Large water reservoirs at the dawn of stellar birth

Herschel’s infrared view of part of the Taurus Molecular Cloud, within which the bright, cold pre-stellar cloud L1544 can be seen at the lower left. It is surrounded by many other clouds of gas and dust of varying density. The Taurus Molecular Cloud is about 450 light-years from Earth and is the nearest large region of star formation. The image covers a field of view of approximately 1 x 2 arcminutes.  Credits: ESA/Herschel/SPIRE .  HI-RES JPEG (Size: 133 kb)

Close-up of L1544 with the water spectrum seen by Herschel, taken from the centre of the pre-stellar core. The peak of the graph shows an excess in brightness, or emission, while the trough shows a deficit, or absorption. These characteristics are used to indicate the density and motions of the water molecules within the cloud. Emission arises from molecules that are approaching the centre where the new star will form, from the back of the cloud from Herschel’s viewpoint. The amount of emission indicates that these molecules are moving within the densest part of the core, which spans about 1000 Astronomical Units. The absorption signature is due to water molecules in front of the cloud flowing away from the observer towards the centre. These water molecules are in less dense regions much further away from the centre. Together, the emission and absorption signatures indicate that the cloud is undergoing gravitational contraction, that is, it is collapsing to form a new star. Herschel detected enough water vapour in L1544 to fill Earth’s oceans more than 2000 times over.  Credits: ESA/Herschel/SPIRE/HIFI/Caselli et al.  HI-RES JPEG (Size: 356 kb)

ESA’s Herschel space observatory has discovered enough water vapour to fill Earth’s oceans more than 2000 times over, in a gas and dust cloud that is on the verge of collapsing into a new Sun-like star.
 
Stars form within cold, dark clouds of gas and dust – ‘pre-stellar cores’ – that contain all the ingredients to make solar systems like our own.

Water, essential to life on Earth, has previously been detected outside of our Solar System as gas and ice coated onto tiny dust grains near sites of active star formation, and in proto-planetary discs capable of forming alien planetary systems.

The new Herschel observations of a cold pre-stellar core in the constellation of Taurus known as Lynds 1544 are the first detection of water vapour in a molecular cloud on the verge of star formation.

More than 2000 Earth oceans-worth of water vapour were detected, liberated from icy dust grains by high-energy cosmic rays passing through the cloud.
  
“To produce that amount of vapour, there must be a lot of water ice in the cloud, more than three million frozen Earth oceans’ worth,” says Paola Caselli from the University of Leeds, UK, lead author of the paper reporting the results in Astrophysical Journal Letters.

“Before our observations, the understanding was that all the water was frozen onto dust grains because it was too cold to be in the gas phase and so we could not measure it."

“Now we will need to review our understanding of the chemical processes in this dense region and, in particular, the importance of cosmic rays to maintain some amount of water vapour."

The observations also revealed that the water molecules are flowing towards the heart of the cloud where a new star will probably form, indicating that gravitational collapse has just started. 

“There is absolutely no sign of stars in this dark cloud today, but by looking at the water molecules, we can see evidence of motion inside the region that can be understood as collapse of the whole cloud towards the centre,” says Dr Caselli. 

“There is enough material to form a star at least as massive as our Sun, which means it could also be forming a planetary system, possibly one like ours.”

Some of the water vapour detected in L1544 will go into forming the star, but the rest will be incorporated into the surrounding disc, providing a rich water reservoir to feed potential new planets. 

“Thanks to Herschel, we can now follow the ‘water trail’ from a molecular cloud in the interstellar medium, through the star formation process, to a planet like Earth where water is a crucial ingredient for life,” says ESA’s Herschel project scientist, Göran Pilbratt.  
 

Notes for Editors:

“First detection of water vapour in a pre-stellar core,” by P. Caselli et al. has been accepted for publication in Astrophysical Journal Letters.

Herschel studied the dark cloud L1544 as part of the Water in Star-forming regions with Herschel (WISH) key programme using the Heterodyne Instrument for the Far-Infrared spectrometer (HIFI) on Herschel.

 Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. HIFI was designed and built by a nationally funded consortium led by SRON Netherlands Institute for Space Research. The consortium includes institutes from France, Germany, USA, Canada, Ireland, Italy, Poland, Russia, Spain, Sweden, Switzerland and Taiwan.

 
For more information, please contact:
 
 Markus Bauer
 ESA Science and Robotic Exploration Communication Officer
 Tel: +31 71 565 6799
 Mob: +31 61 594 3 954
 Email: markus.bauer@esa.int

 Paola Caselli
 University of Leeds
 Email: p.caselli@leeds.ac.uk

 Göran Pilbratt
 ESA Herschel Project Scientist
 Tel: +31 71 565 3621
 Email: gpilbratt@rssd.esa.int

Giant black holes lurking in survey data

 Infrared colour image of ULASJ1234+0907 located 11 billion light years from Earth and one of the reddest objects in the sky. This red colour is caused by the enormous amounts of dust within this system. The dust preferentially absorbs bluer light and is responsible for obscuring this supermassive black hole in the visible wavelengths. Credit: image created using data from UKIDSS and the Wide-field Infrared Survey Explorer (WISE) observator 

 Markarian 231, an example of a galaxy with a dusty rapidly growing supermassive black hole located 600 million light years from Earth. The black hole is the very bright source at the centre of the galaxy. Rings of gas and dust can be seen around it as well as “tidal tails” left over from a recent impact with another galaxy. Credit: hubblesite.org

Scientists at the University of Cambridge have used cutting-edge infrared surveys of the sky to discover a new population of enormous, rapidly growing supermassive black holes in the early Universe. The black holes were previously undetected because they sit cocooned within thick layers of dust. The new study has shown however that they are emitting vast amounts of radiation through violent interactions with their host galaxies. The team publish their results in the journal Monthly Notices of the Royal Astronomical Society.

The most extreme object in the study is a supermassive black hole called ULASJ1234+0907. This object, located in the direction of the constellation of Virgo, is so far away that the light from it has taken 11 billion light years to reach us, so we see it as it appeared in the early universe. The monster black hole has more than 10 billion times the mass of the Sun and 10,000 times the mass of the supermassive black hole in our own Milky Way, making it one of the most massive black holes ever seen.

The research indicates that that there may be as many as 400 such giant black holes in the part of the universe that we can observe. "These results could have a significant impact on studies of supermassive black holes" said Dr Manda Banerji, lead author of the paper. "Most black holes of this kind are seen through the matter they drag in. As the neighbouring material spirals in towards the black holes, it heats up. Astronomers are able to see this radiation and observe these systems."

"Although these black holes have been studied for some time, the new results indicate that some of the most massive ones may have so far been hidden from our view." The newly discovered black holes, devouring the equivalent of several hundred Suns every year, will shed light on the physical processes governing the growth of all supermassive black holes.

Supermassive black holes are now known to reside at the centres of all galaxies. In the most massive galaxies in the Universe, they are predicted to grow through violent collisions with other galaxies, which trigger the formation of stars and provides food for the black holes to devour. These violent collisions also produce dust within the galaxies therefore embedding the black hole in a dusty envelope for a short period of time as it is being fed.

In comparison with remote objects like ULASJ1234+0907, the most spectacular example of a dusty, growing black hole in the local Universe is the well-studied galaxy Markarian 231 located a mere 600 million light years away. Detailed studies with the Hubble Space Telescope have shown evidence that Markarian 231 underwent a violent impact with another galaxy in the recent past. ULASJ1234+0907 is a more extreme version of this nearby galaxy, indicating that conditions in the early Universe were much more turbulent and inhospitable than they are today.

In the new study, the team from Cambridge used infrared surveys being carried out on the UK Infrared Telescope (UKIRT) to peer through the dust and locate the giant black holes for the first time. Prof. Richard McMahon, co-author of the study, who is also leading the largest infrared survey of the sky, said: "These results are particularly exciting because they show that our new infrared surveys are finding super massive black holes that are invisible in optical surveys. These new quasars are important because we may be catching them as they are being fed through collisions with other galaxies. Observations with the new Atacama Large Millimeter Array (ALMA) telescope in Chile will allow us to directly test this picture by detecting the microwave frequency radiation emitted by the vast amounts of gas in the colliding galaxies."

Science contacts

Dr. Manda Banerji
Institute of Astronomy
University of Cambridge
Mob: +44(0)779 294 1499
mbanerji@ast.cam.ac.uk


Prof. Richard McMahon
Institute of Astronomy
University of Cambridge
rgm@ast.cam.ac.uk
Tel: +44(0)1223 337 519




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

Images and captions

Images can be downloaded from http://www.ast.cam.ac.uk/~mbanerji/Press.html

Figure 1: Infrared colour image of ULASJ1234+0907 located 11 billion light years from Earth and one of the reddest objects in the sky. This red colour is caused by the enormous amounts of dust within this system. The dust preferentially absorbs bluer light and is responsible for obscuring this supermassive black hole in the visible wavelengths. Giant dusty black holes have therefore been hidden from view until now when cutting edge surveys at infrared wavelengths are allowing us to peer through the dust and locate them for the first time. Credit: image created using data from UKIDSS and the Wide-field Infrared Survey Explorer (WISE) observatory

Figure 2: Markarian 231, an example of a galaxy with a dusty rapidly growing supermassive black hole located 600 million light years from Earth. The black hole is the very bright source at the centre of the galaxy. Rings of gas and dust can be seen around it as well as "tidal tails" left over from a recent impact with another galaxy. Credit: hubblesite.org

Further information

The new work will appear in "Heavily Reddened Quasars at z~2 in the UKIDSS Large Area Survey: A Transition Phase in AGN Evolution" by Banerji, Manda; McMahon, Richard; Hewett, Paul; Alaghband-Zadeh, Susannah; Gonzalez-Solares, Eduardo; Venemans, Bram, Monthly Notices of the Royal Astronomical Society, in press. A preprint of the paper can be seen on ArXiV at http://arxiv.org/abs/1203.5530

Notes for editors

The team used the UKIRT Infrared Deep Sky Survey (UKIDSS) to detect the new black holes. UKIDSS began in 2005 and will survey around 7500 square degrees of sky at infrared wavelengths.

UKIDSS
http://www.ukidss.org/

The Royal Astronomical Society (RAS, www.ras.org.uk), 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 3500 members (Fellows), a third based overseas, include scientific researchers in universities, observatories and laboratories as well as historians of astronomy and others.

Follow the RAS on Twitter via @royalastrosoc

NASA's Swift Satellite Discovers a New Black Hole in our Galaxy

An X-ray outburst caught by NASA's Swift on Sept. 16, 2012, resulted from a flood of gas plunging toward a previously unknown black hole. Gas flowing from a sun-like star collects into a disk around the black hole. Normally, this gas would steadily spiral inward. But in this system, named Swift J1745-26, the gas collects for decades before suddenly surging inward. Credit: NASA's Goddard Space Flight Center . Download video in high resolution from Goddard's Scientific Visualization Studio

 NASA's Swift satellite recently detected a rising tide of high-energy X-rays from a source toward the center of our Milky Way galaxy. The outburst, produced by a rare X-ray nova, announced the presence of a previously unknown stellar-mass black hole.

 "Bright X-ray novae are so rare that they're essentially once-a-mission events and this is the first one Swift has seen," said Neil Gehrels, the mission's principal investigator, at NASA's Goddard Space Flight Center in Greenbelt, Md. "This is really something we've been waiting for."

 An X-ray nova is a short-lived X-ray source that appears suddenly, reaches its emission peak in a few days and then fades out over a period of months. The outburst arises when a torrent of stored gas suddenly rushes toward one of the most compact objects known, either a neutron star or a black hole.

 The rapidly brightening source triggered Swift's Burst Alert Telescope twice on the morning of Sept. 16, and once again the next day.

 Named Swift J1745-26 after the coordinates of its sky position, the nova is located a few degrees from the center of our galaxy toward the constellation Sagittarius. While astronomers do not know its precise distance, they think the object resides about 20,000 to 30,000 light-years away in the galaxy's inner region.

 Ground-based observatories detected infrared and radio emissions, but thick clouds of obscuring dust have prevented astronomers from catching Swift J1745-26 in visible light.

 The nova peaked in hard X-rays -- energies above 10,000 electron volts, or several thousand times that of visible light -- on Sept. 18, when it reached an intensity equivalent to that of the famous Crab Nebula, a supernova remnant that serves as a calibration target for high-energy observatories and is considered one of the brightest sources beyond the solar system at these energies.

 Even as it dimmed at higher energies, the nova brightened in the lower-energy, or softer, emissions detected by Swift's X-ray Telescope, a behavior typical of X-ray novae. By Wednesday, Swift J1745-26 was 30 times brighter in soft X-rays than when it was discovered and it continued to brighten.

 "The pattern we're seeing is observed in X-ray novae where the central object is a black hole. Once the X-rays fade away, we hope to measure its mass and confirm its black hole status," said Boris Sbarufatti, an astrophysicist at Brera Observatory in Milan, Italy, who currently is working with other Swift team members at Penn State in University Park, Pa.

 The black hole must be a member of a low-mass X-ray binary (LMXB) system, which includes a normal, sun-like star. A stream of gas flows from the normal star and enters into a storage disk around the black hole. In most LMXBs, the gas in the disk spirals inward, heats up as it heads toward the black hole, and produces a steady stream of X-rays.

 But under certain conditions, stable flow within the disk depends on the rate of matter flowing into it from the companion star. At certain rates, the disk fails to maintain a steady internal flow and instead flips between two dramatically different conditions -- a cooler, less ionized state where gas simply collects in the outer portion of the disk like water behind a dam, and a hotter, more ionized state that sends a tidal wave of gas surging toward the center.

 "Each outburst clears out the inner disk, and with little or no matter falling toward the black hole, the system ceases to be a bright source of X-rays," said John Cannizzo, a Goddard astrophysicist. "Decades later, after enough gas has accumulated in the outer disk, it switches again to its hot state and sends a deluge of gas toward the black hole, resulting in a new X-ray outburst."

 This phenomenon, called the thermal-viscous limit cycle, helps astronomers explain transient outbursts across a wide range of systems, from protoplanetary disks around young stars, to dwarf novae -- where the central object is a white dwarf star -- and even bright emission from supermassive black holes in the hearts of distant galaxies.

 Swift, launched in November 2004, is managed by Goddard Space Flight Center. It is operated in collaboration with Penn State, the Los Alamos National Laboratory in New Mexico and Orbital Sciences Corp. in Dulles, Va., with international collaborators in the United Kingdom and Italy and including contributions from Germany and Japan.

Related Links:

• Swift website
• Video on the NASA Explorer YouTube channel

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

ESO Celebrates its 50th Anniversary

  PR Image eso1238a
Thor’s Helmet Nebula imaged on the occasion of ESO’s 50th Anniversary

 PR Image eso1238b 

The Thor’s Helmet Nebula (NGC 2359) in the constellation of Canis Major (The Great Dog)

  PR Image eso1238c
Wide-field view of the sky around the Thor’s Helmet Nebula

Videos

PR Video eso1238a
Video News Release 37: ESO Celebrates its 50th Anniversary (eso1238a)

PR Video eso1238b 

Zooming in on Thor’s Helmet

PR Video eso1238c 

Panning across the Thor’s Helmet Nebula

 PR Video eso1238d
Video News Release (B-roll): ESO Celebrates its 50 Anniversary (eso1238d)

Competition winner observes Thor’s Helmet Nebula with the VLT during live broadcast

Today, 5 October 2012, the European Southern Observatory (ESO) is celebrating 50 years since the signing of its founding convention. Over the last half century ESO has become the world’s most productive ground-based astronomical observatory. This morning, for the first time ever, observations with ESO’s Very Large Telescope were made of an object chosen by the public. The winner of an anniversary competition pointed the VLT towards the spectacular Thor’s Helmet Nebula and the observations were broadcast live over the internet. To mark the occasion ESO and its partners are organising many other activities in the 15 ESO Member States.

The signing of the ESO Convention on 5 October 1962 and the foundation of ESO was the culmination of the dream of leading astronomers from five European countries — Belgium, France, Germany, the Netherlands and Sweden. They had decided to join forces with the primary goal of building a large telescope that would give them access to the magnificent and rich southern sky.

"Fifty years later, the original hopes of the five founding members have not only become reality, but have been greatly surpassed," says Tim de Zeeuw, ESO’s Director General. "ESO has fully taken up the challenge of its mission to design, build and operate the most powerful ground-based observing facilities on the planet."

Operating three unique and world-class observing sites in Chile — La Silla, Paranal and Chajnantor — ESO has become a leader in the astronomical research community [1].

At Paranal, ESO operates the Very Large Telescope (VLT), the world’s most advanced visible-light astronomical observatory, which, since first light in 1998, has been a driving force in a new age of discoveries. On the Chajnantor Plateau in northern Chile, ESO and its international partners [2] are are building a revolutionary astronomical telescope — ALMA, the Atacama Large Millimeter/submillimeter Array [3] will help to unveil the mysteries of the cold Universe.

ESO’s original observatory at La Silla is still very productive and remains at the forefront of astronomical research. In particular the HARPS instrument on the 3.6-metre telescope is the world’s most successful exoplanet hunting machine.

ESO’s huge next telescope is only a few years away. The 39-metre European Extremely Large Telescope (E-ELT) will become "the world’s biggest eye on the sky". With first light planned for early in the next decade, the E-ELT will tackle the biggest scientific challenges of our time and may revolutionise our perception of the Universe as much as Galileo's telescope did more than 400 years ago.

To celebrate the 50th anniversary, ESO and its partners are organising many events and public initiatives during 2012 [4]. A series of special coordinated public events are taking place today in the 15 Member States, as well as a multitude of Awesome Universe exhibitions.

As part of the anniversary celebrations, for the first time ever, this morning the VLT  was pointed towards an object in the sky selected by members of the public — the Thor’s Helmet Nebula [5]. This nebula was picked in the recent Choose what the VLT Observes contest (ann12060). The observations were performed by Brigitte Bailleul — winner of the Tweet Your Way to the VLT! competition — and were broadcast live over the internet from Paranal Observatory. This image, taken in the superb conditions typical of Paranal, is the most detailed ever obtained of this striking object.

"With the VLT, ALMA and the future E-ELT, ESO is entering a new era, one that not even the initial bold dreams of ESO’s founding members could have anticipated. To all of you that have made it possible, on behalf of ESO, thank you!" concludes Tim de Zeeuw.

Notes

[1] Information about the publication statistics at different observatories is given here.

[2] The ALMA project is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile.

[3] ALMA will be a single telescope composed of 66 high-precision antennas. ALMA's construction will be completed in 2013, but early scientific observations with a partial array began in 2011 (eso1137).

[4] A documentary movie is being released to celebrate the  anniversary, together with a sumptuously illustrated book. The movie has been also released as episodes in ESO’s popular ESOcast video podcast series. In addition, a new and very detailed book on the history of ESO’s triumphs and challenges will be published.

[5] The Thor’s Helmet Nebula, also known as NGC 2359, lies in the constellation of Canis Major (The Great Dog). The helmet-shaped nebula is around 15 000 light-years away from Earth and is over 30 light-years across. The helmet is a cosmic bubble, blown as the wind from the bright, massive star near the bubble's centre sweeps through the surrounding molecular cloud. The glowing gas is heated by the energetic radiation provided by the central star. Many different colours, originating from different elements in the gas, are also visible, as well as many dust clouds.

More information
The year 2012 marks the 50th anniversary of the founding of the European Southern Observatory (ESO). 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

Live anniversary webcast
Public 5 October 2012 events
Awesome Universe exhibitions
ESO 50th web page
ESO Top-10 Science achievements

Contacts

 Richard Hook
 ESO, La Silla, Paranal, E-ELT & Survey Telescopes Public Information Officer
 Garching bei München, Germany
 Tel: +49 89 3200 6655
 Cell: +49 151 1537 3591
 Email: rhook@eso.org

Cosmic riches

 Messier 69

Credit: ESA/Hubble & NASA

This dazzling image shows the globular cluster Messier 69, or M 69 for short, as viewed through the NASA/ESA Hubble Space Telescope. Globular clusters are dense collections of old stars. In this picture, foreground stars look big and golden when set against the backdrop of the thousands of white, silvery stars that make up M 69.

Another aspect of M 69 lends itself to the bejewelled metaphor: As globular clusters go, M 69 is one of the most metal-rich on record. In astronomy, the term “metal” has a specialised meaning: it refers to any element heavier than the two most common elements in our Universe, hydrogen and helium. The nuclear fusion that powers stars created all of the metallic elements in nature, from the calcium in our bones to the carbon in diamonds. Successive generations of stars have built up the metallic abundances we see today.

Because the stars in globular clusters are ancient, their metallic abundances are much lower than more recently formed stars, such as the Sun. Studying the makeup of stars in globular clusters like M 69 has helped astronomers trace back the evolution of the cosmos.

M 69 is located 29 700 light-years away in the constellation Sagittarius (the Archer). The famed French comet hunter Charles Messier added M 69 to his catalogue in 1780. It is also known as NGC 6637.

The image is a combination of exposures taken in visible and near-infrared light by Hubble’s Advanced Camera for Surveys, and covers a field of view of approximately 3.4 by 3.4 arcminutes.

Source: ESA/Hubble - Space Telescope

Black hole surprise in ancient star cluster

 

The globular cluster M22 which has been found to unusually host two black holes. 

Image Credit: Hunter Wilson.  

Click here  highest resolution version

Globular cluster M22 on the left with the radio telescope image of the black holes on the right. Dr Miller-Jones and the team observed the black holes using the newly upgraded Karl G. Jansky Very Large Array (VLA) radio telescope. Image Credit Left: Doug Matthews, Adam Block, NOAO, AURA and NSF. Image Credit Right: Assistant Professor Jay Strader, Michigan State University and The Harvard-Smithsonian Center for Astrophysics. Click here highest resolution

Astronomers have made the unexpected discovery of two black holes inside an ancient cluster of stars in our galaxy, the Milky Way.

The research, published today in the prestigious journal Nature, describes the detection of two black holes that are about 10 to 20 times heavier than our Sun in the globular cluster named M22.

Black holes, so dense that even light can’t escape them, are what is left when a massive star reaches the end of its life and collapses in on itself.

Co-author Dr James Miller-Jones, from the Curtin University node of the International Centre for Radio Astronomy Research (ICRAR), said the discovery of two black holes in the same cluster was a complete surprise. All the theory up to now says that should not happen in a globular cluster that is 12 billion years old.

“The study was originally searching for just one larger black hole within the cluster of hundreds of thousands of stars which, when viewed from the naked eye, resembles a hazy round ‘puff’ of light,” he said.

“Simulations of how globular clusters evolve show many black holes are created early in a cluster’s history."

“The many black holes then sink towards the middle of the cluster where they begin a chaotic dance leading to most being thrown out of the cluster until only one surviving black hole remains.

“We were searching for one large black hole in the middle of the cluster, but instead found two smaller black holes a little way out from the centre, which means all the theory and simulations need refinement.”

Dr Miller-Jones said the newly discovered black holes are the first to be found in a globular cluster in our galaxy. M22 is about 10,000 light years from Earth but can be seen clearly with a backyard telescope.

“M22 may contain as many as 100 black holes but we can’t detect them unless they’re actively feeding on nearby stars,” he said.

“We plan to do further study to pin down the properties of the two we’ve already found.”

The research was led by Assistant Professor Jay Strader from Michigan State University and The Harvard-Smithsonian Center for Astrophysics and also involved colleagues from The National Radio Astronomy Observatory, The University of Utah in the United States and The University of Southampton in the United Kingdom.

ICRAR is a joint venture between Curtin University and The University of Western Australia providing research excellence in the field of radio astronomy.

Original Publication:The paper “Two black holes in the globular cluster M22” is available at: http://www.nature.com/nature/journal/v490/n7418/full/nature11490.html

Contacts:
Dr James Miller-Jones
ICRAR, Curtin University
Ph: +61 8 9266 9141 
Email: james.miller-jones@icrar.org 

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

Megan Meates
Media Contact, Curtin University
Ph: +61 8 9266 4241
M: +61 401 103 755
Email: megan.meates@curtin.edu.au

The Helix Nebula: Bigger in Death than Life

 A dying star is throwing a cosmic tantrum in this combined image from NASA's Spitzer Space Telescope and the Galaxy Evolution Explorer (GALEX), which NASA has lent to the California Institute of Technology in Pasadena. In death, the star's dusty outer layers are unraveling into space, glowing from the intense ultraviolet radiation being pumped out by the hot stellar core. Image credit: NASA/JPL-Caltech .  Full image and caption

A dying star is refusing to go quietly into the night, as seen in this combined infrared and ultraviolet view from NASA's Spitzer Space Telescope and the Galaxy Evolution Explorer (GALEX), which NASA has lent to the California Institute of Technology in Pasadena. In death, the star's dusty outer layers are unraveling into space, glowing from the intense ultraviolet radiation being pumped out by the hot stellar core.

This object, called the Helix nebula, lies 650 light-years away in the constellation of Aquarius. Also known by the catalog number NGC 7293, it is a typical example of a class of objects called planetary nebulae. Discovered in the 18th century, these cosmic works of art were erroneously named for their resemblance to gas-giant planets.

Planetary nebulae are actually the remains of stars that once looked a lot like our sun. These stars spend most of their lives turning hydrogen into helium in massive runaway nuclear fusion reactions in their cores. In fact, this process of fusion provides all the light and heat that we get from our sun. Our sun will blossom into a planetary nebula when it dies in about five billion years.

When the hydrogen fuel for the fusion reaction runs out, the star turns to helium for a fuel source, burning it into an even heavier mix of carbon, nitrogen and oxygen. Eventually, the helium will also be exhausted, and the star dies, puffing off its outer gaseous layers and leaving behind the tiny, hot, dense core, called a white dwarf. The white dwarf is about the size of Earth, but has a mass very close to that of the original star; in fact, a teaspoon of a white dwarf would weigh as much as a few elephants!

 The intense ultraviolet radiation from the white dwarf heats up the expelled layers of gas, which shine brightly in the infrared. GALEX has picked out the ultraviolet light pouring out of this system, shown throughout the nebula in blue, while Spitzer has snagged the detailed infrared signature of the dust and gas in red, yellow and green. Where red Spitzer and blue GALEX data combine in the middle, the nebula appears pink. A portion of the extended field beyond the nebula, which was not observed by Spitzer, is from NASA's all-sky Wide-field Infrared Survey Explorer (WISE). The white dwarf star itself is a tiny white pinprick right at the center of the nebula.

More information about Spitzer is online at http://spitzer.caltech.edu and http://www.nasa.gov/spitzer . More information about GALEX is at http://www.galex.caltech.edu .

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

NASA's Infrared Observatory Measures Expansion of Universe

 Astronomers using NASA's Spitzer Space Telescope have greatly improved the cosmic distance ladder used to measure the expansion rate of the universe, as well as its size and age. The cosmic distance ladder, symbolically shown here in this artist's concept, is a series of stars and other objects within galaxies that have known distances. Image credit: NASA/JPL-Caltech .  Full image and caption 

This graph illustrates the Cepheid period-luminosity relationship, which scientists use to calculate the size, age and expansion rate of the universe. The data shown are from NASA's Spitzer Space Telescope, which has made the most precise measurements yet of the universe's expansion rate by recalculating the distance to pulsating stars called Cepheids. Image credit: NASA/JPL-Caltech/Carnegie .

Full image and caption

PASADENA, Calif. -- Astronomers using NASA's Spitzer Space Telescope have announced the most precise measurement yet of the Hubble constant, or the rate at which our universe is stretching apart.

The Hubble constant is named after the astronomer Edwin P. Hubble, who astonished the world in the 1920s by confirming our universe has been expanding since it exploded into being 13.7 billion years ago. In the late 1990s, astronomers discovered the expansion is accelerating, or speeding up over time. Determining the expansion rate is critical for understanding the age and size of the universe.

Unlike NASA's Hubble Space Telescope, which views the cosmos in visible light, Spitzer took advantage of long-wavelength infrared light to make its new measurement. It improves by a factor of 3 on a similar, seminal study from the Hubble telescope and brings the uncertainty down to 3 percent, a giant leap in accuracy for cosmological measurements. The newly refined value for the Hubble constant is 74.3 plus or minus 2.1 kilometers per second per megaparsec. A megaparsec is roughly 3 million light-years.

"Spitzer is yet again doing science beyond what it was designed to do," said project scientist Michael Werner at NASA's Jet Propulsion Laboratory in Pasadena, Calif. Werner has worked on the mission since its early concept phase more than 30 years ago. "First, Spitzer surprised us with its pioneering ability to study exoplanet atmospheres," said Werner, "and now, in the mission's later years, it has become a valuable cosmology tool."

In addition, the findings were combined with published data from NASA's Wilkinson Microwave Anisotropy Probe to obtain an independent measurement of dark energy, one of the greatest mysteries of our cosmos. Dark energy is thought to be winning a battle against gravity, pulling the fabric of the universe apart. Research based on this acceleration garnered researchers the 2011 Nobel Prize in physics.

 "This is a huge puzzle," said the lead author of the new study, Wendy Freedman of the Observatories of the Carnegie Institution for Science in Pasadena. "It's exciting that we were able to use Spitzer to tackle fundamental problems in cosmology: the precise rate at which the universe is expanding at the current time, as well as measuring the amount of dark energy in the universe from another angle." Freedman led the groundbreaking Hubble Space Telescope study that earlier had measured the Hubble constant.

 Glenn Wahlgren, Spitzer program scientist at NASA Headquarters in Washington, said infrared vision, which sees through dust to provide better views of variable stars called cepheids, enabled Spitzer to improve on past measurements of the Hubble constant.

 "These pulsating stars are vital rungs in what astronomers call the cosmic distance ladder: a set of objects with known distances that, when combined with the speeds at which the objects are moving away from us, reveal the expansion rate of the universe," said Wahlgren.

 Cepheids are crucial to the calculations because their distances from Earth can be measured readily. In 1908, Henrietta Leavitt discovered these stars pulse at a rate directly related to their intrinsic brightness.

 To visualize why this is important, imagine someone walking away from you while carrying a candle. The farther the candle traveled, the more it would dim. Its apparent brightness would reveal the distance. The same principle applies to cepheids, standard candles in our cosmos. By measuring how bright they appear on the sky, and comparing this to their known brightness as if they were close up, astronomers can calculate their distance from Earth.

 Spitzer observed 10 cepheids in our own Milky Way galaxy and 80 in a nearby neighboring galaxy called the Large Magellanic Cloud. Without the cosmic dust blocking their view, the Spitzer research team was able to obtain more precise measurements of the stars' apparent brightness, and thus their distances. These data opened the way for a new and improved estimate of our universe's expansion rate.

 "Just over a decade ago, using the words 'precision' and 'cosmology' in the same sentence was not possible, and the size and age of the universe was not known to better than a factor of two," said Freedman. "Now we are talking about accuracies of a few percent. It is quite extraordinary."

The study appears in the Astrophysical Journal. Freedman's co-authors are Barry Madore, Victoria Scowcroft, Chris Burns, Andy Monson, S. Eric Person and Mark Seibert of the Observatories of the Carnegie Institution and Jane Rigby of NASA's Goddard Space Flight Center in Greenbelt, Md.

NASA's Jet Propulsion Laboratory, Pasadena, Calif., 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. 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 and http://www.nasa.gov/spitzer .

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

 J.D. Harrington 202-358-5241
 Headquarters, Washington
 j.d.harrington@nasa.gov

Simulations Uncover 'Flashy' Secrets of Merging Black Holes 09.27.12

According to Einstein, whenever massive objects interact, they produce gravitational waves -- distortions in the very fabric of space and time -- that ripple outward across the universe at the speed of light. While astronomers have found indirect evidence of these disturbances, the waves have so far eluded direct detection. Ground-based observatories designed to find them are on the verge of achieving greater sensitivities, and many scientists think that this discovery is just a few years away. 

Catching gravitational waves from some of the strongest sources -- colliding black holes with millions of times the sun's mass -- will take a little longer. These waves undulate so slowly that they won't be detectable by ground-based facilities. Instead, scientists will need much larger space-based instruments, such as the proposed Laser Interferometer Space Antenna, which was endorsed as a high-priority future project by the astronomical community. 

A team that includes astrophysicists at NASA's Goddard Space Flight Center in Greenbelt, Md., is looking forward to that day by using computational models to explore the mergers of supersized black holes. Their most recent work investigates what kind of "flash" might be seen by telescopes when astronomers ultimately find gravitational signals from such an event.

Supercomputer models of merging black holes reveal properties that are crucial to understanding future detections of gravitational waves. This movie follows two orbiting black holes and their accretion disk during their final three orbits and ultimate merger. Redder colors correspond to higher gas densities. (Credit: NASA's Goddard Space Flight Center; P. Cowperthwaite, University of Maryland) . Download video in high resolution from NASA Goddard's Scientific Visualization Studio

 Studying gravitational waves will give astrophysicists an unprecedented opportunity to witness the universe's most extreme phenomena, leading to new insights into the fundamental laws of physics, the death of stars, the birth of black holes and, perhaps, the earliest moments of the universe.

 A black hole is an object so massive that nothing, not even light, can escape its gravitational grip. Most big galaxies, including our own Milky Way, contain a central black hole weighing millions of times the sun's mass, and when two galaxies collide, their monster black holes settle into a close binary system.

 "The black holes orbit each other and lose orbital energy by emitting strong gravitational waves, and this causes their orbits to shrink. The black holes spiral toward each other and eventually merge," said Goddard astrophysicist John Baker.

 Close to these titanic, rapidly moving masses, space and time become repeatedly flexed and warped. Just as a disturbance forms ripples on the surface of a pond, drives seismic waves through Earth, or puts the jiggle in a bowl of Jell-O, the cyclic flexing of space-time near binary black holes produces waves of distortion that race across the universe.

 While gravitational waves promise to tell astronomers many things about the bodies that created them, they cannot provide one crucial piece of information -- the precise position of the source. So to really understand a merger event, researchers need an accompanying electromagnetic signal -- a flash of light, ranging from radio waves to X-rays -- that will allow telescopes to pinpoint the merger's host galaxy.

 Understanding the electromagnetic counterparts that may accompany a merger involves the daunting task of tracking the complex interactions between the black holes, which can be moving at more than half the speed of light in the last few orbits, and the disks of hot, magnetized gas that surround them. Since 2010, numerous studies using simplifying assumptions have found that mergers could produce a burst of light, but no one knew how commonly this occurred or whether the emission would be strong enough to be detectable from Earth.

 To explore the problem in greater detail, a team led by Bruno Giacomazzo at the University of Colorado, Boulder, and including Baker developed computer simulations that for the first time show what happens in the magnetized gas (also called a plasma) in the last stages of a black hole merger. Their study was published in the June 10 edition of The Astrophysical Journal Letters.

 The simulations follow the complex electrical and magnetic interactions in the ionized gas -- known as magnetohydrodynamics -- within the extreme gravitational environment determined by the equations of Einstein's general relativity, a task requiring the use of advanced numerical codes and fast supercomputers.

 Both of the simulations reported in the study were run on the Pleiades supercomputer at NASA's Ames Research Center in Moffett Field, Calif. They follow the black holes over their last three orbits and subsequent merger using models both with and without a magnetic field in the gas disk.

 Additional simulations were run on the Ranger and Discover supercomputers, respectively located at the University of Texas, Austin, and the NASA Center for Climate Simulation at Goddard, in order to investigate the effects of different initial conditions, fewer orbits and other variations.

 "What's striking in the magnetic simulation is that the disk's initial magnetic field is rapidly intensified by about 100 times, and the merged black hole is surrounded by a hotter, denser, thinner accretion disk than in the unmagnetized case," Giacomazzo explained.

 In the turbulent environment near the merging black holes, the magnetic field intensifies as it becomes twisted and compressed. The team suggests that running the simulation for additional orbits would result in even greater amplification.

 The most interesting outcome of the magnetic simulation is the development of a funnel-like structure -- a cleared-out zone that extends up out of the accretion disk near the merged black hole. "This is exactly the type of structure needed to drive the particle jets we see from the centers of black-hole-powered active galaxies," Giacomazzo said.

 The most important aspect of the study is the brightness of the merger's flash. The team finds that the magnetic model produces beamed emission that is some 10,000 times brighter than those seen in previous studies, which took the simplifying step of ignoring plasma effects in the merging disks.

 "We need gravitational waves to confirm that a black hole merger has occurred, but if we can understand the electromagnetic signatures from mergers well enough, perhaps we can search for candidate events even before we have a space-based gravitational wave observatory," Baker said.

Related Links

• Related visuals from NASA Goddard's Scientific Visualization Studio

• On the Edge: Gravitational Waves

• Paper: General Relativistic Simulations of Magnetized Plasmas around Merging Supermassive Black Holes. DOI: 10.1088/2041-8205/752/1/L15

• Pleiades Supercomputer

• More information on the Laser Interferometer Space Antenna

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

Sharpest-ever Ground-based Images of Pluto and Charon: Proves a Powerful Tool for Exoplanet Discoveries

 

Speckle image reconstruction of Pluto and Charon obtained in visible light at 692 nanometers (red) with the Gemini North 8-meter telescope using the Differential Speckle Survey Instrument (DSSI). Resolution of the image is about 20 milliarcseconds average. This is the first speckle reconstructed image for Pluto and Charon from which astronomers obtained not only the separation and position angle for Charon, but also the diameters of the two bodies. North is up, east is to the left, and the image section shown here is 1.39 arcseconds across. Credit: Gemini Observatory/NSF/NASA/AURA .  Full Resolution JPEG

Despite being infamously demoted from its status as a major planet, Pluto (and its largest companion Charon) recently posed as a surrogate extrasolar planetary system to help astronomers produce exceptionally high-resolution images with the Gemini North 8-meter telescope. Using a method called reconstructive speckle imaging, the researchers took the sharpest ground-based snapshots ever obtained of Pluto and Charon in visible light, which hint at the exoplanet verification power of a large state-of-the-art telescope when combined with speckle imaging techniques. The data also verified and refined previous orbital characteristics for Pluto and Charon while revealing the pair’s precise diameters.

 “The Pluto-Charon result is of timely interest to those of us wanting to understand the orbital dynamics of this pair for the 2015 encounter by NASA's New Horizons spacecraft,” said Steve Howell of the NASA Ames Research Center, who led the study. In addition, Howell notes that NASA’s Kepler mission, which has already proven a powerful exoplanet discovery tool, will benefit greatly from this technique.

 Kepler identifies planet candidates by repeatedly measuring the change in brightness of more than 150,000 stars to detect when a planet passes in front of, or affects the brightness of, its host star. Speckle imaging with the Gemini telescope will provide Kepler's follow-up program with a doubling in its ability to resolve objects and validate Earth-like planets. It also offers a 3- to 4-magnitude sensitivity increase for the sources observed by the team. That’s about a 50-fold increase in sensitivity in the observations Howell and his team made at Gemini. “This is an enormous gain in the effort underway to confirm small Earth-size planets,” Howell added.

 To institute this effort Howell and his team –– which included Elliott Horch (Southern Connecticut State University), Mark Everett (National Optical Astronomy Observatory), and David Ciardi (NASA Exoplanet Science Institute/Caltech) –– temporarily installed a camera, called the Differential Speckle Survey Instrument (DSSI), among the suite of instruments mounted on the Gemini telescope.

 "This was a fantastic opportunity to bring DSSI to Gemini North this past July," said Horch. "In just a little over half an hour of Pluto observations, collecting light with the large Gemini mirror, we obtained the best resolution ever with the DSSI instrument –– it was stunning!"

 The resolution obtained in the observations, about 20 milliarcseconds, easily corresponds to separating a pair of automobile headlights in Providence, Rhode Island, from San Francisco, California. To achieve this level of definition, Gemini obtained a large number of very quick “snapshots” of Pluto and Charon. The researchers then reconstructed them into a single image after subtracting the blurring effects and ever-changing speckled artifacts caused by turbulence in the atmosphere and other optical aberrations. With enough snapshots (each image was exposed for only 60 milliseconds or about 1/20 of a second) only the light from the actual objects remains constant, and the artifacts reveal their transient nature, eventually canceling each other out.

 DSSI was built at SCSU between 2007-2008 as a part of a United States National Science Foundation Astronomical Instrumentation grant and mounted on the Gemini North telescope for a limited observing run. The instrument is likely to return to Gemini North for observations in mid-2013 for general user programs from across the international Gemini partnership. Any such arrangement will be announced along with the call for proposals for Semester 13B, in February 2013.

 This work was funded in part by the National Science Foundation and NASA’s Kepler discovery mission and will be published in the journal Publications of the Astronomical Society of the Pacific in October 2012.

Science Contacts:

Steven Howell
 NASA Ames Research Center
 Moffett Field, CA
 Desk: 605-604-4238
 Cell: 520-461-6925
Steve.b.howell@nasa.gov

Elliott Horch
 Southern Connecticut State University
 New Haven, CT
 Phone: 203-392-6393
Horche2@southernct.edu

Media Contact:

Peter Michaud
 Public Information and Outreach Manager
 Gemini Observatory, Hilo, Hawai'i
 Desk: (808) 974-2510
 Cell: (808) 936-6643
pmichaud@gemini.edu

Background History of DSSI

 The Differential Speckle Survey Instrument (DSSI) was built at Southern Connecticut State University (SCSU) between 2007-2008 as a part of a NSF Astronomical Instrumentation grant on which Elliott Horch was the principal investigator. Together with student collaborators, Horch designed and assembled the instrument, and wrote the instrument control software. In 2008 DSSI was shipped to the WIYN Observatory at Kitt Peak, where it has been used since September 2008 for both Kepler follow-up observations and a NSF-funded project to study binary stars discovered by Hipparcos. In late 2009, the detectors for the instrument were upgraded from two low-noise CCDs to two electron-multiplying CCDs, one purchased by the Kepler Science Office and the other by SCSU. DSSI is the world's first two-channel speckle imaging instrument.

Gone, with the Wind

The case of the missing quasar gas clouds has been solved by a worldwide team of astronomers, and the answer is blowin' in the wind. 

Astronomers Nurten Filiz Ak and Niel Brandt of the Pennsylvania State University led the team, which announced their results in a paper published in today's issue of The Astrophysical Journal. The paper describes 19 distant quasars in which giant clouds of gas seemed to disappear in just a few years. 

"We know that many quasars have structures of fast-moving gas caught up in 'quasar winds,' and now we know that those structures can regularly disappear from view," says Filiz Ak, a graduate student at Penn State and lead author of the paper. "But why is this happening?" 

 

 An artist's impression of a quasar like one of the nineteen found by this study. The black dot in the center represents the supermassive black hole at the center of the quasar. The red-and-yellow spiral surrounding it shows the accretion disk of hot gas falling into the black hole. Some of this gas is ejected as the quasar's wind, which is shown in light blue. The size of the accretion disk shown is comparable to the size of our Solar System. The inset at the top right shows two SDSS spectra for the same quasar (named SDSS J093620.52+004649.2). The upper spectrum (blue) was taken in 2002, while the lower spectrum (red) was taken in 2011. The deep, wide valley in the 2002 spectrum is a so-called "broad absorption line" — a feature which has disappeared from its spectrum by 2011. Credit: NASA/CXC/M. Weiss, Nahks Tr'Ehnl, Nurten Filiz Ak .

Other versions:  B/W  -  300 DPI color TIFF  -  300 DPI B/W TIFF

Image components:   Just quasar art (300 DPI color TIFF)  -  Just spectrum inset (300 DPI color JPG)

 An SDSS image of the quasar  SDSS J093620.52+004649.2, one of the 19 quasars with disappearing BAL troughs. The constellation map on the bottom left shows the quasar's position in the constellation Hydra. Three successive views zoom in closer and closer to the quasar.

Credit: Jordan Raddick (Johns Hopkins University) and the SDSS-III collaboration. Hydra constellation chart from The Constellations, produced by the International Astronomical Union and Sky and Telescope magazine (Roger Sinnott, Rick Fienberg, and Alan MacRobert).

Other versions:    B/W JPG   -   300 DPI color JPG   -   300 DPI B/W JPG

Quasars are powered by gas falling into supermassive black holes at the centers of galaxies. As the gas falls into the black hole, it heats up and gives off light. The gravitational force from the black hole is so strong, and is pulling so much gas, that the hot gas glows brighter than the entire surrounding galaxy.

 But with so much going on in such a small space, not all the gas is able to find its way into the black hole. Much of it instead escapes, carried along by strong winds blowing out from the center of the quasar.

 "These winds blow at thousands of miles per second, far faster than any winds we see on Earth," says Niel Brandt, a professor at Penn State and Filiz Ak's Ph.D. advisor. "The winds are important because we know that they play an important role in regulating the quasar's central black hole, as well as star formation in the surrounding galaxy."

Many quasars show evidence of these winds in their spectra — measurements of the amount of light that the quasar gives off at different wavelengths. Just outside the center of the quasar are clouds of hot gas flowing away from the central black hole. As light from deeper in the quasar passes through these clouds on its way to Earth, some of the light gets absorbed at particular wavelengths corresponding to the elements in the clouds.

 As gas clouds are accelerated to high speeds by the quasar, the Doppler effect spreads the absorption over a broad range of wavelengths, leading to a wide valley visible in the spectrum. The width of this "broad absorption line (BAL)" measures the speed of the quasar's wind. Quasars whose spectra show such broad absorption lines are known as "BAL quasars."

 But the hearts of quasars are chaotic, messy places. Quasar winds blow at thousands of miles per second, and the disk around the central black hole is rotating at speeds that approach the speed of light. All this adds up to an environment that can change quickly.

 Previous studies had found a few examples of quasars whose broad absorption lines seemed to have disappeared between one observation and the next. But these quasars had been found one at a time, and largely by chance — no one had ever done a systematic search for them. Undertaking such a search would require measuring spectra for hundreds of quasars, spanning several years.

 Enter the Sloan Digital Sky Survey (SDSS). Since 1998, SDSS has been regularly measuring spectra of quasars. Over the past three years, as part of SDSS-III's Baryon Oscillation Spectroscopic Survey (BOSS), the survey has been specifically seeking out repeated spectra of BAL quasars through a program proposed by Brandt and colleagues.

 Their persistence paid off — the research team gathered a sample of 582 BAL quasars, each of which had repeat observations over a period of between one and nine years – a sample about 20 times larger than any that had been previously assembled. The team then began to search for changes, and were quickly rewarded. In 19 of the quasars, the broad absorption lines had disappeared.

What's going on here? There are several possible explanations, but the simplest is that, in these quasars, gas clouds that we had seen previously are literally "gone with the wind" —the rotation of the quasar's disk and wind have carried the clouds out of the line-of-sight between us and the quasar.

 And because the sample of quasars is so large, and had been gathered in such a systematic manner, the team can go beyond simply identifying disappearing gas clouds. "We can quantify this phenomenon," says Filiz Ak.

 Finding nineteen such quasars out of 582 total indicates that about three percent of quasars show disappearing gas clouds over a three-year span, which in turn suggests that a typical quasar cloud spends about a century along our line of sight. "Since the universe is 14 billion years old, we're used to astronomical phenomena lasting a very long time," says Pat Hall of York University in Toronto, another team member. "It's fascinating to discover something that changes within a human lifetime."

 Now, as other astronomers come up with models of quasar winds, their models will need to explain this 100-year timescale. As theorists begin to consider the results, the team continues to analyze their sample of quasars — more results are coming soon. "This is really exciting for me," Filiz Ak says. "I'm sitting at my desk, discovering the nature of the most powerful winds in the Universe."

Paper announcing the results

Filiz Ak, N., W. N. Brandt, P. B. Hall, D. P. Schneider, S. F. Anderson, R. R. Gibson, B. F. Lundgren, A. D. Myers, P. Petitjean, N.P. Ross, Y. Shen, D. G. York, D. Bizyaev, J. Brinkmann, E. Malanushenko, D. J. Oravetz, K. Pan, A. E. Simmons, B. A. Weaver. 2012, Broad Absorption Line Disappearance on Multi-Year Timescales in a Large Quasar Sample, The Astrophysical Journal, 757(2), 114, doi:10.1088/0004-637X/757/2/114.

See it for yourself!

The quasar above is part of the SDSS-III's Data Release 9, which means that all its data available free of charge online. Use the links below to see the quasar change right before your eyes!

The three links below will take you to an interactive spectrum viewer for three spectra of this quasar, measured by the Sloan Digital Sky Survey on three different nights. The spectra are labeled at the bottom in Ångstroms — one Ångstrom equals one ten-billionth of a meter.

Zoom in on the area of each spectrum around 4000 Ångströms. In that area, you should see a broad valley in the 2001 and 2002 spectra — a valley that is gone from the 2011 spectrum!

• Spectrum measured on April 28, 2001

• Spectrum measured on February 9, 2002

• Spectrum measured on January 2, 2011 

Contacts:

1. Nurten Filiz Ak, Pennsylvania State University, nfilizak -at- psu.edu, +1 814 865 4536
2. Niel Brandt, Pennsylvania State University, niel -at- psu.edu, +1 814 865 3509
3. Pat Hall, York University, phall -at- yorku.ca, +1 416 736 2100 x77752
4. Michael Wood-Vasey, SDSS-III Spokesperson, University of Pittsburgh, wmwv -at- pitt.edu, +1 412 624 2751
5. Jordan Raddick, SDSS Public Information Officer, raddick -at- jhu.edu, +1 410 516 8889

Source: SDSS-III
Massive Spectroscopic Surveys of the Distant Universe, the Milky Way Galaxy and Extrasolar Planetary Systems
 

Smashing white dwarfs: explaining the brightness of cosmic explosions

Fig. 1: An artist's impression of merging white dwarfs. Such mergers are thought to be potential progenitors of Type Ia supernova explosions. Image courtesy of (c) Nature 2010

Fig. 2: Model peak brightness distribution of merging white dwarfs for a range of allowed mass ratios (coloured lines). The observed peak brightness distribution from Type Ia supernovae (from Li et al. 2011) is shown in grey-scale. The observational data have been scaled up in order to easily compare the distribution shapes. The theoretical brightness distributions cover the range and match the shape of the observed distribution fairly well. 

 Fig. 3: This plot shows the number of violent white dwarf mergers as a function of time (from 100 million to 10 billion years after the stars are first born). The blue line represents the violent white dwarf merger model (cf. the blue histogram in fig. 2). Red squares and the black line show the recovered 'delay time distribution' of SNe Ia from two observational studies (see references at the end of the article). The violent white dwarf merger rate matches the fit from GM12 extremely well, implying that there might be enough violent mergers to account for a large fraction of SNe Ia in field galaxies.

Supernovae are among the brightest and most energetic events to occur in nature. However, the origin of a particular type of supernova - the Type Ia supernova - is still a mystery despite decades of research. What type of stars produce these explosions, and how? Researchers at the Max Planck Institute for Astrophysics in Garching, the Australian National University in Canberra, Heidelberg ITS and collaborators have investigated a particular explosion model involving merging white dwarf stars. They found that the explosion brightnesses from the merger models are strikingly similar to the range of explosion brightnesses that is observed for real Type Ia supernovae. This means that violent white dwarf mergers might be a dominant formation channel for these explosions.

Type Ia supernovae (SNe Ia), which make up about one quarter of all supernovae, are believed to come from exploding white dwarf stars, though how the white dwarf reaches the critical conditions to make it explode is still unclear.

 More than 95% of stars will end their lives as white dwarfs (including our Sun when it runs out of fuel), but only a small fraction of these will actually explode. A lonely white dwarf star is stable - it won't spontaneously erupt. However, if there is a source of matter nearby - e.g. another star - the white dwarf can steal mass from this companion, with explosive consequences. Thus, astronomers have been trying to find out what types of double star systems including at least one white dwarf can lead to the formation of Type Ia supernovae.

 Since white dwarfs are rather faint when they are not exploding, observations alone cannot solve this well-known 'progenitor problem'. Therefore testing of theoretical models has become a critical step in understanding the origin of SNe Ia.

 The biggest mystery shrouding SNe Ia is this: what type of star is 'donating' mass to the white dwarf? Is the companion a normal (Sun-like) star tranquilly passing matter to the white dwarf, thereby slowly pushing it closer and closer to the critical limit, or is it another white dwarf star that violently smashes into the more massive one, immediately causing an explosion?

 Using a detailed model for the evolution of double stars, state-of-the-art hydrodynamic explosion models and a sophisticated method for predicting how the energy from the explosion is turned into observable light (spectra), MPA researchers and collaborators determined that white dwarfs which smash violently into each other give rise to a range of brightnesses that matches the range in brightness that is actually observed for Type Ia supernovae. Even more encouraging, the model brightness distribution peaks at about the same value as the one from observations (see figure 2). Any model scenario that is claimed to account for a large fraction of SNe Ia must be able to explain observational trends. Not only does the violent merger model do very well in terms of reproducing the brightness distribution of real SNe Ia, it also produces the right number of events as a function of time (the 'delay time distribution', see figure 3).

 In this particular model the peak brightness of the explosion is directly related to the mass of the more massive (primary) white dwarf. To get a typical explosion, however, most primary white dwarfs have to grow in mass before they explode. The team has identified an evolutionary pathway which serves to 'beef up' the mass of the primary well before the merger occurs. However, it has yet to be confirmed whether white dwarfs can really be 'beefed up' by their companions sufficiently in large enough numbers.

 While the MPA researchers are excited about their result, they remain slightly cautious. It is still unclear if this formation scenario of pre-merging white dwarfs is realized in nature as efficiently as the binary evolution model indicates. Some further work and (probably) future observations are needed to confirm the various aspects of the model.

 If it turns out that such an 'evolutionary channel' that leads to more massive primary white dwarfs readily contributes to making white dwarf pairs, then it is likely that violent white dwarf mergers are driving the underlying brightness distribution of SNe Ia. If not, then some other explosion scenario could be dominating the SN Ia scene.


 Ashley Ruiter, Stuart Sim, Ruediger Pakmor, Markus Kromer, Ivo Seitenzahl, Stefan Taubenberger


Original publication

 Ruiter, A. J.; Sim, S. A.; Pakmor, R.; Kromer, M.; Seitenzahl, I. R.; Belczynski, K.; Fink, M.; Herzog, M.; Hillebrandt, W.; Roepke, F. K.; Taubenberger, S. "On the brightness distribution of Type Ia supernovae from violent white dwarf mergers", submitted to MNRAS.The draft is available on astro-ph: http://adsabs.harvard.edu/abs/2012arXiv1209.0645R

Further references
Li et al. 2012
Maoz et al. 2012 (MMB12)
Graur and Maoz 2012 (GM12)