The beautiful side of IC 335

IC 335

Credit: ESA/Hubble & NASA

This new NASA/ESA Hubble Space Telescope image shows the galaxy IC 335 in front of a backdrop of distant galaxies. IC 335 is part of a galaxy group containing three other galaxies, and located in the Fornax Galaxy Cluster 60 million light-years away.

As seen in this image, the disc of IC 335 appears edge-on from the vantage point of Earth. This makes it harder for astronomers to classify it, as most of the characteristics of a galaxy’s morphology — the arms of a spiral or the bar across the centre — are only visible on its face. Still, the 45 000 light-year-long galaxy could be classified as an S0 type.

These lenticular galaxies are an intermediate state in galaxy morphological classification schemes between true spiral and elliptical galaxies. They have a thin stellar disc and a bulge, like spiral galaxies, but in contrast to typical spiral galaxies they have used up most of the interstellar medium. Only a few new stars can be created out of the material that is left and the star formation rate is very low. Hence, the population of stars in S0 galaxies consists mainly of aging stars, very similar to the star population in elliptical galaxies.

As S0 galaxies have only ill-defined spiral arms they are easily mistaken for elliptical galaxies if they are seen inclined face-on or edge-on as IC 335 here. And indeed, despite the morphological differences between S0 and elliptical class galaxies, they share a some common characteristics, like typical sizes and spectral features.

Both classes are also early-type galaxies, as they are evolving passively. However, elliptical galaxies may be passively evolving when we observe them, but they had violent interactions with other galaxies in their past. Whereas S0 galaxies are either aging and fading spiral galaxies, which never had any interactions with other galaxies, or they are the aging result of a single merger between two spiral galaxies in the past. The exact nature of these galaxies is still a matter of debate.

Links

• Structure and Formation of S0 and Spheroidal Galaxies
• Can Early Type Galaxies Evolve from Fading the Disks of Late Types?

Source: ESA/Hubble - Space Telescope

Keck’s Cosmic Web Image Awarded Top Ten Breakthrough for 2014

This deep image shows the nebula (cyan) extending across 2 million light-years that was discovered around the bright quasar UM287 (at the center of the image). The energetic radiation of the quasar makes the surrounding intergalactic gas glow, revealing the morphology and physical properties of a cosmic web filament. The image was obtained at the W. M. Keck Observatory. Credit: S.Cantalupo (UCSC); W.M.Keck Observatory,br>

MAUNA KEA, HAWAII – UC Santa Cruz astronomers who used the W. M. Keck Observatory to capture the first image of a filament of the "cosmic web" have been recognized by the editors of Physics World for one of the "Top Ten Breakthroughs of 2014".

The team, led by UC Santa Cruz astronomers Sebastiano Cantalupo (now at ETH Zurich), J. Xavier Prochaska, and Piero Madau, detected the glowing gas of the filament due to its illumination by the intense radiation given off by a distant quasar. Using Keck Observatory’s Keck I telescope in Hawaii, they observed a very large, luminous nebula of gas extending about 2 million light-years across intergalactic space, which they nicknamed the 'Slug Nebula' in honor of UCSC's banana slug mascot.

This is the second time that Prochaska's research group has been recognized by Physics World for a top ten breakthrough. In 2011, his team's discovery of pristine clouds of gas formed shortly after the Big Bang was also featured as one of nine runners-up to the "Breakthrough of the Year" in Science magazine in addition to making the Physics World top ten.

"It may never happen again, so I'm especially amazed to get this acknowledgement a second time," said Prochaska, a professor of astronomy and astrophysics at UCSC.

"This award is also for Keck Observatory and for all the people that work there," said Cantalupo. "Without their wonderful support, this discovery would have not be possible. Many people helped me install and use the filter that enabled this discovery, including Luca Rizzi, Marc Kassis, Dwight Chan, Gary Anderson, Greg Wirth and others."

Prochaska noted that a new instrument is being built for Keck Observatory that will greatly facilitate future research on the cosmic web. The Keck Cosmic Web Imager (KCWI) will be able to perform "spectral imaging," capturing both an image and a spectrum of an object simultaneously. Keck Observatory is currently working with the UC Observatories instrument labs at UC Santa Cruz to develop the camera for KCWI.

Physics World is an international monthly magazine published by the Institute of Physics. In addition to Cantalupo, Prochaska, and Madau, the coauthors of the cosmic web paper included Fabrizio Arrigoni-Battaia and Joseph Hennawi of the Max Planck Institute for Astronomy in Heidelberg. For more information about the cosmic web discovery, see "Distant quasar illuminates a filament of the cosmic web."

 Source: W.M. Keck Observatory

'Perfect Storm' Quenching Star Formation around a Supermassive Black Hole

Artist impression of the central region of NGC 1266. The jets from the central black hole are creating turbulence in the surrounding molecular gas, suppressing star formation in an otherwise ideal environment to form new stars. Credit: B. Saxton (NRAO/AUI/NSF)

Artist illustration of the central region of NGC 1266 near its central black hole with jet and gas motions indicated (yellow and white arrows, respectively). The large-scale gas motions induce turbulence on smaller scales, preventing star formation. Credit: B. Saxton (NRAO/AUI/NSF)

A combined Hubble Space Telescope / ALMA image of NGC 1266. The ALMA data (orange) are shown in the central region. Credit: NASA/ESA Hubble; ALMA (NRAO/ESO/NAOJ)

A combined Hubble/CARMA image of NGC 1266. The zoom-in section shows the molecular gas being propelled by the black hole's jets (red and blue), the central CARMA data (yellow) indicate the dense molecular gas. Credit: NASA/ESA Hubble; CARMA; Katey Alatalo

High-energy jets powered by supermassive black holes can blast away a galaxy’s star-forming fuel, resulting in so-called "red and dead" galaxies: those brimming with ancient red stars yet containing little or no hydrogen gas to create new ones.

Now astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have discovered that black holes don’t have to be nearly so powerful to shut down star formation. By observing the dust and gas at the center of NGC 1266, a nearby lenticular galaxy with a relatively modest central black hole, the astronomers have detected a “perfect storm” of turbulence that is squelching star formation in a region that would otherwise be an ideal star factory.

This turbulence is stirred up by jets from the galaxy’s central black hole slamming into an incredibly dense envelope of gas. This dense region, which may be the result of a recent merger with another smaller galaxy, blocks nearly 98 percent of material propelled by the jets from escaping the galactic center.

“Like an unstoppable force meeting an immovable object, the particles in these jets meet so much resistance when they hit the surrounding dense gas that they are almost completely stopped in their tracks,” said Katherine Alatalo, an astronomer with the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena and lead author on a paper published in the Astrophysical Journal. This energetic collision produces powerful turbulence in the surrounding gas, disrupting the first critical stage of star formation. “So what we see is the most intense suppression of star formation ever observed,” noted Alatalo.

Previous observations of NGC 1266 revealed a broad outflow of gas from the galactic center traveling up to 400 kilometers per second. Alatalo and her colleagues estimate that this outflow is as forceful as the simultaneous supernova explosion of 10,000 stars. The jets, though powerful enough to stir the gas, are not powerful enough to give it the velocity it needs to escape from the system.

“Another way of looking at it is that the jets are injecting turbulence into the gas, preventing it from settling down, collapsing, and forming stars,” said National Radio Astronomy Observatory astronomer and co-author Mark Lacy.

The region observed by ALMA contains about 400 million times the mass of our Sun in star-forming gas, which is 100 times more than is found in giant star-forming molecular clouds in our own Milky Way. Normally, gas this concentrated should be producing stars at a rate at least 50 times faster than the astronomers observe in this galaxy.

Previously, astronomers believed that only extremely powerful quasars and radio galaxies contained black holes that were powerful enough to serve as a star-forming “on/off” switch.

“The usual assumption in the past has been that the jets needed to be powerful enough to eject the gas from the galaxy completely in order to be effective at stopping start formation,” said Lacy.

To make this discovery, the astronomers first pinpointed the location of the far-infrared light being emitted by the galaxy. Normally, this light is associated with star formation and enables astronomers to detect regions where new stars are forming. In the case of NGC 1266, however, this light was coming from an extremely confined region at the center of the galaxy. “This very small area was almost too small for the infrared light to be coming from star formation,” noted Alatalo.

With ALMA’s exquisite sensitivity and resolution, and along with observations from CARMA (the Combined Array for Research in Millimeter-wave Astronomy), the astronomers were then able to trace the location of the very dense molecular gas at the galactic center. They found that the gas is surrounding this compact source of far-infrared light.

Under normal conditions, gas this dense would be forming stars at a very high rate. The dust embedded within this gas would then be heated by young stars and seen as a bright and extended source of infrared light. The small size and faintness of the infrared source in this galaxy suggests that NGC 1266 is instead choking on its own fuel, seemingly in defiance of the rules of star formation.

The astronomers also speculate that there is a feedback mechanism at work in this region. Eventually, the black hole will calm down and the turbulence will subside so star formation can begin anew. With this renewed star formation, however, comes greater motion in the dense gas, which then falls in on the black hole and reestablishes the jets, shutting down star formation once again.

NGC 1266 is located approximately 100 million light-years away in the constellation Eridanus. Leticular galaxies are spiral galaxies, like our own Milky Way, but they have little interstellar gas available to form new stars.

#  #  # 

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.

Contact: 

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

Source:  National Radio Astronomy Observatory

NOAO: Compact Galaxy Groups Reveal Details of Their Close Encounters

View a gallery of images of Compact Galaxy Groups.

Image above, of HCG 07, credit Dane Kleiner.

Galaxies – spirals laced with nests of recent star formation, quiescent ellipticals composed mainly of old red stars, and numerous faint dwarfs – are the basic visible building blocks of the Universe. Galaxies are rarely found in isolation, but rather in sparse groups – sort of galactic urban sprawl. But there are occasional dense concentrations, often found in the center of giant clusters, but also, intriguingly, as more isolated compact groups (and yes, called Compact Galaxy Groups or CGs). The galaxies in these Compact Groups show dramatic differences in the way they evolve and change with time compared with galaxies in more isolated surroundings. Why is this? Collisions between galaxies in these dense groups are common, leading to rapid star formation, but there seems to be more to the puzzle. 

A team led by Dr Iraklis Konstantopoulos of the Australian Astronomical Observatory (AAO) has now obtained spectacular images of some CGs with the Dark Energy camera attached to the Blanco 4-meter telescope at the Cerro Tololo Inter-American Observatory (CTIO). This camera, constructed at the U.S. Department of Energy’s Fermi National Accelerator Laboratory, is able to image large areas of the sky to unprecedented faint limits. The team aims to combine these images with spectroscopic data from the AAO that will reveal the velocities of the galaxies, leading to a much better understanding of their gravitational interactions.

As Dr. David James (CTIO), who planned and obtained the images said, “The new images are absolutely brilliant, and reveal faint streams of gas and stars called tidal tails, created in the mutual gravitational interaction when two galaxies suffer a close encounter.” The tails, one preceding and one trailing the galaxy, persist long after the encounter, and allow the astronomers to calculate how long ago the event took place. The Dark Energy Camera, which can image a field four times the size of the full moon, is able to record these faint tidal tails, and the camera’s wide field will uncover unexpected surprises.

“The imagery reveals the assembly history of these galaxies living so close to each other via their previous interactions,” Dr Konstantopoulos said. “We look for stretched out tidal debris tails and roughly determine their ages. The time when interactions created the tidal debris and the arrangement of those ‘fossils’ tell us which galaxies interacted, and when.”

Not all CGs are alike: in some, the gas is contained within the individual galaxies, while in other groups the gas spreads out among the galaxies. These new data will allow astronomers to untangle the physical mechanism that leads to such differences.

Another new exploration is the census of faint dwarf galaxies. As their name implies, these are minor galaxies in comparison with giant ellipticals and spirals, but they are especially numerous, and the new data will reveal how many are lurking in these Compact Groups. 

The international team consists of astronomers at CTIO (a division of the National Optical Astronomy Observatory), the Australian Astronomical Observatory (the counterpart to the NOAO in Australia), and Monash University in Melbourne.

NOAO is operated by Association of Universities for Research in Astronomy Inc. under a cooperative agreement with the National Science Foundation.

Media Contact:

Dr. Katy Garmany
Deputy Press Officer
National Optical Astronomy Observatory
950 N Cherry Ave
Tucson AZ 85719 USA
+1 520-318-8526
E-mail: kgarmany@noao.edu

 
Science Contact:

Dr. David James
Cerro Tololo Inter-American Observatory
Casilla 603
La Serena, CHILE
E-mail: djj@ctio.noao.edu

Source: National Optical Astronomy Observatory (NOAO)

XMM-Newton Spots Monster Black Hole Hidden in Tiny Galaxy

This artist's illustration shows a black hole within a dwarf galaxy

 Copyright: ESA/ATG mediala
Hi-res image

X-ray emission from dwarf galaxy J1329+3234

Copyright: ESA/XMM-Newton/N. Secrest, et al. (2015) 

Hi-res image 

The galaxy, an irregular dwarf named J1329+3234, is one of the smallest galaxies yet to contain evidence of a massive black hole. Located over 200 million light-years away, the galaxy is similar in size to the Small Magellanic Cloud, one of our nearest neighbouring galaxies, and contains a few hundred million stars.

In 2013, an international team of astronomers was intrigued to discover infrared signatures of an accreting black hole within J1329+3234 when they studied it with the Wide-Field Infrared Survey Explorer (WISE).

The same team has now investigated the galaxy further, using ESA's XMM-Newton to hunt for this black hole in X-rays – and found something very surprising.

"The X-ray emission from J1329+3234 is over 100 times stronger than expected for this galaxy," says Nathan Secrest of George Mason University in Virginia, USA, lead author of the new study published in The Astrophysical Journal. "We would typically expect to find low-level X-ray emission from stellar-mass black holes within the galaxy, but what we found instead was emission consistent with a very massive black hole."

The combined X-ray and infrared properties of this galaxy can only be explained by the presence of a massive black hole residing in J1329+3234, similar to the supermassive black holes found at the centres of much more massive galaxies.

While the exact mass of the black hole is not known, it must be at least 3000 times as massive as the Sun, although it is likely to be much more massive than that. If the black hole in J1329+3234 is similar to known low-mass supermassive black holes, then it has a mass of around 150 000 times that of the Sun.

 A feeding black hole at the centre of a galaxy is known as an active galactic nucleus, or AGN. In the region surrounding the black hole, material from the galaxy emits intensely bright radiation as it swirls inwards towards the centre of the galaxy and is devoured by the black hole. AGNs powered by massive black holes are commonplace in large galaxies, but they appear to be rarer in galaxies without a central "bulge" of stars – dwarf galaxies being a key example.

"This is a really important discovery," says co-author Shobita Satyapal, also from George Mason University. "It's interesting enough that such a tiny galaxy has such a large black hole, but this also raises questions about how these black holes form in the first place."

Astronomers believe that the "seeds" of massive black holes formed very early on in the Universe, along with the first generation of stars. These seed black holes then grew into massive black holes via a string of galaxy mergers. As the galaxies merged, so did their central black holes.

The turbulent merging process would feed the accreting black holes with copious amounts of material while simultaneously building up large, bulge-dominated galaxies. However, with each successive merger information about the properties of the original black hole is lost, meaning that astronomers cannot determine the mass of the original seeds by looking at massive bulge-dominated galaxies – instead they probe their dwarf and bulgeless relatives, such as J1329+3234, for clues.

Finding a massive black hole within such a tiny bulgeless galaxy provides support for the theory that black holes may have grown very efficiently within the gaseous haloes of forming galaxies, originating in massive, collapsing clouds of primordial gas.

Along with J1329+3234, Secrest and his colleagues found several hundred other bulgeless galaxies from the WISE survey that also show intriguing infrared properties – many of which, like J1329+3234, display no evidence for AGNs in optical light.

In recent years, growing numbers of massive black holes have been identified within dwarf and bulgeless galaxies. However, it is much harder to find them than it is to find their supermassive counterparts – they are less likely to show up in optical studies since they are often obscured by dust and are usually much dimmer, making them difficult to detect above surrounding light.

This emphasises the importance of multi-wavelength sky surveys, says ESA's XMM-Newton project scientist Norbert Schartel. "Using a mix of optical, infrared, and X-ray observations was vital here," he adds. "The sensitivity of XMM-Newton made it possible not only to discover this black hole but to also fully characterise its spectrum, meaning we can say with much more certainty that it's a black-hole-fuelled AGN."

More information

"An optically obscured AGN in a low mass, irregular dwarf galaxy: A multi-wavelength analysis of J1329+3234" by N. Secrest et al. is published in The Astrophysical Journal.

The European Space Agency's X-ray Multi-Mirror Mission, XMM-Newton, was launched in December 1999. The largest scientific satellite to have been built in Europe, it is also one of the most sensitive X-ray observatories ever flown. More than 170 wafer-thin, cylindrical mirrors direct incoming radiation into three high-throughput X-ray telescopes. XMM-Newton's orbit takes it almost a third of the way to the Moon, allowing for long, uninterrupted views of celestial objects.

 

Contacts

Nathan Secrest
George Mason University
Fairfax, Virginia, USA
Email: nsecrest@masonlive.gmu.edu
Phone: +1-301-760-0210

Shobita Satyapal
George Mason University
Fairfax, Virginia, USA
Email: ssatyapa@gmu.edu
Phone: +1-703-993-1283

Norbert Schartel
ESA XMM-Newton Project Scientist
Directorate of Science and Robotic Exploration
European Space Agency
Email: Norbert.Schartel@esa.int
Phone: +34-91-8131-184


 

Source: ESA/XMM Newton

Multicoloured view of supernova remnant

Multicoloured view of supernova remnant
Copyright: ESA/XMM-Newton & NASA/Chandra (X-ray); NASA/WISE/Spitzer (Infrared)

Hi-Res (JPG) (893.97 kB) - Hi-Res (TIF) (6.11 MB)

Most celestial events unfold over thousands of years or more, making it impossible to follow their evolution on human timescales. Supernovas are notable exceptions, the powerful stellar explosions that make stars as bright as an entire galaxy for several days.

Although they are very rare – only a few such explosions take place every century in a typical galaxy – supernovas can be seen with the naked eye if they are reasonably nearby. In fact, when supernovas were discovered they were thought to be new stars appearing in the sky – ‘nova’ means new in Latin.

Astronomers have recorded supernovas long before a theoretical understanding of these events as stellar explosions was developed in the 20th century. The most ancient documented record dates back to 185 AD, when Chinese astronomers saw a ‘guest star’ that remained visible for several months, in the vicinity of the two stars Alpha and Beta Centauri.

The material ejected during these explosions sweeps up gas and dust from the surroundings, creating picturesque supernova remnants that can be observed long after the explosion. Modern astronomers believe that the object shown in this image, the supernova remnant RCW 86, is what remains of the supernova that was discovered in 185 AD.

The blue and green glow at the edges of the bubble represents X-ray emission from hot gas, heated to millions of degrees by shock waves generated after the explosion. The diffuse red glow marks infrared emission from warm dust in the interstellar medium around RCW 86. Sprinkled across the image, in yellow, are young stars that shine brightly at infrared wavelengths.

This image combines X-ray data from ESA’s XMM-Newton and NASA’s Chandra X-ray Observatory (combined to form the blue and green colours) with infrared observations from NASA’s Spitzer Space Telescope and Wide-Field Infrared Survey Explorer (yellow and red).

The supernova remnant RCW 86 is some 8000 light-years away.

This image was first published in 2011.

Source: ESA - Space Images

Horsehead of a Different Color

The famous Horsehead nebula of visible-light images (inset) looks quite different when viewed in infrared light, as seen in this newly released image from NASA's Spitzer Space Telescope. Image credit: NASA/JPL-Caltech/ESO.  › Full image and caption

Sometimes a horse of a different color hardly seems to be a horse at all, as, for example, in this newly released image from NASA's Spitzer Space Telescope. The famous Horsehead nebula makes a ghostly appearance on the far right side of the image, but is almost unrecognizable in this infrared view. In visible-light images, the nebula has a distinctively dark and dusty horse-shaped silhouette, but when viewed in infrared light, dust becomes transparent and the nebula appears as a wispy arc.

The Horsehead is only one small feature in the Orion Molecular Cloud Complex, dominated in the center of this view by the brilliant Flame nebula (NGC 2024). The smaller, glowing cavity falling between the Flame nebula and the Horsehead is called NGC 2023. These regions are about 1,200 light-years away.

The two carved-out cavities of the Flame nebula and NGC 2023 were created by the destructive glare of recently formed massive stars within their confines. They can be seen tracing a spine of glowing dust that runs through the image.

The Flame nebula sits adjacent to the star Alnitak, the westernmost star in Orion's belt, seen here as the bright blue dot near the top of the nebula.

In this infrared image from Spitzer, blue represents light emitted at a wavelength of 3.6-microns, and cyan (blue-green) represents 4.5-microns, both of which come mainly from hot stars. Green represents 8-micron light and red represents 24-micron light. Relatively cooler objects, such as the dust of the nebulae, appear green and red. Some regions along the top and bottom of the image extending beyond Spitzer's observations were filled in using data from NASA's Wide-field Infrared Survey Explorer, or WISE, which covered similar wavelengths across the whole sky.

NASA's Jet Propulsion Laboratory, Pasadena, California, manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. 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. 

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

Media Contact

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

Source: JPL-Caltech

A messy star factory

Mrk 209 - UGCA 281

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:

• Nick Rose’s Hidden Treasures entry on Flickr

 Source:   ESA/Hubble - Space Telescope

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)

 

Cambridge, MA -To paraphrase Mark Twain, the report of the Kepler spacecraft's death was greatly exaggerated. Despite a malfunction that ended its primary mission in May 2013, Kepler is still alive and working. The evidence comes from the discovery of a new super-Earth using data collected during Kepler's "second life."

 

"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

Source:  Harvard-Smithsonian Center for Astrophysics (CfA)

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 

Source:  MIT - Massachusetts Institute of Technology

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

• View Past Solar Activity

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

Source:  Solar Dynamics Observatory (SDO) - NASA

The Hot Blue Stars of Messier 47

PR Image eso1441a

The star cluster Messier 47

PR Image eso1441b

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

PR Image eso1441c

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

*************************************************************************************

Videos

PR Video eso1441a

Zooming in on the star cluster Messier 47

PR Video eso1441b

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

• Photos of the MPG/ESO 2.2-metre telescope
• Other photos taken with the MPG/ESO 2.2-metre telescope
• Photos of La Silla

Contacts

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

Source: ESO

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.

Source: Smithsonian Astrophysical Observatory

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

Source:  Royal Astronomical Society (RAS)

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 

Email:  cblue@nrao.edu

Luca Ricci
Harvard-Smithsonian Center for Astrophysics
 Email: lucaricci83@gmail.com

Source: National Radio Astronomy Observatory