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By Linda Copman and Dr. Fred Chaffee
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| Image: Artist’s rendering of a gamma-ray
burst. Original images courtesy of NASA. |
Shri Kulkarni keeps a six-foot tall pencil in his office, inscribed
with the words “think big.” He recently showed the pencil to
the new president of Caltech, reminding him that the school
has a proud tradition of allowing no “mean” projects, meaning
no mediocre efforts will be tolerated.
Kulkarni’s most celebrated discovery came in 1998 when, using
the Keck I Telescope, he and his colleagues were able to show
decisively that the mysterious events known as gamma-ray bursts
were located not in our galaxy but literally at the edges of
our universe. Gamma-ray bursts had been detected by military
surveillance satellites looking for illegal nuclear tests as
long ago as the early 1970s. The satellites detected daily
brief flashes of this very powerful radiation, not emanating
from the earth’s surface, but from somewhere in deep space.
For 25 years the nature of gamma-ray bursts, or GRBs, remained
a mystery. Astronomers postulated that GRBs might be as close
as within our own solar system, or at the farthest reaches
of the universe, or anywhere in between. We had no way of knowing.
Kulkarni combines the methodical approach of a seasoned scientist
with the flash of insight needed to make new discoveries. The
way to his big discovery was paved by, of all things, index
cards of supernovae (exploding stars) with which he had been
intrigued for many years. He took advantage of a sabbatical
in Japan to gain an important insight. Here’s what happened:
“In 1991 I had a box of index cards with data
about 300 supernovae. I used my sabbatical to update my
index card collection. I was very proud of it; it contained
all of the known remnants at the time, with notes, arranged
by location in the galaxy. The cards were arranged by the
angle of the supernovae with respect to the center of our
galaxy, the Milky Way. I was correlating things I knew
about supernovae remnants, when I discovered that they
had the same location as a class of gamma-ray transients
known as soft gamma-ray repeaters. My conclusion was that
the supernovae and the gamma rays occurred together. I
made the simple supposition that one was causing the other.
This was my detective work - I made the conclusion from
my index cards, by correlating two databases.”
Kulkarni's realization of the connection between supernovae
and gamma-ray transients left him poised for discovery when
a GRB was reported, somewhere in deep space, on March 26, 1998.
In the days and months that followed, Kulkarni and his graduate
student Joshua Bloom (now a faculty member in the astronomy
department at the University of California at Berkeley) began
observations of the event with the Keck I Telescope, using
its most powerful spectrograph, the Low Resolution Imaging
Spectrometer (LRIS).
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| Images: A 1998 supernova (SN 1998bw,
left) and the corresponding gamma-ray burst on April
25, 1998 (GRB 980425, right). Courtesy of Dr. Kulkarni. |
Their efforts paid off when they found a telltale signature
for an additional emission from the same location as the gamma-ray
burst, but peaking a month after the GRB event. In a Nature
article (Bloom et al. 401, 453-456, 1999) Kulkarni and Bloom
suggested that all long duration gamma-ray bursts have associated
supernovae. In other words, long duration gamma-ray bursts
arise from the death of massive stars. The paper was very well
received and over time this connection has been firmly established.
Kulkarni wrote several more papers on GRBs over the next ten
years, becoming a supreme authority on this phenomenon.
Kulkarni’s 1998 discovery has spawned an entirely new field
of astrophysics — the study of GRBs. Today about 100 of the
world’s astronomers regularly attend conferences devoted entirely
to this exotic phenomenon. In the years since their discovery,
Kulkarni and his graduate students have continued to study
long duration GRBs (of which their 1998 GRB is the prototype),
and much has been gleaned.
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| Image: This image shows a popular model
for the long duration GRBs, resulting from the collapse
of a massive young star. Courtesy of Dr. Kulkarni. |
Long
duration gamma-ray bursts happen when a massive young star
has burned through the hydrogen in its core. As the pressure
generated by the reactions at the star’s core diminishes, the
pull of gravity forces the star’s matter to collapse into the
core. For very massive stars, the force of this collapse is
powerful enough to create a new black hole. The ensuing explosion
creates an enormous burst of energy, which scientists call
a long duration gamma-ray burst. The afterglow from these GRBs
can last for months, and the beam of light they send out into
the universe illuminates everything in its path. Thus, long
duration GRBs provide an incredible light source astronomers
can use to study the early universe.
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| Image: Artist's rendition of a gamma-ray
burst. Image by Dana Berry, Skyworks & SEW. |
“GRBs have given us some of the most detailed
spectra of the galaxies, and they are the most sensitive
probes we have to study galaxies where stars are being
born. Another thing about long duration GRBs is that the ‘afterglow’ or
embers of the star’s explosion remain for a long time.
We study these embers. We studied the embers from one GRB
for a year.”
And then, about three years ago, Kulkarni decided it was time
to move on to a new arena. Ten years was the longest he had
ever spent on one topic, and he felt he needed a new challenge.
“How do you decide what to do next? I think
most people do not take a critical view. It is very easy
to keep doing what you’re doing, especially when the science
questions are interesting. Yet I believe it is important
to assess your work and see if it is worth continuing.
You can become a guru of the field, and maybe this is comfortable.
It is a judgment call to try to look at your life differently.
First you should figure out who you are. Are you a steady
person who works by accumulating knowledge? Knowledge,
after all, requires this steady accumulation. You might
be a hedgehog, who is very good at one thing, or you might
be a fox, who knows many things, perhaps not as well. My
life has been pleasantly full because of the many discoveries
I have made. By throwing myself into a new area, there
is an opportunity to see things differently. No more than
a quarter of astronomers take this approach.”
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| Image: One of Kulkarni’s favorite cartoons. |
Kulkarni’s fox-like approach has paid off for him and for the
field of astronomy. His groundbreaking discoveries have revolutionized
our understanding of the most luminous objects in the universe,
GRBs, and the most common, brown dwarfs.
Kulkarni challenges the individuals and foundations who fund
astronomical research to be willing to take a chance on daring
new ideas. “Society is very slow to fund innovation,” says
Kulkarni. Most foundations are looking for a guaranteed return
on their investment, but it may be time for a paradigm shift,
Kulkarni explains. Funding daring new projects like the Next
Generation Adaptive Optics (NGAO) system at Keck Observatory
can make all the difference in advancing scientific discovery.
“NGAO will allow astronomers to see anywhere
in the sky with superb resolution, most all of the time.
This is a vast improvement over the current limitations
we have on where we can observe. So NGAO will radically
shift the current paradigm. There is risk, certainly, but
there is great satisfaction to be gained from helping to
fund something new, something which could revolutionize
astronomy.”
Kulkarni is a key spokesperson for the field of astronomy.
In fact, he has long wished for the opportunity to appear on
the Jay Leno Show, to prove that
science can be entertaining, nay, even fun. He wishes to dispel
the myth that astronomers dress in white lab coats and engage
in secretive and sinister pursuits. Stay tuned for Shri Kulkarni
on the Jay Leno Show…
Learn more about Kulkarni’s Jay Leno dream in this short
video clip  (requires Flash 8 player). 
Click here to return to the main page. |
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