Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Astronomers Pin Down Origins of “Mile Markers” for Expansion of Universe

20.11.2012
A study using a unique new instrument on the world’s largest optical telescope has revealed the likely origins of especially bright supernovae that astronomers use as easy-to-spot “mile markers” to measure the expansion and acceleration of the universe.

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.1@osu.edu
Krzysztof Stanek, (614) 292-3433; Stanek.32@osu.edu
Written by Pam Frost Gorder, (614) 292-9475; Gorder.1@osu.edu

Pam Frost Gorder | EurekAlert!
Further information:
http://www.osu.edu

More articles from Physics and Astronomy:

nachricht NASA laser communications to provide Orion faster connections
30.03.2017 | NASA/Goddard Space Flight Center

nachricht Pinball at the atomic level
30.03.2017 | Max-Planck-Institut für Struktur und Dynamik der Materie

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A Challenging European Research Project to Develop New Tiny Microscopes

The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.

To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

'On-off switch' brings researchers a step closer to potential HIV vaccine

30.03.2017 | Health and Medicine

Penn studies find promise for innovations in liquid biopsies

30.03.2017 | Health and Medicine

An LED-based device for imaging radiation induced skin damage

30.03.2017 | Medical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>