Jan. 18, 2007

Saving Arecibo: Observatory's radar and unique precision make it a vital resource, argues NAIC director

On Nov. 3 the Senior Review, an advisory panel to the National Science Foundation (NSF) Division of Astronomical Sciences, issued recommendations for the future of the Arecibo Observatory, which Cornell manages for the agency through the National Astronomy and Ionosphere Center (NAIC). Among the recommendations was a $2 million budget cut over the next three years, and advice that the NAIC find outside partners to cover half of Arecibo's total operating costs by 2011 or risk closure.

Reactions from Cornell and Arecibo astronomers have run from deeply concerned to guardedly optimistic. Many acknowledge the competing need to fund promising new facilities. But above all is strong agreement about Arecibo's unique strengths, its decades-long lifespan and the importance of keeping it running well into the future.

Robert Brown, NAIC director and adjunct professor of astronomy at Cornell, discussed the report's impact on the observatory in a recent interview.

How serious is the threat of closure?

My concern is that people will read the recommendation and expect that the observatory will close. It would be extremely serious if good people begin to leave the observatory for that reason. But personally I'm very optimistic that the future will be actually quite bright for the observatory.

We have looked for external funding and have been successful for some specific programs. But there aren't foreign countries or institutions that say, boy, I'd sure like to cut the grass at the observatory or to pay the electrical bill. That said, it's to the advantage of the U.S. astronomy community for support to continue, and everyone understands that. Yes, the Senior Review had recommendations that are contrary to that point of view -- but the Senior Review is not the only forum in which these subjects are discussed. We believe that we can convince the next decadal survey [2008-2010] of the value of the observatory.

What are the most compelling reasons for saving the observatory?

The technology of the instruments used for astronomy has improved dramatically in recent years. The ability to discover objects in the sky has improved -- not just by a little bit, by a huge amount. So that means that astronomy has had a renaissance. It's basically started over again.

The thrust of all modern observatories is surveys. In our case, we're surveying the sky looking for pulsars; for hydrogen in galaxies near but not in the Milky Way; and a third program looks to study hydrogen in the Milky Way. All in much greater detail than it has in the past.

So what happens now?

It's going to be a year filled with adventure. Institutionally, it's not all bad to say okay, our funding is going to decrease -- let's focus on the most important science we can do; let's do that well, and then we'll grow from there. It's not an unreasonable thing to do, and certainly we and the rest of the astronomy community genuinely want to see new research facilities be built. If you don't build new things, the field gradually will atrophy. The senior review exercise is one that we believe in, so we're prepared to put up with its consequences -- as long as it means paring us back by 25 percent or so, and then allowing us to grow from there. If the recommendations go further than that -- that's not something that I would support as being beneficial to U.S. science.

There is talk of future threats from near-Earth objects, such as asteroids. Why is Arecibo's radar vital for tracking these?

Arecibo has the world's only high-power radar. And it's terrifically good at studying the terrestrial planets in the solar system, the satellites of Jupiter and Saturn, and, in particular, near-Earth asteroids. Many people are quite concerned by the threat that such asteroids pose. We can determine the motion of an asteroid to within about a millimeter per second. That's astonishing precision -- orders of magnitude better than you can do by any other technique. And if you have that information you can reconstruct the orbit of the asteroid, or you can project it into the future to determine whether the asteroid is likely to hit the Earth. Arecibo is the only place in the world where you can do that.

The observatory is also engaged in sky surveys. What do scientists hope to learn from these?

Take pulsars: We know about 1,000 pulsars, and of that 1,000, most rotate between 10 times a second and once a second. Pulsars are neutron stars with the mass of the sun but a diameter of about 10 km. They're the endpoint of the life of a star, formed when a supernova explodes.

A few known pulsars -- less than 20 -- exist as members of a binary system. And some of those -- only five or six -- spin nearly 1,000 times a second. These are hugely important tools for studying general relativity [and for probing properties of matter under extreme conditions]. If you double the number known, which is what we're trying to do at Arecibo, maybe you have 10 or 12. And then maybe you've got enough to answer these fundamental questions. But you have to survey the sky to find them.

What do hydrogen gas surveys reveal about galaxy formation?

In the case of the Milky Way about 10 percent of the matter is gas and 90 percent is stars. In elliptical galaxies there is no gas -- there are just old stars. But it's the exceptions you look at. [The ALFALFA survey, for example, is a project searching for galaxies that consist mainly of hydrogen and dark matter -- but not stars. These galaxies could provide essential clues to how galaxies form.]

Meanwhile, while we're looking for the mass of gas, optical telescopes are looking for the composition of stars. It's these pieces of information in combination that are really valuable for research.