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The Graduate School of Arts and Sciences, which awards the Harvard PhD, offers 55 degree programs, including interfaculty PhD programs with Harvard’s professional schools. PhD students may broaden their programs by enrolling in a growing number of secondary fields of study.


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Happenings in Astronomy

Posted Thursday, 07 February 2013

A Q+A with Department Chair Avi Loeb  

It promises to be a busy spring for Professor Abraham Loeb, chair of Harvard’s Department of Astronomy and director of the Institute for Theory & Computation (ITC). He is just out with a new book, The First Galaxies in the Universe (Princeton; coauthored with his former student Steven Furlanetto, PhD '03), in which he offers a comprehensive exploration of how the earliest objects first formed (“the scientific story of genesis”), uniting decades of theoretical work pioneered by him and his students with the promise of new avenues for observations in the era of large telescopes.  

Abraham LoebAnd closer to home, Loeb will host the department’s first-ever reunion of graduate alumni, set for April 5. The event will bring together some of the world’s most accomplished astronomers and astrophysicists, including two Nobel laureates, for discussions on recent tests of Einstein’s theory of gravity and the latest exploration of extra-solar planets and life. Returning alumni will get a chance to tour the department, meet current graduate students, and gather for a festive lunch. The lunch highlight: A historical review of astronomy at Harvard by Owen Gingerich, PhD '62.

We asked Loeb to talk a bit about current research in the department and the challenges and opportunities facing the field of astronomy today.

GSAS: Talk about your department’s most exciting growth areas. Harvard has long been a leader in exo-planet research; what new lines of inquiry is the department pioneering? 

We are particularly proud of our Institute for Theory & Computation, which attracts the very best students and postdocs in theoretical astrophysics worldwide. A number of research frontiers were pioneered at the ITC, such as the development of new techniques for imaging the glow from diffuse cosmic hydrogen when the very first galaxies formed and dissociated (“re-ionized”) that gas, imaging the silhouettes of black holes, or deciphering the spins of black holes from the spectrum of radiation emitted by the accretion disks around them. Currently, the ITC is seeking an endowment that will establish its success on a firm, long-lasting foundation.

We are also making important advances in observational astronomy. As you mentioned, our faculty, lecturers, and graduate students discovered new planets around other stars, and measured their masses, orbital parameters, and in some cases their atmospheres. We participate in Harvard’s Origin of Life Initiative, which aims to understand how life may form under different environments in astrophysics or the laboratory. Another major frontier that is being led by our faculty involves the time domain of transient phenomena, such as explosions of massive stars of different types (leading to a plethura of supernovae), collapsing stellar cores that produce jets moving near the speed of light and emitting flashes of high-energy radiation (known as “gamma-ray bursts”) that are visible all the way to the edge of the Universe.   Other colleagues within our department lead measurements of the fundamental parameters of the Universe in an attempt to better understand the nature of the dark matter and dark energy that dominate its composition today. The 2011 Nobel Prize in Physics was awarded to two of our former graduate students who discovered that the expansion of the Universe is speeding up due to the dark energy that fills it. 

Harvard is a partner in an effort to build the world’s biggest telescope, called the Giant Magellan Telescope (GMT), in Las Campanas, Chile; a 24-meter aperture that will advance all of the above research frontiers. We are currently engaged in an effort to raise the funds necessary to support our share in this exciting endeavour that will be essential for the research plans of our future students and faculty.

How do graduate students contribute to the department's research efforts?

Our graduate students work on a broad variety of exciting projects. These range from measuring the fraction of Earth-mass planets in the habitable zone (where the chemistry of life, as we know it, is possible) around nearby stars, studying stars that get shredded into a filament of gas (resembling a spaghetti) as they pass near a supermassive black hole at the center of a galaxy, simulating the way that galaxies grow as they accrete diffuse gas from the vast spaces that separate them, or figuring out the way that gas swirls into black holes like water down a sink.  

Your new book predicts great things for observational astronomy, with a new generation of super-large telescopes coming online. What questions do you believe scientists will be able to answer in the decade to come?

Using the observational techniques described in my book, we are likely to find out over the next decade when the first stars and galaxies formed and what impact they had on their environment. The heavy elements that we are made of, such as carbon or oxygen, were not produced in the Big Bang but in the interiors of stars. The first stars started producing these elements and so they represent our cosmic roots. Understanding how and when they formed is similar to gathering clues about ancestors in our family tree.

In 2010 I published a shorter, less technical, book entitled How Did The First Stars and Galaxies Form?, which was aimed at undergraduate-level students and the general public. [That book was just awarded the 2012 Chambliss Award for Scientific Writing from the American Astronomical Society.] The new textbook is 540 pages long, including all the advanced details needed for researchers that will advance the field over the next decade.

The second edition the new textbook will either resemble the first edition or need revision. In the first case, we might celebrate the fact that our theories were validated by observations. But the second case would be more rewarding, because we will know that we have learned something new about the Universe. Nature is full of surprises and our imagination is limited. Science is a learning experience. Irrespective of how old we are, we always remain students humbled by the lessons of new data.  
A rendering of the Giant Magellan Telescope

What excites you, personally, in astronomy today?

Given the latest advances in exo-planet research, I am particularly excited that within our lifetime we might find evidence for life elsewhere and answer the truely fundamental question: “Are we alone?” A positive answer to this question will no doubt have a dramatic impact on philosophical and religious ideas about our place in the Universe.

I am also intrigued by the fact that we do not know what most of the Universe is made of. We  labeled the unknown substances as dark, namely “dark matter” and “dark energy”, but since these substances were inferred by assuming that gravity is unchanged on cosmic scales, it is also possible that gravity itself is modified instead.

Finally, I would like to understand singularities better. We know that Einstein’s theory of gravity breaks down when the density of matter become infinite, for example during the Big Bang (which represents a singularity in time) or at the center of a black hole (which represents a singularity in space). This breakdown simply means that Einstein’s theory of gravity is incomplete and we need to unify it with quantum mechanics. I am very curious to know what the true unification means for the nature of the Big Bang or the central structure of spacetime inside black holes.

The GSAS community is particularly aware of the challenges and constraints faced by any federally funded science endeavor these days. How are research programs grappling with changes to the funding model? How should universities be advocating for research funding — even as we prepare for leaner federal budgets?

Basic research is extremely valuable for the future of our society. One might naively think that looking at the sky carries no practical benefits. However, Newton derived his laws of motion by studying the motion of planets around the Sun, and these laws are now essential for designing buildings, airplanes, and other mechanical devices. Even Einstein’s theory of general relativity, which explains the expansion of the Universe, is needed in order to reach the precision required in navigation (GPS) systems.

I am concerned about two recent developments. First, Europe is taking the lead from the US in many research projects in physics and astrophysics, such as the Large Hadron Collider or the Euclid Space Mission. Second, peer pressure (triggered by concerns about job security) and research in large groups pushes young astrophysicists towards mainstream research with predictable consequences — and away from innovation and risk taking. It is incorrect to think that management of funds plays a secondary role in the development of science. In my view, the rate of discoveries can be accelerated in a culture that nurtures innovation without programmatic reins, since unexpected discoveries often occur at the periphery of our programmatic research.

From the 1930s through the 1970s, Bell Labs recognized the value of non-programmatic research and was responsible for an unusual crop of major discoveries (such as the transistor, solar cell, laser, CCD, the discovery of the microwave background and more). These days, NASA and NSF mainly support “projects” with well-defined goals, instead of supporting creative individuals without programmatic reins. Prestigious academic institutions like Harvard can go a long way towards supporting the abandoned culture of basic research and harvesting its precious fruits.