GONG: New Global Network Poised to Probe Inside the Sun
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A new globe-girdling network has just placed a stethoscope to the sun's natural heartbeats -- probing inside the sun to explore its hidden structure and dynamics with unprecedented clarity. Eleven years in the planning, the six stations built by GONG -- the Global Oscillation Network Group, funded by the National Science Foundation (NSF) -- were turned on October 5.
"We expect the GONG array to reveal much about the deep interior of our own star," said Hugh Van Horn, NSF astronomy director. "For the first time, we'll be able to test some basic theories about the structures and life histories of stars."
The $20 million GONG project is now listening non-stop as our nearest star oscillates, or rings like a bell, producing sound waves that repeat about every five minutes. The sun's sound waves are similar to earthquake waves used by geophysicists to explore the Earth's interior. Study of the sun's own pulsations, called helioseismology, will produce the most detailed picture of any star's interior.
"Despite the exquisite images we have of the sun's surface, we know almost nothing about its interior," explained John Leibacher, lead scientist on the project. "Now we can use GONG to peer into the solar interior from Earth. Then, we can use what we learn about the sun as a Rosetta stone to understand other stars in the rest of the universe. We'll also learn more about how the sun affects our own planet."
The tempestuous sun continuously produces millions of distinct but subtle sound waves. What causes the sun to "ring" this way -- a phenomenon discovered 25 years ago -- may now be known. Energetic explosions near the sun's surface are thought to set up vibrations that last for weeks or even months, propagating back and forth through the sun. This celestial ringing, like a Christmas bell concert given by a million musicians, is "heard" as 10 million different notes -- each one penetrating to a different depth and to a different latitude in the sun, and each with its own score to be decoded.
GONG's extremely sensitive detectors, able to measure velocity at one part in ten million, will reveal the temperature, chemical composition, and motions of different layers in the sun, from the surface to the very core. An analysis center at NSF's National Solar Observatory (NSO) in Tucson, Arizona will separate out each of the sun's 10 million "voices." NSO is part of the National Optical Astronomy Observatories, which are managed by the Association of Universities for Research in Astronomy and supported by NSF.
How stars evolve, how energy circulates within them, and how they rotate -- as well as how sunspots are born and affect the Earth: GONG's helioseismologists expect to bring insight to these and other mysteries.
With better than 93 percent coverage, the sun will rarely set on the GONG stations around the world -- at Big Bear Solar Observatory in California, Mauna Loa Observatory in Hawaii, Learmonth Solar Observatory in western Australia, Udaipur Solar Observatory in India, Observatorio del Teide in the Canary Islands, and Cerro Tololo Interamerican Observatory in Chile. "We are now looking forward to using GONG to probe the changing internal structure of the sun through an entire 11- year solar cycle of magnetic variation," said Leibacher. The first scientific results will be featured at the American Astronomical Society meeting in January, 1996 in San Antonio, Texas.
For a short video of the sun seen through the eyes of GONG, contact John Leibacher, National Solar Observatory, at: (520) 318-8305.
The National Science Foundation (NSF) is an independent federal agency that supports fundamental research and education across all fields of science and engineering. In fiscal year (FY) 2016, its budget is $7.5 billion. NSF funds reach all 50 states through grants to nearly 2,000 colleges, universities and other institutions. Each year, NSF receives more than 48,000 competitive proposals for funding and makes about 12,000 new funding awards. NSF also awards about $626 million in professional and service contracts yearly.
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