A Universe Apart
Astronomy Professor Adrienne Cool produced this detailed
image of star cluster NGC 6397, a dense region of stars on
the edge of the Milky Way in which Cool discovered a
surprising abundance of binary stars with helium white
dwarfs, dead stars commonly made of carbon. Photo by
NASA and the Hubble Heritage Team (STSci/AURA).
The race is on.
Around the world, astronomers are gearing up for the final stretch in the hunt for extrasolar planets: to find the first Earth-like planet amenable to life. Associate Professor of Astronomy Debra Fischer (M.S., '90), one of the world's most prolific planet finders, believes she's found a shortcut.
"The Swiss team, which has always been our rival, is laughing at me right now," she says good-naturedly. "They think I'm mildly eccentric and amusing."
Fischer explains. "Planet-finding has always been a numbers game. You look at lots and lots of stars and find planets around a few percent of them. And then other astronomers confirm them independently. So what am I doing? I'm pouring all my telescope time into two stars that have already been looked at! The stars don't have any big planets, so everybody's moved on. Honestly, it's a real long shot."
Maybe. But SF State is known for encouraging intellectual freedom.
Just ask Fischer's mentor, Geoff Marcy, who as a young SF State astronomy professor spent years perfecting the Doppler effect, a now-standard model for detecting extrasolar planets. In 1996, Marcy and planet-rustling alum Paul Butler (B.S., '85; M.S., '87) became the first Americans to discover planets outside the solar system.
"At conventional research institutions, faculty and students often shy away from risk to avoid failure," says Marcy, now a professor at UC Berkeley and the reigning king of planet hunting. "At SF State, you aren't under pressure to make a great discovery every month, so you can do risky research that might not succeed at first."
These distinctions have attracted a growing cluster of star faculty, making the Department of Physics and Astronomy a down-to-earth center for stellar astronomy.
A Shifting Spectrum
Sitting in her fourth-floor office, backlit by noon sun filtering through tall windows, Fischer discusses the department's latest hire, astrophysicist Andisheh Mahdavi. An expert in dark matter -- the mysterious, invisible glue that holds the universe together -- Mahdavi extends the department's research spectrum to one of the final frontiers of space: our cosmic origins.
"It's really amazing," says Fischer, whose affable, self-effacing manner belies a research reputation so lauded she is a regular consultant to NASA. "With Andi here, we're now pressed up against the same theoretical boundaries as others in trying to understand the very early universe."
Fischer's admiration is genuine, and in the world of high-stakes scientific research, collegiality is often in short supply. This indelible quality holds the department together and is one of the reasons Mahdavi -- who made world headlines last year when he shed new light on dark matter -- joined SF State this fall as assistant professor.
As a ribbon of students streams past his office, which is situated along the department's main artery, Mahdavi chuckles with what seems real surprise. "It's like a family here. Everybody gets along really well. And that's incredibly hard to find in larger departments."
The term family is unusually fitting in describing this brain trust. In descending order of tenure, Adrienne Cool, Ron Marzke, Joe Barranco, and now Mahdavi all trained at Harvard; and while Cool and Marzke pursued their doctorates together, Cool was also mentoring an undergraduate Barranco.
And what of their scientific capabilities?
"We're now covering all the bases in astronomy," explains Fischer, who rejoined her alma mater in 2003 after spending several years as a research astronomer at the University of California, Berkeley.
Warming to the topic, she scoots her chair back -- an enthusiastic professor about to make a point.
"Imagine a montage of images that captures this," she says, her hands framing the empty space before her. As she talks, her hands work outward, painting our solar system onto an unseen canvas. She adds adjacent stars and star clusters, and the hundreds of extrasolar planets she's helped discover around stars in the Milky Way; she moves on to our spiral galaxy itself, and more galaxies beyond, then clusters of galaxies -- each filled with billions and billions of stars, until her arms are spread wide in a gesture meant to convey the entire cosmos.
And for a brief moment, in a small pocket of air molecules, Fischer brings a miniature universe to life.
Starting With Stars
On the galaxy's fringes, dense aggregates of stars -- called globular clusters -- swarm like fireflies on a summer night. Using the world's most powerful telescopes currently in orbit -- Hubble and Chandra -- Professor Adrienne Cool scours these bustling clusters for pairs of stars, called binaries, that twirl about each other in a close-knit gravitational waltz that lasts billions of years.
Current theories suggest that as binary stars careen around the cluster's center, they prevent black holes from forming.
"If clusters only had single stars, their centers would eventually collapse," says Cool, who studies the dynamics of star collisions.
As heavy stars slow down, they sink to the cluster's center, explains Cool, eventually causing it to collapse and create a black hole. Binary stars, whose mass keeps them toward center, whizz about, giving slow-moving stars a gravitational kick outward.
"They're like egg-beaters," says Cool, who identifies binaries in major star clusters like Omega Centauri by measuring their spectral colors. "They keep things stirred up, which prevents -- or at least delays -- the collapse."
Cool's latest observations have revealed the unexpected, including the existence of binaries with white dwarfs -- a common type of dead star -- that have an unusual core made of helium instead of rock-solid carbon, which is the norm.
"This is a new class of binaries that have never really been seen before," says Cool, who has provided both graduate and undergraduate students the opportunity to engage in top-tier research since 1996. "By understanding star clusters, we learn more about galaxy evolution."
Expanding to Galaxies
Excavating the distant universe for clusters of star-filled galaxies that are billions of years old is similar to executing an archaeological dig with a garden spade.
But it can be done.
Just ask Associate Professor Ron Marzke, a leading member of an international team of astronomers working on the Hubble Space Telescope Treasury Survey, the largest survey ever to study the Coma Cluster, a dense clump of galaxies 321 million light years away.
"The difficult thing about analyzing these images is that while we can see within the cluster to great depth, it's hard to determine if very faint galaxies are part of the cluster and simply giving off faint light, or faint because they're on their own in the distant background."
Marzke, who established himself at the prestigious Carnegie Observatory before joining SF State in 2000, measures spectra, the fossil record of light and radiation left by celestial bodies. Like a cache of bones unearthed in an ancient seabed, this light -- which comes in varying wavelengths of color -- allows astronomers to extrapolate about their age and evolution.
Last year Marzke made headlines when he sifted through the red-shift desert -- a vast area of space so deep it holds some of the universe's earliest galaxies -- and found that galaxy formation may not be the long, slow process held by conventional theory.
"This helps us understand not only our own galaxy, but also the large-scale structure of the cosmos," says Marzke. "And that's ultimately the goal."
more we find out that it's actually playing a
huge role in the origin and destiny of the
universe." —Assistant Professor Andisheh
Mahdavi — Photo X:RAY by NASA/CXC/
UVIC./A. Mahdavi et Al. Optical/Lensing:
CFHT/UVIC./H. Hoekstra et Al.
Despite accounting for 80 percent of the universe's mass, with atoms filling the rest, dark matter is one of the least understood and most compelling mysteries of cosmology, says Mahdavi. And it functions on a vast, cosmic scale.
It is invisible and inert -- its particles, which are unknown, do not bounce off each other like air molecules do -- nor does it give off light. What it does do, he says, is exert a tremendous pull on the galaxy clusters it surrounds and heat the gas between them to hundreds of millions of degrees, providing the only clues to its existence. "We really don't know what it is," says Mahdavi, whose specialty is combining observations of these two characteristics to better understand its essence.
"All we know is that for stars to form, for galaxies to exist, maybe even for life to evolve, dark matter needed to be present to hold things together."
Like Marzke, whose groundbreaking work on ancient galaxy clusters does not fit current models of galaxy evolution, Mahdavi's research challenges current theories of dark matter.
Using NASA's Chandra X-ray Observatory, the astronomer captured two galaxy clusters in the midst of a violent collision, showing dark matter separating from the galaxies, which was unexpected. Current models predict that dark matter and galaxies should stay together during a violent collision.
"It's possible that dark matter has properties more complicated than our very simple theories can accommodate," says Mahdavi, who is currently analyzing new data provided by Hubble. "Or it could just be a freak occurrence. We're 99 percent sure it's not, but in science, that's not enough."
According to odds, Assistant Professor Joe Barranco should not be where he is today. Raised on welfare by a single mother of four, in a family that never attended college, Barranco's chances of becoming a high-achieving Harvard undergrad and pocketing a Ph.D. from UC Berkeley were as likely as finding planets outside the solar system.
"Now that I'm a scientist, I feel very strongly about working with youth in a similar situation, which is one of the reasons I came here," says Barranco, whose outreach includes teaching math and physics to young inmates.
Barranco complements Fischer in his research, providing theoretical modeling of planet formation.
"Planetary systems around other stars look nothing like our own," says Barranco. "Our current models can't explain them."
Barranco's research simulates the point at which tiny particles of dust spinning in discs of gas around newly formed stars turn into mountain-sized boulders, called planetesimals, which ultimately form planets. Like those of his maverick colleagues, his latest findings defy conventional theory.
Current models hold that as stellar dust spins, it settles into incredibly thin, dense sheets of matter, which crumple into little clumps of thumb-sized rocks through a process called gravitational instability. These rocks then have enough mass that gravity pulls them together, creating planetesimals.
As one of the first in his field to do three-dimensional computer simulations, Barranco -- who joined SF State last fall -- found that instead of forming little rocks, the sheet of compressed dust would crash like a wave and disperse the dust back into tiny particles.
His take on what brings them together? Stellar storms embedded within these oblong discs of gas and dust, like the great red spot on Jupiter. Over time, says Barranco, particles would get trapped in the storm, eventually clumping into little rocks through gravitational instability.
"Of course right now," says Barranco, "It's just a hypothesis."
Which is where all good science starts.
Back to Earth
When it comes to finding Earth-like planets, Fischer knows what she's doing. In addition to being a seasoned planet hunter, she also served on the NASA-commissioned Exoplanet Taskforce. As part of its advisory committee, she co-authored a 300-page report, just released to Congress, outlining a strategic plan for finding Earth-like planets in our galaxy. Beginning next spring, with the launch of NASA's much-anticipated Kepler Mission, the race will be in full gear.
Like Cool, Fischer is looking at a binary system, Alpha Centauri -- the sun's closest neighbor and the brightest star in the Southern Hemisphere.
"We've looked but have not found planets here before," says Fischer, who is observing them from the Cerro Tololo Inter-American Observatory in Chile. "But that doesn't mean they're not there.
"By understanding how planets are formed in our own solar system, we can predict that small planets like Earth, Venus and Mars could exist around other stars," she explains. "Say you were looking at our sun from another planet outside our solar system. You would only detect Jupiter. So by virtue of being here, we know there's the possibility of others." The hurdle in this race is high. Unlike with giant gas planets, the gravity of small Earth-like planets exerts an almost indiscernible wobble in their parent star.
"Our computer simulations show we can detect them, but we need something like 100,000 observations," explains Fischer. "And you just can't get that much time on big telescopes."
But she can on small, undersubscribed telescopes like the one in Chile. Not surprisingly, the Swiss team has an observatory on a nearby peak. So close, Fischer can see its dome.
"You know that the second we're on to something, they'll be all over it," laughs Fischer. "And that's exactly what we want."
The Expanding Universe
Just as the number of extrasolar planets has grown exponentially over the last dozen years, so has SF State's reputation as a center of excellence in both exoplanet astronomy and astrophysics in general.
Data from the Space Telescope Science Institute (STScI), which manages time allotments on the Hubble Space Telescope, is a strong indicator of the University's standing. According to STScI Science Director Dr. Neill Reid, Hubble received 1,000 proposals last year, with institutions averaging a success rate of one in six. SF State's approval rating was one in three.
"That's twice as successful as the average proposal," says Reid, "And acceptance is based solely on the science and the capabilities of the researchers, not on the institution itself."
NASA, the primary agency in charge of America's scientific ascension into space, not only considers SF State a leader in the field of exoplanet research, but also recognizes its importance in turning out well- prepared students.
"San Francisco State has become one of the nodes of extrasolar planet research in the United States," says Dr. Zlatan Tsvetanov, program scientist at NASA Headquarters in Washington, D.C. "Of course, everybody -- from Harvard to CalTech and the Carnegie Institution -- is trying to get into it. But you have an advantage in that you started early and you have a leader like Debra Fischer producing well-prepared students who end up going to these places to earn their Ph.Ds."
Since 2000, grants awarded to astronomy faculty have jumped from less than $100,000 in a given year to more than $2 million. The money supports a growing number of undergraduate and graduate students pursuing degrees in astronomy, with recent graduates continuing on to prestigious Ph.D. programs at Caltech, Johns Hopkins, UCLA and UC Santa Cruz, to name a few.
"It's an advantage that we're not a Ph.D. institution, because even undergrads here get to be involved in headline-making science," says Sheldon Axler, dean of the College of Science and Engineering. "At larger institutions, where most research is done by Ph.D. students, there's just nothing left for undergrads."
This, say astronomy faculty, is another important draw.
"This is not the Ivory Tower, these are the trenches," says Marzke. "You come here knowing it will be harder to do research, and the teaching load is heavier, but these are real people we're impacting, and I like the fact that I can bring my knowledge to anybody, not just an elite few."
Down the hall, Fischer prepares lecture material for the Astronomy 115 course she teaches. "In a good semester, there will be a couple students where the light just goes on and they'll decide to study physics or astronomy," she says. "That's why I like teaching the intro course. You can inspire them at an early age. That's what I hope, anyway."
Like finding Earth-like planets in the very near future, it's a goal worth betting on.
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