Dr. Dale Gary “tunes in” to the sun
The Owens Valley Radio Observatory (OVRO) and Cerro Coso Community College held the second of their 2012 “Explore Your Universe” Fall Lecture Series, on Wednesday. Dr. Dale E. Gary from the New Jersey Institute of Technology (NJIT) had attendees “Tuning in to the Sun.”
The Sun’s flare and sunspot activity are increasing as we near the 10-year, cyclical 2013 solar maximum. Not unlike his geologist counterparts, who are trying to predict earthquakes, Gary’s objective is to track the Sun’s activity, which he said is to “better understand and predict solar activity, and its effects on the Earth.” To that end, the NJIT and ORVO staff are building a next-generation radio telescope, the Expanded Owens Valley Solar Array (EOVSA).
It’s currently undergoing what Gary quipped was a “facelift,” upgrading the 50-year old antenna complex with new wiring, controllers, computers and processors, receptors and the like. When finished, the two main 27-meter dishes will serve as calibrators for the 13 smaller 2-meter dishes, which Gary said would allow a “full snapshot of the Sun’s entire disc area.”
Originally from Flint, Mich., Gary is no stranger to the Owens Valley, having spent more than 30 years doing research here. He became interested in Astronomy at age 14. After obtaining a B.S. in Physics from the University of Michigan, he earned a Ph.D. in Astrogeophysics from the University of Colorado, and was a research associate in Astrophysics at Caltech before joining the NJIT faculty in 1997, where he is now a Distinguished Professor in Physics. Currently he serves as director of the Owens Valley Solar Array.
His research has yielded much knowledge as to how solar radio bursts can disrupt cellular telephone signals, and recently was part of the discovery that such bursts can also cause failures in Global Positioning System (GPS) receivers.
“The Sun is a very complicated system, and is constantly varying,” he noted. Gary, however, kept his lecture focused on the Sun’s surface and atmosphere, mostly avoiding the basic mechanics of how it operates from inside.
When completed, the EOVSA will be able to take vastly expanded multi-wavelength observations of the Sun, to a detail and resolution far exceeding what is currently available. Of particular interest: sunspots, which he humorously pointed out is actually a technical term.
See Spot’s magnetic field
According to Gary, examinations of the Sun show it really is brighter at its center, and darker at the edges. “It’s not an optical illusion. We’re actually seeing deeper into the Sun when we look at its center,” he explained. At its center, Gary said Sun is about 10,000°F or about 6,000°K (Kelvin), and at the surface, sunspots are actually dome-shaped regions that are somewhat cooler, where their magnetic fields are strong enough to inhibit the heat flow.
Remember in your science class when you poured metal filings on a sheet of paper, and then put magnets under them? The formation of the filings showed the magnetic field of the magnets, and how they are polarized. Sunspots are basically just big magnets, and create loops of plasma similar to the metal filings. All that heat has to go somewhere, and by looking at the non-visible spectrum Gary said they are able see areas around the sunspots that are much hotter than the Sun’s core temperature. Some of those regions can reach as high as 2,000,000°K, or about 3,600,000°F. That’s hot!
Seasons in the Sun
The Sun also has cycles, going through activity changes every decade or so. In 2008, it reached its last solar minimum of diminished sunspot activity. In 2013 it’s set for another solar maximum. This one, Gary suggested, is likely to be different than most cycles. “We’ve seen fewer sunspots in the past five years, and the intervals between them have been getting longer,” he said. Gary expects this next maximum to be weak, and perhaps longer lasting.
Space “weather,” which can be followed on the SpaceWeather.com site edited by Bishop astronomer Dr. Tony Phillips, has an impact on the Earth, he said, affecting everything from spacecraft, solar cells and radio signals to cell phone towers and power grids, and thus, the importance of radio telescopes.
Radio imaging helps filter out so much of the vast amount of energy given off across a broad spectrum of wavelengths, especially the visible spectrum. “It allows us to separate the magnetic signals from the non-magnetic ones and look at the solar cycle and what it does to our atmosphere and ionosphere,” Gary said, adding that includes visually stunning phenomena such as auroras, which are formed in part from plasma eruptions from the Sun, carried past the Earth on what’s known as the solar wind.
Other telescopes conduct similar studies, including the Nobeyama Array in Japan, the Siberian Array in Russia, the National Radio Astronomy Observatory’s “Very Large Array” in New Mexico (which has been seen in many movies) and another under construction in China. The EOVSA will be able to make observations on much lower frequencies, see higher into the Sun’s atmosphere and yield more surface detail than ever before.
Where previous arrays were capable of one image on one frequency, or at most a handful, the EOVSA’s technology will allow images on 500 frequencies … simultaneously! EOVSA is expected to be online in October 2013, just in time for the solar maximum. Data from the first 3 antennas is expected in January.
The sun gives off a lot of heat, but does it contribute to the much-debated concept of climate change? Gary stopped short of entering into that discussion. “The Sun might be associated with our climate, but we’re not really sure exactly how,” he acknowledged. He did cite one period, similar to the current low solar activity cycle, which might have been one of the causes of the “Little Ice Age” between the 16th and 19th centuries. Think the freezing in the hit disaster movie “The Day After Tomorrow” was simply the result of overactive Hollywood imaginations? Perhaps it wasn’t.
During one of the LIA’s lowest solar minimums, winters were particularly harsh. Between 1794-1795, the French army marched on the frozen rivers of the Netherlands, while the Dutch fleet was stuck in the ice in Den Helder Harbor. In the winter of 1780, New York Harbor froze, allowing people to walk from Manhattan to Staten Island. That same year, the ice surrounding Iceland extended for miles in every direction, closing harbors to shipping. And off and on between 1607 and 1814, folks could skate on the frozen River Thames in London, an event that hasn’t happened since.
“The EOVSA gives us an opportunity to observe what could be major changes in the Sun, and upgrade our knowledge of flares, solar activity and how these might impact our climate,” he summarized.
OVRO lectures feature talks by prominent astronomers from OVRO and partner institutions, start at 7 p.m. and are free. The next lecture is on “Super Massive Black Holes,” with Tony Readhead from CalTech, scheduled for Nov. 9 at Bishop Union High School. For info and the complete schedule, call OVRO at 760.938.6015 or visit www.ovro.caltech.edu.