URSI Update #1

Greetings all! I’ve been having a busy, fun, and stimulating time here at the Nat’l Radio Sciences Meeting of URSI in Boulder, CO. The mountains are gorgeous, the skies are clear, and the radio astronomy is diverse and exciting!

I’ve been spending all my time in J commission, which is dedicated to the astronomy side of radio sciences. It’s often been complained about that this session is down in attendance since it always conflicts with the AAS meeting, but the talks are wonderful, nevertheless.

The Monday morning session was dedicated to ALMA science and technology. For those not in the know, ALMA is the Atacama Large Millimeter Array. This observatory, a joint effort among the NRAO in the US, the European Southern Observatory, Japan’s National Radio Observatory, and more, will explore the sky at wavelengths in the millimeter and sub-millimeter regime. That is, higher energy light than the Very Large Array explores, but lower energy than infrared. The NRAO’s Al Wooten gave the first talk, an overview of ALMA science and progress with the instrumentation. The observatory is being touted as an instrument with many uses for many people, but it has three main goals for the near term. The first is to detect molecules such as CO (carbon monoxide) in galaxies up to redshift (z) of 3 (that’s when the universe was just 2 billion years old!) in under 24 hours of observation. Molecular gas is a tracer of star formation, and the evolution of early galaxies depends on how that occurred. Next, ALMA will resolve proto-planetary disks around stars at a distance of up to 150 parsecs (almost 500 light-years!) away. Proto-planetary disks are the dust disks around younger stars from which planets may be forming. Some great simulations showed what the dust disk around the bright star Vega might look like. If the knots in that disk are shown to rotate over a period of years, then they may be harboring newly forming planets! (Ellie, can you hear that?) Finally, as a technical goal, ALMA will be able to do precise imaging with a resolution of 0.1 arcseconds (that’s 0.000028 degrees) with a dynamic range of 1000. This is a new regime for radio astronomy, with unprecedented sensitivities and resolutions at these wavelengths, which opens the door for truly groundbreaking science.

12 antennas are on site at the moment, being fully assembled and wired up.

Image courtesy of NRAO/AUI

They will stay at the “high site” which is at an altitude of 16,500 ft (5000 m)! This is crucial for astronomical work in this wavelength band, since the atmosphere is partially opaque here due to water vapor. To go to high altitude is to go above much of the water vapor.

The rest of Monday morning delved into many of the details of ALMA development. John Webber of the NRAO talked about the front end electronics, and how an international team built all of the parts and then integrated them together beautifully. One such integration center is where I work! Lucy Ziurys of the University of Arizona presented some of the science already being done with ALMA technology on other millimeter-wave telescopes in Arizona. This team discovered the first new molecule in space in 25 years and participated in the groundbreaking VLBI experiment to resolve the black hole at the center of our Milky Way (more to come on that later in the week.) Debra Shepherd of the NRAO gave a recap of the now closed ALMA Test Facility at the VLA site in New Mexico. I was stunned at their excellent and efficient project management, and how different teams worked together and treated it like a real observatory in order to work out the bugs.

There were lots more talks throughout the day, focusing on the real-time control systems, phase corrections (oh yes, light has phase as well as amplitude, and that matters to an interferometer!), Walsh functions, data transmission, gain calibration, and the science that can be done if ALMA’s frequency range is expanded. But I think I have enough of a brain dump for now!

Learn more about ALMA when Richard Drumm’s 365 Days of Astronomy Podcast is broadcast on February 4th! He’ll be interviewing Al Wooten of the NRAO Charlottesville. For now, do check out the main link above for more introductory material on ALMA science and progress. This observatory should begin operations in 2010 and be completed in 2013!

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