||Figure 1: Molecular supershell in the direction of the M16, M17 massive star forming region. We believe that the shell was formed by multiple supernovae, which also triggered the star formation in M16 and M17.
Modern astronomy aims to answer the questions of the origins of life and the universe. Our group's work focuses on radio observations of the processes by which stars are born - aiming to unravel the mysteries of the origin of stars and galaxies.
The raw material from which stars are born is dense clouds of molecular gas. The low temperature of this gas means that it cannot be seen in visible light. But instead we can "see" the details of how gas is gathering and stars are forming by observing the radio emission from hundreds of different types of molecules.
Indeed, it is believed that the Sun itself was born from molecular gas, some 4.6 billion years ago. Although we cannot look back in time to see it, in the present, stars are being born throughout the universe. In the molecular clouds of Taurus and Chamaeleon stars much like our Sun are being formed. And further afield, in the Large Magellanic Cloud, giant clusters of stars, the equivalent of a hundred thousand Suns, are coming into being.
By observing this star formation in progress in the present day, we are seeking to understand how stars and planetary systems are born.
High-precision radio telescopes are used for astronomical observations. Our team uses two radio telescopes that we have developed ourselves. At 4m in diameter, they are comparatively small, but they feature a wide field of view and some of the highest sensitivities in the world.
With the exception of normal optical telescopes, the instrumentation used by professional astronomers is not available over the counter. We have to make the equipment we need ourselves. The sensitivity of the receiver in particular has a large effect on the data we are able to obtain. Our receiver, which was developed on site, utilizes superconductor technology to achieve high sensitivities, and has led to a large number of significant results. Among these is the discovery of a large number of very young objects in the first million years of their lives, which we have christened "stellar eggs" and "newborn stars", and which have helped promote the name of Nagoya University in the astronomical world.
The molecular gas of a "stellar egg" collapses under its own gravity. However, magnetic fields and the centrifugal force caused by the gas's rotation act to oppose this contraction. In order to overcome this, "newborn stars" expel gas from each end. These "bipolar jets" disperse the object's angular momentum, slowing down its rotation, and allowing it to continue its collapse and become a fully fledged young star. The role of this phenomenon in star formation is something that we have begun to understand in recent years.
In 1995 we started a new observing project - to research the under-explored skies of the Southern Hemisphere. Large sections of the Southern sky, including the famous Southern Cross, are completely invisible from Japan, and research is lagging behind the Northern hemisphere.
For that purpose, we transferred one of our telescopes to The Las Campanas Observatory in Chile (altitude: 2400m), and have already obtained a large amount of new and useful data. The Northern part of Chile, at the foot of the Andes, is extremely dry and the air there is clear. With the proportion of clear days topping the 80% mark, it is an ideal site for astronomical observations. American and European institutions had already installed optical telescopes there, but there were hardly any instruments capable of observing the radio waves from molecules. Nagoya University's facility also drew attention for being the first serious observatory Japan had built abroad. The telescope was publicly named NANTEN - which means Southern Sky.
The NANTEN telescope has now mapped the distribution of molecular gas in a succession of southern constellations such as Lupus, Chamaeleon and the Southern Cross. It has also set its sights on the Magellanic Clouds, 160,000 light years away, observing the birth places of the giant stellar associations that hold clues to the formation of globular clusters. Graduate students take it in turns to go to Chile for 3 month shifts to carry out their own observations, with 2-3 students present at any one time.
In 2004, we began the process of transferring the telescope to the Atacama Desert (altitude: 4800m), and recently we have begun sub-mm wavelength observations at the site, which has some of the best observing conditions in the world.
The data observed with the NANTEN telescope forms the focus of the masters and PhD courses. Students collect and report their results in masters and doctoral theses, with 2-3 masters theses, and 1-2 doctoral theses submitted every year. The papers cover a huge variety of themes, ranging from low and high mass star formation in high latitude clouds close to the Solar system, to the origin of giant star clusters in the Magellanic Clouds.
Examples of doctoral theses from 2002 were "An Observational Study of Molecular Clouds Associated with Galactic Supershells" (Matsunaga) and "An Observational Study of Molecular Clouds Associated with Supernova Remnants and Supershells" (Moriguchi). The former investigated the effect of supershells on molecular clouds in around 10 examples of molecular supershells discovered in the Southern Milky Way; of which the "Carina Flare" is a prime example. The latter used detailed observations of the Vela supernova remnant and the M16-M17 supershell to discuss their influence on molecular clouds. 2002 masters theses included a large-scale survey of the Galactic center region, observations of molecular clouds in the third Galactic quadrant, and detailed observations of the "Warp" region of the outer Galaxy.
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