The search for secrets of newborn stars
ATOP MAUNA KEA, HAWAII — Astronomer Antony Schinckel drives his SUV up a final rise and into a dale just shy of this dormant volcano's 13,600-foot summit, the world capital of ground-based astronomy.
His pride and joy sprouts from the dale's floor: An apparently haphazard arrangement of eight antennas that look like satellite-TV dishes on steroids.
In fact, these antennas are linked and their arrangement carefully planned. This array is now subjecting some of the most hidden areas of the universe to the kind of scrutiny currently afforded only to astronomers who use optical and radio telescopes.
Known as the Submillimeter Array (SMA), this group of dishes is named for the tiny wavelengths of radiation it detects - a no man's land in the electromagnetic spectrum between the lowest infrared wavelengths and the highest radio wavelengths (roughly between 0.25 and 1.3 millimeters).
Through this window, Dr. Schinckel and his colleagues hope to gain access to some of the coldest, darkest, and youngest regions of the cosmos - and make those observations in unprecedented detail.
The way signals received by the antennas are combined and the wavelengths at which the array operates will allow scientists to pierce more deeply than ever through the dust and gas in the Milky Way that hides the birth of stars and solar systems. This will allow researchers to track such processes from their earliest stages.
The array, which can yield information about temperatures and pressures, is expected to help scientists unravel the complex chemistry hidden in molecular clouds that can spawn organic molecules, seen as the precursors of life. It also is expected to help shed light on processes inside galaxies currently blocked from view at optical and infrared wavelengths by gas and dust, or at distances so great that the expansion of the universe stretches their light from optical or ultraviolet wavelengths within the galaxy to submillimeter wavelengths on Earth.
Of four ground-based observatories designed exclusively for submillimeter operations, the SMA is the first dedicated to interferometry - a technique that turns several antennas into one super- antenna. The result substantially improves an observatory's ability to distinguish two tightly spaced cosmic objects or regions that a single dish or telescope might see as one oddly-shaped blob.
Peering into cold regions of dust and gas sounds boring, says Schinckel, operations director for the array, "but it's potentially so interesting because it's in areas that are initially cool" that stars and planets begin to form, whether in the universe's earliest epochs or in nearby galaxies. Cold and dark, he maintains, is "where the excitement is."
Beyond its immediate scientific importance, the new array holds symbolic importance for a once-obscure and still technically demanding field of astronomy, researchers say. In short, submillimeter astronomy has come of age. From humble beginnings with single-dish telescopes, research groups are now building large-scale ground arrays and sending submillimeter observatories into orbit.
"We're taking a quantum step" in exploring a relatively new band of wavelength for astronomers, says Schinckel. "Despite what we think we're going to be doing, in five years' time we may be doing something quite different - looking at exciting regimes and topics that we just don't know about today."
Dedicated last November, the SMA was built by the Smithsonian Astrophysical Observatories (SAO) with help from Taiwan's Academia Sinica Institute of Astronomy and Astrophysics. Astronomers at the observatory have started working on a few experiments and plan to fully utilize the array by year's end.
So far, their telescope has taken detailed images of a number of objects, including Mars and its atmosphere, says Paul Ho, an astronomer from the SAO offices in Cambridge, Mass.
In images, the Martian atmosphere stands out as a thin layer above the planet itself. The images yield information on the atmosphere's structure, composition, temperature, and pressure, says Dr. Ho.
"You can track these over time" from Earth to study climate and weather changes on Mars, he says, adding wryly, "You could do this every day, except we have other things we want to do."
The observatory also is planning tests with two other submillimeter observatories that share the summit here with the SMA, the Caltech and James Clerk Maxwell observatories. The tests would link their larger, single dishes to the SMA's interferometer, improving the resolution of images by another 30 to 40 percent. It also would significantly increase the system's sensitivity to fainter signals, allowing the entire array to peer further back in time or observe more subtle details in nearby objects.
Another target for SMA will be a star known as CW Leonis, some 500 light-years away.
In 2001, a smaller, orbiting submillimeter telescope discovered that the star was entering its final stage as a red giant. The star is surrounded by large amounts of water vapor. This was the first time water - a necessary component for life - had been detected in a planetary system outside our solar system.
The team, led by Gary Melnick at the Harvard- Smithsonian Center for Astrophysics, speculated that the vapor might have come from several hundred billion comets that were furiously boiling away as the star expanded. But the satellite could only detect the water vapor and yield an estimate of its amount. The SMA team hopes to train its dishes on the star to see if it can help solve the riddle of the water's source.
Compared with its radio, optical, and infrared counterparts, submillimeter astronomy has been a relatively new kid on the block. Its between-the-cracks wavelengths were too low for infrared detectors to pick up but too high for existing radio detectors - at least until the 1970s, recalls Thomas Phillips, director of Caltech's submillimeter observatory.
At that point, Bell Labs and IBM were locked in a race to build smaller, faster computers using superconductors - devices that, when chilled sufficiently, conduct electricity with no resistance.
Dr. Phillips says he was working at Bell Labs at the time, and while the computer effort proved futile, the superconducting devices he developed looked to be just the ticket for detecting submillimeter radiation. Descendants of that device are now being used at the SMA and at the Atacama Large Millimeter Array (ALMA), a much larger millimeter and submillimeter interferometer still under construction in Chile's Atacama Desert.
Water vapor in the atmosphere blocks incoming submillimeter radiation, so astronomers have searched for places that are high and dry to build full-scale observatories.
By the late '80s, Mauna Kea became home to two facilities, which stand like sentinels at the entrance to Submillimeter Valley: the CalTech Observatory, with a 10.4-meter dish, and the Maxwell Observatory, with a 15-meter dish.
Over the next few years, Phillips continues, these facilities and an airborne observatory run by NASA made several discoveries that awakened the astronomy community to the range of discoveries the fledgling submillimeter field could achieve.
One of the most stunning, he says, was the discovery of a region of intense star formation where the Hubble Space Telecope's deep-field survey, conducted at optical and ultraviolet wavelengths, had showed only empty space. The results, published in the journal Nature in 1998, "woke everybody up," Phillips says.
Using the Maxwell submillimeter telescope, a team of astronomers led by David Hughes, with the University of Edinburgh's Institute for Astronomy, found regions of intense star formation at greater distances than those appearing in optical or ultraviolet telescope surveys.
The new data yielded rates of star formation at those distances - and at a younger period in the universe's history - some five times as high as the other surveys showed.
Until Dr. Hughes and his colleagues had trained the observatory's dish on that region of space, its secrets had been shrouded in thick clouds of dust and gas.
Another one of the research goals at SMA is to return to that region to tease out details the Maxwell telescope couldn't resolve.