Saturday, June 29, 2013

NASA Decommissions Its Galaxy Hunter Spacecraft

Big Brother to the Milky Way
Credit: NASA/JPL-Caltech

Ultraviolet Ring of Stars
Credit: NASA/JPL-Caltech

Galaxy's Pencil-Thin Profile
Credit: NASA/JPL-Caltech

PASADENA, Calif. — NASA has turned off its Galaxy Evolution Explorer (GALEX) after a decade of operations in which the venerable space telescope used its ultraviolet vision to study hundreds of millions of galaxies across 10 billion years of cosmic time.

"GALEX is a remarkable accomplishment," said Jeff Hayes, NASA's GALEX program executive in Washington. "This small Explorer mission has mapped and studied galaxies in the ultraviolet, light we cannot see with our own eyes, across most of the sky."

Operators at Orbital Sciences Corporation in Dulles, Va., sent the signal to decommission GALEX at 12:09 p.m. PDT (3:09 p.m. EDT) Friday, June 28. The spacecraft will remain in orbit for at least 65 years, then fall to Earth and burn up upon re-entering the atmosphere. GALEX met its prime objectives and the mission was extended three times before being cancelled.

Highlights from the mission's decade of sky scans include:
  • Discovering a gargantuan, comet-like tail behind a speeding star called Mira.
  • Catching a black hole "red-handed" as it munched on a star.
  • Finding giant rings of new stars around old, dead galaxies.
  • Independently confirming the nature of dark energy.
  • Discovering a missing link in galaxy evolution -- the teenage galaxies transitioning from young to old.
The mission also captured a dazzling collection of snapshots, showing everything from ghostly nebulas to a spiral galaxy with huge, spidery arms.

In a first-of-a-kind move for NASA, the agency in May 2012 loaned GALEX to the California Institute of Technology in Pasadena, which used private funds to continue operating the satellite while NASA retained ownership. Since then, investigators from around the world have used GALEX to study everything from stars in our own Milky Way galaxy to hundreds of thousands of galaxies 5 billion light-years away.

In the space telescope's last year, it scanned across large patches of sky, including the bustling, bright center of our Milky Way. The telescope spent time staring at certain areas of the sky, finding exploded stars, called supernovae, and monitoring how objects, such as the centers of active galaxies, change over time. GALEX also scanned the sky for massive, feeding black holes and shock waves from early supernova explosions.

"In the last few years, GALEX studied objects we never thought we'd be able to observe, from the Magellanic Clouds to bright nebulae and supernova remnants in the galactic plane," said David Schiminovich of Columbia University, N.Y., N.Y, a longtime GALEX team member who led science operations over the past year. "Some of its most beautiful and scientifically compelling images are part of this last observation cycle."

Data from the last year of the mission will be made public in the coming year.

"GALEX, the mission, may be over, but its science discoveries will keep on going," said Kerry Erickson, the mission's project manager at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

A slideshow showing some of the popular GALEX images is online at: http://go.nasa.gov/17xAVDd
JPL managed the GALEX mission and built the science instrument. The mission's principal investigator, Chris Martin, is at Caltech. NASA's Goddard Space Flight Center in Greenbelt, Md., developed the mission under the Explorers Program it manages. Researchers sponsored by Yonsei University in South Korea and the Centre National d'Etudes Spatiales (CNES) in France collaborated on the mission. Caltech manages JPL for NASA.

Gas-Giant Exoplanets Cling Close to Their Parent Stars

Artist's rendering of a possible exoplanetary system with a gas-giant planet orbiting close to his parent star which is more massive than our sun. Artwork by Lynette Cook. Credit: Gemini Observatory/AURA. Full Resolution TIFF (6MB) | Full Resolution JPEG (2MB) | Medium Resolution JPEG (296KB)

Gemini Observatory’s Planet-Finding Campaign finds that, around many types of stars, distant gas-giant planets are rare and prefer to cling close to their parent stars. The impact on theories of planetary formation could be significant.
 
Finding extrasolar planets has become so commonplace that it seems astronomers merely have to look up and another world is discovered. However, results from Gemini Observatory’s recently completed Planet-Finding Campaign – the deepest, most extensive direct imaging survey to date – show the vast outlying orbital space around many types of stars is largely devoid of gas-giant planets, which apparently tend to dwell close to their parent stars. 

“It seems that gas-giant exoplanets are like clinging offspring,” says Michael Liu of the University of Hawaii’s Institute for Astronomy and leader of the Gemini Planet-Finding Campaign. “Most tend to shun orbital zones far from their parents. In our search, we could have found gas giants beyond orbital distances corresponding to Uranus and Neptune in our own Solar System, but we didn’t find any.” The Campaign was conducted at the Gemini South telescope in Chile, with funding support for the team from the National Science Foundation and NASA. The Campaign’s results, Liu says, will help scientists better understand how gas-giant planets form, as the orbital distances of planets are a key signature that astronomers use to test exoplanet formation theories. 

Eric Nielsen of the University of Hawaii, who leads a new paper about the Campaign’s search for planets around stars more massive than the Sun, adds that the findings have implications beyond the specific stars imaged by the team. "The two largest planets in our Solar System, Jupiter and Saturn, are huddled close to our Sun, within 10 times the distance between the Earth and Sun,” he points out. “We found that this lack of gas-giant planets in more distant orbits is typical for nearby stars over a wide range of masses." 

Two additional papers from the Campaign will be published soon and reveal similar tendencies around other classes of stars. However, not all gas-giant exoplanets snuggle so close to home. In 2008, astronomers using the Gemini North telescope and W.M. Keck Observatory on Hawaii’s Mauna Kea took the first-ever direct images of a family of planets around the star HR 8799, finding gas-giant planets at large orbital separations (about 25-70 times the Earth-Sun distance). This discovery came after examining only a few stars, suggesting such large-separation gas giants could be common. The latest Gemini results, from a much more extensive imaging search, show that gas-giant planets at such distances are in fact uncommon. 

Liu sums up the situation this way: “We’ve known for nearly 20 years that gas-giant planets exist around other stars, at least orbiting close-in. Thanks to leaps in direct imaging methods, we can now learn how far away planets can typically reside. The answer is that they usually avoid significant areas of real estate around their host stars. The early findings, like HR 8799, probably skewed our perceptions.” 

The team’s second new paper explores systems where dust disks around young stars show holes, which astronomers have long suspected are cleared by the gravitational force of orbiting planets. “It makes sense that where you see debris cleared away that a planet would be responsible, but we did not know what types of planets might be causing this. It appears that instead of massive planets, smaller planets that we can’t detect directly could be responsible,” said Zahed Wahhaj of the European Southern Observatory and lead author on the survey’s paper on dusty disk stars. Finally, the third new paper from the team looks at the very youngest stars close to Earth. “A younger system should have brighter, easier to detect planets,” according to the lead author Beth Biller of the Max Planck Institute for Astronomy. 

“Around other stars, NASA's Kepler telescope has shown that planets larger than the Earth and within the orbit of Mercury are plentiful,” explains Biller. “The NICI Campaign demonstrates that gas-giant planets beyond the distance of the orbit of Neptune are rare.” The soon-to-be-delivered Gemini Planet Imager will begin to bridge this gap likely revealing, for the first time, how common giant planets are in orbits similar to the gas-giant planets of our own Solar System. 

The observations for the Campaign were obtained with the Gemini instrument known as NICI, the Near-Infrared Coronagraphic Imager, which was the first instrument for an 8-10 meter-class telescope designed specifically for finding faint companions around bright stars. NICI was built by Doug Toomey (Mauna Kea Infrared), Christ Ftaclas, and Mark Chun (University of Hawai‘i), with funding from NASA.

The first two papers from the Campaign have been accepted for publication in The Astrophysical Journal (Nielsen et al. and Wahhaj et al.), and the third paper (Biller et al.) will be published later this summer. 

The NICI Campaign team is composed of PI Michael Liu, co-PI Mark Chun (University of Hawaii), co-PI Laird Close (University of Arizona), Doug Toomey (Mauna Kea Infrared), Christ Ftaclas (University of Hawaii), Zahed Wahhaj (European Southern Observatory), Beth Biller (Max Planck Institute for Astronomy), Eric Nielsen (University of Hawaii), Evgenya Shkolnik (DTM, Carnegie Institution of Washington), Adam Burrows (Princeton University), Neill Reid (Space Telescope Science Institute), Niranjan Thatte, Matthias Tecza, Fraser Clarke (University of Oxford), Jane Gregorio Hetem, Elisabete De Gouveia Dal Pino (University of Sao Paolo), Silvia Alencar (University of Minas Gerais), Pawel Artymowicz (University of Toronto), Doug Lin (University of California Santa Cruz), Shigeru Ida (Tokyo Institute of Technology), Alan Boss (DTM, Carnegie Institution of Washington), and Mark Kuchner (NASA Goddard), Tom Hayward and Markus Hartung (Gemini Observatory), Jared Males, and Andy Skemer (University of Arizona). 

Media Contacts:



  • Peter Michaud
    Gemini Observatory
    Hilo, HI 96720
    Office: +1 (808) 974-2510
    Cell: +1 (808) 936-6643

    pmichaud@gemini.edu

  • Roy Gal
    Institute for Astronomy
    University of Hawaii at Manoa
    Honolulu, HI 96822
    Office: +1 (808) 956-6235

    rgal@ifa.hawaii.edu

Science Contacts:



  • Michael Liu
    Institute for Astronomy
    University of Hawaii at Manoa
    Honolulu, HI 96822
    Office: +1 (808) 956-6666

    mliu@ifa.hawaii.edu

  • Eric Nielsen
    Institute for Astronomy
    University of Hawaii at Manoa
    Honolulu, HI 96822
    Office: +1 (808) 956-9841
    Cell: 408 394-4582

    enielsen@ifa.hawaii.edu

 

The Gemini Observatory is an international collaboration with two identical 8-meter telescopes. The Frederick C. Gillett Gemini Telescope is located on Mauna Kea, Hawai'i (Gemini North) and the other telescope on Cerro Pachón in central Chile (Gemini South); together the twin telescopes provide full coverage over both hemispheres of the sky. The telescopes incorporate technologies that allow large, relatively thin mirrors, under active control, to collect and focus both visible and infrared radiation from space.

Founded in 1967, the Institute for Astronomy at the University of Hawaii at Manoa conducts research into galaxies, cosmology, stars, planets, and the sun. Its faculty and staff are also involved in astronomy education, deep space missions, and in the development and management of the observatories on Haleakala and Mauna Kea. The Institute operates facilities on the islands of Oahu, Maui, and Hawaii. 


Friday, June 28, 2013

G1.9+0.3: The Remarkable Remains of a Recent Supernova

Credit: X-ray (NASA/CXC/NCSU/K.Borkowski et al.); 
Optical (DSS)


Tour of G1.9+0.3

Click for low-resolution animation


Astronomers estimate that a star explodes as a supernova in our Galaxy, on average, about twice per century. In 2008, a team of scientists announced they discovered the remains of a supernova that is the most recent, in Earth's time frame, known to have occurred in the Milky Way.

The explosion would have been visible from Earth a little more than a hundred years ago if it had not been heavily obscured by dust and gas. Its likely location is about 28,000 light years from Earth near the center of the Milky Way. A long observation equivalent to more than 11 days of observations of its debris field, now known as the supernova remnant G1.9+0.3, with NASA's Chandra X-ray Observatory is providing new details about this important event.

The source of G1.9+0.3 was most likely a white dwarf star that underwent a thermonuclear detonation and was destroyed after merging with another white dwarf, or pulling material from an orbiting companion star. This is a particular class of supernova explosions (known as Type Ia) that are used as distance indicators in cosmology because they are so consistent in brightness and incredibly luminous.

The explosion ejected stellar debris at high velocities, creating the supernova remnant that is seen today by Chandra and other telescopes. This new image is a composite from Chandra where low-energy X-rays are red, intermediate energies are green and higher-energy ones are blue. Also shown are optical data from the Digitized Sky Survey, with appearing stars in white. The new Chandra data, obtained in 2011, reveal that G1.9+0.3 has several remarkable properties.

The Chandra data show that most of the X-ray emission is "synchrotron radiation," produced by extremely energetic electrons accelerated in the rapidly expanding blast wave of the supernova. This emission gives information about the origin of cosmic rays - energetic particles that constantly strike the Earth's atmosphere - but not much information about Type Ia supernovas.

In addition, some of the X-ray emission comes from elements produced in the supernova, providing clues to the nature of the explosion. The long Chandra observation was required to dig out those clues.

Most Type Ia supernova remnants are symmetrical in shape, with debris evenly distributed in all directions. However, G1.9+0.3 exhibits an extremely asymmetric pattern. The strongest X-ray emission from elements like silicon, sulfur, and iron is found in the northern part of the remnant, giving an extremely asymmetric pattern.

Another exceptional feature of this remnant is that iron, which is expected to form deep in the doomed star's interior and move relatively slowly, is found far from the center and is moving at extremely high speeds of over 3.8 million miles per hour. The iron is mixed with lighter elements expected to form further out in the star.

Because of the uneven distribution of the remnant's debris and their extreme velocities, the researchers conclude that the original supernova explosion also had very unusual properties. That is, the explosion itself must have been highly non-uniform and unusually energetic.

By comparing the properties of the remnant with theoretical models, the researchers found hints about the explosion mechanism. Their favorite concept for what happened in G1.9+0.3 is a "delayed detonation", where the explosion occurs in two different phases. First, nuclear reactions occur in a slowly expanding wavefront, producing iron and similar elements. The energy from these reactions causes the star to expand, changing its density and allowing a much faster-moving detonation front of nuclear reactions to occur.
If the explosion were highly asymmetric, then there should be large variations in expansion rate in different parts of the remnant. These should be measurable with future observations with X-rays using Chandra and radio waves with the NSF's Karl G. Jansky Very Large Array.

Observations of G1.9+0.3 allow astronomers a special, close-up view of a young supernova remnant and its rapidly changing debris. Many of these changes are driven by the radioactive decay of elements ejected in the explosion. For example, a large amount of antimatter should have formed after the explosion by radioactive decay of cobalt. Based on the estimated mass of iron, which is formed by radioactive decay of nickel to cobalt to iron, over a hundred million trillion (ie ten raised to the power of twenty) pounds of positrons, the antimatter counterpart to electrons, should have formed. However, nearly all of these positrons should have combined with electrons and been destroyed, so no direct observational signature of this antimatter should remain.

A paper describing these results is available online and will be published in the July 1, 2013 issue of The Astrophysical Journal Letters. The first author is Kazimierz Borkowski of North Carolina State University (NCSU), in Raleigh, NC and his co-authors are Stephen Reynolds, also of NCSU; Una Hwang from NASA's Goddard Space Flight Center (GSFC) in Greenbelt, MD; David Green from Cavendish Laboratory in Cambridge, UK; Robert Petre, also from GSFC; Kalyani Krishnamurthy from Duke University in Durham, NC and Rebecca Willett, also from Duke University.

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


Fast Facts for G1.9+0.3:

Scale: Image is 8 arcmin across (About 60 light years)
Category: Supernovas & Supernova Remnants
Coordinates (J2000): RA 17h 48m 45s | Dec -27° 10' 00"
Constellation: Sagittarius
Observation Date: 15 pointings between Feb 2007 and Jul 2011
Observation Time: 362 hours (15 days 2 hours)
Obs. ID: 6708, 8521, 10111, 10112, 10928, 10930, 12689-95, 13407, 13509
Instrument: ACIS
References: Borkowski, K, et al, 2013, ApJ Letters (Submitted); arXiv:1305.7399
Color Code: X-ray (Red, Green, Blue); Optical (White/Cyan)
Distance Estimate:  About 25,000 light years

Inseparable galactic twins

Credit:ESA/Hubble & NASA
Acknowledgement: Judy Schmidt

Looking towards the constellation of Triangulum (The Triangle), in the northern sky, lies the galaxy pair MRK 1034. The two very similar galaxies, named PGC 9074 and PGC 9071, are close enough to one another to be bound together by gravity, although no gravitational disturbance can yet be seen in the image. These objects are probably only just beginning to interact gravitationally.

Both are spiral galaxies, and are presented to our eyes face-on, so we are able to appreciate their distinctive shapes. On the left of the image, spiral galaxy PGC 9074 shows a bright bulge and two spiral arms tightly wound around the nucleus, features which have led scientists to classify it as a type Sa galaxy. Close by, PGC 9071 — a type Sb galaxy — although very similar and almost the same size as its neighbour, has a fainter bulge and a slightly different structure to its arms: their coils are further apart.

The spiral arms of both objects clearly show dark patches of dust obscuring the light of the stars lying behind, mixed with bright blue clusters of hot, recently-formed stars. Older, cooler stars can be found in the glowing, compact yellowish bulge towards the centre of the galaxy. The whole structure of each galaxy is surrounded by a much fainter round halo of old stars, some residing in globular clusters.

Gradually, these two neighbours will attract each other, the process of star formation will be increased and tidal forces will throw out long tails of stars and gas. Eventually, after maybe hundreds of millions of years, the structures of the interacting galaxies will merge together into a new, larger galaxy.

The images combined to create this picture were captured by Hubble's Advanced Camera for Surveys (ACS). A version of this image was submitted to the Hubble’s Hidden Treasures image processing competition by Judy Schmidt.

 

Thursday, June 27, 2013

Herschel sheds light on role of water

The location of Comet Hartley 2 and the Herschel image of it (inset). 
Click here for more information. Image Credit: ESA/NASA/Herschel/HSSO

Artist's impression of the disc of gas and dust around the star TW Hydrae. 
Click here for more information. Image credit: ESA/NASA/JPL-Caltech/WISH 

One of the most interesting molecules that astronomers like to study is water, which is so abundant on the Earth and though to be crucial for life. Water can form relatively easily, providing the temperature is not too high, and the outer regions of our own Solar system are full of icy bodies. Observations of water are very hard to observed from the Earth as the atmosphere interferes with the measurements, and so studying water requires spacecraft. Far from Earth, the HIFI instrument on board Herschel is studying the role of water in not just our own Solar System, but also in others.

In late 2010 the comet Hartley 2 passed relatively close to Earth, though it has not always ventured this close to the Sun. Hartley 2 originated in an outer region of the Solar System called the Kuiper Belt, but was put on an orbit that brings it in to the inner Solar System after encounters with planets and other large bodies. The HIFI instrument onboard Herschel measured the composition of the water in the comet, and found that it is very similar to that of the water in the Earth's oceans.

The idea that comets seeded the water on Earth has been a favourite among many astronomers for decades, as there are few other ways to explain where the water came from. However the composition of the water in most of the comets studied doesn't match that of the ocean water, and this has long been a thorn in the side of the proponents of the idea. Most of these comets formed relatively close to the Sun, around where Jupiter orbits, but Hartley 2 is the first comet to be investigated that formed much further out. The fact that the composition of the water in Hartley 2 is so similar lends further weight to the theory that comets seeded our oceans, though perhaps it was mainly this particular type of comet that did the seeding.

HIFI is sensitive enough to look at the material orbiting other stars, such as TW Hydrae in the constellation of Hydra. This star is a little less massive than the Sun but which is much, much younger. At only 10 million years old, TW Hydrae is still in its adolescent years, and has a disc of gas and dust around it. It is thought that our own Sun would have started out like this, with the planets forming after tens or hundreds of millions of years.

TW Hydrae is 175 light years away from the Sun, far too distant for any of Herschel's instruments to see in detail. The sensitivity of the HIFI instrument allows it to detect the faint signature of water vapour, and a careful study of the signature allows astronomers to work out the temperature of the water vapour and where it is in the disk. The water vapour is stripped from grains of ice by the light from the star, but is found at temperatures below 100 K (-170 Celsius). This is much colder than has been found previously around other stars, and indicates that the water vapour is present throughout the disc.

Water plays a crucial role in planetary systems, as it allows grains of dust to clump together and form asteroids, which later collect together to form the planets. Studying the presence of water, and the conditions in which it is found, is vital for understanding how Solar Systems such as our own formed.



Wednesday, June 26, 2013

First Transiting Planets in a Star Cluster Discovered

 
In the star cluster NGC 6811, astronomers have found two planets smaller than Neptune orbiting Sun-like stars. Credit: Michael Bachofner. High Resolution Image (jpg) - Low Resolution Image (jpg)

Cambridge, MA - All stars begin their lives in groups. Most stars, including our Sun, are born in small, benign groups that quickly fall apart. Others form in huge, dense swarms that survive for billions of years as stellar clusters. Within such rich and dense clusters, stars jostle for room with thousands of neighbors while strong radiation and harsh stellar winds scour interstellar space, stripping planet-forming materials from nearby stars. 

It would thus seem an unlikely place to find alien worlds. Yet 3,000 light-years from Earth, in the star cluster NGC 6811, astronomers have found two planets smaller than Neptune orbiting Sun-like stars. The discovery, published in the journal Nature, shows that planets can develop even in crowded clusters jam-packed with stars. 

"Old clusters represent a stellar environment much different than the birthplace of the Sun and other planet-hosting field stars," says lead author Soren Meibom of the Harvard-Smithsonian Center for Astrophysics (CfA). "And we thought maybe planets couldn't easily form and survive in the stressful environments of dense clusters, in part because for a long time we couldn't find them." 

The two new alien worlds appeared in data from NASA's Kepler spacecraft. Kepler hunts for planets that transit, or cross in front of, their host stars. During a transit, the star dims by an amount that depends on the size of the planet, allowing the size to be determined. Kepler-66b and Kepler-67b are both less than three times the size of Earth, or about three-fourths the size of Neptune (mini-Neptunes). 

Of the more than 850 known planets beyond our solar system, only four - all similar to or greater than Jupiter in mass - were found in clusters. Kepler-66b and -67b are the smallest planets to be found in a star cluster, and the first cluster planets seen to transit their host stars, which enables the measurement of their sizes. 

Meibom and his colleagues have measured the age of NGC 6811 to be one billion years. Kepler-66b and Kepler-67b therefore join a small group of planets with precisely determined ages, distances, and sizes. 

Considering the number of stars observed by Kepler in NGC 6811, the detection of two such planets implies that the frequency and properties of planets in open clusters are consistent with those of planets around field stars (stars not within a cluster or association) in the Milky Way galaxy. 

"These planets are cosmic extremophiles," says Meibom. "Finding them shows that small planets can form and survive for at least a billion years, even in a chaotic and hostile environment." 

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:

Soren Meibom
Astronomer

smeibom@cfa.harvard.edu
smeibom@gmail.com

 

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




Astronomers spy on galaxies in the raw

The Spiderweb, imaged by the Hubble Space Telescope – a central galaxy (MRC 1138-262) surrounded by hundreds of other star-forming 'clumps'. Credit: NASA, ESA, George Miley and Roderik Overzier (Leiden Observatory). Hi-res

In blue, the carbon monoxide gas detected in and around the Spiderweb
Credit: B. Emonts et al (CSIRO/ATCA). Hi-Res

Antennas of CSIRO's Compact Array telescope
Photo: David Smyth . Hi-Res

video
 The Spiderweb
Zooming into the Spiderweb, as imaged by NASA/ESA's Hubble Space Telescope. Credit: Akira Fujii, Digitized Sky Survey 2 and ESA/Hubble Download (mp4). Transcript: Stars and galaxies seen from far away then the camera zooms in closer to focus on a conglomerate of star-forming 'clumps' or 'proto-galaxies' that are in the process of coming together as a single massive galaxy.
  
A CSIRO radio telescope has detected the raw material for making the first stars in galaxies that formed when the Universe was just three billion years old — less than a quarter of its current age. This opens the way to studying how these early galaxies make their first stars.

The telescope is CSIRO's Australia Telescope Compact Array telescope near Narrabri, NSW. "It one of very few telescopes in the world that can do such difficult work, because it is both extremely sensitive and can receive radio waves of the right wavelengths," says CSIRO astronomer Professor Ron Ekers. 

The raw material for making stars is cold molecular hydrogen gas, H2. It can't be detected directly but its presence is revealed by a 'tracer' gas, carbon monoxide (CO), which emits radio waves.

In one project, astronomer Dr Bjorn Emonts (CSIRO Astronomy and Space Science) and his colleagues used the Compact Array to study a massive, distant conglomerate of star-forming 'clumps' or 'proto-galaxies' that are in the process of coming together as a single massive galaxy. This structure, called the Spiderweb, lies more than ten thousand million light-years away [at a redshift of 2.16]. 

Dr Emonts' team found that the Spiderweb contains at least sixty thousand million [6 x 1010] times the mass of the Sun in molecular hydrogen gas, spread over a distance of almost a quarter of a million light-years. This must be the fuel for the star-formation that has been seen across the Spiderweb. "Indeed, it is enough to keep stars forming for at least another 40 million years," says Emonts.

In a second set of studies, Dr Manuel Aravena (European Southern Observatory) and colleagues measured CO, and therefore H2, in two very distant galaxies [at a redshift of 2.7]. 

The faint radio waves from these galaxies were amplified by the gravitational fields of other galaxies — ones that lie between us and the distant galaxies. This process, called gravitational lensing, "acts like a magnifying lens and allows us to see even more distant objects than the Spiderweb," says Dr Aravena.

Dr Aravena's team was able to measure the amount of H2 in both galaxies they studied. For one (called SPT-S 053816-5030.8), they could also use the radio emission to make an estimate of how rapidly the galaxy is forming stars — an estimate independent of the other ways astronomers measure this rate.

The Compact Array's ability to detect CO is due to an upgrade that has boosted its bandwidth — the amount of radio spectrum it can see at any one time — sixteen-fold [from 256 MHz to 4 GHz], and made it far more sensitive.

"The Compact Array complements the new ALMA telescope in Chile, which looks for the higher-frequency transitions of CO," says Ron Ekers.

Read more media releases in our Media section.

Publications


Emonts BHC and 15 co-authors. CO(1-0) detection of molecular gas in the massive Spiderweb Galaxy (z=2). Monthly Notices of the Royal Astronomical Society 430, 3465 (2013). Online at http://arxiv.org/abs/1301.6012


Aravena M and 28 co-authors. Large gas reservoirs and free-free emission in two lensed star-forming galaxies at z = 2.7. Accepted for publication in Monthly Notices of the Royal Astronomical Society. Online at http://arxiv.org/abs/1305.0614.

More information


Professor Ron Ekers, CSIRO Astronomy and Space Science [in Sydney, Australia]
Mob: +61 419 146 313

Dr Bjorn Emonts, CSIRO Astronomy and Space Science [currently in Spain]
bjornemonts@gmail.com

Mob: +34 692 744 507

Dr Manuel Aravena, European Southern Observatory [in Santiago, Chile]
maravena@eso.org
Office: +56 22 463 3256
 

Contact Information


Ms Helen Sim

Media and Public Relations
Astronomy and Space Science
Phone: +61 2 9372 4251
Alt Phone: +61 419 635 905
Email: Helen.Sim@csiro.au

Dr Ron Ekers
Fellow
CSIRO Astronomy and Space Science
Phone: +61 41914 6313
Email: Ron.Ekers@csiro.au


Tuesday, June 25, 2013

Three Planets in Habitable Zone of Nearby Star

Artist's impression of the Gliese 667C system

The planetary system around Gliese 667C

The sky around the star Gliese 667C

 Videos

Artist's impression of the orbits of the planets in the Gliese 667C system
Artist's impression of the orbits of the planets in the Gliese 667C system

Artist's impression of the Gliese 667C system
Artist's impression of the Gliese 667C system

Artist's impression of the Gliese 667C system
Artist's impression of the Gliese 667C system

Gliese 667C reexamined

A team of astronomers has combined new observations of Gliese 667C with existing data from HARPS at ESO’s 3.6-metre telescope in Chile, to reveal a system with at least six planets. A record-breaking three of these planets are super-Earths lying in the zone around the star where liquid water could exist, making them possible candidates for the presence of life. This is the first system found with a fully packed habitable zone.

Gliese 667C is a very well-studied star. Just over one third of the mass of the Sun, it is part of a triple star system known as Gliese 667 (also referred to as GJ 667), 22 light-years away in the constellation of Scorpius (The Scorpion). This is quite close to us — within the Sun’s neighbourhood — and much closer than the star systems investigated using telescopes such as the planet-hunting Kepler space telescope.

Previous studies of Gliese 667C had found that the star hosts three planets (eso0939, eso1214) with one of them in the habitable zone. Now, a team of astronomers led by Guillem Anglada-Escudé of the University of Göttingen, Germany and Mikko Tuomi of the University of Hertfordshire, UK, has reexamined the system. They have added new HARPS observations, along with data from ESO's Very Large Telescope, the W.M. Keck Observatory and the Magellan Telescopes, to the already existing picture [1]. The team has found evidence for up to seven planets around the star [2]

These planets orbit the third fainter star of a triple star system. Viewed from one of these newly found planets the two other suns would look like a pair of very bright stars visible in the daytime and at night they would provide as much illumination as the full Moon. The new planets completely fill up the habitable zone of Gliese 667C, as there are no more stable orbits in which a planet could exist at the right distance to it. 

We knew that the star had three planets from previous studies, so we wanted to see whether there were any more,” says Tuomi. “By adding some new observations and revisiting existing data we were able to confirm these three and confidently reveal several more. Finding three low-mass planets in the star’s habitable zone is very exciting!

Three of these planets are confirmed to be super-Earths — planets more massive than Earth, but less massive than planets like Uranus or Neptune — that are within their star’s habitable zone, a thin shell around a star in which water may be present in liquid form if conditions are right. This is the first time that three such planets have been spotted orbiting in this zone in the same system [3].

The number of potentially habitable planets in our galaxy is much greater if we can expect to find several of them around each low-mass star — instead of looking at ten stars to look for a single potentially habitable planet, we now know we can look at just one star and find several of them,” adds co-author Rory Barnes (University of Washington, USA).

Compact systems around Sun-like stars have been found to be abundant in the Milky Way. Around such stars, planets orbiting close to the parent star are very hot and are unlikely to be habitable. But this is not true for cooler and dimmer stars such as Gliese 667C. In this case the habitable zone lies entirely within an orbit the size of Mercury's, much closer in than for our Sun. The Gliese 667C system is the first example of a system where such a low-mass star is seen to host several potentially rocky planets in the habitable zone.

The ESO scientist responsible for HARPS, Gaspare Lo Curto, remarks: “This exciting result was largely made possible by the power of HARPS and its associated software and it also underlines the value of the ESO archive. It is very good to also see several independent research groups exploiting this unique instrument and achieving the ultimate precision.

And Anglada-Escudé concludes: “These new results highlight how valuable it can be to re-analyse data in this way and combine results from different teams on different telescopes.

Notes

[1] The team used data from the UVES spectrograph on ESO’s Very Large Telescope in Chile (to determine the properties of the star accurately), the Carnegie Planet Finder Spectrograph (PFS) at the 6.5-metre Magellan II Telescope at the Las Campanas Observatory in Chile, the HIRES spectrograph mounted on the Keck 10-metre telescope on Mauna Kea, Hawaii as well as extensive previous data from HARPS (the High Accuracy Radial velocity Planet Searcher) at ESO’s 3.6-metre telescope in Chile (gathered through the M dwarf programme led by X. Bonfils and M. Mayor 2003–2010 described here).

[2] The team looked at radial velocity data of Gliese 667C, a method often used to hunt for exoplanets. They performed a robust Bayesian statistical analysis to spot the signals of the planets. The first five signals are very confident, while the sixth is tentative, and seventh more tentative still. This system consists of three habitable-zone super-Earths, two hot planets further in, and two cooler planets further out. The planets in the habitable zone and those closer to the star are expected to always have the same side facing the star, so that their day and year will be the same lengths, with one side in perpetual sunshine and the other always night.

[3] In the Solar System Venus orbits close to the inner edge of the habitable zone and Mars close to the outer edge. The precise extent of the habitable zone depends on many factors.

More information

This research was presented in a paper entitled “A dynamically-packed planetary system around GJ 667C with three super-Earths in its habitable zone”, to appear in the journal Astronomy & Astrophysics.

The team is composed of G. Anglada-Escudé (University of Göttingen, Germany), M. Tuomi (University of Hertfordshire, UK), E. Gerlach (Technical University of Dresden, Germany), R. Barnes (University of Washington, USA), R. Heller (Leibniz Institute for Astrophysics, Potsdam, Germany), J. S. Jenkins (Universidad de Chile, Chile), S. Wende (University of Göttingen, Germany), S. S. Vogt (University of California, Santa Cruz, USA), R. P. Butler (Carnegie Institution of Washington, USA), A. Reiners (University of Göttingen, Germany), and H. R. A. Jones (University of Hertfordshire, UK).

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

Guillem Anglada-Escudé
Institut fur Astrophysik, University of Göttingen
Göttingen, Germany
Tel: +49 0551 39 9988
Email:
guillem.anglada@gmail.com

Mikko Tuomi
Center for Astrophysics Reseach, Hertfordshire University
Hatfield, UK
Tel: +44 01707 284095
Email:
miptuom@utu.fi

Rory Barnes
Department of Astronomy, University of Washington
Seattle, USA
Tel: +1 206 543 8979
Email:
rory@astro.washington.edu

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

 

Ten Thousandth Near-Earth Object Unearthed in Space

Asteroid 2013 MZ5 as seen by the University of Hawaii's PanSTARR-1 telescope. In this animated gif, the asteroid moves relative to a fixed background of stars. Asteroid 2013 MZ5 is in the right of the first image, towards the top, moving diagonally left/down. Image credit: PS-1/UH.  › Larger view | Unannotated version

More than 10,000 asteroids and comets that can pass near Earth have now been discovered. The 10,000th near-Earth object, asteroid 2013 MZ5, was first detected on the night of June 18, 2013, by the Pan-STARRS-1 telescope, located on the 10,000-foot (convert) summit of the Haleakala crater on Maui. Managed by the University of Hawaii, the PanSTARRS survey receives NASA funding.

Ninety-eight percent of all near-Earth objects discovered were first detected by NASA-supported surveys.

"Finding 10,000 near-Earth objects is a significant milestone," said Lindley Johnson, program executive for NASA's Near-Earth Object Observations Program at NASA Headquarters, Washington. "But there are at least 10 times that many more to be found before we can be assured we will have found any and all that could impact and do significant harm to the citizens of Earth." During Johnson's decade-long tenure, 76 percent of the NEO discoveries have been made.

Near-Earth objects (NEOs) are asteroids and comets that can approach the Earth's orbital distance to within about 28 million miles (45 million kilometers). They range in size from as small as a few feet to as large as 25 miles (41 kilometers) for the largest near-Earth asteroid, 1036 Ganymed.

Asteroid 2013 MZ5 is approximately 1,000 feet (300 meters) across. Its orbit is well understood and will not approach close enough to Earth to be considered potentially hazardous.

"The first near-Earth object was discovered in 1898," said Don Yeomans, long-time manager of NASA's Near-Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, Calif. "Over the next hundred years, only about 500 had been found. But then, with the advent of NASA's NEO Observations program in 1998, we've been racking them up ever since. And with new, more capable systems coming on line, we are learning even more about where the NEOs are currently in our solar system, and where they will be in the future."

Of the 10,000 discoveries, roughly 10 percent are larger than six tenths of a mile (one kilometer) in size - roughly the size that could produce global consequences should one impact the Earth. However, the NASA NEOO program has found that none of these larger NEOs currently pose an impact threat and probably only a few dozen more of these large NEOs remain undiscovered.

The vast majority of NEOs are smaller than one kilometer, with the number of objects of a particular size increasing as their sizes decrease. For example, there are expected to be about 15,000 NEOs that are about one-and-half football fields in size (460 feet, or 140 meters), and more than a million that are about one-third a football field in size (100 feet, or 30 meters). A NEO hitting Earth would need to be about 100 feet (30 meters) or larger to cause significant devastation in populated areas. Almost 30 percent of the 460-foot-sized (140-meter-sized) NEOs have been found, but less than 1 percent of the 100-foot-sized NEOs have been detected.

When it originated, the NASA-instituted Near-Earth Object Observations Program provided support to search programs run by the Massachusetts Institute of Technology's Lincoln Laboratory (LINEAR); the Jet Propulsion Laboratory (NEAT); the University of Arizona (Spacewatch, and later Catalina Sky Survey) and the Lowell Observatory (LONEOS). All these search teams report their observations to the Minor Planet Center, the central node where all observations from observatories worldwide are correlated with objects, and they are given unique designations and their orbits are calculated.

"When I began surveying for asteroids and comets in 1992, a near-Earth object discovery was a rare event," said Tim Spahr, director of the Minor Planet Center. "These days we average three NEO discoveries a day, and each month the Minor Planet Center receives hundreds of thousands of observations on asteroids, including those in the main-belt. The work done by the NASA surveys, and the other international professional and amateur astronomers, to discover and track NEOs is really remarkable."

Within a dozen years, the program achieved its goal of discovering 90 percent of near-Earth objects larger than 3,300 feet (1 kilometer) in size. In December 2005, NASA was directed by Congress to extend the search to find and catalog 90 percent of the NEOs larger than 500 feet (140 meters) in size. When this goal is achieved, the risk of an unwarned future Earth impact will be reduced to a level of only one percent when compared to pre-survey risk levels. This reduces the risk to human populations, because once an NEO threat is known well in advance, the object could be deflected with current space technologies.

Currently, the major NEO discovery teams are the Catalina Sky Survey, the University of Hawaii's Pan-STARRS survey and the LINEAR survey. The current discovery rate of NEOs is about 1,000 per year.

NASA's Near-Earth Object Observations Program manages and funds the search for, study of and monitoring of asteroids and comets whose orbits periodically bring them close to Earth. The Minor Planet Center is funded by NASA and hosted by the Smithsonian Astrophysical Observatory in Cambridge, MA. JPL manages the Near-Earth Object Program Office for NASA's Science Mission Directorate in Washington. JPL is a division of the California Institute of Technology in Pasadena. More information about asteroids and near-Earth objects is available at: http://neo.jpl.nasa.gov/, http://www.jpl.nasa.gov/asteroidwatch and via Twitter at http://www.twitter.com/asteroidwatch .


DC Agle
Jet Propulsion Lab., Pasadena, Calif.
818-393-9011

agle@jpl.nasa.gov


Monday, June 24, 2013

Solar Splashdown

This photograph from NASA's Solar Dynamics Observatory catches the beginning of the eruption that took place on June 7, 2011. At lower right, dark filaments of solar plasma arc away from the Sun. The plasma lofted off, then rained back down to create "hot spots" that glowed in ultraviolet light. This representative-color image shows light at a wavelength of 171 Angstroms (17.1 nm). Credit: NASA / SDO / P. Testa (CfA).  High Resolution Image (jpg) - Low Resolution Image (jpg)
 
This photograph from NASA's Solar Dynamics Observatory catches the beginning of the eruption that took place on June 7, 2011. It shows light at a wavelength of 304 Angstroms (30.4 nm). A bright flare is visible at lower right, as well as hot, glowing plasma blasting outward.Credit: NASA / SDO / P. Testa (CfA). High Resolution Image (jpg) - Low Resolution Image (jpg)

Cambridge, MA - On June 7, 2011, our Sun erupted, blasting tons of hot plasma into space. Some of that plasma splashed back down onto the Sun's surface, sparking bright flashes of ultraviolet light. This dramatic event may provide new insights into how young stars grow by sucking up nearby gas. 

The eruption and subsequent splashdown were observed in spectacular detail by NASA's Solar Dynamics Observatory. This spacecraft watches the Sun 24 hours a day, providing images with better-than-HD resolution. Its Atmospheric Imaging Assembly instrument was designed and developed by researchers at the Harvard-Smithsonian Center for Astrophysics (CfA).

"We’re getting beautiful observations of the Sun. And we get such high spatial resolution and high cadence that we can see things that weren’t obvious before," says CfA astronomer Paola Testa.

Movies of the June 7th eruption show dark filaments of gas blasting outward from the Sun's lower right. Although the solar plasma appears dark against the Sun's bright surface, it actually glows at a temperature of about 18,000 degrees Fahrenheit. When the blobs of plasma hit the Sun's surface again, they heat up by a factor of 100 to a temperature of almost 2 million degrees F. As a result, those spots brighten in the ultraviolet by a factor of 2 – 5 over just a few minutes.

The tremendous energy release occurs because the in falling blobs are traveling at high speeds, up to 900,000 miles per hour (400 km/sec). Those speeds are similar to the speeds reached by material falling onto young stars as they grow via accretion. Therefore, observations of this solar eruption provide an "up close" view of what happens on distant stars.

"We often study young stars to learn about our Sun when it was an 'infant.' Now we’re doing the reverse and studying our Sun to better understand distant stars," notes Testa.

These new observations, combined with computer modeling, have helped resolve a decade-long argument over how to measure the accretion rates of growing stars. Astronomers calculate how fast a young star is gathering material by observing its brightness at various wavelengths of light, and how that brightness changes over time. However, they got higher estimates from optical and ultraviolet light than from X-rays.

The team discovered that the ultraviolet flashes they observed came from the in falling material itself, not the surrounding solar atmosphere. If the same is true for distant, young stars, then by analyzing the ultraviolet light they emit, we can learn about the material they are accreting.

"By seeing the dark spots on the Sun, we can learn about how young stars accrete material and grow." explains Testa.

These results were published in the online journal Science Express.

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
 

Friday, June 21, 2013

Messier 61 looks straight into the camera

Credit: ESA/Hubble & NASA
Acknowledgements: G. Chapdelaine, L. Limatola, and R. Gendler. 

The NASA/ESA Hubble Space Telescope has captured this image of nearby spiral galaxy Messier 61, also known as NGC 4303. The galaxy, located only 55 million light-years away from Earth, is roughly the size of the Milky Way, with a diameter of around 100 000 light-years. The galaxy is notable for one particular reason — six supernovae have been observed within Messier 61, a total that places it in the top handful of galaxies alongside Messier 83, also with six, and NGC 6946, with a grand total of nine observed supernovae.

In this Hubble image the galaxy is seen face-on as if posing for a photograph, allowing us to study its structure closely. The spiral arms can be seen in stunning detail, swirling inwards to the very centre of the galaxy, where they form a smaller, intensely bright spiral. In the outer regions, these vast arms are sprinkled with bright blue regions where new stars are being formed from hot, dense clouds of gas.

Messier 61 is part of the Virgo Galaxy Cluster, a massive group of galaxies in the constellation of Virgo (the Virgin). Galaxy clusters, or groups of galaxies, are among the biggest structures in the Universe to be held together by gravity alone. The Virgo Cluster contains more than 1300 galaxies and forms the central region of the Local Supercluster, an even bigger gathering of galaxies.

The image was taken using data from Hubble’s Wide Field Camera 2. Different versions of this image were submitted to the Hubble’s Hidden Treasures image processing competition by contestants Gilles Chapdelaine, Luca Limatola, and Robert Gendler.

Links


Thursday, June 20, 2013

Hubble spots galaxies in close encounter

Hubble image of Arp 142
 
The area around merging galaxy duo Arp 142 (ground-based image)

 

Videos

Hubblecast 67: Of galaxies and penguins — Arp 142
Hubblecast 67: Of galaxies and penguins — Arp 142

3D visualisation of Arp 142
3D visualisation of Arp 142

Zooming in on Arp 142
Zooming in on Arp 142

Zoom and 3D visualisation of Arp 142
Zoom and 3D visualisation of Arp 142

Looking through the eye of Hubble
Looking through the eye of Hubble

The NASA/ESA Hubble Space Telescope has produced this vivid image of a pair of interacting galaxies known as Arp 142. When two galaxies stray too close to each other they begin to interact, causing spectacular changes in both objects. In some cases the two can merge — but in others, they are ripped apart.

Just below the centre of this image is the blue, twisted form of galaxy NGC 2936, one of the two interacting galaxies that form Arp 142 in the constellation of Hydra. Nicknamed "the Penguin" or "the Porpoise" by amateur astronomers, NGC 2936 used to be a standard spiral galaxy before being torn apart by the gravity of its cosmic companion.

The remnants of its spiral structure can still be seen — the former galactic bulge now forms the "eye" of the penguin, around which it is still possible to see where the galaxy's pinwheeling arms once were. These disrupted arms now shape the cosmic bird's "body" as bright streaks of blue and red across the image. These streaks arch down towards NGC 2936's nearby companion, the elliptical galaxy NGC 2937, visible here as a bright white oval. The pair show an uncanny resemblance to a penguin safeguarding its egg.

The effects of gravitational interaction between galaxies can be devastating. The Arp 142 pair are close enough together to interact violently, exchanging matter and causing havoc.

In the upper part of the image are two bright stars, both of which lie in the foreground of the Arp 142 pair. One of these is surrounded by a trail of sparkling blue material, which is actually another galaxy. This galaxy is thought to be too far away to play a role in the interaction — the same is true of the galaxies peppered around the body of NGC 2936. In the background are the blue and red elongated shapes of many other galaxies, which lie at vast distances from us — but which can all be seen by the sharp eye of Hubble.

This pair of galaxies is named after the American astronomer Halton Arp, the creator of the Atlas of Peculiar Galaxies, a catalogue of weirdly-shaped galaxies that was originally published in 1966. Arp compiled the catalogue in a bid to understand how galaxies evolved and changed shape over time, something he felt to be poorly understood. He chose his targets based on their strange appearances, but astronomers later realised that many of the objects in Arp's catalogue were in fact interacting and merging galaxies [1].

This image is a combination of visible and infrared light, created from data gathered by the NASA/ESA Hubble Space Telescope Wide Field Planetary Camera 3 (WFC3).

Notes

[1] The birth and evolution of various sets of merging galaxies was the subject of the book Cosmic Collisions – The Hubble Atlas of Merging Galaxies, produced by Springer and the European Southern Observatory. The book is illustrated with a range of stunning Hubble Space Telescope images.

More information

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

Image credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

Links

Contacts

Nicky Guttridge
ESA/Hubble
Garching, Germany
Tel: +49-89-3200-6855
Email:
nguttrid@partner.eso.org