Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Distance to nearest galaxy measured

07.03.2013
A team of astronomers including Carnegie's Ian Thompson have managed to improve the measurement of the distance to our nearest neighbor galaxy and, in the process, refine an astronomical calculation that helps measure the expansion of the universe. Their work is published March 7 by Nature.

The Hubble constant is a fundamental quantity that measures the current rate at which our universe is expanding. It is named after 20th Century Carnegie astronomer Edwin P. Hubble, who astonished the world by discovering that our universe has been growing continuously since its inception.

Determining the Hubble constant (a direct measurement of the rate of this continuing expansion) is critical for gauging the age and size of our universe. One of the largest uncertainties plaguing past measurements of the Hubble constant has involved the distance to the Large Magellanic Cloud (LMC), our nearest neighboring galaxy, which orbits our own Milky Way.

Astronomers survey the scale of the Universe by first measuring the distances to close-by objects (for example Cepheid variable stars studied by Wendy Freedman, director of the Carnegie Observatories, and her collaborators) and then using observations of these objects in more distant galaxies to pin down distances further and further out in the Universe. But this chain is only as accurate as its weakest link. Up to now finding a precise distance to the LMC has proved elusive. Because stars in this galaxy are used to fix the distance scale for more remote galaxies, an accurate distance is crucially important.

"Because the LMC is close and contains a significant number of different stellar distance indicators, hundreds of distance measurements using it have been recorded over the years," Thompson said. "Unfortunately, nearly all the determinations have systemic errors, with each method carrying its own uncertainties."

The international collaboration worked out the distance to the Large Magellanic Cloud by observing rare close pairs of stars, known as eclipsing binaries. These pairs are gravitationally bound to each other, and once per orbit, as seen from Earth, the total brightness from the system drops as each component eclipses its companion. By tracking these changes in brightness very carefully, and also measuring the orbital speeds of the stars, it is possible to work out how big the stars are, how massive they are, and other information about their orbits. When this is combined with careful measurements of the apparent brightness, remarkably accurate distances can be determined.

This method has been used before in taking measurements to the LMC, but with hot stars. As such, certain assumptions had to be made and the distances were not as accurate as desired. This new work, led by Grzegorz Pietrzynski of the Universidad de Concepcion in Chile and Warsaw University Observatory in Poland, used 16-years-worth of observations to identify a sample of intermediate mass binary stars with extremely long orbital periods, perfect for measuring precise and accurate distances.

The team observed eight of these binary systems over eight years, gathering data at Las Campanas Observatory and the European Southern Observatory. The LMC distance calculated using these eight binary stars is purely empirical, without relying on modeling or theoretical predictions. The team refined the uncertainty in the distance to the LMC down to 2.2 percent. This new measurement can be used to decrease the uncertainty in calculations of the Hubble constant to 3 percent, with prospects of improving this to a 2 percent uncertainty in a few years as the sample of binary stars is increased.

This work was supported by BASAL Centro de Astrofisica y Tecnologias Afines (CATA), the Polish Ministry of Science, the Foundation for Polish Science (FOCUS, TEAM), the Polish National Science Centre, and the GEMINI-CONICYT fund. The OGLE project has received funding from the European Research Council "Advanced Grant" program.

The Carnegie Institution for Science is a private, nonprofit organization headquartered in Washington, D.C., with six research departments throughout the U.S. Since its founding in 1902, the Carnegie Institution has been a pioneering force in basic scientific research. Carnegie scientists are leaders in plant biology, developmental biology, astronomy, materials science, global ecology, and Earth and planetary science.

Ian Thompson | EurekAlert!
Further information:
http://www.carnegiescience.edu

More articles from Physics and Astronomy:

nachricht Meteoritic stardust unlocks timing of supernova dust formation
19.01.2018 | Carnegie Institution for Science

nachricht Artificial agent designs quantum experiments
19.01.2018 | Universität Innsbruck

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: Artificial agent designs quantum experiments

On the way to an intelligent laboratory, physicists from Innsbruck and Vienna present an artificial agent that autonomously designs quantum experiments. In initial experiments, the system has independently (re)discovered experimental techniques that are nowadays standard in modern quantum optical laboratories. This shows how machines could play a more creative role in research in the future.

We carry smartphones in our pockets, the streets are dotted with semi-autonomous cars, but in the research laboratory experiments are still being designed by...

Im Focus: Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...

Im Focus: The first precise measurement of a single molecule's effective charge

For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.

Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...

Im Focus: Paradigm shift in Paris: Encouraging an holistic view of laser machining

At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.

No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...

Im Focus: Room-temperature multiferroic thin films and their properties

Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.

Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

10th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Münster, 10-11 April 2018

08.01.2018 | Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

 
Latest News

Let the good tubes roll

19.01.2018 | Materials Sciences

How cancer metastasis happens: Researchers reveal a key mechanism

19.01.2018 | Health and Medicine

Meteoritic stardust unlocks timing of supernova dust formation

19.01.2018 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>