The Big Picture, continued
 |
Two
years later,
speaking from his office inside Penn’s David Rittenhouse Laboratory, Koerner
recalls how his co-investigator called him in with bad news: A team from
the Harvard-Smithsonian Center for Astrophysics and the University of
Florida had observed the same disk two days later, from Chile’s Cerro
Tololo Observatory. Although they had less data, the other scientists
planned to publish their findings in Nature and promptly hold a
press conference. Astronomers may have stars in their eyes, but theirs
is as cutthroat a field as any. Deliberations ensued, and the two groups
ultimately made a joint announcement. Widely reported, the discovery was
pronounced “what appears to be the clearest evidence yet of a budding
solar system around a nearby star.” (In this case, nearby means
1320 trillion miles away.) “In a sense,” Koerner said at the time, “we’ve
already peeked into the stellar family album and seen baby pictures and
middle-aged photos. With HR 4796, we’re seeing a picture of a young adult
star starting its own family of planets.”
While
such “big discovery moments” occur infrequently, Koerner’s work, ranging
from the study of circumstellar disks, which appear to be construction
zones for planets outside our solar system, to brown dwarfs, which occupy
a mysterious categorical niche between planets and stars, puts him on
the frontiers of planetary-origins research.
“I
would characterize his work in the big picture as really trying to find
out in great detail our place in the universe,” says Dr. Anneila Sargent,
professor of
astronomy at Caltech and Koerner’s former Ph.D. thesis adviser. “Dave
looks at not just, are there other stars out there right now with planets,
but how did these planets come about and can we see evidence of their
physical and chemical evolution that tells us how solar systems came about?
If you can see the beginning of these various chemicals [around] stars
that are much younger looking, the way our solar system looked four and
a half billion years ago,” Sargent says, “then we can get some idea of
how we came about and how common or rare we are likely to
be.”
Sargent,
director of the Owens Valley Radio Observatory in Bishop, California,
and president of the American Astronomical Society, describes discoveries
such as HR 4796 as “pioneering.” Over the past decade, astronomers have
detected more than 50 planets outside our solar system—mostly by measuring
the minute gravitational wobble of a star that indicates a massive object
is orbiting it. But the instruments don’t yet exist to spot a planet of
any size directly. It’s easier to observe the dust and gas swirling
around a young star that will eventually become a system of extrasolar
planets than it is to detect a planet itself—swamped by the glare, at
least a billion times brighter, of the star it orbits. According to Sargent,
“The evidence for what we see in individual [planet construction] systems
is very direct. What you see is what you get.” The dust spread out in
circumstellar disks emits strongly at infrared wavelengths which scientists
can view. In contrast, the light of a star observed in the infrared
is relatively dim.
Scientists
are now developing Earth- and space-based telescopes that will, over the
next decade, refine techniques such as interferometry and coronagraphy
to search directly for other planets. Says Sargent, “David is kind of
down in the foundations of building the ‘skyscraper’ that’s going to come
up and look for all of these.”
There’s
an old joke
among those who study stars for a living: You’re riding on a plane and
the person in the next seat asks your occupation. If you want to chat
with them, you say you’re an astronomer. If you want to be left alone,
you say you’re an astrophysicist. Fortunately for this article, Koerner—accessible,
funny and enthusiastic—puts himself in the first category. With his goatee,
a faint twinkle of an earring in his left ear and almost rectangular glasses,
he’s a youthful looking 45-year-old. But he’s older than the typical assistant
professor, having gotten a late start in his field due to a 10-year detour
from academics.
Sargent,
his former adviser, found his age to be an asset. “I think he was much
more mature in his attitude and really understood what he actually wanted
to do in life [compared to] younger people who came into my office.” Not
only that, she adds with a laugh, but Koerner “is not some nerdy person.
He’s a bon vivant.
“People
envied me having Dave as a student,” Sargent says. “Let’s face it, we
have to go to isolated areas where there are telescopes with the people
we are working with. It’s important to pick and choose your collaborators.
You can’t pick your students to the same degree, but having students like
Dave is a pleasure, because there’s lots of entertaining conversation
and wonderful music.” (To keep the momentum going on tedious nights, most
observatories are equipped with stereos, and Koerner, a trained classical
pianist, was always bringing in new and unusual CDs to play for his colleagues.)
“The science gets done,” Sargent says, “and the overwhelming ambiance
is just plain pleasant.”
Dr.
Eric Jensen, an assistant professor of astronomy at Swarthmore College
and a colleague of Koerner, says, “I love working with Dave. Not only
is he an excellent scientist who has lots of good ideas and is very knowledgeable,
but he gets very excited about this stuff. When Dave and I sit down and
have a conversation about what we’re going to work on, he gets me excited
about doing it all over again.”
Koerner
uses some of the largest observatories in the world, but owns no telescope
of his own. He has, however, occasionally gone out to amateur telescope
nights, where he doesn’t let on that he is a professional astronomer.
“They have all the latest telescopes and will talk to you ad nauseum about
the details of their eyepieces,” he says. “They’ll go, ‘Wow! I have a
24-inch, you know, which is really quite large.’ Aperture envy is a big
thing. Size matters. I’ve always wanted to come in with a T-shirt that
says, ‘My other telescope is a Keck.’ Or say something like, ‘Well, you
know, I was looking through my 394-inch the other night … ’”
It’s
not fancy lenses or equipment which excite Koerner, but the Big Questions
stirred when he takes out a pair of binoculars on a dark night and trains
them on the Milky Way: What is the place of life in the universe? Are
we unique? A fluke? Or does the universe easily make life and do so everywhere?
On weekend nights, when he has found himself working alone, he has spent
“hair-raising” moments watching the stars from the Owens Valley observatory,
which is desolately tucked in the California desert between two mountain
ranges.
Interestingly,
Koerner says, many astronomers are musicians like himself. “I think the
desire to be in the musical realm is not totally different from the desire
to immerse yourself in thought about the cosmos. In some sense, they’re
both imaginary realms,” he contends, “because you don’t really go to the
circumstellar disk and touch it and feel it; it’s based on evidence, but
it still requires a great deal of your own imagination to interpret that
evidence.”
Nov/Dec Contents | Gazette
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