Sunday, June 05, 2011

Watching Our Favorite Star

"The problem is with the sun."
"The sun? What is it?"
"A big ball of gas at the center of our solar system, but that isn't important right now."
--Airplane 2: The Sequel

Most of us have general notions about the star at the center of our solar system: bright, big (compared to Earth, average or small compared to a lot of other stars), yellow, type G, 4.6 billion years old (but wearing it well), warm enough to allow liquid water 93 million miles out, boring.

So why should we be concerned about it in Huntsville, Alabama, aside from the fact that we've had temperatures in the upper 90s for the last week? Well, the latest telescope for sun watching is being built for an observatory at Haleakala, a mountain in Maui, Hawai'i. The administrative and research offices for this new telescope need to be attached to a research university, and the competition is down to Boulder, Colorado, and Huntsville. The team here in Huntsville includes the National Space Science and Technology Center (NSSTC) and the University of Alabama-Huntsville, and they gave a public talk on Saturday about the Haleakala Advanced Technology Solar Telescope (ATST--yep, another acronym). The talk was sponsored by my friends at Huntsville Space Professionals, who hosted the space career fair at ISDC.

Dr. John Horack, head of UAH's research office, gave some introductory remarks about ATST, explaining the importance of attaching "the premier ground-based solar observatory to the premier space-based observatories"--specifically, the Japanese probe Hinode, the Solar Dynamics Observatory, and the Marshall Space Flight Center-based Solar Physics group, which had a hand in developing the big X-shaped solar telescope in Skylab back in the 1970s.

The bulk of the talk was given by Mr. David Dooling, who is also a member of the Huntsville pitch team. He provided some eye-opening pictures and thoughts about why we should be concerned about our allegedly "boring" stellar neighbor.

Let's start with what the sun is: a naturally occurring nuclear bomb, converting billions of tons of hydrogen into helium through nuclear fusion and generating radiation in nearly every wavelength. This bomb also has a very intense magnetic field, which twists around its axis of rotation and interacts with its charged outer reaches in cells, loops, and whorls, "as if the sun was covered with tens of millions of lava lamps," as Dooling put it. Sometimes those loops of magnetic force, many times the size of Earth itself, burst forth from the sun's surface as fiery arcs called prominences or escape the sun's gravity entirely and blast forth into the solar system as solar flares.

Solar "weather" events can be deadly to astronauts outside the Earth's magnetosphere, as they consist of highly charged particles. One of the largest solar flares ever recorded occurred between Apollo 16 and Apollo 17; had it occurred while our astronauts were on the moon, it is likely that the astronauts would of died of radiation sickness.

The sun can't just create havoc in space--it can do so here on Earth. In the 19th century, a solar event overloaded what was then the world telegraph network. During World War II, the German fleet was able to escape the British fleet in broad daylight, in part because a geomagnetic storm blinded British radar. A massive blackout in Quebec in 1989 was caused by solar activity, also damaging global positioning satellites in the process. For such a "quiet" or "boring" star, why does our sun have such violent tendencies? How are those tendencies created, and when are they likely to cause damage? These are the sorts of mysteries the new 4-meter telescope at Haleakala will attempt to unravel.

The Haleakala telescope is being designed to observe the sun in wavelengths ranging from near-ultraviolet to optical to far-infrared. It is being built and deployed on the ground because launching a 4-meter telescope into space is cost-prohibitive. Plus, thanks to adaptive optics developed by the Strategic Defense Initiative (SDI, formerly known as the "Star Wars" program), Earth-based telescopes can now account for distortions in the atmosphere, giving the ATST a clear view of the sun without needing to go into space. It will concentrate its studies on the 630.2 and 430 nanometer wavelengths, as these will provide the best views of the sun's magnetic field activities as well as provide high-contrast images of the sun's bright surface, enabling scientists on Earth to see the details of the sun in action.

How does a telescope this big work? Most people's personal experience with telescopes are with the optical telescopes one can buy at a science-themed hobby shop, where one looks right down the barrel toward the objects in question. Given that it's a bad idea to stare at the sun with the naked eye, it's an even worse idea to gaze up close at the sun. Like most modern astronomical telescopes, the ATST is a reflecting telescope, capturing light from a 4-meter opening in a rotating/elevating building, the primary mirror reflects it to another mirror, and then several others before it is broken up by a series of prisms and filters. The images of the sun are then directed into several different instruments, each looking for specific aspects of the sun's behavior in specific wavelengths. The instruments for ATST are still in development, and are expected to be finished in five years, just around the time the building itself is completed.

What all goes into building such a complex piece of equipment? The ATST has a budget ceiling of $298 million, $145 of that paid out of the "stimulus" bill, the rest to come through regular National Science Foundation funding. It's not going to be an easy project. The Hawai'ians are concerned about the ATST's location on a sacred mountain. It's also on literally shaky ground because Hawai'i lies on a fault line and is subject to regular earthquakes. The heat generated by all that reflected light of the telescope can create difficult heat management issues inside and outside the observatory, where temperatures must be kept constant within 1 degree. And at the end of its 50-year life, ATST is to be dismantled as part of its environmental remediation plans. It is not an easy project, and development work will no doubt continue throughout the mission.

And Huntsville is in the running to be the administrative and research center for the project. I'm cheering on the home team, of course, but I'm looking forward to the outcome of ATST's research, regardless. If you had a bomb in your back yard, wouldn't you want to know what makes it tick?

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