Baby Stars May Grow Massive From Feeding Enabled Collectively By Older Stars

Stars ten times as massive as the Sun, or more, should not exist: as they grow, they tend to push away the gas they feed on, starving their own growth. Scientists have been struggling to figure out how some stars overcome this hurdle.

Now, a group of researchers led by two astronomers at the University of Toronto suggests that baby stars may grow to great mass if they happen to be born within a corral of older stars –with these surrounding stars favorably arranged to confine and thus feed gas to the younger ones in their midst. The astronomers have seen hints of this collective feeding, or technically “convergent constructive feedback,” in a giant cloud of gas and dust called Westerhout 3 (W3), located 6,500 light years from us. Their results are published in The Astrophysical Journal (ApJ, 766, 85), available online at http://stacks.iop.org/0004-637X/766/85.

“This observation may lift the veil on the formation of the most massive stars which remains, so far, poorly understood,” says Alana Rivera-Ingraham, who led the study while she was a graduate student in the Department of Astronomy and Astrophysics at the University of Toronto, Canada, and is currently a postdoctoral researcher at the Institut de Recherche en Astrophysique et Planétologie in Toulouse, France.

To study the formation of high-mass stars, Rivera-Ingraham and collaborators used high-quality and high-resolution far-infrared images from a space telescope launched by the European Space Agency in 2009 —the Herschel Space Observatory. This telescope’s two cameras recorded light that is not visible to the naked eye, spanning a range from infrared radiation partway to the microwave region. Exploiting these cameras, scientists including Peter Martin, Professor in the Canadian Institute for Theoretical Astrophysics at the University of Toronto, created the HOBYS Key Programme to study the birth of very massive stars in nearby giant clouds of gas and dust in our own Galaxy, including W3. Research on HOBYS at the University of Toronto is supported in part by the Canadian Space Agency and the Natural Sciences and Engineering Research Council of Canada.

Scientists track the regions of the gas cloud where stars are about to form by mapping the density of dust and its temperature, looking for the most dense regions where the dust is shielded and cold. “We can now see where stars are about to be born before it even happens, because we can detect the cold dust condensations,” says Martin. “Until Herschel, we could only dream of doing that.”

Stars are born in the denser parts of gas clouds, where the gas gets compressed enough by gravity to trigger nuclear fusion. The more massive the newborn star, the more visible and ultraviolet light it emits, heating up its surroundings —including the dust studied by Herschel.
“The radiation during the birth of high-mass stars is so intense that it tends to destroy and push away the material from which they need to feed for further growth,” says Rivera-Ingraham. Scientists have modeled this process and found that stars about eight times the mass of our Sun would stop growing because they run out of gas.

But astronomers do see stars that are more massive than this theoretical limit. And by looking at W3, Rivera-Ingraham and her collaborators have found clues to how this might be possible.

The researchers noticed that the densest region of the cloud, in the upper left of the image, was surrounded by a congregation of old high-mass stars. It is as if previous generations of large stars enabled the next ones to grow also massive, and close to each other. The scientists suggest that this is no coincidence: each generation of stars might have created the right conditions for another generation to grow comparably or even more massive in its midst, ultimately leading to the formation of a rare, massive cluster of high-mass stars.

Like young high-mass stars, older stars also radiate and push gas away. If such older stars happen to be arranged favorably around a major reservoir of gas, they can compress it enough to ignite new stars. The process is similar to the way a group of street cleaners armed with leaf blowers can stack leaves in a pile —by pushing from all sides at the same time. This corralling of dense gas can give birth to new, high-mass stars. A large newborn star will push its food source away, but if it is surrounded by enough large stars, these can keep nudging gas back at it. With such collective feeding at play, the young star could grow very massive indeed.

Next on the to-do list of the astronomers is to test their idea by simulating the situation with computer modeling, by measuring gas motions, and by comparing their results with data from other giant clouds studied by HOBYS. Only then will they be able to discern the mechanism —collective feeding or not— that gives rise to high-mass stars in these giant clouds.

LINKS:
UofT press release: http://universe.utoronto.ca/embargo/w3
ESA press release: http://www.esa.int/Our_Activities/Space_Science/Herschel/Hunting_high-mass_stars_with_Herschel
Official image and credits: http://oshi.esa.int/image.html?id=96

CONTACTS:
Prof. Peter Martin
Canadian Institute for Theoretical Astrophysics
University of Toronto
Toronto, Canada
pgmartin@cita.utoronto.ca

Dr. Alana Rivera-Ingraham
Institut de Recherche en Astrophysique et Planétologie (IRAP)
Toulouse, France
arivera@irap.omp.eu

Johannes Hirn
Outreach and Communications
Dunlap Institute for Astronomy & Astrophysics
University of Toronto
Toronto, Canada
hirn@di.utoronto.ca
(+1) 416 978 6840

Planck space mission sheds light on the universe’s age, evolution and composition

The best map ever made of the most ancient light in the universe — the remnant radiation left over from the Big Bang some 13 billion years ago — deepens our understanding of the universe.
The highly detailed image of the universe — produced by the European Space Agency’s Planck Space Telescope and the Planck collaboration of international scientists including a team from U of T — reveals that the universe is slightly older, expanding more slowly and has more matter than previously thought.
“For all of us, the magic is how we translate the observations of the spatial patterns in this ‘first light’ of the universe to the structure that must have been there in the earliest moments when our observable universe — currently some giga-giga-giga-metres across — was compressed to smaller than a nano-nano-nano metre across,” said University Professor J. Richard Bond.
Bond and Douglas Scott of the University of British Columbia co-lead a Canadian science team that played a key role in the Planck collaboration. Bond is on the faculty at the Canadian Institute for Theoretical Astrophysics and directs the Cosmology and Gravity Program of the Canadian Institute for Advanced Research (CIFAR), and the team included astrophysicists at the University of Toronto, University of Alberta, Université Laval and McGill University.
Planck’s evidence confirms and refines previous models of how astronomers believe the universe originated and evolved, but with intriguing new details:

  • The Planck team has calculated that the universe is 13.82 billion years old — 80 million years older than earlier estimates.
  • the Planck Space Telescope has revealed that the universe is expanding slower than the current standard determined with the Hubble Space Telescope.
  • Planck has also allowed cosmologists to confirm the universe’s composition more accurately than ever before: normal matter, the stuff of stars and galaxies like our own Milky Way, makes up just 4.9 per cent of the universe. Dark matter — the presence of which so far has been inferred only through the effects its gravity causes — accounts for 26.8 per cent. Dark energy — a mysterious force that behaves the opposite way to gravity, pushing and expanding our universe — makes up 68.3 per cent of the universe — slightly less than previously thought.

Planck’s precision has also given astrophysicists a number of new puzzles to solve. “For more than three decades, I have been trying to unveil the structure imprinted on the universe from an epoch of accelerated expansion in its earliest moments,” said Bond. “Planck has now shown that the evidence for this early inflation is much stronger than before. The patterns we see are quite simple, resulting in many formerly viable theories falling victim to our Planckian knife. Our maps reveal unexplained, large-scale features that excite the imaginations of physicists who have been eagerly awaiting what Planck has to say about the early universe.”
Launched in 2009, the Planck telescope has been scanning the skies ever since, shedding light on the beginnings of the universe and the birth of stars. The telescope’s incredible accuracy allows it to pinpoint faint, minute patterns — differences in light and temperature that correspond to slightly different densities in the matter left over from the Big Bang.
The data was released today at ESA headquarters in Paris, France and is from the first 15 months of the mission. It shows a map of the universe when it was just 380,000 years old.
“We now have a precise recipe for our universe: how much dark and normal matter it is made of; how fast it is expanding; how lumpy it is and how that lumpiness varies with scale; and how the remnant radiation from the Big Bang is scattered,” said University of British Columbia Professor Douglas Scott. “It is astonishing that the entire universe seems to be describable by a model using just these six quantities. Now, Planck has told us the values of those numbers with even higher accuracy.”
Twenty-eight scientific papers from the Planck mission were will be published tomorrow on-line today covering many aspects of how the universe is put together and how it has evolved. Planck’s instruments allow astronomers to separate the primordial light from the effects of dust and other emissions coming from our Milky Way Galaxy. U of T and CITA astrophysicist Peter Martin is working on a series of papers that will be published in another upcoming release on this data: “We do not simply sweep away the dust signal into the trash bin, but rather treasure it for what it tells us about the workings of the Galaxy. It enables us to discover the evolution of structure in the interstellar medium leading from a diffuse state to star formation in dense molecular clouds,” he said.
Hundreds of astronomers from around the world will continue to study Planck’s data as the telescope continues its observations.
The complete results of the mission are scheduled to be released in 2014.
In addition to Bond and Martin, the current U of T scientists in the Planck mission include CITA’s Mike Nolta and Marc Antoine Miville Deschenes (based in Paris), and Professor Barth Netterfield of the Department of Astronomy and Astrophysics who led the large software effort at UofT used to check the data as it poured in from the satellite.

The Canadian Space Agency funds two Canadian research teams who are part of the Planck science collaboration, and who helped develop both of Planck’s complementary science instruments, the High Frequency Instrument (HFI) (LINK) and the Low Frequency Instrument (LFI).

Press release issued by the University of Toronto.

Additional Links:

Distant Planetary System is Super-Sized Solar System (March 14, 2013)

TORONTO, ON (11 March 2013) – A team of astronomers, including Quinn Konopacky of the Dunlap Institute for Astronomy & Astrophysics, University of Toronto, has made the most detailed examination yet of the atmosphere of a Jupiter-like planet beyond our Solar System.

According to Konopacky, “We have been able to observe this planet in unprecedented detail because of the advanced instrumentation we are using on the Keck II telescope, our ground-breaking observing and data-processing techniques, and because of the nature of the planetary system.”

Konopacky is lead author of the paper describing the team’s findings, to be published March 14th in Science Express, and March 22nd in the journal Science.

The team, using a high-resolution imaging spectrograph called OSIRIS, uncovered the chemical fingerprints of specific molecules, revealing a cloudy atmosphere containing carbon monoxide and water vapour. “With this level of detail,” says Travis Barman, a Lowell Observatory astronomer and co-author of the paper, “we can compare the amount of carbon to the amount of oxygen present in the planet’s atmosphere, and this chemical mix provides clues as to how the entire planetary system formed.”

There has been considerable uncertainty about how systems of planets form, with two leading models, called core accretion and gravitational instability. Planetary properties, such as the composition of a planet’s atmosphere, are clues as to whether a system formed according to one model or the other.

“This is the sharpest spectrum ever obtained of an extrasolar planet,” according to co-author Bruce Macintosh of the Lawrence Livermore National Laboratory. “This shows the power of directly imaging a planetary system. It is the exquisite resolution afforded by these new observations that has allowed us to really begin to probe planet formation.”

The spectrum reveals that the carbon to oxygen ratio is consistent with the core accretion scenario, the model thought to explain the formation of our Solar System.

The core accretion model predicts that large gas giant planets form at great distances from the central star, and smaller rocky planets closer in, as in our Solar System. It is rocky planets, not too far, nor close to the star, that are prime candidates for supporting life.

“The results suggest the HR 8799 system is like a scaled-up Solar System,” says Konopacky. “And so, in addition to the gas giants far from their parent star, it would not come as a surprise to find Earth-like planets closer in.”

Konopacky and her team will continue to study the super-sized planets to learn more details about their nature and their atmospheres. Future observations will be made using the recently upgraded OSIRIS instrument which utilizes a new diffraction grating—the key component of the spectrograph that separates light according to wavelength, just like a prism. The new grating was developed at the Dunlap Institute and installed in the spectrograph in December 2012.

“These future observations will tell us much more about the planets in this system,” says Dunlap Fellow Konopacky. “And the more we learn about this distant planetary system, the more we learn about our own.”

CONTACT INFORMATION:

Dr. Quinn Konopacky
Dunlap Fellow
Dunlap Institute for Astronomy & Astrophysics
University of Toronto
e: konopacky@dunlap.utoronto.ca
p: 416-946-5465
www.dunlap.utoronto.ca/
www.di.utoronto.ca/~konopacky

Chris Sasaki
PIO; Communications and New Media Specialist
Dunlap Institute for Astronomy & Astrophysics
University of Toronto
e: csasaki@dunlap.utoronto.ca
p: 416-978-6613

The Dunlap Institute for Astronomy & Astrophysics continues the legacy of the David Dunlap Observatory of developing innovative astronomical instrumentation, including instrumentation for the largest telescopes in the world. The research of its faculty and Dunlap Fellows spans the depths of the Universe, from the discovery of exoplanets, to the formation of stars, the evolution and nature of galaxies, dark matter, the Cosmic Microwave Background, and SETI. The institute also continues a strong commitment to developing the next generation of astronomers and fostering public engagement in science. For more information: www.dunlap.utoronto.ca

CASCA/RASC/FAAQ Qilak Award Presented to Dr. James E. Hesser (March 3, 2013)

 
The Qilak award recognizes outstanding contributions to public understanding and appreciation of astronomy in Canada. CASCA is pleased to announce that the winner of the 2013 Qilak Award is Dr. James E. Hesser of the National Research Council.

 
Dr. Hesser has been a prominent figure in Canadian and international astronomy for many years. The director of the Dominion Astrophysical Observatory since 1986, Dr. Hesser is a past president of both CASCA (2004-2006) and the Astronomical Society of the Pacific (1987-1989), and a former vice-president of the American Astronomical Society (1991-1994). In 1997, Dr. Hesser was one of the first recipients of the prestigious Michael Smith Award, given through NSERC Canada to “honour people and groups that are inspirational in the way that they promote science to the general public”. He received the Queen’s Golden Jubilee Medal in 2002 in recognition of his services to the National Research Council and to all aspects of astronomy. In 2004, he received the CASCA Executive Award for exceptional service to CASCA, and he holds the title of Honorary President of the Royal Astronomical Society of Canada (RASC).

 
With a career-long commitment to astronomy education and public outreach, Dr. Hesser has led by example to forge an effective, efficient partnership between the main organizations of professional and amateur astronomy in Canada: CASCA, RASC, and the Fédération des astronomes amateurs du Québec (FAAQ). In collaboration with others, he worked diligently to establish respectful partnerships with Canada’s Aboriginal communities to preserve and celebrate indigenous knowledge of astronomy, and to illustrate pathways by which Aboriginal youth can aspire to and enter careers in science and technology. A longtime supporter of community outreach programmes, he often gives enthusiastic talks at astronomy conferences and other venues across Canada to encourage, motivate, and inspire his professional and amateur colleagues to participate in EPO activities.

 
Perhaps most significantly, Dr Hesser worked tirelessly to lead International Year of Astronomy (IYA) efforts within Canada. From 2005 to well beyond 2009, he led and guided this highly visible international project by serving as Canada’s “single point of contact” and as chair of the Executive Committee and Advisory Board for IYA within Canada. Under his direction, the IYA provided a “Galileo Moment” (i.e., “an engaging astronomy experience”) to more than two million people in Canada through more than 3600 separate events, from coast to coast to coast, and in both official languages. Always mindful of the need to cultivate lasting partnerships that sustain public interest in astronomy, Dr. Hesser has been a driving force behind “Beyond IYA” efforts within Canada.

 
CASCA thanks Dr. Hesser for his commitment to deepening the public’s understanding and appreciation of astronomy.

 
Laura Ferrarese, President, on behalf of the CASCA Board
Patrick Cote, Chair, on behalf of CASCA’s Awards Committee

CASCA’s Peter G. Martin Award Presented to Dr. Victoria Kaspi (March 3, 2013)

 
The Peter G. Martin Award is awarded to a Canadian astronomer, or astronomer working in Canada, within ten to twenty years of receipt of his or her PhD degree, to recognize significant contributions to astronomical research. CASCA is pleased to announce that the recipient of the 2013 Peter G. Martin award is Prof. Victoria Kaspi of McGill University.

 
Dr. Kaspi received her Ph.D. in 1993 from Princeton University, under the supervisor of Nobel laureate Joseph Taylor. Following postdoctoral fellowships at Caltech and JPL, she was a professor at the Massachusetts Institute of Technology from 1997 to 2002. In 1999, she moved to McGill University, where she is currently the Lorne Trottier Chair in Astrophysics and Cosmology. Her numerous awards and distinctions include the Annie Jump Cannon Prize (1998), Steacie Prize (2006), Rutherford Medal (2007) and John C. Polanyi Award (2011). She is a Fellow of both the Royal Society, and the Royal Society of Canada, and in 2011 was elected to the U.S. National Academy of Sciences.

 
The author of more than 200 refereed publications, Prof. Kaspi’s research interests focus on neutron stars, radio pulsars and magnetars, with an emphasis on observational radio and X-ray astrophysics. Scientific highlights from Prof. Kaspi’s career include pioneering efforts in high-precision radio timing of millisecond pulsars, the use of binary pulsars in tests of General Relativity, the connection between pulsars and magnetars, and the study of highly magnetic radio pulsars in the field.

 
Please join us in congratulating Prof. Kaspi on the receipt of the 2013 Peter G. Martin Award.

 
Laura Ferrarese, President, on behalf of the CASCA Board
Patrick Cote, Chair, on behalf of CASCA’s Awards Committee

CASCA/RASC Plaskett Medal Presented to Dr. Yasuhiro Hasegawa (March 3, 2013)

 
The J.S. Plaskett Medal is awarded annually by CASCA and the Royal Astronomical Society of Canada (RASC) to the Ph.D. graduate from a Canadian university who is judged to have submitted the most outstanding doctoral thesis in astronomy or astrophysics during the preceding two calendar years. CASCA is pleased to announce that the recipient of the 2013 J.S. Plaskett Medal is Dr. Yasuhiro Hasegawa.
 

Dr. Hasegawa completed his doctoral studies in 2012 at McMaster University. His thesis, entitled “Planet Traps in Protoplanetary Disk and the Formation and Evolution of Planetary Systems”, was carried out under the supervision of Prof. Ralph Pudritz. This work explores in detail — from both a theoretical and computational perspective — the possibility that inhomogeneous structure in protostellar accretion disks can create ‘planet traps’ where major planets are built up primarily through the capture of rapidly migrating planetary cores, followed by the accretion of dense gas.
 

CASCA extends its congratulations to Dr. Hasegawa, who is currently an East Asian Core Observatories Association (EACOA) Fellow at the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA) in Taiwan.
 

Laura Ferrarese, President, on behalf of the CASCA Board
Patrick Cote, Chair, on behalf of CASCA’s Awards Committee