Space Science in Australia; Henrique Schmitt of the Naval Research Laboratory; and Vicki Toy and Sylvain Veilleux of the University of Maryland. The scientists are reporting their findings in the Monthly Notices of the Royal Astronomical Society.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

Contact:

Dave Finley, Public Information Officer
(575) 835-7302

dfinley@nrao.edu