New telescopes for Mexico – Magazine ?

The SPM-Twin megaproject, led by the Institute of Astronomy, is underway. Two twin telescopes are planned to be built, with primary mirrors of 6.5 meters in diameter, which will be placed in one of the best places in the northern hemisphere for sky observation: the Sierra de San Pedro Mártir, in Baja California.

One Sunday, at the end of 2004, I met astrophysicist Vladimir Ávila Reese, from the Institute of Astronomy, getting off the subway at the Universidad station in Mexico City. He was rushing to the institute, eager to know if the National Astronomical Observatory’s 2.1-meter telescope had recorded a gamma-ray burst recently detected by a special satellite. The 2.1 meter telescope belongs to the National Astronomical Observatory in Baja California, in the San Pedro Mártir mountain range (observatory known as OAN-SPM). This region is considered one of the best locations for astronomy in the northern hemisphere due to the low turbulence of the atmosphere, its transparency and the darkness of the sky. Vladimir had already participated prominently in the difficult detection of gamma ray bursts. These very powerful flashes of energy were discovered in 1967 and are still not well understood by astrophysicists. The gamma rays (very high-energy electromagnetic radiation) from a burst can only be detected with instruments located in space. But to fully understand these explosions it is important to also examine the visible radiation they emit; For this, terrestrial telescopes such as the 2.1 meter one from San Pedro Mártir are used.

Size does matter

The most important dimension of a reflecting telescope like the ones at the OAN-SPM is the diameter of the main mirror with which it captures and concentrates the light. The larger the diameter, the finer the details that the instrument can show and at the same time the greater its ability to capture light. Today there are reflecting telescopes of eight meters in diameter and up to 10 (such as the twin Keck telescopes, located at the top of the Mauna Kea volcano, in Hawaii, and the Gran Telescopio de Canarias, in the Canary Islands, of which Mexico is a partner). ) and even larger telescopes are planned (see Huge Earth Eyes: Giant Telescopes, As you see? No. 71).

The OAN-SPM’s 2.1 meter telescope is already becoming too small for certain investigations, such as that of Vladimir Ávila Reese. Some time after our meeting in the subway, Vladimir told me: With a larger telescope we could undoubtedly follow the light curve of most of the explosions for several nights. With the determined light curves we could measure the distance, as well as understand many aspects of the physics of these objects. The desire of Vladimir, and of many other astronomers, is on the way to becoming a reality.

International collaboration

In November 2005, at the end of the III Mexico-Korea Astrophysics Workshop, held at the National College in Mexico City, the creation of an international consortium was announced to build two 6.5-meter telescopes at the OAN-SPM. The project, called SPM Twin, is estimated to cost about $150 million. South Korea wishes to participate with the financing of 50% of the project, the rest would come from US and Mexican institutions; For example, the University of Arizona and the National Institute of Astrophysics, Optics and Electronics (INAOE) each already contribute four million dollars. The Ministry of Public Education has contributed one million dollars. The Institute of Astronomy will put the infrastructure and experience of the OAN-SPM at the service of the construction and operation of the telescopes.

The project has made great progress as the consortium was integrated and its scope was scientifically defined. Basically, it is increasingly viable, Jesús González, a researcher at the Institute of Astronomy, who is responsible for the AI ​​in this project, tells me, both in the scientific and technical parts.

The twins of Saint Peter the Martyr

The SPM Twin project consists of two telescopes with 6.5 meter primary mirrors. To make them competitive and interesting in the era of giant telescopes, SPM Twins will have separate specialties difficult to perform with larger telescopes. One is the Wide Field Spectroscopic Telescope; Its field of view will cover relatively large patches of sky to be able to observe a large number of objects at the same time.

The larger a telescope is, the closer distant objects get, but this magnifying power comes at a price. It’s like seeing an elephant up close: we can examine the details of the skin at the expense of the overall view of the animal. With a large telescope you gain detail, but lose the width of the field of view. Today’s large telescopes can be optimized to examine broader fields, but the modification is extremely expensive. In this way, a 6.5-meter telescope optimized for wide-field observations will be very competitive even when telescopes of 20 meters or larger are built.

The Wide Field Spectroscopic Telescope can be used to simultaneously obtain the complete optical spectrum of objects captured in the observation field, with a resolution or spectral fineness high enough to extract information about the chemical composition, temperature and movement of the objects. these objects. This telescope will have a viewing angle of one and a half degrees in diameter, while conventional telescopes have a field of about a quarter of a degree. In a patch of sky of that size, the number of observable objects can reach tens of thousands of galaxies. With this system you can obtain the spectrum of thousands of objects at the same time.

The other instrument, which will be called the High Spatial Resolution Infrared Telescope, will be used to study the infrared radiation emitted by objects. It will be equipped with a system of adaptive optics, a computer-controlled mechanism that allows correction of light distortions of celestial objects caused by atmospheric turbulence. Adaptive optics correct distortion through small movements of the instrument’s mirror surface and significantly improve the sharpness of images that can be obtained with ground-based telescopes.

To minimize the cost of design and construction, the SPM Twin telescopes will incorporate design advances already proven in other 6.5-meter instruments: the twin Magellan telescopes at the Cerro Las Campanas Observatory, Chile, operated by the Carnegie Institution of Washington, and of the MMT telescope (Multiple Mirror Telescope), in Arizona, operated by the Smithsonian Institution and the University of Arizona.

José Franco, director of the Institute of Astronomy, specifies: In the case of the adaptive optics telescope, it will basically be a copy of the Magellan, so it will not require much new engineering. For all practical purposes, that of the telescope is already designed. The difficult case is that of the wide field telescope. We started from the Magallanes design and are incorporating some solutions from the MMT, which is older and more complex, but is designed for a larger field. In addition, modifications and measurement instruments must be designed comprehensively.

The Magellan is a very efficient and cheap telescope. Not the MMT, rather it is like a Frankenstein that was modified long after it was built; but it has the virtue of being a broader field. Both use the same type of 6.5 meter mirror that the SPM Twin will have, so they are ideal for use as a base design. From the Magallanes we will use the structure, optics and mount solutions for the two Twins and from the MMT we will use the wide field optics.