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Reflection of October Maunakea Skies with Dr. Masanori Iye

by Emily Peavy on November 3rd, 2016

Scientific and Engineering Challenges of the Thirty Meter Telescope: A Perspective from Japan

‘Imiloa invited Dr. Masanori Iye, Thirty Meter Telescope Japan Representative, to give a talk as a part of the monthly lecture series Maunakea Skies. As Professor Emeritus of NAOJ (Subaru telescope), Dr. Iye compared the scientific and engineering challenges of the Subaru telescope to those of the planned Thirty Meter Telescope (TMT).
“It was my honor to have a chance to talk at ‘Imiloa Maunakea Skies. Maunakea is so special for all of us who have a special love to the mountain. I am sure we shall be able to overcome eventually not just the scientific and engineering challenges but also the cultural [challenges],” said Dr. Iye.

The evening began with a brief look at the night sky where the audience compared what is visible with the naked eye verses with a telescope. Dr. Iye began by discussing the challenges with Subaru Telescope throughout its planning and construction. Subaru is a unique observatory, as it pushed the limit of how large a single mirror could be constructed. Unique systems were implemented to correct for astigmatism with the mirror and innovations of adaptive optics technology was also developed to properly subtract out the adverse effects of the atmosphere.

The Thirty Meter Telescope’s mirror will be very different from Subaru’s mirror, as it is simply not possible to build a single mirror that large. However, the design of the mirror will be similar to M. W. Keck Telescopes’ in that it will use multiple segmented mirrors which are precisely designed and aligned to act together as one single large mirror.

Japan assumes the responsibility of building TMT’s main telescope structure using their experience of Subaru’s construction to guide them. Japan is currently producing the mirrors for TMT, with the telescope requiring 492 mirrors total with an additional 82 spares; so far 164 of the 584 required mirrors have been produced.

Astronomers use the term “magnitude” to describe how bright or faint an object is. The magnitude scale is often confusing as bright objects are low numbers, while fainter objects have higher numbers; for example the sun has a magnitude of -26.7, while the star Hikianalia, also known as Spica, has a magnitude of 1.04 as it is much fainter than the sun. The Thirty Meter Telescope is projected to be sensitive to light as faint as 32 magnitude. For comparison, the human eye is sensitive to 6 magnitude while current telescopes are sensitive to 28 magnitude.  Detecting light as faint as 32 magnitude would be the equivalent to seeing a firefly blink on the dark side of the moon.


With its increased sensitivity the Thirty Meter Telescope will see closer objects in greater detail, and see new, farther away objects that have never been observed before. As astonomers look farther away into the Universe they are also looking back in time, as it took so long for the light of distant objects to reach us. This will allow astronomers to study the new planets now being discovered around other stars, and gain a better understanding of the Cosmic Dawn of the universe and our own origins.


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Click here to read about November’s Maunakea Skies Talk on Nov. 18

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