Solving the mystery of a superluminous supernova

Study suggests a lens amplified the light of an extra-bright supernova

2014-04-24

(Press-News.org) This release is available in Japanese.

An exceptionally bright supernova reported in 2013 is so luminous, a new study reports, because a lens in the sky amplified its light. The discovery of the lens settles an important controversy in the field of astronomy.

In 2010, a team of scientists observed a supernova, PS1-10afx, shining brighter than any other in its class.

"PS1-10afx is like nothing we have seen before," said senior author Robert Quimby of the University of Tokyo's Kavli Institute for the Physics and Mathematics of the Universe.

Its exceptional glow puzzled many, leading to some to conclude it was a new type of extra-bright supernova, while others suggested it was a normal Type Ia supernovae (SNIa) magnified by a lens in the form of a massive object, such as supermassive black hole, nearby.

"The team that discovered it," Quimby said, "proposed that it was a new type of supernova, one that no theory predicted."

There are a few, rare supernovae that have been found with comparable luminosities, according to Quimby "but PS1-10afx was different in just about every way. It evolved too fast, its host galaxy is too big, and it was way, way too red."

His team had another idea. "We proposed that [its exceptional glow] could be explained as a gravitationally lensed SNIa, but we had no direct evidence for the lens. Thus each explanation [to date] required a bit of magic--new physics or an unseen magnifier--and scientists don't generally buy into magic."

Quimby's hypothesis, however, came with a testable prediction. If there was a gravitational lens there to magnify the supernova, it would still be there after the supernova faded away. "Thus we could go back and get new and better data to check for a signature of the lens," he said.

His team compared spectroscopic data from PS1-10afx's peak brightness period to data from the period after it had faded. If there were an additional galaxy coincident with PS1-10afx during the bright period, serving as the lens, the scientists would expect to see two sets of gas emission lines -- and that is indeed what they saw.

In this way, the researchers inferred the presence of another galaxy right in front of PS1-10afx – one that, at just the right angle and distance to amplify the supernova's light, served as a sort of magnifying glass.

Quimby explained why the lens for PS1-10afx was missed before: "It turns out that PS1-10afx's host galaxy appears brighter than the lens galaxy…so the light of the lens was simply lost in the host's glare."

Critically, the lens identified here is the first to strongly magnify a Type Ia supernova. "We have lots of examples of gravitational lensing," Quimby explained, "but most of these are so-called 'weak' gravitational lensing."

Strong gravitational lensing is different.

"It means that there were multiple images of the supernova formed," Quimby explained. That's what created the extra-bright appearance.

The multiple images created through strong lensing offer a means to test cosmic expansion, the increase in distance between two parts of the universe over time. "Each image will arrive at a different time with the exact delay dependent on how fast the universe is expanding. In principle, measuring this delay provides a direct way [more so than existing methods] to measure cosmic expansion."

The scientists couldn't do this with PS1-10afx because it faded away before they identified its importance.

"But now we know what to look for," Quimby said. And this may enable scientists to use future lensed supernova events to measure expansion in the universe.

INFORMATION:

The American Association for the Advancement of Science (AAAS) is the world's largest general scientific society, and publisher of the journal, Science as well as Science Translational Medicine and Science Signaling. AAAS was founded in 1848, and includes some 261 affiliated societies and academies of science, serving 10 million individuals. Science has the largest paid circulation of any peer-reviewed general science journal in the world, with an estimated total readership of 1 million. The non-profit AAAS is open to all and fulfills its mission to "advance science and serve society" through initiatives in science policy; international programs; science education; and more. For the latest research news, log onto EurekAlert!, the premier science-news Web site, a service of AAAS.

ELSE PRESS RELEASES FROM THIS DATE:

A scourge of rural Africa, the tsetse fly is genetically deciphered

2014-04-24

New Haven, Conn. – An international team of researchers led by the Yale School of Public Health has successfully sequenced the genetic code of the tsetse fly, opening the door to scientific breakthroughs that could reduce or end the scourge of African sleeping sickness in sub-Saharan Africa. The study is published in the journal Science. It took nearly 10 years and more than 140 scientists from numerous countries to map the genome of the fly, also known as Glossina morsitans. Tsetse flies are the sole insect vectors of a disease that threatens the health of millions ...

Breakthrough harnesses light for controlled chemical reaction

2014-04-24

MADISON – When chemist Tehshik Yoon looks out his office window, he sees a source of energy to drive chemical reactions. Plants "learned" to synthesize chemicals with sunlight eons ago; Yoon came to the field a bit more recently. But this week, in the journal Science, he and three collaborators detail a way to use sunlight and two catalysts to create molecules that are difficult to make with conventional techniques. In chemistry, heat and ultraviolet (UV) light are commonly used to drive reactions. Although light can power reactions that heat cannot, UV has disadvantages, ...

Researchers build new 'off switch' to shut down neural activity

2014-04-24

Nearly a decade ago, the era of optogenetics was ushered in with the development of channelrhodopsins, light-activated ion channels that can, with the flick of a switch, instantaneously turn on neurons in which they are genetically expressed. What has lagged behind, however, is the ability to use light to inactivate neurons with an equal level of reliability and efficiency. Now, Howard Hughes Medical Institute (HHMI) scientists have used an analysis of channelrhodopsin's molecular structure to guide a series of genetic mutations to the ion channel that grant the power to ...

You may have billions and billions of good reasons for being unfit

2014-04-24

This news release is available in French. Although our chromosomes are relatively stable within our lifetimes, the genetic material found in our mitochondria is highly variable across individuals and may impact upon human health, say researchers at the University of Montreal and its affiliated CHU Sainte-Justine Hospital. Genomes are changing, not just from generation to generation, but even and in fact within our individual cells. The researchers are the first to identify the extent to which the editing processes of RNA code can vary across a large number of individuals. ...

Ocean microbes display remarkable genetic diversity

2014-04-24

CAMBRIDGE, Mass-- The smallest, most abundant marine microbe, Prochlorococcus, is a photosynthetic bacteria species essential to the marine ecosystem. An estimated billion billion billion of the single-cell creatures live in the oceans, forming the base of the marine food chain and occupying a range of ecological niches based on temperature, light and chemical preferences, and interactions with other species. But the full extent and characteristics of diversity within this single species remains a puzzle. To probe this question, scientists in MIT's Department of Civil ...

Channel makeover bioengineered to switch off neurons

2014-04-24

Scientists have bioengineered, in neurons cultured from rats, an enhancement to a cutting edge technology that provides instant control over brain circuit activity with a flash of light. The research funded by the National Institutes of Health adds the same level of control over turning neurons off that, until now, had been limited to turning them on. "What had been working through a weak pump can now work through a highly responsive channel with many orders of magnitude more impact on cell function," explained Karl Deisseroth, M.D., Ph.D., of Stanford University, Stanford, ...

Tsetse fly genome reveals weaknesses

2014-04-24

Mining the genome of the disease-transmitting tsetse fly, researchers have revealed the genetic adaptions that allow it to have such unique biology and transmit disease to both humans and animals. The tsetse fly spreads the parasitic diseases human African trypanosomiasis, known as sleeping sickness, and Nagana that infect humans and animals respectively. Throughout sub-Saharan Africa, 70 million people are currently at risk of deadly infection. Human African trypanosomiasis is on the World Health Organization's (WHO) list of neglected tropical diseases and since 2013 ...

Stanford team makes switching off cells with light as easy as switching them on

2014-04-24

STANFORD, Calif. — In 2005, a Stanford University scientist discovered how to switch brain cells on or off with light pulses by using special proteins from microbes to pass electrical current into neurons. Since then, research teams around the world have used the technique that this scientist, Karl Deisseroth, MD, PhD, dubbed "optogenetics" to study not just brain cells but heart cells, stem cells and the vast array of cell types across biology that can be regulated by electrical signals — the movement of ions across cell membranes. Optogenetics gave researchers a powerful ...

Cosmic illusion revealed

2014-04-24

This press release is available in Japanese. Kashiwa Japan - A team of researchers led by Robert Quimby at the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) has announced the discovery of a galaxy that magnified a background, Type Ia supernova thirtyfold through gravitational lensing. This is the first example of strong gravitational lensing of a supernova confirms the team's previous explanation for the unusual properties of this supernova. The team has further shown how such discoveries of supernovae of Type Ia (SNIa) can be made far ...

Untangling Brazil's controversial new forest code

2014-04-24

Approved in 2012, Brazil's new Forest Code has few admirers. Agricultural interests argue that it threatens the livelihoods of farmers. Environmentalists counter that it imperils millions of hectares of forest, threatening to release the billions of tons of carbon they contain. A new study, co-authored by Woods Hole Research Center (WHRC) scientists Michael Coe, Marcia Macedo and Brazilian colleagues, published this week in Science, aims to clarify the new law. Entitled "Cracking Brazil's Forest Code," the article is the first to quantify the implications of recent changes ...

LAST 30 PRESS RELEASES:

Global cervical cancer vaccine roll-out shows it to be very effective in reducing cervical cancer and other HPV-related disease, but huge variations between countries in coverage

Personalised “cocktails” of antibiotics, probiotics and prebiotics hold great promise in treating a common form of irritable bowel syndrome, pilot study finds