In a paper to appear in the Astrophysical Journal, researchers describe observations of recent supernova 2011fe that they captured with the Large Binocular Telescope (LBT) using a tool created at Ohio State University: the Multi-Object Double Spectrograph (MODS).
MODS measures the frequencies and intensities of light shining from a star. Stars shine at different frequencies depending on the chemical elements they are made of; a star like the sun, which is made mostly of hydrogen, shines at different frequencies than a star that is made mostly of helium. So astronomers can use spectra to determine what a particular star is made of.
Based on the frequencies of light emanating from supernova 2011fe, this type of supernova – known as Type Ia – is most likely caused by the interaction between a pair of dead stars known as white dwarfs, the astronomers concluded. One white dwarf orbits the other and sheds material onto it, until the other white dwarf becomes unstable and explodes, shining billions of times brighter than the sun.
Astronomers worldwide have tried to confirm the origin of Type Ia supernovae for decades. Groups have proposed several different hypotheses, including exotic scenarios involving white dwarfs paired with still-“living” giant stars, or even stars like the sun.
Kris Stanek, professor of astronomy at Ohio State and a co-author of the study, explained why settling this issue is important.
“We really want to know more about these supernovae, given their importance in our understanding of how the universe is expanding,” he said. “Many observations have been done over the years, and I think many astronomers are starting to accept one explanation – that two white dwarfs are probably responsible.”
Still, the alternative theories keep re-emerging, he said: “like zombies that won’t die.”
“With this study, we were looking for a zombie ‘kill shot,’ and we think we found it.”
Rick Pogge, professor of astronomy and lead designer of MODS, said that the spectrograph is the ideal tool for settling the debate.
“MODS is one of the most sensitive optical spectrometers in operation today, and being used on what is currently the world's largest optical telescope. If we couldn't kill this debate with MODS and the LBT, something would be dreadfully wrong,” he added.
Type Ia supernovae make good mile markers for the universe because their extreme brightness – 5 billion times brighter than the sun – makes them easy to see, and their distinctive pattern of brightening and dimming in the weeks after they appear makes them easily identifiable.
Astronomers use that information to calculate the distance from Earth to the supernova, and in turn, calculate how fast the universe is expanding. Knowing more about the composition of the stars that create the supernovae could open up new ideas in the understanding of that expansion.
Here’s what nearly all astronomers agree on: Type Ia supernovae originate in binary systems, where one star or star-like object is orbiting another. The main object – the one that initiates the explosion – is a white dwarf, the massive remnants of a dead star. Over time, the white dwarf’s gravity peels off gas and dust from the companion and absorbs that material. Eventually, the white dwarf becomes unstable, and explodes in a supernova.
At issue, explained lead study author and doctoral student Ben Shappee, is the identity of the white dwarf’s companion – is it another white dwarf, or a giant star, or even a star like our sun?
The Ohio State astronomers found their answer in the light spectrum emanating from the supernova. If the companion were a star like ours, or even a giant star, a sizeable portion of the debris blown away from the supernova would contain atoms of the element hydrogen.
Supernova 2011fe provided a good chance for the researchers to test for the presence of hydrogen. Located in the Pinwheel Galaxy some 21 million light-years away, it was the closest near-Earth Type Ia supernova to occur in the last 20 years.
“If the companion were a star such as ours or even a red giant, we would expect to see a lot of hydrogen in the signal – maybe even half a solar mass’ worth, as the companion was blown away. But instead, we saw at most only one tenth of one percent of a solar mass’ worth of hydrogen. That suggests that the white dwarf’s companion had very little if any hydrogen in it, and is likely another white dwarf,” Shappee said.
Pogge called the study “a beautiful demonstration of the kind of data we are able to get on a routine basis with the LBT and MODS. Our entire instrument team is very proud of how well MODS is working.”
In fact, this study was done with only one half of the MODS system – MODS1 – which is currently installed on one mirror of the LBT. It’s twin, MODS2, is currently under construction in Columbus and scheduled to be installed on the second mirror in early 2013.
Shappee pursued this work for his doctoral degree, with funding from a National Science Foundation (NSF) Graduate Research Fellowship. In keeping with the Department of Astronomy’s tradition of training graduate students to defend their work through informal debate, he presented the paper at a “morning coffee” discussion, and posted a video explanation of the work on YouTube.
Coauthors on the paper also include Peter Garnavich from the University of Notre Dame. This research was supported by the NSF, and the MODS spectrographs are being built with funding from NSF along with additional funds from the Ohio Board of Regents and the Ohio State University Ofﬁce of Research.Contact: Ben Shappee, (614) 292-7881; Shappee.email@example.com
Pam Frost Gorder | EurekAlert!
New research identifies how 3-D printed metals can be both strong and ductile
11.12.2017 | University of Birmingham
Three kinds of information from a single X-ray measurement
11.12.2017 | Friedrich-Schiller-Universität Jena
Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.
To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...
The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.
Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...
With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong
Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...
An interdisciplinary group of researchers interfaced individual bacteria with a computer to build a hybrid bio-digital circuit - Study published in Nature Communications
Scientists at the Institute of Science and Technology Austria (IST Austria) have managed to control the behavior of individual bacteria by connecting them to a...
Physicists in the Laboratory for Attosecond Physics (run jointly by LMU Munich and the Max Planck Institute for Quantum Optics) have developed an attosecond electron microscope that allows them to visualize the dispersion of light in time and space, and observe the motions of electrons in atoms.
The most basic of all physical interactions in nature is that between light and matter. This interaction takes place in attosecond times (i.e. billionths of a...
11.12.2017 | Event News
08.12.2017 | Event News
07.12.2017 | Event News
11.12.2017 | Information Technology
11.12.2017 | Power and Electrical Engineering
11.12.2017 | Event News