A Day in the Life of an Astronomer: Jonathan Grindlay '66

9:00 a.m.: The Park Circle bus stops at the corner of Pleasant Street on the Arlington-Belmont line. It is a bright morning. The bus is crowded as it grinds its way down the bill to Cambridge. Jonathan Grindlay '66 is already reviewing "preprints" of papers about .to, be published. The bus stops at the Harvard-Smithsonian Center for Astrophysics in Cambridge. "Josh" Grindlay gets off.

Grindlay's interest in astronomy and physics began in what now seems a primordial era. Sputnik was orbiting the earth when 13-year- old Grindlay was sending up experimental rockets, fueled by a homemade propellant, in an abandoned quarry in Rochester, Minn.

Then came Dartmouth. National Science Fair honorees with demonstrated aptitude in physics usually go to Cal Tech or M.I.T. But Grindlay likes to ski: a rural environment and a solid academic reputation were enough to entice him to Hanover.

After quickly completing his major require- ments, Grindlay delved in his senior year into advanced studies in plasma physics (the study of gases at high temperatures). The sense of adventure nurtured in that last year in Hanover led to a year studying physics and philosophy on a Reynolds Scholarship at the University of Munich.

After his year in Munich, he had to decide whether to pursue a traditional physics pro- gram or commit himself to his interest in space. Until that point he had had no formal educa- tion in the physics of the stars, but, he says now, "To me the choice was obvious. Astro- physics, as a major branch of physics, was charged with opportunities. There were really only a handful of serious researchers, relatively speaking." So followed four years at Harvard to earn a Ph.D. in astrophysics, then another three years of research at Harvard on. a presti- gious junior fellowship.

9:30 a.m.: The first cup of coffee is three-quartersgone. Grindlay is engrossed in writing additionalsections of a paper entitled "The Central X-raySource in 55433-" Recent observations suggest thissource might be a black hole.

In 1967, the discovery of pulsars col- lapsed. stellar objects or neutron stars had started a whole new wave in astronomy x-ray astronomy. Grindlay's interest in the field had evolved from his early graduate work in devel- oping new methods for detecting very high- energy gamma rays at Whipple Observatory in Arizona. Later, from 1972 to 1974, he carried out observations in Australia that resulted in the discovery of the first extragalactic source of these rays. Then in 1974, Grindlay was invited to join a new group at the Smithsonian Astro- physical Observatory (S. A.0.) in Cambridge to study stellar x-ray sources.

The scientific process of hypothesis, experi- mentation, and observation is carried out in astronomy on a grand scale. The discovery of x- rays in space was made from an early sub-orbital sounding rocket in 1962. In 1970 the first satellite devoted entirely to x-ray astronomy was put in orbit, and in 1978 the Einstein Observatory was launched. This was a mile- stone in astronomical engineering, allowing a thousand-fold increase in sensitivity over pre- vious cosmic x-ray detectors.

Grindlay's work as a project scientist on the S.A.O. task force using these space telescopes led to his discovery in late 1975 of a new phe- nomenon in space "x-ray bursts." These flashes of x-ray brilliance, achieving a million times the sun's total brightness, in the space of one second and fading away over the next ten, were totally unprecedented. But observing ga- lactic phenomena is one thing, and developing theoretical constructs to explain them is an- other. Grindlay advanced his own theory that the origin of these bursts was black holes.

Black holes, the end-point of stellar evolu- tion, are incredibly dense objects in space. They can result when a star expells its outer atmosphere and the gravitational pull of the exposed core causes the star's remnants to liter- ally collapse on themselves. However, black holes seem to be relatively uncommon. Only one or two concrete examples have been identi- fied in our entire galaxy. Grindlay's theory re- lating x-ray bursts to black holes would dictate a much greater number of these objects than previously thought possible.

10:30 a.m.: It's time to go downstairs to a com-puter programmer's office. Development of more so-phisticated programs for analyzing data generated bythe Einstein Observatory Continues. Data originallygathered over four years ago is still being analyzedand interpreted for the first time.

The impact of new technologies for observ- ing the heavens has pushed new analytical tech- niques as well. Optical observation gave way to photographic plates. Photography evolved into "digital" astronomy and computer printouts. Today many astronomers don't even look up, with observing at all wave-lengths (including the traditional optical) done from a computer terminal.

11:00 a.m.: The conference on analyzing datafrom the past gives way to work on future experiments. With project engineers and his gradtiate students, Grindlay gives his attention to designing newways to detect high-energy cosmic x-rays from highaltitude balloons. This experiment requires buildinga "mirrorless" telescope, something new, at least onthis scale. If successful, it will go up in a spacishuttle. Two years ago, a similar proposal for aN.A.S.A. satellite was rejected in favor of a mortconventional experiment.

Pushing the technological frontier forward involves risk. Theoretical formulations requiring years of research may prove wrong. But Grindlay says, "You have to try or else you stagnate." He has experienced these risks. His "black hole" model to explain x-ray bursts was eventually disproved partly by precise new x-ray studies he carried out himself.

12:00 noon: Time to peruse the morning mail,then take a "brown bag" to the conference room andlisten to that day's lunchtime talk, "The LymanAlpha Forest in Quasar Spectra."

Grindlay's commitment to his field is obvious, from, among other benchmarks, his academic promotions: in 1976 he was made an assistant professor and in 1981 he was appointed a professor of astronomy.

1:30 p.m.: An undergraduate research assistantfinds Grindlay, and together they work on "finding"charts, photographic aids for optical observation.

For Grindlay, the bridge beween digital printouts and optical observation is important: "You have to keep your 'feel' for the stars."

2:00 p.m.: A graduate student reviews withGrindlay his progress on improving a computer mossimulating the production of x-rays in the centers ofactive galaxies.

Though the theory that x-ray bursts might be produced by black holes has been disproved, it is still a problem to explain the sources ofxrays from galactic nuclei. Many astrophysicists feel, that these x-ray sources really are black holes. Grindlay's pursuit of an answer to this phenomenon goes on.

4:00 p.m.: A brief respite is provided by tlxhumdrum of opening the afternoon mail; returningphone calls, and doing some more work on his paperThen Grindlay returns to the laboratory to run mmtests on the new high-energy x-ray detector.

The thrust of astronomical investigation is toward experiments at relatively unexplored wavelengths to find the upper limit. Thus, a means for detecting the higher energy levels at increasing resolution and sensitivity is necessary. The Einstein Observatory, a marvel at the time, could only detect energies at half the leve which will be possible with the Advanced X ray Astrophysics Facility, to be launched m 1990. The mirrorless telescope Grindlay 11 working on for the high-altitude balloon ex periment will have the capability of detecting (though with lower sensitivity) cosmic soutc- emissions 50 times still more energetic.

6:00 p.m.: The Park Circle bus winds its way out of Cambridge to Arlington. An early Springsunset provides enough light for a last glimpsejscientific "preprints" read that morning. Grindlay is home, and the stars are just coming out.