World's Largest Radio Telescope Network Goes Live

The world's largest collection of radio telescopes is beingtied together for 24 hours starting today to observe more than two hundredenergetic galaxies known as quasars.

During those 24 hours, 35 telescopes on all seven continentswill observe 243 distant quasars in an effort to improve the precision of thereference frame scientists use to measure positions in the sky.

The quasars, galaxies withsupermassive black holes at their cores, are profuse emittersof radio waves, and also are so distant that, despite their actual motionsin space, they appear stationary as seen from Earth.

This lack of apparent motion makes them ideal celestiallandmarks for anchoring a grid system, similar to earthly latitude andlongitude, used to mark the positions of celestial objects.

In a technique called verylong baseline interferometry (VLBI), data from all the radio telescopeswill be combined to make them worktogether as a system capable of measuring celestial positions withextremely high precision.

The previous record for such an effort was a 23-telescopeobservation.

The International VLBI Service for Geodesy and Astrometry is coordinating the record-breaking effort.

At a meeting in Brazil last August, the InternationalAstronomical Union adopted a new reference frame that uses a set of 295 quasarsto define celestial positions that will be used starting on January 1.

Improving the celestial positional grid will allowastronomers to better pinpoint the locations and measure the motions of objectsin the sky. As astronomers increasingly study objects using multiple telescopesobserving at different wavelengths, such as visible light, radio and infrared,the improved positional grid will allow more accurate overlaying of thedifferent images.

This set of quasars also serves as a guiding post forEarth's GPS systems.

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