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 Study offers new theoretical approach to describing non-equilibrium phase transitions
27.04.2017 | DOE/Argonne National Laboratory

nachricht SwRI-led team discovers lull in Mars' giant impact history
26.04.2017 | Southwest Research Institute

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: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Fighting drug resistant tuberculosis – InfectoGnostics meets MYCO-NET² partners in Peru

28.04.2017 | Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

 
Latest News

Wireless power can drive tiny electronic devices in the GI tract

28.04.2017 | Medical Engineering

Ice cave in Transylvania yields window into region's past

28.04.2017 | Earth Sciences

Nose2Brain – Better Therapy for Multiple Sclerosis

28.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>