Date: June 12, 2010

Title: The Great Millimeter Telescope at Sierra Negra in Mexico


Podcaster: The Great Millimeter Telescope at Sierra Negra in Mexico

Description: The “Gran Telescopio Milimétrico” (GTM for short), built in México, is nowadays the largest and most powerful radio-telescope of its kind in the world. It operates at wavelengths as short as 1mm, it will allow to probe the early universe to study the processes which ultimately formed the galaxies, stars, and planets that we observe today.

Organization: Pleiades. Research and Astronomical Studies A.C. (web site soon to be presented also in English)

Bio: Edgardo Molina. B.S. in Mechanical Engineering from the Anahuac University in Mexico City. Post graduate studies in IT Engineering and a Masters Degree in IT Engineering. Working for IPTEL, an IT firm delivering solutions to enterprises since 1998. Space exploration enthusiast who participated in several Mexican space related activities. Licensed amateur radio operator with call sign XE1XUS. Amateur astronomer since childhood and actual founder and president of the Pleiades. Research and Astronomical Studies A.C. in Mexico City, Mexico. Avid visual observer and astrophotography fan. Public reach through education in exact sciences, engineering and astronomy. Lectures and teaching in several universities since 1993.

Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by Elizabeth Fracek, and dedicated to Linda Dunham, my 11th grade science teacher, who taught me more about the universe than anyone else did.

Additional sponsorship for this episode of 365 Days of Astronomy has been provided by Kylie Sturgess and the Token Skeptic podcast, a weekly show about superstition, science and why we believe – at


Hello. This is your host Edgardo Molina from Pleiades. Research and Astronomical Studies in Mexico City, Mexico. We will be talking a little bit on one of the most recent radio-astronomical projects in Mexico. The Great Millimeter Telescope. Thank you for joining us for this episode of the 365 Days of Astronomy Podcast. We hope you will enjoy the show.

The “Gran Telescopio Milimétrico” (GTM for short), built in México, is nowadays the largest and most powerful telescope of its kind in the world. It operates at wavelengths as short as 1mm, it will allow to probe the early universe to study the processes which ultimately formed the galaxies, stars, and planets that we observe today. GTM has been designed and constructed by a joint venture between The University of Massachusetts Amherst in the United States and by the Instituto Nacional de Astrofísica, Óptica y Electrónica
in México.

The GTM includes a single, extremely high precision alt-azimuth antenna which measures 50 meters in diameter. It is located at an altitude of 4580 m above sea level on an extinct volcano, the Tliltépetl, within the National Park Pico de Orizaba, about 100 km east of the city of Puebla and to the west of the Gulf of México.

The GTM is the largest scientific project ever undertaken in México in any field. The national development of novel technologies was set as a requirement for approving the project, a test in itself of the capabilities of México to construct large and sophisticated scientific instruments.

Why are observations at mm wavelengths important? Much of the material in the universe is in “dust” or “grains”, too cold to radiate at wavelengths shorter than the mm/submm range, and so only observable in emission at these longer wave-lengths.

Moreover, the dust in the Milky Way and other spiral galaxies is concentrated in the clouds where new stars form, and it obscures the most interesting interior regions of these clouds at optical, ultraviolet, and even infrared wavelengths. However, it is transparent at mm wavelengths, since the dust grain dimensions are smaller than this. The dust is concentrated in the plane of a typical spiral galaxy. Much of the ultraviolet and visible radiation emitted by young stars is absorbed by dust and re-radiated in the infrared.

Galaxies that are forming massive stars or that contain active galactic nuclei (AGN), presumably powered by super massive black holes, emit the bulk of their energy in the mid and far infrared. But the expansion of the universe shifts this emission for very distant galaxies into the millimeter and submillimeter range. onsequently,
one of the major research areas for the GTM will be the study of the early universe and the origin of the structures that became galaxies, stars, and planets.

GTM is an open-air telescope with no radome enclosure. Much of the improvement over existing telescopes can be obtained with an open loop active surface that includes 180 moveable surface segments. In each segment eight sandwiches of electroformed nickel are supported by a very stiff reaction structure, which is attached to the reflector back structure by a space frame: a 1440 ensemble of such panels.

Four actuators can adjust each space frame in relation to the back structure to correct for deformations due to gravity, thermal gradients and wind. Temperature sensors on all relevant parts of the structure will report to the control system, and the surface will be periodically measured by holographic techniques. Simulations indicate that the GTM should be able to maintain surface accuracy in the presence of winds up to 10 m/s.

The GTM will produce definitive descriptions of massive cores in the interstellar medium of the Milky Way. Mapping of the thermal dust continuum emission with the AzTEC and SPEED bolometer arrays will reveal the column density distribution of material and identify protostellar objects within the massive cores. The local
dynamics and chemistry of the massive core will be determined by imaging of spectral line emission that directly traces the dense gas. Such measurements will define the coupling of the dynamics to the protostellar condensation.

The high sensitivity, angular resolution, and mapping speed of the GTM will enable detailed investigations of the chemistry of interstellar molecular clouds, protoplanetary disks, and comets. The mapping speed of the GTM will allow detailed comparisons of the chemical content of a variety of molecular clouds in differing stages of evolution and with differing physical conditions and environments. Likewise, the high spectral resolution and sensitivity available with the GTM will produce data on isotopic fractionation and its dependence on cloud physical parameters and evolution. Such results will address the relative importance of purely gas phase versus grain surface synthesis of complex molecules in the Interstellar Medium (ISM), and the relation between interstellar molecules, the chemistry of primitive solar system bodies such as comets, the delivery of organic molecules to the early Earth from space, and the role of such molecules in the origin of life.

The GTM is an important station in the millimeter Very Long Baseline Interferometry (VLBI) network as it provides a large collecting area at 1 and 3mm bands and a valuable north-south baseline connecting with Atacama Large Milimeter Array (ALMA). Its participation in the millimeter VLBI campaigns is critical to efforts to resolve the event horizon of the SgrA* Super Massive Black Hole, to reveal shadowing generated by orbiting or infalling plasma, and to measure the spin of the Super Massive Black Hole from flaring events.

The terrestrial planets, planetary satellites, asteroids, and comets have all proved to be fruitful objects for study by radar astronomy. In addition, radar measurements of Near Earth Objects would provide distance and velocity data vastly more accurate than that available from optical images, a critical consideration for the protection of Earth from potentially impacting asteroids and comets.

This is a truly unique combined effort that clearly shows what a good coordination between international institutions can achieve. On the next podcast I will give you more information on other proyects that are currently taking place here in Mexico. There are just too many reasons for this great land and it’s people to pursue a brilliant future, particularly when there is a will to reach for the stars!

Before closing this podcast I would like to send all my respects and appreciation to all the team members
behind the GTM, who kindly posted this and other information online for the people interested in this
exciting project and for you people listening every day to this enthusiastic podcast.

For the 365 Days of Astronomy Podcast, this is Edgardo Molina, from Pleiades. Research and Astronomical Studies in Mexico City, Mexico wishing you enjoy the upcoming summer star party season. Thank you for listening.

End of podcast:

365 Days of Astronomy
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