The Universe Tonight
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Submillimeter Astronomy on Mauna Kea
By Dr. Hiroko Shinnaga
(Staff Research Scientist at the Caltech Submillimeter Observatory)
Hiroko Shinnaga is a staff research scientist at the Caltech Submillimeter Observatory. She acquired her Doctor of Science degree at Ibaraki University in Japan. Before she start working at the CSO, she was a postdoctoral fellow at Academia Sinica Institute for Astronomy and Astrophysics in Taiwan and at Harvard-Smithsonian Center for Astrophysics for the Submillimeter Array (SMA) project.
When you look up at the dark night sky, you'll find so many stars are shining above you. How and where were they born? How do they evolve? And how do they end their lives? Those are some of the research questions in submillimeter astronomy.
Submillimeter waves (300 – 1000 microns) are longer than infrared and shorter than radio waves. For this reason, the technology used for submillimeter instruments makes use of both radio and infrared technologies. Water vapor in the Earth's atmosphere strongly absorbs submillimeter radiation therefore, submillimeter telescopes need to be located at high, very dry sites such as the summit of Mauna Kea. Submillimeter astronomy is one of the newest and least explored areas of astronomy because of technical challenges and because it requires very dry weather condition.
Submillimeter radiation is mainly generated in very cold dusty regions of space. Stars are born inside dense cold clouds where visible light cannot penetrate. When stars reach a certain age, like ten billion years old, for Sun-like stars, they start shedding their outer envelope material into space before they end their lives. A large submillimeter telescope, like the one that the Caltech Submillimeter Observatory (CSO) has, can catch these scenes that cannot be seen in other wavelengths.
The CSO is a 10.4 meter (34.1feet) diameter radio telescope, one of the world's pioneering telescopes dedicated to submillimeter astronomy. A world-famous Physicist, Dr. Robert Leighton, designed the telescope. The CSO has been in operation since 1987 and been led by Professor Thomas Phillips in the Physics Department at Caltech. The radio style dish has a homologous steel tube back-up structure. The eighty-four panels of the telescope are light weight aluminum honeycomb hexagons. The hexagon concept was later followed by the Keck telescopes. Many key instruments at the observatory were developed by current/former graduate students and staff members at the California Institute of Technology (Caltech) and at the CSO.
The CSO has two types of instruments, namely, SIS (Superconductor-Insulator-Superconductor) heterodyne receivers, and bolometers. The heterodyne receivers can measure motions of interstellar material. On the other hand, the bolometers are submillimeter cameras, and they can take pictures of astronomical objects at submillimeter wavelengths.
Mauna Kea is one of the best sites in the world for submillimeter astronomy. At Mauna Kea, are the top three observatories for submillimeter astronomy. They are the CSO (10.4 meter diameter), the James Clerk Maxwell Telescope (JCMT, 15 meter diameter), and the Submillimeter Array (SMA, 6 meter diameter with eight dishes). These observatories are operated by different institutions. However, they can work together to create the very best submillimeter instrument in the world. The name is the Expanded Submillimeter Array (eSMA). The eSMA is able to observe with a very high spatial resolution. Using this very special instrument, astronomers acquired initial science results.
At CSO, locally in Hilo, there are ten staff members, including one technical manager, one administrative assistant, two electro-mechanical technicians, two electronics technicians, one electronics engineer, and three scientists. Dr. Walter Steiger who used to be a technical manager at the CSO contributes to our outreach activities as a volunteer. Although we don't have many staff members, the CSO team maintains the telescope as a world premier telescope and the performance and the efficiency are exceptionally high. The CSO is open to astronomers from all over the world. You can find more information about our observatory at our websites, www.submm.caltech.edu/cso/ and www.cso.caltech.edu/outreach/kiosk/newresults_cso.html.