David Aguilar
(617) 495-7462

Christine Pulliam
(617) 495-7463

pubaffairs@cfa


CfA Press Release
 
 Release No.: 02-04
For Release: 9:30 am EST, January 9, 2002

The SubMillimeter Array Opens One of Astronomy's Last Frontiers

Cambridge, MA - With four out of the eight antennas now operational, the collection of images from the world's first sub millimeter array (SMA) has begun. Exploring one of astronomy's last frontiers at a site near the summit of Mauna Kea in Hawaii, the SMA offers a unique opportunity to observe objects in unprecedented detail. Acting as an interferometer similar to the Very Large Array in New Mexico, the SMA will ultimately combine the electronic signals from eight 6-meter antennas to imitate the resolving power of a much larger telescope. When placed at their widest separation, the SMA's eight antennas will act like a single giant telescope more than 1,600 feet in diameter, equivalent to the length of five football fields.

"An imaging array at submillimeter wavelengths has applications in many exciting areas of astrophysics", says James Moran, SMA Director at the Harvard-Smithsonian Center for Astrophysics. "The SMA will allow us to peer into regions that are obscured at optical and infrared wavelengths to study low-energy emissions from cold dust and molecules. These emissions often arise in star-forming regions, protoplanetary disks, active regions of distant galaxies, and solar system bodies - all the places where discerning more detail using the high-resolution of the SMA will be invaluable."

The SMA project is a collaboration between the Smithsonian Astrophysical Observatory (SAO) in Cambridge, MA, and the Academia Sinica Institute of Astronomy & Astrophysics (ASIAA) in Taipei, Taiwan. "The collaboration on the SMA has been very beneficial for both our organizations", says K.Y. Lo, Director of ASIAA. "The addition of the two telescopes by ASIAA to the six built by SAO will double the observing speed of the SMA. ASIAA has also been able to build up rapidly to an international level, both scientifically and technically, through the involvement in the construction of this unique facility."

High-resolution observations at submillimeter wavelengths are very difficult from the ground because of the partial transparency and turbulence of the atmosphere. The high altitude of the site mitigates the transparency problem and special techniques add the equivalent of adaptive optics.

The SMA is a natural next step following the highly successful millimeter wave arrays operating at longer wavelengths. It has been under construction in Hawaii since 1995 and is expected to be fully operational by mid 2003.

In its current configuration, the Array utilizes 4 antennas at wavelengths of 1.3 and 0.9 mm with a restricted bandwidth of 320 MHz. In its final configuration the Array will have a bandwidth of 2000 MHz. In addition, the nearby radio facilities of the Caltech Submillimeter Observatory (CSO) and the James Clerk Maxwell Telescope (JCMT) will be connected to the SMA to form a 10-antenna array for special observations.

Initial observations made in the Fall of 2001 resulted in the first interferometric images ever made at a radio wavelength shorter than 1.3 mm. "These results clearly demonstrate the range of applications and great potential of the instrument as it approaches completion. We are about to explore one of the last windows to the Universe," says Paul Ho, SMA Project Scientist at the Center for Astrophysics.

The first submillimeter wavelength images obtained were of the molecular outflow of carbon monoxide in the Egg Nebula (AFGL 2688), a proto-planetary nebula. The image revealed two bipolar outflows that were previously documented from longer wavelength observations.

When an image of Mars was taken, profiles of carbon monoxide were measured across the planetary disk clearly revealing the difference in temperatures between the planet's surface and atmosphere. A vertical profile of the atmospheric temperature was also obtained. Further development of these capabilities will lead to a better understanding of weather patterns on Mars and other planets and their satellites.

Nineteen observations, spaced over a year, were made of the luminosity of the radio source surrounding the black hole in the center of the Galaxy known as Sagittarius A*. The results clearly show that the source is highly variable. This type of measurement will help establish the nature of the accretion disk and possible jet associated with this black hole and others.

In its final configuration the Array will be able to study the most distant objects in the universe. For example the most distant quasar known, J104433.04-012502.2 at a redshift of 5.8 has been detected by the JCMT at a level of 10 mJy, but no information about its structure or radio spectral lines has been determined.

With its high spectral and angular resolution the SMA will be able to trace astronomical gas flows in great detail and is expected to provide important insight into the mechanism by which molecular clouds collapse into stars and planets.

Headquartered in Cambridge, Massachusetts, the Harvard-Smithsonian Center for Astrophysics (CfA) is a collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into seven research divisions, study the origin, evolution, and ultimate fate of the Universe.

ASIAA is headquartered in Taipei, Taiwan. The Institute of Astronomy and Astrophysics is part of the Academia Sinica.

For more information on the SMA program:

Visit our website at: http://sma-www.harvard.edu/

Or contact:

David A. Aguilar, Public Affairs
Harvard-Smithsonian Center for Astrophysics
Phone: 617-495-7462 Fax: 617-495-7468
daguilar@cfa.harvard.edu

 
 
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