Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Distance to nearest galaxy measured

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:

More articles from Physics and Astronomy:

nachricht First results of NSTX-U research operations
26.10.2016 | DOE/Princeton Plasma Physics Laboratory

nachricht Scientists discover particles similar to Majorana fermions
25.10.2016 | Chinese Academy of Sciences Headquarters

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: Etching Microstructures with Lasers

Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.

This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...

Im Focus: Light-driven atomic rotations excite magnetic waves

Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion

Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Greater Range and Longer Lifetime

26.10.2016 | Power and Electrical Engineering

VDI presents International Bionic Award of the Schauenburg Foundation

26.10.2016 | Awards Funding

3-D-printed magnets

26.10.2016 | Power and Electrical Engineering

More VideoLinks >>>