Scientists to Unveil 'Major Discovery' at Harvard Astrophysics Center

This illustration summarizes the almost 14-billion-year-long history of our universe. 

It shows the main events that occurred between the initial phase of the cosmos, where its properties were almost uniform and punctuated only by tiny fluctuations, to the rich variety of cosmic structure that we observe today, ranging from stars and planets to galaxies and galaxy clusters. 

Credit: ESA and the Planck Collaboration

A team of scientists will unveil what they bill as a "major discovery" in the field of astrophysics on Monday (March 17) in a presentation at the Harvard-Smithsonian Center for Astrophysics.

CfA officials did not detail the nature of the astrophysics discovery in a media alert. They only stated that the center will "host a press conference at 12:00 noon EDT (16:00 UTC) on Monday, March 17th, to announce a major discovery."

The Harvard-Smithsonian Center for Astrophysics is made up of the Harvard College Observatory and the Smithsonian Astrophysics Observatory.

Scientists at the center pursue studies of those basic physical process that determine the nature and evolution of the universe," according to the CfA website's official description.

Astronomers Modeling galaxy mergers

An generated optical image of stars in a pair of colliding galaxies after a time of 0.5 billion years, as simulated with a new computer code. 

Credit: P. Hopkins

Astronomers think that many galaxies, including our own Milky Way, have undergone similar collisions during their lifetimes.

Although galaxy collisions are important and common, what happens during these encounters is not very well understood.

For example, it seems likely that massive black hole(s) will form during the interactions, as the two galaxies' nuclei approach each other.

Galaxy-galaxy interactions also stimulate vigorous star formation as gravitational effects during the encounters induce interstellar gas to condense into stars.

The starbursts in turn light up the galaxies, especially at infrared wavelengths, making some systems hundreds or even thousands of times brighter than the Milky Way while the starbursts are underway.

Studying these luminous galaxies not only sheds light on how galaxies evolve and form stars, since they act as lanterns over cosmological distances it also helps scientists study the early universe.

All this impressive progress, however, hinges on an accurate understanding of mergers and how they work.

The general approach is to study many local examples to categorize their behaviors, and then model these cases with computational codes that simulate mergers.

The combination of precise observations and detailed modeling, iteratively applied, helps scientists improve both their understanding of the galaxies and the physical parameters and processes included in the modeling codes.

With these in hand, astronomers can start to probe the more distant universe where the objects are not as easy to measure.

Lars Hernquist

CfA astronomer Lars Hernquist and five of his Harvard colleagues (many of whom were his past students) have now shown that feedback processes from bursts of star formation play a key role in determining how merging galaxies develop, at least when two massive galaxies collide.

Prior models did not fully account for the role played by gas that is driven away by the radiation from a star burst, but which can sometimes fall back the galaxy.

The new paper is particularly effective in describing star formation in the tails and bridges of interacting systems, something had previously been lacking.

Carnegie Astronomers Discover New Kind of Supernova; Type Iax

This artist's conception shows the suspected progenitor of a new kind of supernova called Type Iax. 

Material from a hot, blue helium star at right is funneling toward a carbon/oxygen white dwarf star at left, which is embedded in an accretion disk. In many cases the white dwarf survives the subsequent explosion. 

Credit: Image is provided courtesy of Christine Pulliam (CfA)

Supernovae were always thought to occur in two main varieties but a team of astronomers including Carnegie's Wendy Freedman, Mark Phillips and Eric Persson is reporting the discovery of a new type of supernova called Type Iax.

This research has been accepted for publication in The Astrophysical Journal.

Previously, supernovae were divided into either core-collapse or Type Ia categories. Core-collapse supernovae are the explosion of a star about 10 to 100 times as massive as our sun. Type Ia supernovae are the complete disruption of a tiny white dwarf.

Wendy Freedman

This new type, Iax, is fainter and less energetic than Type Ia. Although both types come from exploding white dwarfs, Type Iax supernovas may not completely destroy the white dwarf.

Ryan Foley

"A Type Iax supernova is essentially a mini supernova," says lead author Ryan Foley, Clay Fellow at the Harvard-Smithsonian Center for Astrophysics (CfA). "It's the runt of the supernova litter."

The research team, which also included Max Stritzinger identified 25 examples of the new type of supernova.

Max Stritzinger

None of them appeared in elliptical galaxies, which are filled with old stars. This suggests that Type Iax supernovas come from young star systems.

Based on a variety of observational data, the team concluded that a Type Iax supernova comes from a binary star system containing a white dwarf and a companion star that has lost its outer hydrogen, leaving it helium dominated. The white dwarf collects helium from the normal star.

Researchers aren't sure what triggers a Type Iax. It's possible that the outer helium layer ignites first, sending a shock wave into the white dwarf.

Alternatively, the white dwarf might ignite first due to the influence of the overlying helium shell.

Either way, it appears that in many cases the white dwarf survives the explosion, unlike in a Type Ia supernova where the white dwarf is completely destroyed.

Mark Phillips

The team calculates that Type Iax supernovae are about a third as common as Type Ia supernovae. The reason so few have been detected is that the faintest are only one-hundredth as bright as a Type Ia supernova.

"The closer we look, the more ways we find for stars to explode," Mark Phillips said.

The Large Synoptic Survey Telescope could discover thousands of Type Iax supernovas over its lifetime.

Reference
Type Iax Supernovae: A New Class of Stellar Explosion. The Astrophysical Journal, 2013; 767 (1): 57 DOI: 10.1088/0004-637X/767/1/57

Geo-engineering: Guiding responsible research on Climate Change

Geoengineering, the use of human technologies to alter Earth's climate system -- such as injecting reflective particles into the upper atmosphere to scatter incoming sunlight back to space -- has emerged as a potentially promising way to mitigate the impacts of climate change.

Credit: © Kobes / Fotolia

Geoengineering, the use of human technologies to alter Earth's climate system -- such as injecting reflective particles into the upper atmosphere to scatter incoming sunlight back to space -- has emerged as a potentially promising way to mitigate the impacts of climate change.

But such efforts could present unforeseen new risks. That inherent tension, argue two professors from UCLA and Harvard, has thwarted both scientific advances and the development of an international framework for regulating and guiding geoengineering research.

Edward Parson

In an article published March 15 in the journal Science, Edward Parson of UCLA and David Keith of Harvard University outline how the current deadlock on governance of geoengineering research poses real threats to the sound management of climate risk.

Their article advances concrete and actionable proposals for allowing further research -- but not deployment -- and for creating scientific and legal guidance, as well as addressing public concerns.

"We're trying to avoid a policy train wreck," said Keith, a professor of public policy at the John F. Kennedy School of Government and Gordon McKay Professor of Applied Physics at the School of Engineering and Applied Sciences at Harvard University. "Informed policy judgments in the future require research now into geoengineering methods' efficacy and risks. If research remains blocked, in some stark future situation, only untested approaches will be available."

David Keith

"Our proposals address the lack of international legal coordination that has contributed to the current deadlock," said Parson, a professor of law and faculty co-director of the Emmett Center on Climate Change and the Environment at the UCLA School of Law.

"Coordinated international governance of research will both provide the guidance and confidence to allow needed, low-risk research to proceed and address legitimate public concerns about irresponsible interventions or a thoughtless slide into deployment."

In their paper, the authors state that progress on research governance must advance four aims:

• Allow low-risk, scientifically valuable research to proceed.
• Give scientists guidance on the design of socially acceptable research.
• Address legitimate public concerns.
• End the current legal void that facilitates rogue projects.

Parson and Keith argue that scientific self-regulation is not sufficient to manage risks and that scientists need to accept government authority over geoengineering research.

They emphasize that initial steps should not require new laws or treaties but can come from informal consultation and coordination among governments.

The authors also propose defining two thresholds for governance of geoengineering research: a large-scale threshold to be subject to a moratorium and a separate, much smaller threshold below which research would be allowed.

Keith, for example, is currently developing an outdoor experiment to test the risks and efficacy of stratospheric aerosol geoengineering, which would fall below the proposed allowable threshold.

The above story is reprinted from materials provided by Harvard School of Engineering and Applied Sciences. 

Harvard Astronomer Pays Tribute to Van Gogh with Hubble Mosaic

One night, Harvard astronomer Alex Parker was camped out at the telescope for a spot of star-gazing, and found himself facing a long, dry period of waiting for the clouds to clear.

To pass the time, he started playing around with various images from the Hubble Space Telescope, and ended up assembling them into a colorful mosaic.

The resulting image? A recreation of Vincent van Gogh's most famous painting, "Starry Night".

Alex Parker, a postdoctoral fellow at the Harvard-Smithsonian Center for Astrophysics’ Institute for Theory and Computation, has created several astronomical videos on his own time and posted them on the Internet. 

His latest video depicts the 2,299 planet candidates Kepler has found since it began searching for planets around stars in 2009. 

According to sources "Parker used photo-mosaicing software to assemble the digital collage."

He had been thinking about using Hubble images to make a mosaic for awhile, since the telescope's 22nd anniversary was approaching; he just needed the right circumstances to find the time -- a cloudy night.

"Observing can be all over the map," Parker reported about his artistic endeavour. "You will be shut out by clouds on some nights, have to evacuate the mountain because of high winds and ice on other nights, and other times there isn't a moment to pause because you're taking data at such a high rate all night."

Caltech and Harvard Bioengineers Explain Artificial Jellyfish Research - YouTube

Learning from the Jellyfish: Squishy pumps for biomedical and engineering applications

A big goal of our study was to advance tissue engineering,” says Janna Nawroth, a doctoral student in biology at the California Institute of Technology (Caltech) and lead author of the study. “In many ways, it is still a very qualitative art, with people trying to copy a tissue or organ just based on what they think is important or what they see as the major components—without necessarily understanding if those components are relevant to the desired function or without analyzing first how different materials could be used.”

Because a particular function—swimming, say—doesn’t necessarily emerge just from copying every single element of a swimming organism into a design, “our idea,” she says, “was that we would make jellyfish functions—swimming and creating feeding currents—as our target and then build a structure based on that information.”

Their method for building the tissue-engineered jellyfish, dubbed Medusoid, is outlined in a Nature Biotechnology paper.

NASA Chandra: Supermassive Black Holes Grow Faster Than Galaxies

Nasa astronomers have found that supermassive black holes grow faster than galaxies themselves. They discovered this with the Nasa's Chandra X-ray Observatory.

Earlier, astronomers believed that super massive black holes and the bulge of stars at the centre of the host galaxy grow at the same rate - the bigger the bulge, the bigger the black hole. Now, astronomers have discovered that black holes grow much faster than the galaxies.

Scientists discovered this when they were studying two galaxies NGC 4342 and NGC 4291. NGC 4342 and NGC 4291 are close to earth in cosmic terms, at distances of 75 million and 85 million light years.

During the study, scientists were analysing the mass of the black hole and the mass of the galaxy in NGC 4342 and NGC 4291. They were stunned to find that the black holes were 10 to 35 times more massive than the galaxy.

Astronomers believe that two supermassive black holes and their evolution are tied to their dark matter halos and did not grow in tandem with the galactic bulges. In this view, the black holes and dark matter halos are not overweight, but the total mass in the galaxies is too low.

"This gives us more evidence of a link between two of the most mysterious and darkest phenomena in astrophysics - black holes and dark matter - in these galaxies," said Akos Bogdan, scientist at the Harvard-Smithsonian Centre for Astrophysics (CfA), in a statement.

Astronomers earlier believed that the main reason behind this loss in mass of the galaxies was tidal stripping. Tidal stripping occurs when some of a galaxy's stars are stripped away by gravity during a close encounter with another galaxy.

If such tidal stripping had taken place, the halos mostly would have been missing because dark matter extends farther away from the galaxies; it is more loosely tied to them than the stars and more likely to be pulled away.

To find out about tidal stripping, astronomers used Chandra to look for evidence of hot, X-ray-emitting gas around the two galaxies. They found that the hot gas was distributed widely around NGC 4342 and NGC 4291, implying that each galaxy has an unusually massive dark matter halo and that tidal stripping is unlikely.

"This is the clearest evidence we have, in the nearby universe, for black holes growing faster than their host galaxy," said Bill Forman, astronomer at the Harvard-Smithsonian Center for Astrophysics. "It's not that the galaxies have been compromised by close encounters, but instead they had some sort of arrested development."

Then how can the mass of a black hole grow faster than the stellar mass of its host galaxy?

According to Nasa astronomers, a large concentration of gas spinning slowly in the galactic centre is what the black hole consumes. The blackhole grows quickly compared to galaxy, and as it grows, the amount of gas it can accrete, or swallow, increases along with the energy output from the accretion.

So there by it leads to increase in the mass of the black hole. Once the black hole reaches a critical mass, outbursts powered by the continued consumption of gas prevent cooling and limit the production of new stars.

So this is probably the reason as to why black holes have more mass than their galaxies

"It's possible that the supermassive black hole reached a hefty size before there were many stars at all in the galaxy," said Bogdan. "That is a significant change in our way of thinking about how galaxies and black holes evolve together."