Free Newsletters - Space - Defense - Environment - Energy - Solar - Nuclear
..
. 24/7 Space News .




SPACE SCOPES
Radio telescopes settle controversy over distance to Pleiades
by Staff Writers
Washington DC (SPX) Sep 02, 2014


Optical image of the Pleiades. Image courtesy NOAO/AURA/NSF. For a larger version of this image please go here.

Astronomers have used a worldwide network of radio telescopes to resolve a controversy over the distance to a famous star cluster -- a controversy that posed a potential challenge to scientists' basic understanding of how stars form and evolve. The new work shows that the measurement made by a cosmic-mapping research satellite was wrong.

The astronomers studied the Pleiades, the famous "Seven Sisters" star cluster in the constellation Taurus, easily seen in the winter sky. The cluster includes hundreds of young, hot stars formed about 100 million years ago.

As a nearby example of such young clusters, the Pleiades have served as a key "cosmic laboratory" for refining scientists' understanding of how similar clusters form. In addition, astronomers have used the measured physical characteristics of Pleiades stars as a tool for estimating the distance to other, more distant, clusters.

Until the 1990s, the consensus was that the Pleiades are about 430 light-years from Earth. However, the European satellite Hipparcos, launched in 1989 to precisely measure the positions and distances of thousands of stars, produced a distance measurement of only about 390 light-years.

"That may not seem like a huge difference, but, in order to fit the physical characteristics of the Pleiades stars, it challenged our general understanding of how stars form and evolve," said Carl Melis, of the University of California, San Diego. "To fit the Hipparcos distance measurement, some astronomers even suggested that some type of new and unknown physics had to be at work in such young stars," he added.

To solve the problem, Melis and his colleagues used a global network of radio telescopes to make the most accurate possible distance measurement.

The network included the Very Long Baseline Array (VLBA), a system of 10 radio telescopes ranging from Hawaii to the Virgin Islands; the Robert C. Byrd Green Bank Telescope in West Virginia; the 1,000-foot-diameter William E. Gordon Telescope of the Arecibo Observatory in Puerto Rico; and the Effelsberg Radio Telescope in Germany.

"Using these telescopes working together, we had the equivalent of a telescope the size of the Earth," said Amy Miouduszewski, of the National Radio Astronomy Observatory (NRAO). "That gave us the ability to make extremely accurate position measurements -- the equivalent of measuring the thickness of a quarter in Los Angeles as seen from New York," she added.

The astronomers used this system to observe several Pleiades stars over about a year and a half to precisely measure the apparent shift in each star's position caused by the Earth's rotation around the Sun. Seen at opposite ends of the Earth's orbit, a star appears to move slightly against the backdrop of more-distant cosmic objects. Called parallax, the technique is the most accurate distance-measuring method astronomers have, and relies on simple trigonometry.

The result of their work is a distance to the Pleiades of 443 light-years, accurate, the astronomers said, to within one percent. This is the most accurate and precise measurement yet made of the Pleiades distance.

"This is a relief," Melis said, because the newly-measured distance is close enough to the pre-Hipparcos distance that the standard scientific models of star formation accurately represent the stars in the Pleiades.

"The question now is what happened to Hipparcos?" Melis said. Over four years of operation, the spacecraft measured distances to 118,000 stars. The cause of its error in measuring the distance to the Pleiades is unknown. Another spacecraft, Gaia, launched in December of 2013, will use similar technology to measure distances of about one billion stars.

"Radio-telescope systems such as the one we used for the Pleiades will provide a crucial cross-check to insure the accuracy of Gaia's measurements," said Mark Reid, of the Harvard-Smithsonian Center for Astrophysics.

Many ancient cultures, including Native Americans, used the Pleiades as a test of vision. The more Pleiades stars one can discern -- typically five to nine -- the better one's vision.

"Now we've used a system that provides modern astronomy's sharpest 'vision' to solve a longstanding scientific debate about the Pleiades themselves," said Melis.

Melis, Miouduszewski, and Reid worked with John Stauffer of the Spitzer Science Center, and Geoffrey Bower of the Academia Sinica Institute of Astronomy and Astrophysics. The scientists published their findings in the 29 August issue of the journal Science.

.


Related Links
National Radio Astronomy Observatory
Space Telescope News and Technology at Skynightly.com






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News





SPACE SCOPES
A "NIRSpec-tacular View" of NASA's Webb Telescope Instrument
Greenbelt MD (SPX) Aug 29, 2014
A NASA photographer recently captured a "NIRSpec-tacular" photo of an instrument that will fly aboard NASA's James Webb Space Telescope when it launches in 2018. Access into a clean room to get a close-up view of a complicated, high-value scientific instrument is carefully controlled, but NASA photographers get such exclusive entry all the time. Photographer Chris Gunn took this image of t ... read more


SPACE SCOPES
China Aims for the Moon, Plans to Bring Back Lunar Soil

Electric Sparks May Alter Evolution of Lunar Soil

China to test recoverable moon orbiter

China to send orbiter to moon and back

SPACE SCOPES
Opportunity Flash-Memory Reformat Planned

Memory Reformat Planned for Opportunity Mars Rover

Scientist uncovers red planet's climate history in unique meteorite

A Salty, Martian Meteorite Offers Clues to Habitability

SPACE SCOPES
Aurora Season Has Started

Russian, US Scientists to Prepare Astronauts for Extreme Situations in Space

Russia's Space Geckos Die Due to Technical Glitch Two Days Before Landing

US to Stop Using Soyuz Spacecraft, Invest in Domestic Private Space Industry

SPACE SCOPES
Same-beam VLBI Tech monitors Chang'E-3 movement on moon

China Sends Remote-Sensing Satellite into Orbit

More Tasks for China's Moon Mission

China's Circumlunar Spacecraft Unmasked

SPACE SCOPES
Science and Departure Preps for Station Crew

3-D Printer Could Turn Space Station into 'Machine Shop'

Russia May Continue ISS Work Beyond 2020

NASA Awaits Boeing's Completion of Soyuz Replacement

SPACE SCOPES
Sea Launch Takes Proactive Steps to Address Manifest Gap

SpaceX rocket explodes during test flight

Russian Cosmonauts Carry Out Science-Oriented Spacewalk Outside ISS

Optus 10 delivered to French Guiana for Ariane 5 Sept launch

SPACE SCOPES
Orion Rocks! Pebble-Size Particles May Jump-Start Planet Formation

Rotation of Planets Influences Habitability

Planet-like object may have spent its youth as hot as a star

Young binary star system may form planets with weird and wild orbits

SPACE SCOPES
Experiments explain why some liquids are 'fragile' and others are 'strong'

The fluorescent fingerprint of plastics

Atoms to Product: Aiming to Make Nanoscale Benefits Life-sized

Argonne scientists pioneer strategy for creating new materials




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.